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Biology Chapter 8 Outline
8:1
X Chromosome: one of the chromosomes that determine a sex; sex chromosomes
Y Chromosome: one of the chromosomes that determine sex,
Sex chromosome
Sex chromosomes: because the two chromosomes differ between the sexes, we call them sex chromosomes.
Autosomes: chromosomes not related to an organism’s sex.
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Sex-linked characteristic: trait whose genes are carried on the X chromosome.
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Nondisjunction: failure of homologs to segregate during meiosis.
Chromosome theory of heredity: the theory that genes are located on chromosomes.
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Gene linkage: the genes that occur on the same chromosome (linked)
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Crossing-over: exchange of segments of chromosomal material between two strands of a tetrad; occurs during prophase of meiosis.
Recombination gametes: gametes with a set of linked genes different than that found in the parent.
Genetic map: the location of genes on a chromosome.
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Continuous variation: the presence of many multiple length offspring.
Multiple genes: three or more different alleles controlling a trait.
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Modifier genes: genes that affect the expression of other alleles.
Genetic counseling: type of counseling in which parents can be advised of their chances of having offspring with a hereditary disease.
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Lethal gene: an allele that causes death.
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Ultrasonography: a technique used to determine the position and anatomy of a fetus.
Fetoscopy: allows direct observation of the fetus and surrounding tissues.
Endoscope: device that allows a fetus to be viewed while it is still in the uterus.