Understanding X-Linked Traits: Tips for Midterm Success

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University of British Columbia**We aren't endorsed by this school

Course

BIO 121

Subject

Biology

Date

Dec 12, 2024

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Uploaded by KidSquirrel2213

Today’s class (L8) –Probabilities (X-linked traits) & using information from genetic crosses to determine mode of inheritanceHappy October!UBC Applefest 2007 https://www.flickr.com/photos/magtravels/2053482907/

Midterm #1 –next Tuesday •20% of your grade•50 minutes in length (in class)•Total number of questions –not finalized (currently 3 major questions with subquestions)•Expect a variety of question types, e.g. multiple choice, select all, explanations, drawings•Testable content – all concepts that we have covered up to and including today’s class. Pedigrees will not be tested until the final exam. Please see learning objectives on Canvas.•You can bring a one-page 8.5 x 11” study sheet (2-sides) Any content is allowed but ALL CONTENT MUST be in your handwriting. Any content that, e.g. is a copy/paste or snip or photo of an image or text will result in a 10% penalty, and the potential for an academic misconduct penalty.•Exams may be written in pencil or pencil, but exams written in pencil or erasable pen cannot be remarked.•I recommend bringing a calculator.•Apple watches cannot be worn.

Study tip –related to study sheetWhy we are asking you to handwrite your study sheet….https://writingcenterofprinceton.com/handwriting-vs-typing-which-improves-learning/

Review sessionA review session will be run by our awesome team of peer tutors (Eric, Jessica, Samuella & Christine)•This Saturday (October 5th)•On Zoom (link on Canvas homepage). •Will be recorded•~90 minutes•Pre-review session slides and post-review session slides will be provided (I will provide links on the Canvas homepage under the Zoom link)The Saturday review session will include:•an overview of content testable for midterm 1, with an emphasis on content that students commonly struggle with. •'peer-tutor tips‘; and •how to format answers on exams.

Time of review session –iClicker QuestionWhich of the 3 possible times is your first choice?A.Saturday (Oct 5) 10 AMB.Saturday (Oct 5) 1 PMC.Saturday (Oct 5) 7 PMNote –I will be having extra office hours on Monday.I will be available on the weekend too.Please stay tuned for dates/times.Also, please note that the incredible Dr. Bridgette Clarkston will be hosting a review session. Details to follow.

Error in L6v2 slides –slide #19 (fixed in v3)

iClicker QuestionIf a gene is X-linked, and the male parent in the P-generation is carrying the dominant allele (XD/Y) and the female parent is homozygous recessive (Xd/Xd), in which generation will the male and female offspring have different phenotypes?A.F1 generationB.F2 generationC.Not sure

AnswerIf a gene is X-linked, and the male parent in the P-generation is carrying the dominant allele (XD/Y) and the female parent is homozygous recessive (Xd/Xd), in which generation will the male and female offspring have different phenotypes?A.F1 generationB.F2 generationC.Not sure

iClicker QuestionIf a gene is X-linked, and the male parent in the P-generation is carrying the recessive allele (Xd/Y) and the female parent is homozygous dominant (XD/XD), in which generation will the male and female offspring have different phenotypes?A.F1 generationB.F2 generationC.Not sure

AnswerIf a gene is X-linked, and the male parent in the P-generation is carrying the recessive allele (Xd/Y) and the female parent is homozygous dominant (XD/XD), in which generation will the male and female offspring have different phenotypes?A.F1 generationB.F2 generationC.Not sure

iClicker QuestionIs this a 3:1 phenotypic ratio for both sexes?A.YesB.NoC.Not sure

AnswerIs this a 3:1 phenotypic ratio for both sexes?A.Yes B.No C.Not sureAll F2 females have the dominant phenotype red coat1:1 ratio of dominant:recessive phenotypes or red:blue coats in the F2 males

Learning goals –sex-linked traits •Determine whether a gene is on an autosome or a sex chromosome (X only)•Determine whether two alleles have a dominant/recessive relationship or a co-dominant or incomplete dominance relationship•Predict what gamete genotypes a parent can produce and in what ratios/frequencies - for genes that are unlinked or linked, or on an autosome or sex chromosome•Predict offspring genotypes and phenotypes and in what ratios/frequencies –for genes that are unlinked or linked, on an autosome or sex chromosome, and whether alleles have a dominant/recessive relationship or co-dominance or incomplete dominance relationship•Be able to calculate the probability that two parents will have an offspring with a specific phenotype (one and two traits) –if the genes are autosomal or X-linked.

iClicker Question - probabilityWhat is the probability that this cross (a heterozygous female x a male carrying dominant allele) will result in a fawn (baby deer) that is male andred?XRXrXRXRXRRed coatXRXrRed coatYXRYRed coatXrYBlue coatF1F1A.0%B.25%C.37.5%D.50%E.Not sure

