Using Mendel's Ideas
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Transcript of Using Mendel's Ideas
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Applying Mendel’s Principles
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Learning Objectives
Explain how geneticists use the principles of probability to
make Punnett squares.
Explain the principle of independent assortment.
Explain how Mendel’s principles apply to all organisms.
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Determining Probability
Probability: the likelihood an event
will occur
• Probability of either outcome:
• Three coin tosses?
• Each flip is an independent event.
50% or 1/2
1/2 × 1/2 × 1/2 = 1/8
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Using Segregation to Predict Outcomes
Probability of a gamete receiving a T?
Probability of tall offspring is .
Probability of short offspring is .
50%, or 1/2
50%, or 1/2
3/4
1/4
Probability of gamete receiving a t?
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Genotype and Phenotype
Two organisms may share the same
but have different .genotypes
phenotype
Genotype: genetic makeup Phenotype: physical traits
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Heterozygous and Homozygous
Homozygous: has two identical
alleles for a gene
Heterozygous: has two different
alleles for a gene
Which are:
homozygous?
heterozygous?
1 2 3
1, 4
2, 3
4
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Making a Punnett Square
Combine gamete genotypes
Gametes for a parent
along one side
Possible gametes
A cross of ospreys:
beak size (B, b)
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Making a Punnett Square: Two Factors
Combine gamete genotypes A cross of pea plants:
size (T, t) and pod color (G, g)
All possible gametes
All gametes for a parent
along one side
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The Two-Factor Cross: F1
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The Two-Factor Cross: F2
Independent assortment: Genes for different traits can
segregate independently during gamete formation.
9:3:3:1 ratio of
phenotypes
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Summary of Mendel’s Principles, Part I
Inheritance is determined by units called , which are
passed from parents to offspring.
Where more than one form of a gene for a single trait exists,
some alleles may be and others .
genes
dominant recessive
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Summary Mendel’s Principles, Part II
• Each adult has two copies of each gene—one from each
parent. These genes from each other when
gametes are formed.
• Alleles for different genes usually segregate
of each other.
segregate
independently