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Mendelian Genetics Topics: -Transmission of DNA during cell division -Transmission of DNA during cell division Mitosis and Meiosis Mitosis and Meiosis - Segregation - Segregation - Sex linkage (problem: how to get a white-eyed female) - Sex linkage (problem: how to get a white-eyed female) - Inheritance and probability - Inheritance and probability - Independent Assortment - Independent Assortment - Mendelian genetics in humans - Mendelian genetics in humans - Linkage - Linkage - Gene mapping - Gene mapping -Gene mapping in other organisms (fungi, bacteria) (fungi, bacteria) - Extensions to Mendelian Genetics - Gene mutation - Chromosome mutation (- Quantitative and population genetics) B2900 B2900           

Mutation Source of genetic variation: Gene Mutation - somatic, germinal - somatic, germinal Chromosome mutations (Ch. 11) Chromosome mutations (Ch. 11) - structure (deletion, duplication, inversion, translocation) - structure (deletion, duplication, inversion, translocation) - number - number  

Chromosome Mutation (2. changes in number) Euploidy: variation in complete sets of chromosomes chromosomes Aneuploidy: variation in parts of chromosome sets sets

Euploidy 1x monoploid (1 set) = n 2x diploid (2 sets) = 2n 3x triploid 4x tetraploid 5x pentaploid polyploid (> 2 sets) 6x hexaploid n = # chromosomes n = # chromosomes in the gametes 2n4n

Polyploids Autopolyploids: within one species Allopolyploids: from different, closely related species related species

Polyploids Larger than Diploids

Polyploids Triploids: = 3n - problems with pairing during - problems with pairing during meiosis meiosis - unbalanced gametes - unbalanced gametes - usually sterile - usually sterile Applications: seedless fruits, sterile fish Applications: seedless fruits, sterile fish aquaculture aquaculture

Formation of Triploids n n n = 3n = 3n n Polarbodies n 2n2n2n2n n

Triploids (3x) Why can’t a triploid produce viable gametes ?

Fig. 11-5

Triploids (3x) x = 1 Gametes

Triploids x = 2 Gametes or viable Non-viable

Viable Gametes from Triploids Probability (2x or x gamete) = ( ) if x = 10 Prob. = of viable gametes 1 2 x - 1 # of chrs 2 3 4

Triploid Fish Frankenfish-Biotech 3n carp

Autotetraploid

Autotetraploid Doubling of chromosomes: 2x----> 4x Even number of chromosomes: normal meiosis 2 2 segregation------> functional gametes 2 2 segregation------> functional gametes

Polyploids Autopolyploids: within one species Allopolyploids: from different, closely related species related species Hybridization Hybridization

Triploid 2n = 42 x = 7 n = 21 2n = 14, n = x = 7 Chromosome sets: A, B, D hybrid Origin of Wheat Fig n = 28 n = Allopolyploid

Polyploidy Plants: speciation (wheat) Animals: - rare (sex determination) - fish (salmon: tetraploid) - fish (salmon: tetraploid) - parthenogenetic animals - parthenogenetic animals

Plant Polyploids

Chromosome Mutation (changes in number) Euploidy: variation in complete sets of chromosomes chromosomes Aneuploidy: variation in parts of chromosome sets sets 

Aneuploidy Nullisomics (2n - 2) Monosomics (2n - 1) Trisomics (2n + 1) normal

Aneuploidy Nullisomics (2n - 2) - lethal in diploids - lethal in diploids - tolerated in polyploids - tolerated in polyploids Monosomics (2n - 1) - disturbs chromosome balance - disturbs chromosome balance - recessive lethals hemizygous - recessive lethals hemizygous Trisomics (2n + 1) - sex chromosomes vs autosomes - sex chromosomes vs autosomes - size of chromosome - size of chromosome

Aneuploidy Non-disjunction: Gametes Meiosis I n + 1 n - 1 Meiosis II n + 1 n - 1 n n x n > 2n - 1 monosomic n x n > 2n + 1 trisomic

Human Aneuploids X Y

Aneuploidy Humans: (live births) Monosomics - XO Turner syndrome Monosomics - XO Turner syndrome - no known autosomes - no known autosomes Trisomics XXY Klinefelter sterile male Trisomics XXY Klinefelter sterile male XYY fertile male ( X or Y gametes) XYY fertile male ( X or Y gametes) XXX sometimes normal XXX sometimes normal 21 Down 21 Down 18 Edwards syndromes 18 Edwards syndromes 13 Patau 13 Patau

Downs Births per %

0.62 % 50 %

Mutations Causing Death and Disease in Humans % of live births % of live births Gene mutations: 1.2 Chromosome mutations: 0.61

Chromosome Mutations (Humans) % of spontaneous abortions % of spontaneous abortions Trisomics 26 % XO 9 % Triploids 9 % Tetraploids 3 % Others 3 % Chromosome 50 % abnormalities abnormalities

