Lecture 4 Flashcards

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1
Q

DNa+ histones is
In the form of

A

Chromatin
Beads on a thread

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2
Q

1st order packaging

A

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

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3
Q

Why DNA loops around histones

A

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

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4
Q

2nd and 3rd packaging order

A

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

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5
Q

What is chromosomal aberrations
Leads to

A

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

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6
Q

Number abnormalities

A

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

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7
Q

Aneuploidy is sometimes related to
Found in
It is… except

A

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

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8
Q

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

A

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

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9
Q

Cri du chat, deletion symptoms

A

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

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10
Q

Inversion

A

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

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11
Q

A disease due to translocation

A

Burkitts lymphoma
Aggressive lymphoma affecting b lymphocyted

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12
Q

Translocation

A

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

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13
Q

Isochromosomes

A

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

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14
Q

Disease due to isochromosome

A

Turner syndrome

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15
Q

Ring chromosme

A

Loss of both ends causing rejoining as a circle very rare

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16
Q

Robertsonian changes

A

Fusion
Fission

17
Q

DNA in every chromosome band

A

Replicates during s phase

18
Q

Molecular hybridisation

A

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

19
Q

FISH

A

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

20
Q

What lead to introns and exons discovery

A

Autoradiographic in situ hybridisation

21
Q

Banding techniques

A

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

22
Q

Aneuploidy ex
Polyploidy ex

A

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