Ch 6 Chromosome Variation

Question 1

chromosome mutations

Answer 1

individual chromosomes may lose or gain parts, and the order of genes within a chromosome may become altered

Question 2

4 basic types of chromosomes

Answer 2

metacentric, submetacentric, acrocentric, telocentric

Question 3

karotype

Answer 3

complete set of chromosomes possessed by an organism

Question 4

chromosome rearrangements

Answer 4

mutations that change the structure of individual chromosomes
can also arise through errors in crossing over or when crossing over occurs between repeated DNA sequences

Question 5

4 basic types of rearrangements

Answer 5

duplications, deletions, inversions, translocations

Question 6

chromosome duplication

Answer 6

a mutation in which part of the chromosome has been doubled

Question 7

tandem duplication

Answer 7

the duplicated segment is immediately adjacent to the original segment
Ex: AB-CDEFEFG

Question 8

displaced duplication

Answer 8

the duplicated segment is located some distance from the original segment
Ex: AB-CDEFGEF

Question 9

reverse duplication

Answer 9

the duplication is inverted

Ex: AB-CDEFFEG

Question 10

segmental duplications

Answer 10

the human genome contains numerous duplicated sequences; defined as duplications greater than 1000 base pairs (1000 bp) in length

Question 11

chromosome deletion

Answer 11

the loss of a chromosome segment

Ex: AB-CDEFG will go to AB-CDG

Question 12

pseudodominance

Answer 12

expression of a normally recessive mutation and it is an indication that one of the homologous chromosomes has a deletion

Question 13

haploinsufficient gene

Answer 13

when a single copy of a gene is not sufficient to produce a wild-type phenotype

Question 14

chromosome inversion

Answer 14

a chromosome segment is inverted-turned 180 degrees

Question 15

paracentric inversions

Answer 15

inversions that do not include the centromere

Question 16

pericentric inversions

Answer 16

inversions that include the centromere

Question 17

position effect

Answer 17

if a genes position is altered by an inversion, their expression may be altered

Question 18

dicentric chromatid

Answer 18

one of the four chromatids has two centromeres

Question 19

acentric chromatid

Answer 19

a chromatid that lacks a centromere

Question 20

dicentric bridge

Answer 20

the action of two homologous chromosomes stretching the dicentric chromatid across the center of the nucleus forming this structure

Question 21

translocation

Answer 21

the movement of genetic material between nonhomologous chromosomes or within the same chromosomes

Question 22

nonreciprocal translocation

Answer 22

genetic material moves from one chromosome to another without any reciprocal exchange
Ex: AB•CDEGF and MN•OPQRS
Segment EF moves to second without any transfer, now AB•CDG and MN•OPEFQRS

Question 23

reciprocal translocation

Answer 23

two-way exchange of segments between the chromosomes

Ex: AB•CDEFG and MN•OPQRS will become AB•CDQRS and MN•OPEFG

Question 24

Robertsonian translocation

Answer 24

the long arms of two acrocentric chromosomes become joined to a common centromere through a translocation, generating a metacentric chromosome with two long arms and another chromosome with two very short arms

Question 25

aneuploidy

Answer 25

change in the number of individual chromosomes

Three types: 1) acentric chromosome, 2) small chromosomes can get lost (Robertsonian), 3) nondisjunction

Question 26

polyploidy

Answer 26

an increase in the number of chromosome sets

Question 27

nondisjunction

Answer 27

the failure of homologous chromosomes or sister chromatids to separate in meiosis or mitosis
leads to some gametes or cells that contain an extra chromosome and other gametes or cells that are missing a chromosome

Question 28

4 types of aneuploidy conditions

Answer 28

nullisomy, monosomy, trisomy, tetrasomy

Question 29

nullisomy

Answer 29

loss of both members of a homologous pair of chromosomes; represented as 2n-2

Question 30

monosomy

Answer 30

loss of a single chromosome, represented as 2n-1

Question 31

trisomy

Answer 31

the gain of a single chromosome, represented as 2n+1

Question 32

tetrasomy

Answer 32

gain of two homologous chromosomes, represented as 2n+2

Question 33

down syndrome, or trisomy 21

Answer 33

is the most common autosomal aneuploidy in humans

Question 34

primary down syndrome

Answer 34

three full copies of chromosome 21 (and therefore a total of 47 chromosomes)
usually arises from spontaneous nondisjunction in egg formation

Question 35

familial down syndrome

Answer 35

has a tendency to run in families
about 4% of people have 46 chromosomes, but an extra copy of part of chromosome 21 is attached to another chromosome through a translocation

Question 36

translocation carriers

Answer 36

people with this translocation do not have down syndrome
possess only 45 chromosomes, their phenotypes are normal because they have two copies of the long arms of chromosomes 14 and 21 and apparently the short arms of these chromosomes carry no essential genetic information

Question 37

two types of polyploidy

Answer 37

autopolyploidy and allopolyploidy

Question 38

autopolyploidy

Answer 38

all chromosome sets are from a single species

Question 39

allopolyploidy

Answer 39

chromosome sets are from two or more species

Question 40

gene dosage effect

Answer 40

Imbalances in the amounts of gene products
The amount of a particular protein synthesized by a cell is often directly related to the number of copies of its corresponding gene
More sensitive in animals; plants more tolerant