• Like
Ch 11 intro mendelian genetics sp11
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

Ch 11 intro mendelian genetics sp11

  • 958 views
Published

 

  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
No Downloads

Views

Total Views
958
On SlideShare
0
From Embeds
0
Number of Embeds
0

Actions

Shares
Downloads
45
Comments
0
Likes
3

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. Mendelian Genetics
    Chapter 11
  • 2. Gregor Mendel – “Father of Genetics”, first Geneticist, one of the most important scientists in history
    Austrian Monk (1822-1884
    Worked with ordinary garden peas
    Used science and math skills learned from University.
  • 3. Genetics – the scientific study of heredity
  • 4. Mendel’s Peas – background information
    • The anther (♂, male) produces sperm
    • 5. The ovary (♀, female) produces eggs
    • 6. Sperm + Eggs: FERTILIZATION
    • 7. The peas Mendel started with were TRUE-BREEDING.
    Gametes
  • 8. More Peas
    True-breeding: parents always have offspring identical to themselves when allowed to self-pollinate. (Is self-pollination sexual or asexual reproduction?)
    For example: Plants with white flowers produce only offspring with white flowers.
  • 9. Important terms
    Trait = specific observable characteristic
    Mendel produced hybrids
    Hybrid
    The offspring produced by parents with differing forms of a trait.
    Some genetics notation
    Parent generation = P
    F1 = first generation of offspring from a cross, (F2= second generation, etc.)
    Contrast with true-breeding
  • 10. Mendel’s crosses…results
    Seed Shape
    Flower Position
    Seed Coat
    Color
    Seed Color
    Pod Color
    Plant Height
    Pod
    Shape
    Round
    Yellow
    Gray
    Smooth
    Green
    Axial
    Tall
    Wrinkled
    Green
    White
    Constricted
    Yellow
    Terminal
    Short
    Round
    Yellow
    Gray
    Smooth
    Green
    Axial
    Tall
  • 11. Mendel’s crosses…results
    Seed Shape
    Flower Position
    Seed Coat
    Color
    Seed Color
    Pod Color
    Plant Height
    Pod
    Shape
    Round
    Yellow
    Gray
    Smooth
    Green
    Axial
    Tall
    Wrinkled
    Green
    White
    Constricted
    Yellow
    Terminal
    Short
    Round
    Yellow
    Gray
    Smooth
    Green
    Axial
    Tall
  • 12. Genes
    Mendel eventually concluded that traits are passed from one generation to the next.
    Today, we know that…
    Traits are determined by GENES
    Chemical factors that determine a trait.
    Consist of DNA sequences
    Alleles - Different forms of a gene
    Ex. Eye color is a trait, you could have 2 blue eye color alleles, you could have 2 brown eye color alleles, you could have one of each.
    You get one allele from each parent for each trait.
    Mendel did not know anything about genes, DNA, chromosomes, meiosis, etc.
  • 13. Dominant and Recessive Genes
    Principle of Dominance: Some alleles are dominant and others are recessive.
    Dominant: An allele that is expressed (visible) whether it is the only version of the gene present or when in combination with a recessive allele.
    Recessive: An allele ONLY expressed when dominant allele is NOT present
  • 14. Symbols to represent Dominant Genes
    If the symbol “T” represents the dominant allele (or form of the gene), then…
    it doesn’t matter whether both of the alleles an individual has are dominant (TT) or…
    there is just one copy of the dominant allele (Tt).
    Either way, the individual looks the same (it has the dominant trait).
  • 15. Symbols to represent Recessive Genes
    If the symbol “t” represents the recessive allele (or form of the gene), then…
    both of the alleles an individual has must be recessive (tt) to have the recessive trait.
    The presence of one dominant allele (T) hides the recessive allele (t) when there is one of each (Tt).
  • 16. Important vocabulary
    Homozygous
    two identical alleles for a trait. (ex. SS or ss)
    TRUE-BREEDING for a trait
    Heterozygous
    two DIFFERENT alleles for a trait (ex. Ss)
    HYBRID for a trait
    Phenotype
    physical characteristics, appearance
    Genotype
    genetic make up, the information in DNA
  • 17. End part one
  • 18. Mendelian Genetics
    Chapter 11
  • 19. Segregation
    SEGREGATION
    Separation of alleles during gamete formation (meiosis)
    Gamete
    Sex cells
    carry a single copy of each gene (ex. The allele for short OR the allele for tall, not both)
