Lecture 4

Question 1

DNa+ histones is
In the form of

Answer 1

Chromatin
Beads on a thread

Question 2

1st order packaging

Answer 2

Nucleosomes of a histones octamer
H2A, H2B, H3, H4
2 copies of each
10 nm diameter
1.65 around histones

Question 3

Why DNA loops around histones

Answer 3

As it is -vely charged due to phosphate groups while histones are positively charged

Question 4

2nd and 3rd packaging order

Answer 4

Solenoid fibers, 6 nucleosomes 30nm diameter
Scaffold loops the chromosomes

Question 5

What is chromosomal aberrations
Leads to

Answer 5

A change in number or structure of chromosomes
Death/mental retardation/genetic abnormalities/ infertility/spontaneous abortions

Question 6

Number abnormalities

Answer 6

Aneuploidy only. Chromosome is the difference, 47, 45
Polyploidy whole set of chromosomes replicated

Question 7

Aneuploidy is sometimes related to
Found in
It is… except

Answer 7

Age
Oocytes and early embryos (trisomies and monosomies)
Lethal, down syndrome and sex chromosomes

Question 8

Some syndromes
10
Cri du chat
Patau
Down
Edward
Jacobson
Klinfelter
turner
Triple
Triple
Wolf hirschhorn

Answer 8

Cri du chat&raquo_space;del 5p
Patau» trisomy 13
Down»trisomy 21
Edward&raquo_space;trisomy 18
Jacobson» terminal 11q del
Klinfelter&raquo_space; XXY
turner» X0
Triple xxx
Triple YYY
Wolf hirschhorn&raquo_space; partial del of 4p

Question 9

Cri du chat, deletion symptoms

Answer 9

Cat like cry disappears with age
Severe mental retardation
congenital heart disease
low birth weight
poor growth
behavioral issues
Hypertelorism widely separated eyes

Question 10

Inversion

Answer 10

180 reverse in a chromosome segment by breaking and reassociation
Paracentric , centromere not involved
Pericentric, centromere involved

Question 11

A disease due to translocation

Answer 11

Burkitts lymphoma
Aggressive lymphoma affecting b lymphocyted

Question 12

Translocation

Answer 12

A piece of chromosome breaking off and joining another one.
Balanced/reciprocal&raquo_space; no loss or gain
Unbalanced/ nonreciprocal» loss and gain

Question 13

Isochromosomes

Answer 13

1 arm is missing and the other arm id duplicated by centromere dividing transversely instead on longitudinally
2 copies of p arm or q arm

Question 14

Disease due to isochromosome

Answer 14

Turner syndrome

Question 15

Ring chromosme

Answer 15

Loss of both ends causing rejoining as a circle very rare

Question 16

Robertsonian changes

Answer 16

Fusion
Fission

Question 17

DNA in every chromosome band

Answer 17

Replicates during s phase

Question 18

Molecular hybridisation

Answer 18

*Cytological preparations of chromosomes and nuclei where used for in situ hybridization with labelled DNA

Question 19

FISH

Answer 19

mapped thousands of loci
Reliable
Time efficient
Precise compared to autoradiographic detection of radioactively labelled DNA

Question 20

What lead to introns and exons discovery

Answer 20

Autoradiographic in situ hybridisation

Question 21

Banding techniques

Answer 21

Q banding
G/giesma banding
R /reverse G banding
C /centromeric heterochromatin banding

Question 22

Aneuploidy ex
Polyploidy ex

Answer 22

Autosomal 47, sex 45,47,48,49
Whole set in plants only, triploidy 69, tetraploidy 92