Biochemistry Courses - SOS I

Question 1

Most cells in the body are in which cell phase?

Answer 1

G0 - RESTING CELLS.

Question 2

Cells in G1 phase:

Answer 2

1. GI epithelial cells.

2. Nucleated RBCs.

Question 3

DNA replication occurs only in which cell phase?

Answer 3

S phase.

Question 4

Transcription takes place during which phase of the cell cycle?

Answer 4

During the ENTIRE INTERPHASE.

Question 5

Signals for the G1 –> S step:

Answer 5

Growth factors –> GH, IGF-1 etc.

Question 6

Purines:

Answer 6

1. Adenine.

2. Guanine.

Question 7

Pyrimidines:

Answer 7

1. Cytosine.
2. Uracil.
3. Thymine.
   “CUT”

Question 8

Purines have 1 or 2 rings?

Answer 8

2 rings.

Pyrimidines –> 1 ring.

Question 9

Difference between the adenine and guanine:

Answer 9

12 o clock position –> Adenine has NH2.

Guanine has O.

Question 10

Difference between the pyrimidines:

Answer 10

12 o clock –> Cytosine has NH2.
Uracil –> O.
Thymine –> O + a methyl group (CH3) in 2 o clock.

Question 11

Nucleoside = …?

Answer 11

BASE + SUGAR (ribose or deoxyribose).

Question 12

Nucleotide = …?

Answer 12

BASE + SUGAR + P (1, 2 or 3 P, eg AMP, ADP, ATP).

Question 13

Base –> Nucleoside:

Answer 13

Adenine --> Adenosine.
Guanine --> Guanosine.
Cytosine --> Cytidine.
Uracil --> Uridine.
Thymine --> (Deoxythymidine).

Question 14

Difference between RNA and DNA:

Answer 14

1. Pyrimidine base.

2. Ribose type –> 2’ carbon has OH in RNA ribose - DNA is DEoxyribonucleic acid.

Question 15

Histones are + or - charged?

Answer 15

+ charged, because they have too many ARGININES + LYSINES.

Question 16

DNA is - charged due to …?

Answer 16

PHOSPHATES.

Question 17

10nm chromatin refers to …?

Answer 17

NUCLEOSOME.

Question 18

H1 is …?

Answer 18

NOT FOUND WITHIN THE NUCLEOSOME - Found out of it.

Question 19

Difference between a 10nm chromatin and a 30nm chromatin?

Answer 19

30nm chromatin has H1 (condense nucleosomes together).

Question 20

DNA packaging:

Answer 20

DNA double helix –> 10nm chromatin –> 30nm chromatin –> 30nm fibers forms loops attached to scaffolding proteins –> Higher order packaging (heterochromatin).

Question 21

Euchromatin is light or dark-staining:

Answer 21

Light –> Euchromatin –> ACTIVE genes.

Dark –> Heterochromatin –> INACTIVE genes - If FEMALE, then the right answer might be a BARR BODY.

Question 22

Euchromatin - When DNA is exposed (light staining spots) …?

Answer 22

If there is no option “active genes”, APOPTOSIS may also be correct!
Nucleases can take care of the DNA during apoptosis.

Question 23

DNA pauses and checks:

Answer 23

Has 3’ –> 5’ EXONUCLEASE ACTIVITY.

Question 24

RNA polymerase DOES NOT require a …?

Answer 24

PRIMER.

Question 25

How many genes do we have?

Answer 25

20.000-25.000 genes.

Question 26

Why proofreading during DNA replication?

Answer 26

TO AVOID INHERITABLE MUTATIONS.

Question 27

Why do we don’t care about the NON-Proofreading ability of the RNA polymerase?

Answer 27

1. NOT INHERITED.
2. SHORT half life of protein.
3. Only happening in 1 cell.

Question 28

Does reverse transcriptase require a primer?

Answer 28

YES - Because it is a RNA-dependent DNA DNA DNA polymerase.

ALL DNA POLYMERASES REQUIRE A PRIMER.

Question 29

Why do we need to fragment DNA and not RNA in order to analyze it?

Answer 29

Because DNA is MUCH longer than RNA.