  • 20. Genetics and Probability
    Probability
    likelihood that a particular event will occur.
    For example: What is the probability of rain tomorrow?
    How likely is it that a flipped penny will land heads-up? Tails-up?
    Probability is used to predict the outcomes of genetic crosses.
  • 21. Steps to a setting up a Punnett Square
    Identify parental genotypes for the cross (ex. TT, tt, Tt)
    Draw the Punnett Square--a grid with each set of parental alleles on its own side.
    Separate the alleles (why?)
    Match alleles from rows and columns to make offspring genotypes.
    Identify the kinds (and their numbers) of offspring you have.
    Gametes (sperm or eggs) are haploid (one set of chromosomes)
  • 22. Steps to a setting up a Punnett Square: An Example
    Both parents are heterozygous for plant height, with tall being dominant to short.
    Describe their offspring.
  • 23. Probability
    Look at the cross we just did.
    How many offspring have two alleles for tallness (TT)?
    Two for shortness (tt)?
    Both (Tt)?
  • 24. Probabilities
    ¼ or 25% have two alleles for tallness.
    ¼ or 25% have two alleles for shortness.
    ½ or 50% have one allele for tallness and one for shortness.
    We write this in terms of a ratio 1TT: 2Tt: 1tt
    This ratio of allele combination types is called the genotypic ratio.
  • 25. Probabilities
    How many plants will be tall and how many will be short?
    We also write this in terms of a ratio (3 tall: 1 short).
    This ratio of physical types is called the phenotypic ratio.
  • 26. 3 tall (75%), 1 short (25%)expressed as a ratio, 3:1
    Why?
    1 homozygous for tallness (TT) and the
    2 heterozygous plants (Tt)
    You lump these together because you cannot tell any of these offspring apart for this trait—TT offspring look exactly like Tt offspring.
    1 homozygous recessive (tt)
  • 27. This is exactly what Gregor Mendel did in his pea experiments.
  • 28. A brief explanation…
    All of the reproduction we will be discussing regarding Mendel’s garden peas will be sexual reproduction (a new organism formed by the joining together of a male and a female gamete).
    However, pay close attention to who the parents are — sometimes there is a cross between two different parents (usually with contrasting forms of some trait, like flower color or height). Other times, the peas are allowed to do what comes naturally to peas—self-pollination (the same plant fertilizes itself).
  • 29. Sexual Reproduction in Plants
    Male (♂) sexual organs
    Female (♀) sexual organs
  • 30. Cross-pollination – either by wind, insect or geneticist
    Pollen (containing male gametes)
  • 31. Self-pollination
    Convenient, but boring
  • 32. Mendel’s Monohybrid cross
    Mendel’s first crosses
    The parent generation (P) is a combination of two different pure-breeding types
    The first generation (F1) produced only TALL plants
    The second generation (F2 ) produced tall and short plants
    Tall allele/Tall allele
    TT
    short allele/short allele
    tt
  • 33. Predictions
    Mendel found that the approximately three dominant to one recessive ratios showed up consistently.
    Probabilities predict average outcomes for a LARGE number of events, not exact outcomes.
    Flip a coin twice
    Heads once, tails once
    Heads twice
    Tails twice
    Flip a coin many times, likely to get very close to a 50:50 ratio
  • 34. Predicting Genetics
    Genetics is similar
    Larger numbers result in closer to expected values.
    This explains why humans don’t always have the same number of male children and female children despite the fact that the odds of any one child’s gender is 50% female, 50% male.
  • 35. Mendel’s Principle
    Independent Assortment
    Genes for different traits segregate independently during gamete formation
    Accounts for much of the genetic variation in living things
    Usually, all combinations of traits are possible,
    ex. Tall round seeds, purple flowers
    Short round seeds, white flowers
    Short wrinkled seeds purple flowers
    Tall wrinkled seeds white flowers
    Etc.
  • 36. Summary of Mendel’s Principles
    Genes determine inheritance. Genes are passed from parent to offspring.
    Some genes may be dominant and others recessive
    Adults (sexually reproducing) have two copies of each gene—one from each parent. They segregate during gamete formation.
    Alleles for different traits assort independently (Independent Assortment)