1 / 22

11-1 The Work of Mendel

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 a list of some of the traits that are inherited. What did Mendel already know…. Each flower produces pollen (sperm) and egg cells

nero
Télécharger la présentation

11-1 The Work of Mendel

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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 a list of some of the traits that are inherited.

  2. What did Mendel already know… • Each flower produces pollen (sperm) and egg cells • Cross fertilization (sexual) – male and female cells join • Self-pollination (asexual) – pollen fertilizes eggs from same plant • Mendel’s pea plants were true-breeding • A tall plant with green seeds would produce a tall plant with green seeds

  3. Genes, Alleles and Dominance • Trait – specific characteristic • Mendel studied 7 different pea plant traits • What 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: height • Alleles – 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 arerecessive • Dominant allele – the trait is always shown • Capital letter (T = tall) • Recessive allele – the trait that will only show if there is no dominant allele • Lower case letter (t = short)

  6. Heterozygous – organisms that have 2 different alleles for the same trait • Hybrid for that trait • Ex: Tt • Homozygous – organisms that have 2 identical alleles for a particular trait • True-breeding for a particular trait • Ex: TT or tt

  7. Genes, Alleles and Dominance • Phenotype – physical characteristics • Ex: tall, short, yellow, green • Genotype – genetic make-up • Ex: TT, Tt, tt • Tall 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 = 1/8 • The greater the number or trials, the closer to the expected ratio • Past outcomes do not affect future outcomes • Alleles segregate randomly (like a coin)

  10. Principle of Segregation • Segregation = separation • The alleles for tall vs. short separate during the formation of gametes – sex cells • Each gamete carries one allele for each gene

  11. The Two-factor Cross: F1 • 4 alleles (2 genes) at the same time • Provides 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 ways • Dominant vs. Recessive – one allele completely masks another allele. • Incomplete Dominance • Definition : one allele is not completely dominant over another Ex: flowers – white x red flowers = pink flowers

  13. 11.3 Beyond Dominant and Recessive • Codominance • Definition: both alleles contribute to the phenotype of the organism Ex: chicken feather – black and white alleles = black and white feathers Colors 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 Types Ex: rabbit’s coat color Ex: human’s blood type

  15. 11.3 Polygenic Traits • Definition: traits that are controlled by 2 or more genes Ex: fruit fly red eyes - 3 genes involved in making pigment • Diff. combo of genes produce different eye colors Ex: Human skin color – more than 4 different genes Human 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 hatch • Hydrangea flowers are different colors depending on soil pH.

  17. Mendel Questions Using 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.

  18. Meiosis

  19. Ttrr x ttRr

  20. ttRr x TtRr

  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?

More Related