Chromosome Mutations Comparison of euploidy with aneuploidy Aneuploids more abnormal than euploids: likely due to gene imbalance likely due to gene imbalance Plants more tolerant than animals to aneuploidy and polyploidy (animal sex determination) (animal sex determination)

Summary Mutation - gene - chromosome - chromosome (structure, number) (structure, number) Detecting - cytology - phenotype - phenotype Rate of mutation - low Mutation - source of genetic variation - evolutionary change - evolutionary change geneticanalysis

Chapter References Mitosis and Meiosis Ch. 4 p. 100 – 112 Prob: 10, 11, 12, 18, 19 Ch. 4 p. 100 – 112 Prob: 10, 11, 12, 18, 19 Mendelian Inheritance Ch. 5 p. 118 – 129 Prob: 1 – 3, 5, 6, 7, 8, 9 Recombination, linkage maps Ch. 6 p. 148 – 165 Prob: 1-5, 7, 8, 10, 11, 14 Extensions to Mendelian Genetics Ch. 14 p. 459 – 473 Prob: 2, 3, 4, 5, 6, 7 Chromosome Mutations Ch. 11 p. 350 – 377 Prob: 1, 2

Mendelian Genetics Topics: -Transmission of DNA during cell division -Transmission of DNA during cell division Mitosis and Meiosis Mitosis and Meiosis - Segregation - Segregation - Sex linkage - Sex linkage - Inheritance and probability - Inheritance and probability - Independent Assortment - Independent Assortment - Mendelian genetics in humans - Mendelian genetics in humans - Linkage - Linkage - Gene mapping - Gene mapping -Gene mapping in other organisms (fungi, bacteria) (fungi, bacteria) - Extensions to Mendelian Genetics - Gene mutation - Chromosome mutation            

Genetics Part I Part II Part I Part II Molecular Mendelian

Chromosome Theory of Inheritance - genes organized into chromosomes - genes organized into chromosomes - correlation: Genetics & Cytology - correlation: Genetics & Cytology - theory can explain segregation and - theory can explain segregation and independent assortment independent assortment

Two types of nuclear division 1. Mitosis (somatic tissue) 1. Mitosis (somatic tissue) 2. Meiosis (germ tissue) 2. Meiosis (germ tissue)

Mendelian Genetics Meiosis and mitosis Meiosis and mitosis Segregation and independent assortment Segregation and independent assortment Sex linkage, sex determination Sex linkage, sex determination Pedigrees Pedigrees Linkage, recombination and linkage maps Linkage, recombination and linkage maps

Mendelian Genetics Gene linkage: 3 point test cross, tetrad analysis Gene linkage: 3 point test cross, tetrad analysis Extensions (dominance, multiple alleles, pleiotropy, epistasis, Extensions (dominance, multiple alleles, pleiotropy, epistasis, penetrance and expressivity) penetrance and expressivity) Mutation: gene mutation Mutation: gene mutation chromosome mutation (number chromosome mutation (number structure) structure)

Mendelian Genetics Applications Genetic markers as tools: Genetic markers as tools: - human diseases - human diseases - population genetics - population genetics - genetic structure (gene flow) - genetic structure (gene flow) - systematics and phylogeny - systematics and phylogeny - forensics - forensics

Mendelian Genetics in Humans Determining mode of inheritance Problems: 1. long generation time 1. long generation time 2. can not control matings 2. can not control matingsAlternative: * information from matings that have already occurred “Pedigree” * information from matings that have already occurred “Pedigree”

Human Pedigrees Pedigree analysis: trace inheritance of disease or condition trace inheritance of disease or condition provide clues for mode of inheritance provide clues for mode of inheritance however, some pedigrees ambiguous however, some pedigrees ambiguous

Human Pedigrees Pedigree analysis: dominant vs recessive dominant vs recessive autosomal vs sex linked autosomal vs sex linked

Linkage: Human Genetic Diseases Linkage: organization of genes and genome organization of genes and genome marker genes linked to:marker genes linked to: Disease genes Disease genes

Mutation Gene Mutation - somatic, germinal - somatic, germinal - detecting mutations - detecting mutations Chromosome mutations Chromosome mutations - structure - structure - number - number

Chromosome Mutation (changes in number) Euploidy: variation in complete sets of chromosomes chromosomes Aneuploidy: variation in parts of chromosome sets sets

Careers in Genetics cytogenetics cytogenetics molecular genetics molecular genetics human genetics human genetics population genetics population genetics quantitative genetics quantitative genetics developmental genetics developmental genetics immunogenetics immunogenetics etc. etc. etc. etc.

Genetics Courses B2900 Principles of Evolution and Systematics B2060 Principles of Cell Biology B3530 Developmental Biology B4241 Advanced Genetics B4250 Evolutionary Genetics B4900 Biotechnology Honours Thesis Research in Genetics Honours Thesis Research in Genetics

Announcement NSERC Undergraduate Student Research Awards (USRA) in Universities 16 weeks $5,625 MUN deadline Early Jan, 2006