AnswerWhat is the probability that this cross will result in a fawn (baby deer) that is male andred?XR(1/2)Xr(1/2)XR(1/2)XRXRRed coatXRXrRed coatY(1/2)XRYRed coatXrYBlue coatF1F1A.0%B.25%C.37.5%D.50%E.Not sureFor an autosomal trait, you would have to calculate the probability of having a “male” offspring, and the probably of having a red coat separately.But, the probabilities of these two outcomes are already included in the Punnett Square

iClicker Question –probabilities #2What is the probability that this same cross (a heterozygous female and a male carrying the dominant allele) will result in a fawn that is a blue male ora red female?XRXrXRXRXRRed coatXRXrRed coatY XRYRed coatXrY Blue coatF1F1A.18.75%B.25%C.50%D.75%E.Not sure

AnswerWhat is the probability that this cross will result in a fawn that is a blue male ora red female?XR(1/2)Xr(1/2)XR(1/2)XRXRRed coatXRXrRed coatYXRYRed coatXrYBlue coatF1F1A.18.75%B.25%C.50%D.75%E.Not sureThe question specifies “OR”, so we should add the probabilities:Probability of blue male = 0.25Probability of red female = 0.50Probability of either blue male or red female = 0.25 + 0.50 = 0.75

Learning goals - summary •Determine whether a gene is on an autosome or a sex chromosome (X only)•Determine whether two alleles have a dominant/recessive relationship or a non-dominant relationship•Predict what gamete genotypes a parent can produce and in what proportions -for genes that are unlinked or linked, or on an autosome or sex chromosome•Predict offspring genotypes and phenotypes and in what proportions –for genes that are unlinked or linked, on an autosome or sex chromosome, and whether alleles have a dominant/recessive relationship or a non-dominant relationship•Be able to calculate the probability that two parents will have an offspring with a specific phenotype (one and two traits)

Genetic Crosses•Biologists can use their knowledge about parental genotypes and/or phenotypes & offspring genotypic and phenotype ratios to determine the most likely mode of inheritance for a trait.•This requires doing genetic crosses, i.e., mating numerous individuals and looking at the phenotypes of the offspring to establish a hypothesis.•Remainder of today’s class –how to use genetic crosses to determine the mode of inheritance (or test a given mode of inheritance).•Thursday’s class –Using pedigrees to determine the mode of inheritance in humans (not testable until the final exam).

Genetic Crosses - Learning goalsWhen provided with information about the outcome of genetic crosses, be able to:- make inferences* regarding the inheritance of the trait/phenotype, i.e.:•Autosomal dominant•Autosomal recessive•X-linked Dominant•X-linked Recessive•Non-dominant (autosomal genes only)*we could ask you to identify the most likely mode of inheritance OR we could suggest a mode of inheritance and ask you to assess the claim. - be able to explain your claim about the mode of inheritance using evidence(quantified, if possible) and reasoning/logic to support your claim.

If asked to determine the mode of inheritance for a trait - my approach: 6 steps•Step #1–Carefully read the scenario and scan the data*- looking for key information,e.g.Are parents true-breeding parents or not (scenario)?Who are the F1s being crossed with? Other F1s? A test cross?Do you notice any patterns in the F1 and F2 generation?-Do males and females have different phenotypes in the F1 orF2 generation, suggesting X-linked trait?-What are the phenotypic ratios, e.g.3:1?1:1?1:2:1?*ALWAYS lookat each trait separately (because the different traits mayhave different modes of inheritance = potentially messy data)

Optional –6-steps continued•Step 2:After scanning data for one trait, you should have a hunch or a starting hypothesis for mode of inheritance (if you are asked for the mode of inheritance).(*You could also be given a mode of inheritance –to be discussed later in lecture).•Step 3:Define your genes/alleles/genotypes based on this hypothesis (or the provided hypothesis).•Step 4:Use a Punnett Square to make PREDICTIONS about the EXPECTED genotype/phenotype frequencies for the F1 and F2 generation, ifthat hypothesis is true•Step 5: Compare PREDICTED frequencies with OBSERVED frequencies QUANTIFY –arethey similar or not?If yes - go to Step 6.No–return to step 1 (and re-evaluate your hypothesis–the exception is if we give you a mode of inheritance to evaluate).•Step 6:Conclusion - explicitly state whether your results support your hypothesis aboutthe mode of inheritance for the trait.

