Chapter 15: The Chromosomal Basis of Inheritance

Question 1

aneuploidy

Answer 1

A chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number.

Question 2

Barr body

Answer 2

A dense object lying along the inside of the nuclear envelope in cells of female mammals, representing a highly condensed, inactivated X chromosome.

Question 3

chromosome theory of inheritance

Answer 3

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.

Question 4

crossing over

Answer 4

The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.

Question 5

cytogenetic map

Answer 5

A map of a chromosome that locates genes with respect to chromosomal features distinguishable in a microscope.

Question 6

deletion

Answer 6

(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.

Question 7

genetic map

Answer 7

An ordered list of genetic loci (genes or other genetic markers) along a chromosome.

Question 8

genetic recombination

Answer 8

General term for the production of offspring with combinations of traits that differ from those found in either parent.

Question 9

genomic imprinting

Answer 9

A phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent.

Question 10

hemophilia

Answer 10

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.

Question 11

inversion

Answer 11

An aberration in chromosome structure resulting from reattachment of a chromosomal fragment in a reverse orientation to the chromosome from which it originated.

Question 12

linkage map

Answer 12

A genetic map based on the frequencies of recombination between markers during crossing over of homologous chromosomes.

Question 13

map unit

Answer 13

A unit of measurement of the distance between genes. One map unit is equivalent to a 1% recombination frequency.

Question 14

monosomic

Answer 14

Referring to a diploid cell that has only one copy of a particular chromosome instead of the normal two.

Question 15

nondisjunction

Answer 15

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.

Question 16

polyploidy

Answer 16

A chromosomal alteration in which the organism possesses more than two complete chromosome sets. It is the result of an accident of cell division.

Question 17

recombinant type (recombinant)

Answer 17

An offspring whose phenotype differs from that of the true-breeding P generation parents; also refers to the phenotype itself.

Question 18

sex-linked gene

Answer 18

A gene located on either sex chromosome. Most sex-linked genes are on the X chromosome and show distinctive patterns of inheritance; there are very few genes on the Y chromosome.

Question 19

translocation

Answer 19

(1) An aberration in chromosome structure resulting from attachment of a chromosomal fragment to a nonhomologous chromosome. (2) During protein synthesis, the third stage in the elongation cycle, when the RNA carrying the growing polypeptide moves from the A site to the P site on the ribosome. (3) The transport of organic nutrients in the phloem of vascular plants

Question 20

trisomic

Answer 20

Referring to a diploid cell that has three copies of a particular chromosome instead of the normal two.

Question 21

wild type

Answer 21

The phenotype most commonly observed in natural populations; also refers to the individual with that phenotype.

Question 22

X-linked genes

Answer 22

A gene located on the X chromosome; such genes show a distinctive pattern of inheritance.