Chromosome Structure 1

Question 1

what are the two types of interphase chromatin

Answer 1

1. euchromatin - DNA that is active and is being expressed as protein
2. heterochromatin- mostly inactive DNA
   a) constitutive: never expressed and is near the centromere (mostly repetitive DNA)
   b) faculative: sometimes expressed

Question 2

what are the 4 types of chromosomal morphology

Answer 2

metacentric: close to midpoint
submetacentric: centromere not in middle so a P and Q arm can be seen
acrocentric: centromere near end and the short arm can barely be seen (sometimes has satellites)
telocentric: centromere at end and only one arm can be seen

Question 3

define karyotype

Answer 3

complete set of diploid chromosomes

Question 4

what sort of stain reveals G banding patterns

Answer 4

giemsha staining - helps discriminate between the chromosomes

Question 5

what are the two categories of numerical abnormality in a chromosome

Answer 5

aneuploidy and polyploidy

Question 6

what does aneuploidy mean

Answer 6

due to meiosis abnormalities
occurs when someone is missing a chromosome from the pair (monosomy) or has more than two chromosomes in the pair ( trisomy). examples are trisomy 21 (down syndrome), trisomy 18 (edwards syndrome)

Question 7

what does polyploidy mean

Answer 7

extra complete sets of chromosomes - arises from abnormal cell division in meiosis

Question 8

what are the types of structural abnormalities in a chromosome

Answer 8

deletions, duplications, inversions, rings, translocations

Question 9

describe a deletion abnormality

Answer 9

part of the chromosome is missing
i.e cri de chat syndrome

Question 10

describe a duplication abnormality

Answer 10

part of the chromosome is duplicated = extra genetic material

Question 11

describe an inversion abnormality

Answer 11

some part of a chromosome has detached, flipped itself and reattached= genetic matierial is inverted

Question 12

what is a pericentric inversion

Answer 12

involves p and q arm

Question 13

what is a paracentric inversion

Answer 13

involves only one arm - either p or q

Question 14

describe a ring abnormality

Answer 14

a chromosomal portion has broken off and formed a circle or a ring- can happen with or without loss of genetic material- can cause mental delays and epilepsy

Question 15

describe a translocation abnormality

Answer 15

where bit of one chromosome is added to another chromosome

Question 16

what is a reciprocal translocation

Answer 16

segments from two diff chromosomes have been exchanged

Question 17

what is a robertsonian translocation

Answer 17

an entire chromosome has attached to another at the centromere
only happens in 13,12,15 , 21 and 22 in humans

Question 18

what does homologous acrocentric mean

Answer 18

robertsonian transloaction between one pair of chromosomes i.e joining of chromosome 14 together

Question 19

non- homologous acrocentric

Answer 19

robertsonian transloaction occurs between two diff chromosomes i.e 14 & 21= down syndromw