11 1-11 genetics
TRANSCRIPT
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Evolution: Genetics
Mr. KastelerZoologyDay 22
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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
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Basic Genetics
• Brief review: • What is DNA?• How many nucleotide bases are
there?• Which ones pair together?
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Some more important definitions:
• GENOTYPEGENOTYPE: the actual GENES (technically, ALLELES) an organism has
• PHENOTYPEPHENOTYPE: the PHYSICAL CHARACTERISTIC exhibited by the organism
• HOMOHOMOZYGOUSZYGOUS: when an organism has two identical (the SAMESAME) alleles
• HETEROHETEROZYGOUSZYGOUS: when an organism has two differentdifferent alleles
• Dominant & Recessive…
• Ex. Mendel’s Peas…
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A few definitions you just gotta know…
• A GENEGENE is a location on your DNA is a location on your DNA that codes for a physical trait (i.e. height, hair color, eye color)
• An ALLELEALLELE is a form of a gene is a form of a gene coding for a given trait (i.e. tall, short, blonde, brunette, blue eyed, brown eyed, etc.)
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Basic Inheritance
• What’s inheritance?• Let’s talk about basic inheritance patterns
• Animals have varying numbers of chromosomes…
• Background CFU: What’s a chromosome?Background CFU: What’s a chromosome?• A chromosome is bundled up DNAA chromosome is bundled up DNA
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These are chromosomes…
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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?
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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.
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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.
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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
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The Basics: Gender Alleles
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• What is the likelihood that this couple will have a boy? A girl?
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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
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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 homogeneoushomogeneous, 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
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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
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Ways to vary the Gene Pool
• Genetic Mutations • Genetic Recombination• Gene Flow (Immigration &
Emigration)• Genetic Drift
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Genetic Mutations
There are two main types of genetic mutations you need to know:
1. Point Mutation2. Frame Shift Mutation
• Insertion• Deletion
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Point Mutation
• This is where a single base pair is changed
• Example: The dog bit the cat• Point Mutation: The dog bit the car• 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
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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
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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?
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Let’s Discuss…
• What is worse- a deletion or an insertion? Why?• Answer: Deletion
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Genetic Recombination
• This occurs during meiosis• Meiosis: formation of sex cells
• Recombination/Crossing Over is when two gametes exchange pieces of genetic information
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Genetic Recombination
• The gamete genotypes went from aa AA… (homozygous)
…to aA aA(heterozygous)
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• X =
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Gene Flow
• Genes flow into the gene pool when new individuals are added to the population through IMMIGRATION• INCREASES GENETIC VARIATION
• Genes flow out of the gene pool when individuals leave the population through EMIGRATION• DECREASES GENETIC VARIATION
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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
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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**