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Terms in this set (27)
the phenotype of the heterozygote is intermediate to the phenotypes of the homozygotes.
both alleles are expressed and both phenotypes are manifested simultaneously.
occurs when an individual with a particular genotype does not express the expected phenotype.
What causes incomplete penetrance?
Environmental factors, as well as the effects of other genes, may alter the phenotypic expression of a particular genotype.
What is gene interaction?
the determination of a single trait or phenotype by genes at more than one locus; the effect of one gene on a trait depends on the effects of a different gene located elsewhere in the genome.
gene masks or represses the effects of alleles at another gene
gene whose alleles are masked or repressed
What is a recessive epistatic gene?
the epistatic gene in a homozygous recessive state masks the interacting gene or genes.
What is a complementation test?
It is used to determine whether different recessive mutations affect the same gene or locus (are alleles) or whether they affect different genes.
What is a complementation test used for?
The two mutations are introduced into the same individual by crossing homozygotes for each of the mutants. If the progeny show a mutant phenotype, then the mutations are allelic (in the same gene). If the progeny show a wild-type (dominant) phenotype, then the mutations are in different genes and are said to complement each other because each of the mutant parents can supply a functional copy (or dominant allele) of the gene mutated in the other parent.
What characteristics are exhibited by a cytoplasmically inherited trait?
inherited traits are encoded by genes in the cytoplasm. Because the cytoplasm usually is inherited from a single (most often the female) parent, reciprocal crosses do not show the same results. Cytoplasmically inherited traits often show great variability because different egg cells (female gametes) may have differing proportions of cytoplasmic alleles from random sorting of mitochondria (or plastids in plants).
What is genomic imprinting?
This is a genetic inheritance pattern that results from the fact that certain alleles seem to be encoded differently depending upon which parent the allele comes from.
genetic maternal effect
the phenotypes of the progeny are determined by the genotype of the mother only. The genotype of the father and the genotype of the affected individual have no effect.
the phenotype of the progeny differs based on
whether a particular allele is inherited from the mother or the father. The phenotype is
therefore based on both the individual's genotype and the paternal or maternal origins of the genotype
What is the difference between a sex-influenced gene and a gene that exhibits genomic imprinting?
For a sex-influenced gene, the phenotype is influenced by the sex of the individual
bearing the genotype. For an imprinted gene, the phenotype is influenced by the sex of
the parent from which each allele was inherited.
What characteristics do you expect to see in a trait that exhibits anticipation?
Traits that exhibit anticipation become stronger or more pronounced, or are expressed earlier in development, as they are transmitted to each succeeding generation.
What are continuous characteristics and how do they arise?
also called quantitative characteristics, exhibit many phenotypes with a continuous distribution. They result from the interaction of multiple genes (polygenic traits), the influence of environmental factors on the phenotype, or both.
a trait that is determined by an environmental effect and has the same phenotype as a genetically determined trait
a gene affects more than one phenotype
a trait determined by genes at many loci
the percentage of individuals with a particular
genotype that express the expected phenotype
a trait determined by an autosomal gene that is expressed in only one sex
genetic maternal effect
the genotype of the maternal parent influences the phenotype of the offspring
the expression of a trait is affected by the sex of the parent that transmits the gene to the offspring
a trait determined by an autosomal gene that is more easily expressed in one sex
the trait appears earlier or more severely in succeeding generations
Assume that long ear lobes in humans are an autosomal dominant trait that exhibits 30%
penetrance. A person who is heterozygous for long ear lobes mates with a person who is
homozygous for normal ear lobes. What is the probability that their first child will have long ear lobes?
To have long ear lobes, the child must inherit the dominant allele and also express it. The
probability of inheriting the dominant allele is 50%; the probability of expressing it is
30%. The combined probability of both is 0.5(0.3) = 0.15, or 15%
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