Lecture 2

Question 1

The 2 DNA strands have

Answer 1

Opposite polarity

Question 2

Why AT and CG

Answer 2

due to the nature of pyrimidines and purines by this conformation balance is ensured by maintaining 3 rings.

Question 3

Nuclear lamina is

Answer 3

Intermediate filaments beneath the inner membrane

Question 4

Nuclear lamina and outer membrane filaments

Answer 4

Support the nuclear pore complex

Question 5

When can we view heterochromatin and euchromatin

Answer 5

Feulgen stain under the cytophotometer
Somatic cells only
S phase

Question 6

Why heterochromatin is hard to transcribe

Answer 6

Tightly coiled and condensed

Question 7

Are heterochromatin and euchromatin the same in all cells

Answer 7

No, in fact the whole chromosome can become inactivated like dose compensation in females
Growth hormones somatostatin and somatotropin are heterochromatin after 18

Question 8

Some liver cells are

Answer 8

Polyploidy
2n/4n/8n

Question 9

Chromatin can be isolated biochemically by
Appears
Contains

Answer 9

Cell lysis in hypotonic solution
Viscous and gelatinous
DNA/RNA/histones/non histones
31/5/36/28

Question 10

Why the pea embryo rna is so much different in comparison with dna than liver cells

Answer 10

As pea embryo are ready to germinate whenever conditions are suitable

Question 11

During mitosis the chromosome split is visible due to
.. but not in
.. where it already happened

Answer 11

Condensation
S phase

Question 12

Centromere replicates at

Answer 12

Anaphase

Question 13

Chromatin thread is the same as

Answer 13

Chromonemata

Question 14

Chromomeres are

Answer 14

Bead like structured that are sometimes visible during interphase
Obv in polytene chromosomes
Due to close coiling of chromonemata

Question 15

Polytene chromosomes z

Answer 15

Very buffed areas in drosophila salivary glands abt 1000 chromatin fibers successive replication but no cytokinesis endomitosis
Large diameter

Question 16

Centromere

Answer 16

Primary constriction
Non stainable gap

Question 17

Centromere Has….chromatid…appears…

Answer 17

Very thin as it is uncoiled
Unstained with feulgen so stained with centromeric stain

Question 18

Centromere function

Answer 18

Spindle fibers attach to it at metaphase to ensure chromosomes arrive to daughter cells without it the chromosomes will be lost

Question 19

Spindle fibers are

Answer 19

Discontinuous

Question 20

More than 1 centromere

Answer 20

Dicentric
Tricentric
Holocentric
Acentric

Question 21

Centromere positions

Answer 21

Meta v
Telo/acro i
Submeta j

Question 22

S.cerevisae centromeres length
Plasmid importance

Answer 22

100-120bp with 3 essential regions
2um fragments

Question 23

The centromeres of different chromosomes are …without…

Answer 23

CEN
Interchangable
Having any detectable effect

Question 24

Region I and III
Region II
In s.cerevisae

Answer 24

Conserved, binding sites for spindle
AT rich 90bp length and nature important than sequence

Question 25

2ndry constriction must be.... Has...... But not.... They are in....chromosmes

Answer 25

In every chromosome NOR (nucleolar organising regions) Every 2ndry constriction has them 5 acrocentric with staellites 13,14,15,21,22

Question 26

NOR has genes that code for

Answer 26

45 s RNA/ 18 s RNA/28s rRNA/ 5.8 s rRNA

Question 27

Chromosome+NOR

Answer 27

Nucleolar chromosome Usually 2 in a diploid cell

Question 28

Telomeres function

Answer 28

Prevent DNases from degrading the DNA molecule Prevents ends fusion Facilitate replication without loss of material

Question 29

Telomeres are.... repeated In humans From 1-4

Answer 29

Short sequence tandemly 500-3000 5'TAG3' TTAGGG T or G

Question 30

Enzyme of telomere End proteins of telomere Telomere associated sequence

Answer 30

Telonerase Sheltrin Repetitve DNA near the telomeres

Question 31

Most telomeres terminate with.... Called.... Length

Answer 31

C rich single strand 3'overhang 125-175 bp

Question 32

10nm ellipsodial beads DNA in bacterial chromosomes is...and..

Answer 32

Nucleosomes Circular, contains 50 -vely supercoiled domains

Question 33

Heterochromatin beneath nuclear lamins around nucleolus is called

Answer 33

Nucleolus associated chromatin

Question 34

Chromosome duplication occurs in

Answer 34

S phase

Question 35

How cell distinguishes telomeres from sites of damage

Answer 35

Due to sheltrin proteins TIN2,TPP1,RAP1 complex