Dragon example–scale colourTruebreeding female dragons with redscales and long horns were crossed with true breedingmale dragons with greenscales and short horns.The results for scale colour were as follows:Cross 1:Females, red scalesxMales, green scalesF1s:Allhad red scalesCross 2:F1 females were crossed with F1 males:F2s:RedGreenMales3911Females4116Hmmm –F1 females (at least) carrying an allele for both red scale colour and green scale colour. What does this suggest about relationship between alleles? Hmmm–a 3:1 phenotypic ratio in F2 generation for both sexes. Where have we seen thatratio before?

Step 2–hypothesis for mode of inheritance: scale colouriClicker Question–What is your hypothesis about the mode of inheritance for scalecolour.A.Autosomal, with red scales dominant to green scalesB.Autosomal, with green scales dominant to red scalesC.X-linked, with red scales dominant to green scalesD.X-linked, with green scales dominant to red scalesE.Non dominantCross 1:F1s:Cross 2:Females, red scales xAll had red scalesMales, green scalesF1 females x F1 malesF2s (see table)RedGreenMales3911Females4116

Step 2–hypothesis for mode of inheritance: scale colourAnswer–What is your hypothesis about the mode of inheritance for scale colour.A.Autosomal, with red scales dominant to green scalesB.Autosomal, with green scales dominant to red scalesC.X-linked, with red scales dominant to green scalesD.X-linked, with green scales dominant to red scalesE.Non dominantCross 1:F1s:Cross 2:Females, red scales xAll had red scalesMales, green scalesF1 females from cross 1 x F1 males from cross 1F2s (see table)RedGreenMales3911Females4116F1 males and females all have thesame phenotype (red scales).Females are heterozygotes, and havered scales, indicating red>green.Autosomal or X-linked? See F2F2: 3:1 phenotypic ratio (red:green) (ratio that Mendel observed when gene was autosomal, dominant/recessive relationship)

Step 3–define genes, alleles, genotypes•Scale Colour Gene: R•AllelesR= redr =green•GenotypesRR = red Rr = red rr = greenI recommend that you avoid using letters that are similar in both capitaland lower case, e.g.c, s, o…..

Step 4–Calculate PREDICTED phenotype frequencies if hypothesis is trueTrait #1–Scale colour:Autosomal, red scales dominant to green scales (R > r)Cross parents: True breeding females, red scales (RR)xTrue breeding males, green scales (rr)F1s:Predicted genotype: RrPredicted phenotype: Red scales (all F1 dragons)Cross F1s:F1 females (Rr) x F1 males (Rr)F2s:Predicted phenotype ratio: 3:1 phenotypic ratio, red to green scalesRrRRRRrrRrrrrRRr

Step 5. Compare observed and predicted frequencies for hypothesis –scale colourCrossGenerationPredicted Phenotype freq.Observed Phenotype freq.RR x rr (P)F1Rr–all red scalesAll red scales–both sexesRr x Rr (F1)F2RR, Rr, Rr, rr3:1 phenotypic ratio–redscales:green scales80:27 = 3:1 (red to green)Males: 39:11 = 3:1 (red to green)Females: 41:16 = 3:1 (red to green)RedGreenMales3911Females4116Observed F2s (by sex)Predicted F2s (overall, not broken down by sex):Note –on an exam I would NOT expect you to include a table comparing observed and expected frequencies.

Step 6:Concluding statement (reasoning) - do data support hypothesis?CrossGenerationPredicted Phenotypefreq.Observed Phenotype freq.Consistent?RR x rr (P)F1Rr–all red scalesAll red scales–both sexesYesRr x Rr (F1)F2RR, Rr, Rr, rr3:1 phenotypic ratio–red scales:green scales80:27 = 3:1 (red to green)Males: 39:11 = 3:1 (red to green)Females: 41:16 = 3:1 (red to green)Yes

Explanation - recommendationCheck-list: After making your claim about the mode of inheritance, you can start with either observed or expected phenotype frequencies. For this example –I will start with observed frequencies.oStatement of hypothesis about mode of inheritance (claim) –if neededEvidence:oStatement of observed phenotype frequencies for the F1 generation –quantified if possible.oComparison of observed frequencies to predicted phenotype frequencies (Punnett Square provided). Are the frequencies consistent or not?oStatement of observed phenotype frequencies for the F2 generation. Quantified, if possibleoComparison of observed frequencies to predicted frequencies (Punnett Square provided). Are the frequencies consistent or not.Conclusion

