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Vocabulary: Mouse Genetics (Two Traits)
Vocabulary
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Allele – one of two or more forms that a gene could take.
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Dominant alleles are always expressed in the organism when they are present.
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Recessive alleles are only expressed when the dominant allele is not present.
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Usually dominant alleles are represented by capital letters. Recessive alleles are
represented by lowercase letters.
Genotype – the genetic makeup of an organism.
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Phenotype – the physical appearance of an organism.
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Probability can be expressed as a fraction, decimal, or percentage. If the odds of
an event are one in four, the probability is 1/4, 0.25, or 25%.
Punnett square – a diagram that shows the possible offspring of two parents.
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Organisms with different genotypes can have the same phenotype. For example,
an FF mouse and an Ff mouse both have black fur.
Probability – the likelihood of an event.
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The alleles possessed by an organism are represented by symbols. For
example, a mouse with white fur might have the genotype ff.
Punnett squares allow for the determination of the probability of each offspring’s
genotype.
Monohybrid cross – genetic cross between two organisms differing in only one trait;
simple Mendelian genetic cross.
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The character(s) being studied in a monohybrid cross are governed by two
alleles for a single locus.
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To carry out such a cross, each parent is chosen to be homozygous or truebreeding for a given trait (P1 generation).
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When a cross satisfies the conditions for a monohybrid cross, the dominant
factor is usually detected by a 100% characteristic distribution in the first
generation (F1).
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The recessive phenotype reappears in the second generation (F2) offspring in a
3:1 ratio that is sometimes called the monohybrid ratio.
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A monohybrid cross is useful in identifying the dominance of certain traits.
Dihybrid Cross – a study of Mendelian inheritance patterns for organisms differing in two
traits.
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This type of cross can be used to determine if the alleles of two different genes
are assorted independently of one another during the formation of gametes.
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Provides evidence for law of independent assortment.