Transcript Probability of Heredity

Coulter
Principles of Probablity
Probability: to predict the results of a
particular event.
 Probability is a number that describes
how likely it is that an event will occur.
 The laws of probability predict what is
likely to occur, not necessarily what will
occur.
 Think about the coin, there is a 1 in 2
chance you will get head and a 1 in 2
chance you will get tails. 50%
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Probability and genetics

Punnett square is a chart that shows all
the possible combinations of alleles that
can result from a genetic cross.
Using the Punnett square
In a genetic cross, the
allele that each parent
will pass on to its
offspring is based on
probability.
 The probability that an
offspring will be PP is
1 in 4 (25%).
 The probability that an
offspring will be pp is
1 in 4 (25%)
 The probability that an
offspring will be Pp is
2 in 4 (50%)

Predicting probability

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The black feather
bird is dominant.
The grey feather
bird is recessive.
What will the allele
combination be?
What is the
probability of black
feathers?
Phenotype vs genotype

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Is its physical
appearance, or visible
traits.
What is the phenotypes
in the diagram below?
phenotype
Is its genetic makeup, or
allele combinations.
 What is the genotypes in
the diagram below?

genotype
Genotype
Geneticists use two additional terms to
describe an organism’s genotype;
homozygous, heterozygous
 Homozygous is an organism that has
two identical alleles for a trait.
 Heterozygous is an organism that has
two different alleles for a trait.

Co-dominance

In co-dominance, the alleles are neither
dominant or recessive. As a result, both
alleles are expressed in the offspring.