chapter 4 probability and heredity
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I can… explain the role of probability in a genetic cross Warm Up: If a mother rabbit is hybrid for black fur, and black fur is dominant, how would you write her alleles? Wrap Up: Draw a punnett square for the cross: Hh x HhTRANSCRIPT
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Chapter 4Probability and HereditySection 2
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I can… explain the role of probability in a genetic cross Warm Up: If a mother rabbit is hybrid for
black fur, and black fur is dominant, how would you write her alleles?
Wrap Up: Draw a punnett square for the cross: Hh x Hh
![Page 3: Chapter 4 Probability and Heredity](https://reader035.vdocuments.us/reader035/viewer/2022081605/5a4d1af07f8b9ab05997de28/html5/thumbnails/3.jpg)
Principles of Probability Probability: the number that
describes how likely it is that an event will occur
Coin toss: two possible ways that the coin will land (heads up or tails up) 1 in 2 chance, ½, 50%
The Laws of Probability predict what is LIKELY to occur
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Independence of Events When you toss a coin more than once,
the results of one toss do not affect the results of the next toss
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Principles of Probability with Genetics
Mendel realized that the mathematical principles of probability applied to his work
He could say that the probability of producing… A tall plant was 3 in 4 A short plant was 1 in 4
HOW?!
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Something called….PUNNETT SQUARES Punnett square: a chart that shows
all the possible combinations of alleles that result from a genetic cross They show all the possible outcomes of a
genetic cross and determine the probability of that outcome
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Example Hybrid (one dominant, one recessive)
R: round seed (dominant) r: wrinkled seed (recessive)
RR Rr
Rr rr
R r
R
r
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Using a Punnett Square Use a Punnett square to calculate the
probability In a genetic cross, the allele that each
parent will pass on to its offspring is based on probability
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What is the probability that the offspring will be RR? 25% or 1 in 4
What is the probability that the offspring will be rr? 25% or 1 in 4
What is the probability that the offspring will be Rr? 50% or 2 in 4
What is the probability that the offspring will be a round seed? 75% or 3 in 4
What is the probability that the offspring will be a wrinkled seed? 25% or 1 in 4
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Predicting Probabilities Dominant: black fur Recessive: white fur
What are the possible allele combinations? Bb
What is the probability the guinea pig has black fur? 100%
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Phenotypes and Genotypes Phenotype: physical appearance, or visible traits Genotype: genetic makeup, or allele combination
What is the dominant trait? Smooth pods
What is the recessive trait? Pinched
How many different phenotypes? How many different genotypes?
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Homozygous and Heterozygous
Purebred = two identical alleles = homozygous SS or ss
Hybrid = two different alleles = heterozygous Ss
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Codominance Codominance: the
alleles are neither dominant nor recessive Both results are
expressed in the offspring, black and white feathers
Will the offspring be heterozygous? Or homozygous?