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when males produce two different types of gametes with respect to the sex chromosomes
when females produce gametes that are all the same with respect to the sex chromosomes
small region of the X and Y chromosomes that contains homologous gene sequences
genic sex determination
sex determination in which the sexual phenotype is specified by genes at one or more loci, but there are no obvious differences in the chromosomes of males and females
differential expression of a gene that depends on the sex of the parent that transmitted the gene. If the gene is inherited from the father, its expression is different from that if it is inherited from the mother
genic balance system
sex determining system in which sexual phenotype is controlled by a balance between genes on the X chromosome and genes on the autosomes
2. underdeveloped secondary sex characteristics
4. chromosome complement - XO
1. feminine males
2. small testes, sterile
3. reduced facial hair
4. chromosome complement - cells have one or more y chromosome, XXY, XXXY, XXYY
2. few are sterile, most menstruate regularly
3. severity of mental retardation increases with the amount of X chromosomes
4. chromosome complement - XXX+
condensed, darkly staining structure that is found in most cells of female placental mammals and is an inactivated X chromosome
When does random X inactivation takes place?
Early in development, within the first weeks of development
the idea that an individual organism possesses two different alleles for a characteristic, but the trait encoded by only one of the alleles is observed in the phenotype
Phenotype of the heterozygote is intermediate (falls within the range) between the phenotypes of the two homozygotes
Refers to a genotype that does not always express the expected phenotypes. When an individual will possess the genotype but does not always express the phenotype - EX. polydactyly
Percentage of individuals with a particular genotype that express the phenotype expected of that genotype
(T or F) Incomplete Penetrance and variable expressivity are due to the effects of other genes and to environmental factors that can alter or completely suppress the effect of a particular gene.
causes the death of an individual organism, often early in development, and so the organism does not appear in the progeny of a genetic cross. Recessive lethal alleles kill individual organisms that are homozygous for the allele; dominant lethals kill both heterozygotes and homozygotes
type of interaction between the effects of genes at different loci (genes that are not allelic)
type of gene interaction in which a gene at one locus masks or suppresses the effects of a gene at a different locus
when a probability associated with the chi-square value is >.05
there is a good fit between the observed results and the ratio
test designed to determine whether two different mutations are at the same locus (are allelic) or at different loci (are nonallelic).
two different mutations in the heterozygous condition are exhibited as the wild-type phenotype; indicates that the mutations are at different loci
inheritance of characteristics encoded by genes located in the cytoplasm, because cytoplasm is usually contributed entirely by only one parent, most cytoplasmically inherited characteristics are inherited from a single parent
encoded by autosomal genes that are more readily expressed in one sex.
genetic maternal effect
determines the phenotype of an offspring. offspring inherits genes for the characteristics from both parents, but the offspring's phenotype is determined not by its own genotype but by the nuclear genotype of its mother
Phenomena due to alterations to DNA that do not include changes in the base sequence; often affect the way in which DNA sequences are expressed. Alterations are often stable and heritable in the sense that they are passed from one cell to another
Norm of Reaction
range of phenotypes produced by a particular genotype in different environmental conditions
Genes on autosomal chromosomes that are more readily expressed in one sex
Cytoplasmic genes, which are usually inherited entirely from only one parent
phenotype that is produced by environmental effects is the same as the phenotype produced by a genotype
characteristics that exhibit a continuous distribution of phenotypes (height, weight)
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