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MCT Exam 2 > Chromosomes and Disease > Flashcards

Flashcards in Chromosomes and Disease Deck (30)
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1
Q

Cytogenetics definition

A

study of chromosomes

2
Q

When is most clinical analysis of chromosomes done?

A

Metaphase;

when chromosomes are condensed

3
Q

G banding definition

A

visual inspection of chromosomes stained or labeled using dyes or fluorescent molecules;
Giemsa is US standard

4
Q

How does the staining of chromosomes work?

A

Stains AT enriched regions;

genes are usually GC rich so light bands correspond to the regions of the chromosome with higher density of genes

5
Q

How many bases does each band represent?

A

5-10 million bases on low resolution of chromosomes

6
Q

Centromere definition

A

contain repetitive sequences and serve as the attachment point for the machinery that separates the chromosomes

7
Q

Metacentric

A

centromere near middle of chromosome

8
Q

Submetacentric

A

centromere located towards one end of the chromosome; results in short arm at the top (p arm) and long arm at the bottom (q arm)

9
Q

Acrocentric

A

centromere is very close to one end of the chromosome

10
Q

Telomeres

A

found at ends of chromosomes;

protect the chromosomes from getting too short

11
Q

System for naming bands on chromosomes

A
  • First part of name is the number of the chromosome followed by the arm (p or q)
  • next number designates the region on the arm followed by the band number in that region;
    (ex: 14q32 - q arm of chromosome 14, region 3, band 2)
12
Q

Karyogram

A

organized image of a patient’s chromosomes

13
Q

Karyotype

A

describes the total number of chromosomes, identifies the sex chromosomes, and specifies any numeric or structural abnormalities

14
Q

Two classes of chromosomal abnormalities

A

Numerical abnormality;

Structural abnormality

15
Q

Numerical abnormality

A

changes in chromosome number from usual 46

16
Q

Structural abnormality

A

changes that affect how a chromosome is organized

17
Q

Trisomy (numerical abnormality)

A

there is an extra copy of a chromosome;

1-3% of pregnancies, 15-20% of chromosomal abnormal spontaneous abortions

18
Q

Monosomy (numerical abnormality)

A

there is a missing chromosome

19
Q

Translocation (structural abnormality)

A

parts of two chromosomes are exchanged

20
Q

Reciprocal translocation (structural abnormality)

A

parts of two chromosomes are exchanged in a balanced manner;

phenotypically normal unless break is in middle of the gene

21
Q

Euploidy

A

loss or gain of entire chromosome set;

69 triploid, 92 tetraploid

22
Q

Aneuploidy

A

loss or gain of less than entire chromosome set;

monosomy, trisomy

23
Q

Mosaicism

A

presence of more than 1 cell line;

often results as a function of trisomy rescue

24
Q

Synaptonemal complex

A

protein structure that forms mediating chromosome pairing

25
Q

Chiasma

A

physical points along chromosome where crossing over has occurred

26
Q

Recombination is essential…

A

avg 50 chiasmata in male meiosis;
>1 chiasma/chromosome arm is required for normal segregation;
recombination decreases near centromeres and increases near telomeres

27
Q

What are two causes of aneuploidy in meiosis and mitosis

A

Nondisjunction and anaphase lag

28
Q

Nondisjunction

A

failure of chromatids (during mitosis or meiosis II) or chromosomes (during meiosis I) to separate at anaphase

29
Q

Anaphase lag

A

failure of a chromatid of chromosome to attach to the spindle and segregate into a daughter cell

30
Q

Pseudoautosomal regions (PAR)

A

at x y of p arm, and q arm;
recombination in these regions is a challenge due to size difference;
leads to significant number of aneuploidy