Presentation on theme: "11-1 The Work of Mendel What does every living thing inherit from their parents? Genetics – the study of heredity Look around at your classmates and make."— Presentation transcript:
1 11-1 The Work of MendelWhat does every living thing inherit from their parents?Genetics – the study of heredityLook around at your classmates and make a list of some of the traits that are inherited.
2 What did Mendel already know… Each flower produces pollen (sperm) and egg cellsCross fertilization (sexual) – male and female cells joinSelf-pollination (asexual) – pollen fertilizes eggs from same plantMendel’s pea plants were true-breedingA tall plant with green seeds would produce a tall plant with green seeds
3 Genes, Alleles and Dominance Trait – specific characteristicMendel studied 7 different pea plant traitsWhat are some examples? Plant Height, Seed Shape, Pod Color
4 Genes, Alleles and Dominance Genes – the chemical factors that determine traits (the segment of DNA) ex. pea plant: heightAlleles – different forms of a gene from each parent ex. pea plants: tall and short (T or t)
5 Principle of Dominance Principle of dominance: some alleles are dominant and others are recessiveDominant allele – the trait is always shownCapital letter (T = tall)Recessive allele – the trait that will only show if there is no dominant alleleLower case letter (t = short)
6 True-breeding for a particular trait Heterozygous – organisms that have 2 different alleles for the same traitHybrid for that traitEx: TtHomozygous – organisms that have 2 identical alleles for a particular traitTrue-breeding for a particular traitEx: TT or tt
7 Genes, Alleles and Dominance Phenotype – physical characteristicsEx: tall, short, yellow, greenGenotype – genetic make-upEx: TT, Tt, ttTall plants have the same phenotype (tall), but not the same genotype (TT or Tt)Why are TT and Tt genotypes for tallness, but tt is not???
8 11-2 Probability and Punnett Squares Mendel realized…the principles of probability could be used to explain the results of genetic crosses.
9 Genetics and Probability Probability – the likelihood a particular event will occur.Ex: probability of flipping a coin to heads = ½ or 50%Probability of head 3 times in a row = ½ x ½ x ½ = 1/8The greater the number or trials, the closer to the expected ratioPast outcomes do not affect future outcomesAlleles segregate randomly (like a coin)
10 Principle of Segregation Segregation = separationThe alleles for tall vs. short separate during the formation of gametes – sex cellsEach gamete carries one allele for each gene
11 The Two-factor Cross: F1 4 alleles (2 genes) at the same timeProvides the hybrid plants (F2 generation)Crossed a homozygous RRYY (round yellow peas) with a homozygous rryy (wrinkled, green peas)
12 11.3 Beyond Dominant and Recessive Alleles Genes can act in various waysDominant vs. Recessive – one allele completely masks another allele.Incomplete DominanceDefinition : one allele is not completely dominant over anotherEx: flowers – white x red flowers = pink flowers
13 11.3 Beyond Dominant and Recessive CodominanceDefinition: both alleles contribute to the phenotype of the organismEx: chicken feather – black and white alleles = black and white feathersColors don’t blend like incomplete dominance
14 11.3 Multiple Alleles Definition: more than two alleles (more than 2 alleles exist in a population not an individual) Blood TypesEx: rabbit’s coat colorEx: human’s blood type
15 11.3 Polygenic TraitsDefinition: traits that are controlled by 2 or more genesEx: fruit fly red eyes - 3 genes involved in making pigmentDiff. combo of genes produce different eye colorsEx: Human skin color – more than 4 different genesHuman height – more than 50 genes
16 11.3 Genetics and the Environment Genes provide a plan for development, but how the plan unfolds also depends on the environment:Ex. Butterflies have different wing colors depending on when they hatchHydrangea flowers are different colors depending on soil pH.
17 Mendel QuestionsUsing tall and short pea plants and the letters T = dominant and t = recessive describe Mendel’s F1 generation and F2 generation.Provide the genotype and phenotype for each of four offspring from each generation. You do not need to use a punnett square.
21 Questions Genetics is the study of ________. Alternate characteristics of an organism such as height, hair color, eye color, etc. are called _______.Why did pea plants make such a good subject for Mendel to study?What does “true breeding” mean?
22 Considering the allele related to short and tall pea plants. Plants of the P generation (tall) will produce only_____________ if not crossed with plants having other alleles.Describe the phenotype (what we can see) of Mendel’s F1 Generation.What was the genotype (use letters “T” and “t”) for Mendel’s F1 generation?How did the F2 generation suggest that genes were simply segregated, not lost?