Chapter 15 - The Chromosomal Basis of Inheritance

Question 1

chromosome theory of inheritance

Answer 1

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 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 generation) phenotypes; also refers to the phenotype itself.

Question 11

recombinant type (recombinant)

Answer 11

An offspring whose phenotype differs from that of the true-breeding P generation 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 chromosomes.

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

cytogenetic map

Answer 16

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

Question 17

nondisjunction

Answer 17

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 18

aneuploidy

Answer 18

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

Question 19

monosomic

Answer 19

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

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

polyploidy

Answer 21

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 22

deletion

Answer 22

(1) A deficiency in a chromosome resulting form the loss of a fragment through breakage. (2) A mutational loss of one or more nucleotide pairs from a gene.

Question 23

duplication

Answer 23

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 24

inversion

Answer 24

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

Question 25

translocation

Answer 25

(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 26

Down syndrome

Answer 26

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 27

genomic imprinting

Answer 27

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