Chapter 17 Flashcards
1
Q
Define acentric chromosome
A
- a chromosome having no centromere
2
Q
Define acentric fragment
A
- a chromosome fragment having no centromere
3
Q
Define adjacent-1 segregation
A
- in a reciprocal translocation, the passagr of a translocated and a normal chromosome to each of the pole
4
Q
Define allopolyploid
A
- a polyploid formed from the union of 2 separate chromosome sets and their subsequent doubling
5
Q
Define alternate segregation
A
- in a reciprocal translocation the passage of both normal chromosomes to one pole and both translocated chromosomes to the other pole
6
Q
Define amphidiploid
A
- a polyploid formed from the union of 2 separate chromosome sets and their subsequent doubling
- an allopolyploid
7
Q
Define anaphase bridge
A
- in a dicentric chromosome, the segment between the centromeres being drawn to opposite poles at nuclear division
8
Q
Define aneuploid
A
- a genome having a chromosome number that differs from the normal chromosome number for the species by a small number of chromosomes
9
Q
Define autopolyploid
A
- polyploid formed from the doubling of a single genome
10
Q
Define balanced rearrangement
A
- a change in the chromosomal gene order that does not remove or duplicate any DNA
- the 2 classes of balanced rearrangement are inversions and reciprocal translocations
11
Q
Define balancer
A
- a chromosome with multiple inversions, used to retain favourable allele combinations in the uninverted homolog
12
Q
Define bivalent
A
- 2 homologous chromosomes paired at meiosis
13
Q
Define chromosome mutation
A
- any type of change in chromosome structure or number
14
Q
Define deletion
A
- the removal of a chromosomal segment from a chromosome set
15
Q
Define deletion loop
A
- the loop formed at meiosis by the pairing of a normal chromosome and a deletion-containing chromosome
16
Q
Define deletion mapping
A
- the use of a set of known deletions to map new recessive mutations by pseudodominance
17
Q
Define dicentric bridge
A
- in a dicentric chromosome, the segment between the centromeres being drawn to opposite poles at nuclear division
18
Q
Define dicentric chromosome
A
- a chromosome with 2 centromeres
19
Q
Define disomic
A
- an abnormal haploid carrying 2 copies of one chromosome
20
Q
Define dosage compensation
A
- the process in organisms using a chromosomal sex-determination mechanism (such as XX vs XY) that allows standard structural genes on the sex chromosome to be expressed at the same levels in females and males, regardless of the number of chromosomes
- in mammals, dosage compensation operates by maintaining only a single active X chromosome in each cell
- in Drosophoila, it operates by hyperactivating the male X chromosome
21
Q
Define Down syndrome
A
- an abnormal human phenotype, including mental retardation, due to a trisomy on chromosome 21
- more common in babies born to older mothers
22
Q
Define duplication
A
- more than one copy of a particular chromosomal segment in a chromosome set
23
Q
Define embryoid
A
- a small dividing mass of monoploid cells, produced from a cell destined to become a pollen cell by exposing it to cold
24
Q
Define euploid
A
- a cell having any number of complete chromosome sets or an individual organism composed of such cells