Scale colour in dragons has an autosomal mode of inheritance with the allele for red scales dominant to the allele for green scales. A cross between two pure-breeding dragons with red scales (RR) and green scales (rr) produced heterozygous (Rr) F1 offspring that all had red scales. This observed frequency is consistent with our prediction that all F1s will have red scales if the gene for scale colour is autosomal with the allele for red colour dominant to the allele for green colour. A cross between the heterozygous F1s produced a F2 generation with a 3:1 phenotypic ratio of red scales to green scales. Specifically, in the F2 generation, there were 80 offspring with red scales (39 males and 41 females) and 27 offspring had green scales (11 males and 16 females), which is approximately the 3:1 predicted ratio.This 3:1 phenotypic frequency in the F2 generation is consistent with our expectations if scale colour is autosomal with red scales dominant to green scales.So (or in conclusion) the observed phenotypic frequencies are consistent with the predicted phenotype frequencies for both the F1 and F2 generation, which supports the hypothesis that scale colour in dragons is an autosomal trait, with red scales dominantto green scales.Example explanationRrRr (red colour)R.rRRR (red)Rr (red).rRr (red).rr (green)

If we provide you with a mode of inheritance and ask you to assess that mode of inheritance•Do NOT try to prove what the actual mode of inheritance is –that is not the question.•Define alleles, genotypes, etc. based on the provided mode of inheritance, and compare observed/expected values.

Dragon example–horn lengthF1s:All (100%) had long hornsTruebreeding female dragons with red scales and longhorns were crossed with true breedingmale dragonswith green scales and shorthorns.The results were asfollows:Cross 1:Females, long hornsxMales, shorthornsShortLongMales2624Females047Cross 2:F1 females from cross 1 x F1 males from cross 1F2s:Long horns in dragons are hypothesized to have an X-linked dominant mode of inheritance. Is this hypothesis supported by the data? Explain your reasoning.

Jump to step 3 (as we have provided you with a hypothesis)Gene for horn length:XHAlleles for horn length: XH= long horns and Xh= short hornsDefining genotypes for horn lengthXHXH= female with long hornsXHXh= female with long horns XhXh= female with short horns XHY = males with long horns XhY = males with short hornsRemember –an individual’s sex is part of their phenotype

Step 4–Predicted F1 & F2 phenotype frequencies if hypothesis is correct (long horn length = X-linked dominant phenotype)Cross 1:Females -long hornsxMales –short horns XHXHxXhYCross 2:F1 females from cross 1 x F1 males from cross 1F2s:XHXhXHXHXHXHXhYXHYXhYXHXhXHXhYXHYF1 prediction:-All F1 females & males have long horns F2 prediction (sex bias):-F2 females all have long horns -F2 males - 1:1 ratio of short:long horns.

Step 5. Compare observed and predicted frequencies–horn lengthCrossTo create: Predicted Phenotype freq.Observed Phenotype freq.Consistent?XHXHx XhY(P)F1XHXh- females all long hornsXHY–males all long hornsAll long horns–both sexesXHXhx XHY(F1)F2XHXH, XHXh –females –all long hornsXHY, XhY –males 1:1 phenotypic ratio long horns:short hornsAll females (47)- long horns;Males 26:24 or 1:1

Step 6. Conclusion - do the data support claim about mode of inheritance?CrossTo create: Predicted Phenotype freq.Observed Phenotype freq.Consistent?XHXHx XhY (P)F1XHXh- females all long hornsXHY–males all long hornsAll long horns–both sexesYesXHXhx XHY(F1)F2XHXH, XHXh –females –all long hornsXHY, XhY –males 1:1 phenotypic ratio long horns:short hornsAll females (47)- long horns;Males 26:24 or 1:1Yes

Example ExplanationIf horn length in dragons is an X-linked trait with long horns dominant to short horns, I would predictthat:-If a true-breeding female with the dominant phenotype of long horns (XHXH) was crossed with a short-horned male (XhY), all F1 females (XHXh) and males (XHY) will have long horns, as they will inherit the dominant allele from their female parent. As predicted, all of the F1s have long horns. -I would also predict that if a heterozygous F1 female was crossed with an F1 male carrying the dominant allele, all F2 females would have the dominant phenotype of long horns, because they would inherit the dominant allele from their male parent. And, the F2 males would exhibit a 1:1 phenotypic ratio of long horns:short horns because the F1 females would donate the dominant allele for longhorns to 50% of her offspring and the recessive allele for short horns to the other 50%. As predicted, all 47 F2 females had long horns, and we observed a 1:1 phenotypic ratio of long horns to short horns in the F2 males (26:24 long:short)So, in conclusion, the observed phenotype frequencies are consistent with the predicted frequencies for both the F1 and F2 generation, which supports the hypothesis that horn length in dragons is an X-linked trait with long horns dominant to short horns.

Note•I could also have made the claim and long horns in dragons is an X-linked recessive trait.•If so, define the alleles based on this new hypothesis.•The observed data would not match the predicted data, which would allow you to reject the hypothesis about the mode of inheritance.

