BIOB51 Lecture 8
.docx
School
St Joan of Arc Catholic High School**We aren't endorsed by this school
Course
BIOLOGY 1
Subject
Biology
Date
Dec 17, 2024
Pages
7
Uploaded by ChefTitanium14499
Lecture 8Genes, Heredity & EvolutionE&Z, Chapter 5In DNA, the number of adenine bases will always be equal to the number of _____ bases.A. cytosineB. guanineC. thymineD. uracilThe transcription of a DNA strand with this nucleotide sequence of A-T-A-C-A-A-C-T-G resultswhich mRNA sequence?A. T-A-T-G-T-T-G-A-CB. C-A-G-U-U-G-U-A-UC. U-A-U-G-U-U-G-A-CD. C-A-G-T-T-G-T-A-TPolytomy occurs whenA. the root of a phylogeny has more than one branch; therefore, the common ancestor of the species is not identified.B. an internal node of a phylogeny leads to more than two branches; therefore, the order inwhich the branchings occurred is not resolved.C. the order in which consecutive branchings occurred in a phylogenetic tree is resolved.D. the tree topology has the least number of character-state changes.Isocladus armadus (Marine isopod (New Zealand))-Colour changes comes from mutations -Multiple mutation lead to larger scale variationMutation-Mutation: any change to genomic sequence of an individual-errors during DNA replication-Can be harmful, beneficial, or neutral-Most are eliminated but some persist-somatic mutations passed to daughter cells-germline mutations (eggs & sperm) are heritableHow much variation is there?-Craig Venter
-pioneer in genome sequencing-the first draft sequence of human genome ... was his genome!-3.2 million places (nucleotides) differed just between his paired chromosomes->100 million when consider humans from across world (about 1/1000 bp)Point Mutations-Due to the redundancy of codons (64 codons, 20 amino acids), a change in the third base pair may not cause a change in amino acidEffect of deletions (or insertions) in coding regions-In-frame - base pair is removed in three which corresponds to one codon and one amino acid; animal may still beagle to function without that amino acid-Frame-shift - deletion is not in three so there is a shift in the order of the codonsChromosomal mutations
Examples of point mutationsA. Albinism – FGFR3 .....serine to prolineB. Polydactylism – LMBR1 .....C-T transitionC. Webbed digits – GLI3 .....proline to serineD. Piebaldism – KIT .....arginine to glycineE. Fibrodisplasial ossifications – AVCR1 .....arginine to histidineF. Progeria – mutation in Lamin ASources of heritable genetic variationLocation of MutationType of MutationConsequence for Gene ActionCoding regionSubstitution, insertion, deletion, duplicationAlters the product of the gene and thus its function or activity.Cis-regulatory regionsSubstitution, insertion, deletion, duplication that alters the binding affinity of promoters, activators, repressors, etc.Alters the timing, location, or level of expression of the gene. Alters the developmental or environmentalcontext in which the gene is expressed.Trans-regulatory regionsMutation to coding regions of trans-acting factorMutation to cis- or trans-regulatory regions of trans-acting factorsAlters the binding affinity and thus the activity of a promoter, activator, repressor, etc. Alters where, when, or to what extent inhibitory, activating, or other trans-acting regulatory factors are expressed.Physiological pathways(e.g., hormones)Mutations altering where, when, or how much an endocrine signal is producedAlters the timing, location, or level of expression of the gene.Alters the developmental or environmental context in which the gene is expressed.Cis vs. Trans-Cis-Regulatory Regions-near/within the focal gene-upstream, downstream, intron-e.g. binding sites for activators orrepressors-Trans-Regulatory Regions-far away (e.g. different chromosome)-e.g. proteins, some miRNA/siRNA-interact and affect the focal gene
Key concepts I-Germline mutations are uncommon; affect gametes; are heritable and relevant to evolution-Mutations in genes other than those coding for proteins may affect gene expression; can also affect the direction of evolution-Somatic mutations affect cells in the body of an organism; not heritableEffects of Mutation-Directly affect protein sequence-change amino acid sequence-alter protein activity, efficiency, shape, functionality-Affect protein function-no change in amino acid sequence-levels of expression-timing of expression-location of expression-e.g. transcription factor-binds better-binds more poorlyGene expression can be regulated in several waysmicroRNA can block translation-When microRNA binds, translation is stopped-This can lead to drastic changes in flowermorphologyAlternative splicing: multiple proteins from a single gene-Exon code for proteins
-Introns are non-coding sequences-The primary transcript contains all exons and introns and is able to exons but would cometo a stop when it hits the introns-Mature RNA from primary transcript-One gene can have multiple functionality due to alternate splicing-This allows evolution to act on different versions of proteinsKey concepts II-Transcription factors, microRNAs, & other regulatory molecules control gene expression within a cell-Individual genes can generate many different protein variants, each with different functionsHeredity-Bacteria & Archaea – simple – fission (clones)-variation largely via mutation-(other mechanisms that we won’t discuss here)-Eukaryotes – more complex-only germline mutations are inherited-sex introduces genetic variation via recombination-Meiotic recombination-Independent AssortmentCrossing-over-Meiosis-Creates variationRecombination generates variation-These are all the same chromosome, colour denotes origin only
Independent assortment ensures novel combinations of alleles-Randomizes which combination of chromosomes are passed down-Considering two chromosomes-** Not showing recombination, just chromosome assortment **Other than identical twins, is it possible for two children from the same parent to be genetically identical?A. No, it is not possible because of the number of ways in which genetic variability is produced. B. No, it is not possible because the process of meiosis has built-in mechanisms preventing it. C. Yes, it is possible, but chances are so remote that they should be considered negligible. D. Yes, it is possible and common.Key concepts III-Meiosis generates considerable genetic variation-Recombination-Independent assortment-Fusion of egg and sperm results in great genetic diversity among offspring, even from thesame parents-e.g. considerable differences between siblingsGenotype & Phenotype-Genotype: genetic makeup of an individual-Phenotype: manifestation of the genotype of an organism (e.g., observable, measurable characteristic)-morphological (antlers)
-developmental (learning)-physiological (metabolism)-behavioural (mating display)Linking genotype & phenotype-Understanding this link is challenging because traits don’t come with labels-We must search for the genes or for variation in expression-Breeding experiments; e.g. Mendel (peas)-Genetic Mapping; e.g. Hischhorn (height) (save this for Ch7)Gregor Mendel-Published in 1866-Darwin – Origin 1859-Mendel’s work was buried, not “found” until 1900