The Chromosomal Basis of Inheritance: Chp 15

Question 1

chromosome theory of inheritance

Answer 1

states that genes have specific locations on chromosomes and that it is chromosomes that segragate and assort independently

Question 2

sex-linked gene

Answer 2

located on a sex chromosome

Question 3

duchenne muscular dystrophy

Answer 3

an x-linked disorder characterized by a progressive weakening of the muscles and loss of coordination

Question 4

hemophilia

Answer 4

an x-linked disorder characterized by having blood with an inability to clot normally, caused by the absence of proteins required for blood clotting

Question 5

x inactivation

Answer 5

regulates gene dosage in females. although female mammals inherit two x chromosomes, one of the x chromosomes in each cell of the body becomes inactivated during embryonic development by methylation. as a result, males and females have the same effective dose of genes with loci on the X chromosome

Question 6

barr body

Answer 6

when the inactive chromosomes condense and lies along the inside of the nuclear envelope

Question 7

linked genes

Answer 7

located on the same chromosome and therefore tend to be inherited together during cell division

Question 8

genetic recombination

Answer 8

the product of offspring with a new combination of genes inherited from the parents. many genetic crosses yield some offspring with the same phenotype as one of hte parents and some offspring with phenotypes different from either parent

Question 9

linkage map

Answer 9

a genetic map that is based on the percentage of crossover events

Question 10

map unit

Answer 10

equal to a 1% recombination frequency. map units are used to express relative distances along the chromosome

Question 11

nondisjunction

Answer 11

occurs when the members of a pair of homologous chromosomes do not separate properly during meiosis 1, or sister chromatids don’t separate properly during meiosis 2

Question 12

aneuploidy

Answer 12

if the offsping has an incorrect chromosome number as a result of disjunction

Question 13

trisomatic

Answer 13

fertilized eggs that have received three copies of the chromosome

Question 14

monosomic

Answer 14

fertilized egg that has received just one copy of a chromosome

Question 15

polyploidy

Answer 15

the condition of having more than two complete sets of chromosomes, forming a 3n or 4n individual.

Question 16

deletion

Answer 16

occurs when a chromosomal fragment is lost, resulting in a chromosome with missing genes

Question 17

duplication

Answer 17

occurs when a chromosomal segment is repeated

Question 18

inversion

Answer 18

occurs when a chromosomal fragment breaks off and reattaches to its original position-but backwards

Question 19

translocation

Answer 19

occurs when the deleted chromosome fragment joins a nonhomologous chromosome

Question 20

down syndrome

Answer 20

an aneuploid condition that is the result of having an extra chromosome 21

Question 21

klinefelter syndrome

Answer 21

an aneuploid condition in which males possess the sex chromosomes XXY causing them to have male sex organs but are sterile

Question 22

turner syndrome

Answer 22

a monosomic condition in which the female has just one sex chromosome, an X

Question 23

genoic imprinting

Answer 23

the phenotypic effect of a gene may depend on which allele is inherited from each parent