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11 1-11 genetics

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  • 1. Evolution: Genetics Mr. Kasteler Zoology Day 22
  • 2. The Standards:
    • SC.912.L.15.15 Describe how mutation and genetic recombination increase genetic variation
    • SC.912.L.15.14 Discuss mechanisms of evolutionary change other than natural selection such as genetic drift and gene flow
  • 3. Basic Genetics
    • Brief review:
      • What is DNA?
      • How many nucleotide bases are there?
      • Which ones pair together?
  • 4. Some more important definitions:
    • GENOTYPE : the actual GENES (technically, ALLELES) an organism has
    • PHENOTYPE : the PHYSICAL CHARACTERISTIC exhibited by the organism
    • HOMO ZYGOUS : when an organism has two identical (the SAME ) alleles
    • HETERO ZYGOUS : when an organism has two different alleles
    • Dominant & Recessive…
    • Ex. Mendel’s Peas…
  • 5. A few definitions you just gotta know…
    • A GENE is a location on your DNA that codes for a physical trait (i.e. height, hair color, eye color)
    • An ALLELE is a form of a gene coding for a given trait (i.e. tall, short, blonde, brunette, blue eyed, brown eyed, etc.)
  • 6. Basic Inheritance
    • What’s inheritance?
    • Let’s talk about basic inheritance patterns
    • Animals have varying numbers of chromosomes…
    • Background CFU: What’s a chromosome?
      • A chromosome is bundled up DNA
  • 7. These are chromosomes…
  • 8. How many chromosomes do you have?
    • how many do you have?
    • 46! … How many from Dad? From Mom?
    • What’s the genotype for a female? Male?
  • 9. Mendel’s Peas:
    • The brief synopsis: Gregor Mendel (the Father of Genetics) did experiments on pea plants. Some of them were tall (Is this a genotype or phenotype?) and some of them were short (Is this a genotype or phenotype?). He found that some of his tall plants were TT while others were Tt, with T coding for Tall and t coding for short (Is this a genotype or phenotype?). All of his short pea plants were tt (Is this a genotype or phenotype?) He crossed plants with different genotypes to see what kinds of phenotypes the offspring would exhibit. He developed Punnett squares.
  • 10. Punnett Squares
    • Hopefully, we’ve all dealt with punnett squares in previous biology classes… but if not…here’s a quick reminder of how you set them up.
  • 11. Punnett Square Set Up
    • You put the trait alleles of one parent across the top, and the trait alleles of the other parent down the side.
      • An allele is a gene coding for a given trait (i.e. tall, short, blonde, brunette, blue eyed, brown eyed, etc.)
    • This can get tricky with complicated variable genetic traits, such as eye color
  • 12. The Basics: Gender Alleles
  • 13.
    • What is the likelihood that this couple will have a boy? A girl?
  • 14. A little reminder of where you came from…
    • So, we get half of our genome from Mom, and half of our genome from Dad.
    • How much of your Dad’s genome will your children get?
      • This will help us determine relatedness for the next unit on animal behavior
  • 15. Genetic Variation
    • Just as biodiversity increases the stability of an ecosystem, greater genetic variation improves the genetic stability of a population
      • More potential alleles means a higher likelihood that one or more individuals carry genes that could adapt to a new environment
      • When a population becomes too homogeneous , they are susceptible to genetic disorders and disease
      • Think… this is why it’s not a good idea to marry your brother or sister… or cousin
  • 16. DIFFERENT is GOOD
    • When two individuals with similar genomes mate, they have a higher likelihood of passing down a recessive, deleterious (harmful) trait and having that trait expressed in the offspring
  • 17. Ways to vary the Gene Pool
    • Genetic Mutations
    • Genetic Recombination
    • Gene Flow (Immigration & Emigration)
    • Genetic Drift
  • 18. Genetic Mutations
    • There are two main types of genetic mutations you need to know:
    • Point Mutation
    • Frame Shift Mutation
      • Insertion
      • Deletion
  • 19. Point Mutation
    • This is where a single base pair is changed
    • Example: The dog bit the cat
    • Point Mutation: The dog bit the ca r
    • NOTICE: The severity of the mutation depends on the exact place of the change, not necessarily whether the mutation occurs earlier or later in the gene
    • It’s like a schedule change that just swaps one class for another, same period
  • 20. Frame Shift Mutations
    • An insertion occurs when a base pair is inserted into the genome, shifting the genetic reading frame
      • Example: The dog mbi tth eca t
      • *Notice: The gene is fine upstream (before) of the mutation
    • It’s like a schedule change that alters one class… and messes up your whole schedule
  • 21. Frame Shift Mutations
    • A deletion occurs when a base pair is deleted from the genome, also shifting the genetic reading frame
      • Example: The dob itt hec at
      • *Notice: Again, the gene is fine upstream of the mutation
    • What do you think is more serious, a mutation in the earlier part of the gene or later on? Why?
  • 22. Let’s Discuss…
    • What is worse- a deletion or an insertion? Why?
      • Answer: Deletion
  • 23. Genetic Recombination
    • This occurs during meiosis
      • Meiosis: formation of sex cells
    • Recombination/Crossing Over is when two gametes exchange pieces of genetic information
  • 24. Genetic Recombination
    • The gamete genotypes went from aa AA… (homozygous)
    • … to aA aA
    • (heterozygous)
  • 25.
    • X =
  • 26. Gene Flow
    • Genes flow into the gene pool when new individuals are added to the population through IMM IGRATION
      • INCREASES GENETIC VARIATION
    • Genes flow out of the gene pool when individuals leave the population through EM IGRATION
      • DECREASES GENETIC VARIATION
  • 27. Genetic Drift
    • Think: CHANCE
    • Genetic Drift occurs when the allelic frequency within a population changes due to chance sampling from the gene pool
      • It is particularly potent in SMALL populations
  • 28. Genetic Drift
    • Example: If I flip a coin 10,000 times, how many times would I get heads? Tails?
    • If I flip the same coin 10 times, how many times will I get heads? Tails?
    • Which example has a higher likelihood of being wrong (especially in percent)?
    • **FOUNDER EFFECT & Islands**
    • **Bottleneck Effect**

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