5-minute break

Octopus Worksheet –At front, and on CanvasThe Pacific Northwest Tree Octopus (Octopus paxarbolis), is native to western North America. It can live both on land and in water. This species displays a variety of skin colours (e.g. brown, green, grey, blue, red and yellow). The white dots on the skin of some individuals glow in the dark. While in other individuals the spots do not glow.A geneticist performed a series of crosses to determine the mode of inheritance for skin colour and spot glowing. For their experiment, the researcher only had access to octopuses that had red and grey phenotypes.In the first cross (P generation), the geneticist crossed true-breeding female octopi with red skin and spots that glow in the dark with true-breeding male octopi with grey skin and spots that do not glow in the dark. The results are as follows:Cross 1 (P generation): Female octopi with red skin and spots that glow in the dark x Male octopi with grey skin and spots that do not glow in the dark.Progeny (F1):248 female octopi with red skin and spots that glow in the dark252 male octopi with red skin and spots that glow in the darkCross 2:Female F1s x Male F1sF2 Progeny:Note –two errors in handout: 1. Front of 2ndpage -last two points should say “skin colour” not “glowing spots”.2. Back of second page should say “F1 males” not “F2 males”Note –this question would have been worth about 20 marks on an exam

Based on the data from the above crosses, what is the most likely mode of inheritance for spots that glow in the Pacific Northwest Tree Octopus? Define alleles and all possible genotypes for glowing spots in this species of octopus. X-linked dominantAlleles, e.g. XG= spots that glow, Xg= spots that do not glow5 genotypes –3 females, 2 males XG/XG= female, spots that glowXG/Xg= female, spots that glowXg/Xg= female, spots that do not glowXG/Y = male, spots that glowXg/Y = male, spots that do not glow

Support your claim about the mode of inheritance for glowing spots in the Pacific Northwest Tree Octopus using evidence from both crosses and sound reasoning. As part of your explanation, compare the observed and expected offspring phenotype frequencies. Please show your work using Punnett Squares. Please write your explanation –5 minutesConclusion: The data support the hypothesis that glowing spots has an X-linked dominant mode of inheritance.

What is the most likely mode of inheritance for skin colour in the Pacific Northwest Tree Octopus? Define alleles and all possible genotypes for skin colour in this species of octopus. Support your claim about the mode of inheritance for skin colour in the Pacific Northwest Tree Octopus using evidence from both crosses and sound reasoning. As part of your explanation, compare the observed and expected offspring phenotype frequencies. Please show your work using Punnett Squares. 10-minutes

Unexpectedly the octopus researchers received a shipment of a male and female Pacific Tree octopus that were found in the trees around Stanley Park. Both of these octopi had a yellow skin colour. The researchers mated these octopi. The results are shown in the table below.What is the most likely mode of inheritance of yellow skin in these octopi? What was the likely genotype of the two octopi that were shipped to the researchers? If you crossed an F1 octopus with yellow skin with an F1 octopus with green skin, what phenotypic ratio would you expect to observe in the offspring? Parent #1Parent #2F1 FemalesF1 MalesYellow skinYellow skin6 green skin4 red skin10 yellow skin4 green skin4 red skin10 yellow skinNote –handout incorrectly states F2 males

Unexpectedly the octopus researchers received a shipment of a male and female Pacific Tree octopus that were found in the trees around Stanley Park. Both of these octopi had a yellow skin colour. The researchers mated these octopi. The results are shown in the table below.What is the most likely mode of inheritance of yellow skin in these octopi? Autosomal non-dominance/incomplete dominance (between green and red alleles)What was the likely genotype of the two octopi that were shipped to the researchers? Heterozygous for the allele for red skin and green skin, e.g. SR/SGIf you crossed an F1 octopus with yellow skin with an F1 octopus with green skin, what phenotypic ratio would you expect to observe in the offspring? Parent #1Parent #2F1 FemalesF2 MalesYellow skinYellow skin6 green skin4 red skin10 yellow skin4 green skin4 red skin10 yellow skinSGSRSRSGyellow skinSGSGSGgreen skinSRSGSRSRSRredSRSGyellowSGSRSGyellowSGSGgreen

iClicker Question - Worksheet #5 -DrosophilaWhat is the most likely mode of inheritance for scarlet eyes in Drosophila melanogaster?A.Autosomal dominantB.Autosomal recessiveC.X-linked dominantD.X-linked recessiveE.I am not sureDue this Sunday, October 6th@ 11 pm

AnswerWhat is the most likely mode of inheritance for scarlet eyes in Drosophila melanogaster?A.Autosomal dominantB.Autosomal recessiveC.X-linked dominantD.X-linked recessiveE.I am not sure

iClicker Question - Worksheet #5 -DrosophilaWhat is the most likely mode of inheritance for smooth bristles in Drosophila melanogaster?A.Autosomal dominantB.Autosomal recessiveC.X-linked dominantD.X-linked recessiveE.I am not sure

