Chapter 12

Question 1

syntenic segments

Answer 1

blocks of chromosomes in which the identity, order and transcriptional direction of the genes are almost exactly the same in the two genomes.

Question 2

What two types of events reshape genomes?

Answer 2

• rearrangements

- changes in chromosome number

Question 3

Four types of chromosomal rearrangements

Answer 3

• deletions
• duplications
• inversions
• reciprocal translocations

Question 4

gene dosage

Answer 4

(the number of times a given gene is present in the genome

Question 5

tandem duplications

Answer 5

the repeated copies lie adjacent to each other, either in the same order or in reverse order

Question 6

nontandem (dispersed) duplications

Answer 6

the copies of the region are not adjacent to each other and may lie far apart on the same chromosome or on different chromosomes

Question 7

unequal crossing-over

Answer 7

recombination resulting from such out-of-register pairing, generates gametes containing increases to three and reciprocal decreases to one in the number of copies of the duplicated region

Question 8

pericentric

Answer 8

inversions that include the centromere

Question 9

paracentric

Answer 9

inversions that exclude the centromere

Question 10

inversion loop

Answer 10

allows the tightest possible alignment of homologous regions

Question 11

acentric fragment

Answer 11

lacking a centromere

Question 12

dicentric chromatid

Answer 12

two centromeres

Question 13

crossover suppressors

Answer 13

fewer or no recombinants among the viable progeny of an inversion heterozygote.

Question 14

translocation

Answer 14

large scale mutations in which part of one chromosome becomes attached to a nonhomologous chromosome

Question 15

alternate segregation pattern

Answer 15

the two translocation chromosomes (T1 and T2) go to one pole, while the two normal chromosomes (N1 and N2) move to the opposite poles

Question 16

adjacent-1 segregation pattern

Answer 16

homologous centromere disjoin so that T1 and N2 go to one pole, while N1 and T2 go to the opposite pole.

Question 17

adjacent-2-segregation pattern

Answer 17

homologous centromeres N1 and T1 go to the same spindle pole, while the homologous centromeres N2 and T2 go to the other spindle pole
-result in genetic imbalances that are lethal to zygotes after fertilization

Question 18

semisterility

Answer 18

a condition in which the capacity of generating viable offspring is diminished by at least 50%

Question 19

pseudolinkage

Answer 19

behave as they’re linked

Question 20

Robertsonian translocation

Answer 20

arise from breaks at or near the centromeres of two acrocentric chromosomes.

Question 21

transposition

Answer 21

movement of small segments of DNA from one position in the DNA to another

Question 22

transposable elements (TE)

Answer 22

small segments of DNA

Question 23

retrotransposons

Answer 23

transpose via reverse transcription of an RNA intermediate

Question 24

transposons (DNA transposons)

Answer 24

move their DNA directly without the requirement of an RNA intermediate.

Question 25

What are two major types of poly-A-containing retrotransposons?

Answer 25

- LINEs (long interspersed elements) | - SINEs( short interspersed elements)

Question 26

transposase

Answer 26

a protein that catalyzes transposition through its recognition of those repeats.

Question 27

nonautonomous elements

Answer 27

defective TEs that require the activity of nondeleted copies of the same TE for movement

Question 28

autonomous elements

Answer 28

the nondeleted copies that can move by themselves

Question 29

aneuploids

Answer 29

: individuals whose chromosome number is not an exact multiple of the haploid number (n) for the species

Question 30

monosomic

Answer 30

(2n-1) | lacking one chromosome

Question 31

trisomic

Answer 31

(2n+1) | an individual having a single additional chromosome

Question 32

meiotic nondisjunction

Answer 32

occurs during meiosis II, only two of the four resulting gametes will be aneuploidy

Question 33

euploid

Answer 33

complete sets of chromosomes

Question 34

polyploids

Answer 34

carry three of more complete sets of chromosomes

Question 35

basic chromosome number

Answer 35

the number of different chromosomes that make up a single complete set

Question 36

triploid

Answer 36

three complete sets of chromosomes (3x)

Question 37

tetraploid

Answer 37

species with four complete sets of chromosomes (4x)

Question 38

monoploid

Answer 38

have only one set of chromosomes.

Question 39

parthenogenesis

Answer 39

reproduction in which offsprings are produced by an unfertilized female

Question 40

autopolyploidy

Answer 40

a kind of polyploid that derives all its chromosome sets from the same species

Question 41

bivalents

Answer 41

pairs of synapsed homologous chromosomes

Question 42

gene families

Answer 42

set of closely related genes with slightly different function

Question 43

Haploinsufficiency

Answer 43

Half of the normal gene dosage that does not produce enough protein product for a normal phenotype