Chapter 15: The Chromosomal Basis of Inheritance Flashcards
aneuploidy
A chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number.
Barr body
A dense object lying along the inside of the nuclear envelope in cells of female mammals, representing a highly condensed, inactivated X chromosome.
chromosome theory of inheritance
A basic principle in biology stating that genes are located at specific positions (loci) on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns.
crossing over
The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.
cytogenetic map
A map of a chromosome that locates genes with respect to chromosomal features distinguishable in a microscope.
deletion
(1) A deficiency in a chromosome resulting from the loss of a fragment through breakage. (2) A mutational loss of one or more nucleotide pairs from a gene.
genetic map
An ordered list of genetic loci (genes or other genetic markers) along a chromosome.
genetic recombination
General term for the production of offspring with combinations of traits that differ from those found in either parent.
genomic imprinting
A phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent.
hemophilia
A human genetic disease caused by a sex-linked recessive allele resulting in the absence of one or more blood-clotting proteins; characterized by excessive bleeding following injury.
inversion
An aberration in chromosome structure resulting from reattachment of a chromosomal fragment in a reverse orientation to the chromosome from which it originated.
linkage map
A genetic map based on the frequencies of recombination between markers during crossing over of homologous chromosomes.
map unit
A unit of measurement of the distance between genes. One map unit is equivalent to a 1% recombination frequency.
monosomic
Referring to a diploid cell that has only one copy of a particular chromosome instead of the normal two.
nondisjunction
An error in meiosis or mitosis in which members of a pair of homologous chromosomes or a pair of sister chromatids fail to separate properly from each other.