Answer - Worksheet #5 -DrosophilaWhat is the most likely mode of inheritance for smooth bristles in Drosophila melanogaster?A.Autosomal dominantB.Autosomal recessiveC.X-linked dominantD.X-linked recessiveE.I am not sure

Predictions & Observations (phenotype frequencies) –for both traits

Scarlet EyesHypothesis –Scarlet eyes is an autosomal recessive traitDefine alleles, e.g. E = dark red eyes, e = scarlet eyesGenotypes, e.g. EE & Ee = dark red eyes, ee = scarlet eyesPrediction: EE x eeAll F1s are heterozygotes (Ee) with dark red eyesE.eEeDark red eyesObserved F1 phenotype frequency (all 161 F1 offspring have dark red eyes) is consistent with predicted phenotype frequencies.

Scarlet EyesHypothesis –Scarlet eyes is an autosomal recessive traitPrediction for the F2 generation: A 3:1 phenotype ratio of dark red eyes: scarlet eyesE.eEEEDark red eyesEeDark red eyes.eEeDark red eyes.ee scarlet eyesObserved F2 phenotype frequencies (117 dark red eyes: 38 scarlet eyes, with no sex bias) is consistent with the predicted phenotype frequencies.

Singed BristlesHypothesis –Singed bristles is a X-recessive traitDefine alleles, e.g. XB= smooth bristles, Xb= singed bristlesGenotypes (5): XB/XB and XB/Xb= females with smooth bristlesXb/Xb= female with singed bristlesXB/Y = male with smooth bristlesXb/Y = male with singed bristlesPrediction: Xb/Xbx XB/Y XbF1 phenotypes:XBXB/XbFemales with smooth bristlesYXb/YMales with singed bristles

Singed bristles continued?XbF1 phenotypes:XBXB/XbFemales with smooth bristlesYXb/YMales with singed bristlesF1 observed phenotype frequencies consistent with predicted frequencies?XBXbXbXB/XbFemale, smooth b.Xb/XbFemale, singed b.YXB/YMale, smooth b.Xb/YMale, singed b.F2 observed phenotype frequencies consistent with predicted frequencies, i.e. a 1:1 phenotypic ratio of smooth:singedbristles for both males and females?

DrosophilaWorksheet continuedPredict the outcome of a cross between a pure breeding female with scarlet eyes and smoothbristles, and a pure breeding male with dark red eyes and singed bristles. Show the genotype of theparents, a Punnett square representing this particular cross, and the predicted phenotypes of theprogeny (including their respective ratios).XB= smooth bristlesXb= singed bristlesE = dark red eyes.e = scarlet eyes

DrosophilaWorksheet continuedPredict the outcome of a cross between a pure breeding female with scarlet eyes and smoothbristles, and a pure breeding male with dark red eyes and singed bristles. Show the genotype of theparents, a Punnett square representing this particular cross, and the predicted phenotypes of theprogeny (including their respective ratios).XB/XB;eex Xb/Y;EEXBeXbEXB/Xb;E/eFemale with smooth bristles and dark red eyesYEXB/Y;E/eMale with smooth bristles and dark red eyes1:1 ratio of females with smooth bristles and dark red eyes: males with smooth bristles and dark red eyes

Next class (Thursday)•Using pedigrees to determine the mode of inheritance in people (not testable the final exam).•If we have extra time (likely), I will have a question/answer period.

Kiwi Fruit –an extra scenario –if timeGreen kiwi fruit has a fuzzy brown skin and green fruit. In contrast, the golden kiwi has smooth brown skin and yellow fruit.You are studying the mode of inheritance of fruit colour and skin phenotype in kiwis. The parents of the initial cross come from pure-breeding populations (Table 1). You then make a cross using the F1 offspring (Table 2)Table 2Green fruit,fuzzy skinGreen fruit, smooth skinGolden fruit, fuzzy skinGolden fruit, smooth skinF2 Females620220F2 Males3031109What is the most likely mode of inheritance for smooth skin in kiwis:A.Autosomal dominantB.Autosomal recessiveC.X-linked dominantD.X-linked recessiveE.Not sure Table 1PhenotypesPFemale: Green Fruit, fuzzy skinMale: Golden Fruit, smooth skinF1Females:100% green fruit, fuzzy skinMales: 100% green fruit, fuzzy skin

