Chapter 15

Question 1

Chromosome Theory of Inheritance

Answer 1

A basic principle in biology stating that genes are located at specific positions on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns.

Question 2

Wild Type

Answer 2

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

Question 3

Sex-linked gene

Answer 3

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 4

X-linked gene

Answer 4

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

Question 5

Duchenne muscular dystrophy

Answer 5

A human genetic disease caused by a sex-linked recessive allele; characterized by progressive weakening and a loss of muscle tissue.

Question 6

Hemophilia

Answer 6

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 7

Barr body

Answer 7

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

Question 8

Linked genes

Answer 8

Genes located close enough together on a chromosome that they tend to be inherited together.

Question 9

Genetic recombination

Answer 9

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

Question 10

Parental type

Answer 10

An offspring with a phenotype that matches one of the true-breeding parental (P gen) phenotypes; also refers to the phenotype itself.

Question 11

Recombinant type

Answer 11

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

Question 12

Crossing over

Answer 12

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

Question 13

Genetic Map

Answer 13

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

Question 14

Linkage map

Answer 14

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

Question 15

Map units

Answer 15

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

Question 16

Nondisjunction

Answer 16

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 17

Aneuploidy

Answer 17

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

Question 18

Monosomic

Answer 18

Referring to a diploid cell that has only one copy of a particular chromosome instead of the normal 2

Question 19

trisomic

Answer 19

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

Question 20

Polyploidy

Answer 20

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

Question 21

Deletion

Answer 21

A deficiency in chromosome resulting from the loss of a fragment through breakage.
A mutational loss of one or more nucleotide pairs from a gene.

Question 22

Duplication

Answer 22

An aberration in chromosome structure due to fusion with a fragment from a homologous chromosome, such that a portion of a chromosome is duplicated.

Question 23

Inversion

Answer 23

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

Question 24

Translocation

Answer 24

During protein synthesis, the 3rd stage in the elongation cycle, when the RNA carrying the growing polypeptide moves from the A site to the P site on the ribosome.

Question 25

Down syndrome

Answer 25

A human genetic disease usually caused by the presence of an extra chromosome 21. Characterized by developmental delays and heart and other defects that are generally treatable or non-life-threatening.

Question 26

Genomic imprinting

Answer 26

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