Some Vocab. Genotype allele combination. Phenotype physical appearance

Transcription

1 Genetics

2 Some Vocab. Genotype allele combination Capital letter = dominant allele Lowercase letter = recessive allele Ex AA, Aa, aa Phenotype physical appearance Ex green, yellow

3 Some Vocab. Homozygous two alleles same Homozygous dominant: AA Homozygous recessive: aa Heterozygous two alleles different Aa

4 Gregor Mendel Father of genetics Austrian monk, mid-1800s Researched pea plant inheritance Easy to grow, fast reproduction Studied plant height, pea shape/color, pod color, etc.

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6 Pea Plant Reproduction Self-pollination Male gametes (pollen) fertilize egg of same flower Produces pure-bred offspring True-breeding: produce offspring identical to parent when selfpollinated

7 Pea Plant Reproduction Cross-pollination Pollen from one plant fertilizes egg of another plant Offspring have two parents

8 Mendel s Experiments P = Parent generation F 1 = First filial generation F 2 = Second filial generation (F 1 X F 1 ) Monohybrid cross: Cross involving one trait P F 1 F 2 Pure Purple X Pure White All Purple 3 Purple:1 White

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10 Dihybrid Cross wpure.co m/mehz7t CxjSE?ref= bkmk Mendel looked at the inheritance patterns of two traits Seed shape and seed color Found that the traits were inherited independently of each other P F 1 F 2 Pure Yellow/Smooth X Pure Green/Wrinkled All Yellow/Smooth 9 Yellow/Smooth:3 Yellow/Wrinkled:3 Green/Smooth:1 Green/Wrinkled

11 Mendel s Conclusions 1. Law of Dominance: one allele (form of a gene) is dominant, one is recessive Recessive trait was hidden in F 1 generation Purple = dominant White = recessive

12 Mendel s Conclusions 2. Law of Segregation: alleles for a gene separate when gametes form Due to separation of homologous chromosomes during Anaphase I Each gamete gets one copy of each gene

13 Mendel s Conclusions 3. Law of Independent Assortment Genes on separate chromosomes are inherited at random Due to random chromosome shuffling in Metaphase I

14 Independent Assortment Metaphase I

15 Punnett Squares Used to show probability of certain genetic outcomes in offspring First must determine possible gametes Heterozygous tall plant = Tt Half of gametes will get T, the other half will get t Homozygous tall plant = TT All gametes will get T

16 Punnett Squares Gametes go on the top and side Combine gametes to find possible offspring

17 Punnett Squares Tt X Tt Genotype ratio 1TT: 2Tt: 1tt Phenotype ratio 3 tall: 1 short

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19 Non-Mendelian Genetics Not all traits follow Mendel s Law of Dominance Four Variations Incomplete Dominance (blending) Codominance (two phenotypes) Multiple Alleles Polygenic Traits

20 Incomplete Dominance Neither allele is dominant, only 50% of protein is produced Heterozygous phenotype is a blend of both homozygous phenotypes Ex wavy hair, pink flowers

21 Incomplete Dominance

22 Codominance Neither allele dominates the other, both produce a protein Heterozygous phenotype is a combination of both homozygous phenotypes Ex checkered chicken, human blood types, roan cattle

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24 Multiple Alleles Some genes have more than two alleles Each individual only inherits two, but there are more than two in the population Ex Rabbit fur color

25 Multiple Alleles Rabbit fur alleles (in order of dominance) C: dark gray c ch : chinchilla c h : himalayan c: albino

26 Multiple Alleles

27 Polygenic Traits Traits-Advanced-BIO-ADV/ Many traits are controlled by more than one gene Traits show wide variation Ex human height, eye color, bell pepper colors

28 Linked Genes Each chromosome contains 100s of genes Those genes are said to be linked, because they are inherited together If genes are far apart on chromosome, crossing over will happen frequently between them Genes are mapped based on rate of crossing over

29 Linked Genes Genes A & B are completely linked Will not show Independent Assortment Genes A & C are incompletely linked Crossing over frequent Genes A & D are unlinked Will show Independent Assortment