AnswerGreen kiwi fruit has a fuzzy brown skin and green fruit. In contrast, the golden kiwi has smooth brown skin and yellow fruit.You are studying the mode of inheritance of fruit colour and skin phenotype in kiwis. The parents of the initial cross come from pure-breeding populations (Table 1). You then make a cross using the F1 offspring (Table 2)Table 2Green fruit,fuzzy skinGreen fruit, smooth skinGolden fruit, fuzzy skinGolden fruit, smooth skinF2 Females620220F2 Males3031109What is the most likely mode of inheritance for smooth skin in kiwis:A.Autosomal dominantB.Autosomal recessiveC.X-linked dominantD.X-linked recessiveE.Not sure Table 1PhenotypesPFemale: Green Fruit, fuzzy skinMale: Golden Fruit, smooth skinF1Females:100% green fruit, fuzzy skinMales: 100% green fruit, fuzzy skin

iClicker QuestionGreen kiwi fruit has a fuzzy brown skin and green fruit. In contrast, the golden kiwi has smooth brown skin and yellow fruit.You are studying the mode of inheritance of fruit colour and skin phenotype in kiwis. The parents of the initial cross come from pure-breeding populations (Table 1). You then make a cross using the F1 offspring (Table 2)Table 2Green fruit,fuzzy skinGreen fruit, smooth skinGolden fruit, fuzzy skinGolden fruit, smooth skinF2 Females620220F2 Males3031109What generation did you use to determine that smooth skin was a recessive trait? A.F1 dataB.F2 dataC.Not sure Table 1PhenotypesPFemale: Green Fruit, fuzzy skinMale: Golden Fruit, smooth skinF1Females:100% green fruit, fuzzy skinMales: 100% green fruit, fuzzy skin

AnswerGreen kiwi fruit has a fuzzy brown skin and green fruit. In contrast, the golden kiwi has smooth brown skin and yellow fruit.You are studying the mode of inheritance of fruit colour and skin phenotype in kiwis. The parents of the initial cross come from pure-breeding populations (Table 1). You then make a cross using the F1 offspring (Table 2)Table 2Green fruit,fuzzy skinGreen fruit, smooth skinGolden fruit, fuzzy skinGolden fruit, smooth skinF2 Females620220F2 Males3031109What generation did you use to determine that smooth skin was a recessive trait? A.F1 dataB.F2 dataC.Not sure Table 1PhenotypesPFemale: Green Fruit, fuzzy skinMale: Golden Fruit, smooth skinF1Females:100% green fruit, fuzzy skinMales: 100% green fruit, fuzzy skin

iClicker QuestionGreen kiwi fruit has a fuzzy brown skin and green fruit. In contrast, the golden kiwi has smooth brown skin and yellow fruit.You are studying the mode of inheritance of fruit colour and skin phenotype in kiwis. The parents of the initial cross come from pure-breeding populations (Table 1). You then make a cross using the F1 offspring (Table 2)Table 2Green fruit,fuzzy skinGreen fruit, smooth skinGolden fruit, fuzzy skinGolden fruit, smooth skinF2 Females620220F2 Males3031109What evidence did you use to identify whether the gene for the inheritance for skin texture was autosomal or X-linked? A.F1 dataB.F2 dataC.Not sure Table 1PhenotypesPFemale: Green Fruit, fuzzy skinMale: Golden Fruit, smooth skinF1Females:100% green fruit, fuzzy skinMales: 100% green fruit, fuzzy skin

AnswerGreen kiwi fruit has a fuzzy brown skin and green fruit. In contrast, the golden kiwi has smooth brown skin and yellow fruit.You are studying the mode of inheritance of fruit colour and skin phenotype in kiwis. The parents of the initial cross come from pure-breeding populations (Table 1). You then make a cross using the F1 offspring (Table 2)Table 2Green fruit,fuzzy skinGreen fruit, smooth skinGolden fruit, fuzzy skinGolden fruit, smooth skinF2 Females620220F2 Males3031109What evidence did you use to identify whether the gene for the inheritance for skin texture was autosomal or X-linked? A.F1 dataB.F2 dataC.Not sure Table 1PhenotypesPFemale: Green Fruit, fuzzy skinMale: Golden Fruit, smooth skinF1Females:100% green fruit, fuzzy skinMales: 100% green fruit, fuzzy skin

Crosses QuestionGreen kiwi fruit has a fuzzy brown skin and green fruit. In contrast, the golden kiwi has smooth brown skin and yellow fruit.You are studying the mode of inheritance of fruit colour and skin phenotype in kiwis. The parents of the initial cross come from pure-breeding populations (Table 1). You then make a cross using the F1 offspring (Table 2)Table 2Green fruit,fuzzy skinGreen fruit, smooth skinGolden fruit, fuzzy skinGolden fruit, smooth skinF2 Females620220F2 Males3031109Using the information provided in the tables, assess the hypothesis that green fruit colour in kiwis is an autosomal recessive. Table 1PhenotypesPFemale: Green Fruit, fuzzy skinMale: Golden Fruit, smooth skinF1Females:100% green fruit, fuzzy skinMales: 100% green fruit, fuzzy skinYou can skip steps 1 and 2; as you were given the hypothesis to test.

Step 3 –define alleles/genotypes based on given hypothesisGreen kiwi fruit has a fuzzy brown skin and green fruit. In contrast, the golden kiwi has smooth brown skin and yellow fruit.You are studying the mode of inheritance of fruit colour and skin phenotype in kiwis. The parents of the initial cross come from pure-breeding populations (Table 1). You then make a cross using the F1 offspring (Table 2)Table 2Green fruit,fuzzy skinGreen fruit, smooth skinGolden fruit, fuzzy skinGolden fruit, smooth skinF2 Females620220F2 Males3031109Using the information provided in the tables, assess the hypothesis that green fruit colour in kiwis is an autosomal recessive. Table 1PhenotypesPFemale: Green Fruit, fuzzy skinMale: Golden Fruit, smooth skinF1Females:100% green fruit, fuzzy skinMales: 100% green fruit, fuzzy skinG = golden fruit.g = green fruitGG = golden fruitGg = golden fruit.gg = green fruit

Step 4 –predicted phenotype frequencies for given hypothesisGreen kiwi fruit has a fuzzy brown skin and green fruit. In contrast, the golden kiwi has smooth brown skin and yellow fruit.You are studying the mode of inheritance of fruit colour and skin phenotype in kiwis. The parents of the initial cross come from pure-breeding populations (Table 1). You then make a cross using the F1 offspring (Table 2)Table 2Green fruit,fuzzy skinGreen fruit, smooth skinGolden fruit, fuzzy skinGolden fruit, smooth skinF2 Females620220F2 Males3031109Using the information provided in the tables, assess the hypothesis that green fruit colour in kiwis is an autosomal recessive. Table 1PhenotypesPFemale: Green Fruit, fuzzy skinMale: Golden Fruit, smooth skinF1Females:100% green fruit, fuzzy skinMales: 100% green fruit, fuzzy skinFemale (.gg) x Male (GG) = Prediction: F1 Offspring = Gg, with golden fruit*Prediction: F2 Offspring Gg x Gg = 3:1 phenotypic ratio of golden to green fruit. Note –as soon as one cross is impossible, you can stop

Step 5 –compare observed phenotype frequencies with expected phenotype frequenciesGreen kiwi fruit has a fuzzy brown skin and green fruit. In contrast, the golden kiwi has smooth brown skin and yellow fruit.You are studying the mode of inheritance of fruit colour and skin phenotype in kiwis. The parents of the initial cross come from pure-breeding populations (Table 1). You then make a cross using the F1 offspring (Table 2)Table 2Green fruit,fuzzy skinGreen fruit, smooth skinGolden fruit, fuzzy skinGolden fruit, smooth skinF2 Females620220F2 Males3031109Using the information provided in the tables, assess the hypothesis that green fruit colour in kiwis is an autosomal recessive. Table 1PhenotypesPFemale: Green Fruit, fuzzy skinMale: Golden Fruit, smooth skinF1Females:100% green fruit, fuzzy skinMales: 100% green fruit, fuzzy skinIf green fruit colour is an autosomal recessive trait, then I would predict that when crossing a female with green fruit (gg) with a male with golden fruit (GG), all F1s would be hybrids with the dominant phenotype (golden fruit). However, we observed that all F1 kiwis have green fruit. So our F1 observations do not match our predicted phenotype.

Step 5 –ConclusionGreen kiwi fruit has a fuzzy brown skin and green fruit. In contrast, the golden kiwi has smooth brown skin and yellow fruit.You are studying the mode of inheritance of fruit colour and skin phenotype in kiwis. The parents of the initial cross come from pure-breeding populations (Table 1). You then make a cross using the F1 offspring (Table 2)Table 2Green fruit,fuzzy skinGreen fruit, smooth skinGolden fruit, fuzzy skinGolden fruit, smooth skinF2 Females620220F2 Males3031109Using the information provided in the tables, assess the hypothesis that green fruit colour in kiwis is an autosomal recessive. Table 1PhenotypesPFemale: Green Fruit, fuzzy skinMale: Golden Fruit, smooth skinF1Females:100% green fruit, fuzzy skinMales: 100% green fruit, fuzzy skinThe data do not support the hypothesis that green fruit colour in kiwis is an autosomal recessive trait. Note –I am not saying what the mode of inheritance is. Proving the actual mode of inheritance does not disprove the provided mode of inheritance.