The Central Dogma- Week 7/8

Question 1

Define molecular biology as a subject

Answer 1

the study of the formation, Structure and function of MACROMOLECULES essential for life (e.g. amino acids) & their role in STORAGE & TRANSMISSION of genetic information.

Question 2

Define the “central dogma” of molecular biology

Answer 2

The sequences of DNA,RNA & proteins contain the information required for translation & transcription and protein function

Question 3

Describe the building blocks of DNA

Answer 3

-Nucleic acids (linear polymers made up of nucleotides)
-Pentose Sugars (ribose & deoxyribose)
-Organic bases (purine-2 rings & pyrimidine-1 ring)
-Phosphate group-linked by phosphodiester bonds

Question 4

what does DNA and RNA stand for

Answer 4

DNA; Deoxyribonucleic acid
RNA; Ribonucleic acid

Question 5

what way are phosphodiester bonds formed in DNA

Answer 5

from 5’-3’

Question 6

Describe the mechanism of DNA replication

Answer 6

BOTH strands serve as templates for replication of a complementary strand

Question 7

Define the molecular machinery involved in DNA replication & describe how it works

Answer 7

DNA polymerase- catalyses DNA synthesis
- begins at ‘replication origin’
- requires RNA primer
- adds dNTPs to 3’ -OH group (as it goes in 5’–3’ direction)

Question 8

what direction does DNA polymerase ONLY synthesises at

Answer 8

5’ to 3’

Question 9

how does the strand of DNA which is anti-parallel to the 5’—3’ strand get synthesised

Answer 9

-Lagging strand copied as short fragments: 1000 bases long in the 5’ to 3; direction

Question 10

what are the lagging short fragments called

Answer 10

Okazaki fragments

Question 11

what are the enzymes & primers called and what is their role that aid the synthesis of lagging strand

Answer 11

• Fragments started on by RNA primer made by DNA primase
• Fragments joined by DNA ligase enzyme

Question 12

what are the enzymes & proteins required for DNA replication

Answer 12

-Helicase: Unwinds strands of DNA
-Topoisomerase: Relieves twists in DNA ahead
-Single Strand Binding Proteins(SSBP): prevent rewinding of DNA
-DNA Primase: Synthesis of RNA primer
-DNA Polymerase: Synthesis of new DNA
-Clamp Proteins: Hold polymerase in place
-DNA Ligase: joins Okazaki fragments

Question 13

what are the purines nitrogenous bases

Answer 13

adenine and guanine

Question 14

what are the pyrimidines nitrogenous bases

Answer 14

uracil
thymine
cytosine

Question 15

Cellular DNA replication requires:

a. Transfer RNA
b. Primase
c. Ribosomes
d. Nucleosomes
e. Reverse transcriptase

Answer 15

b. Primase

Question 16

The principle difference between a nucleoside and nucleotide is:

a. Phosphate group
b. Phosphoester bond
c. 5-carbon sugar
d. Organic base
e. Methyl residue

Answer 16

a. Phosphate group

Question 17

What does the abbreviation dATP stand for?

a. 5’-deoxyadenosine-3′-triphosphate
b. 3’-deoxyadenosine-2′-triphosphate
c. 2’-deoxyadenosine-4′-triphosphate
d. 2’-deoxyadenosine-5′-triphosphate
e. 3’-deoxyadenosine-1′-triphosphate

Answer 17

d. 2’-deoxyadenosine-5’-triphosphate

Question 18

1. How many copies of the rRNA genes are there in the human genome?

a. 2
b. 20
c. 200
d. 2000
e. 20000

Answer 18

c. 200

Question 19

The combined error rate for DNA replication is roughly:

a. 1 in 10
b. 1 in 100
c. 1 in 10^2
d. 1 in 10^4
e. 1 in 10^9

Answer 19

e. 1 in 10^9

Question 20

Which of the following is not part of mRNAs processing?

a. Exon excision repair
b. Intron removal
c. RNA cap structure
d. Poly(A) tail
e. UTRs

Answer 20

a. exon excision repair

Question 21

6. Cellular RNA synthesis:

a. Requires primers
b. Employs helicase and gyrase
c. Is also known as transcription
d. Is also known as translation
e. Takes place in a 3´ to 5´ direction

Answer 21

c. is also known as transcription

Question 22

Mature eukaryotic mRNA:

a. Contains only exons
b. Is polycistronic
c. Is found only in the cytoplasm
d. Has a poly(A) tail
e. Is usually short-lived

Answer 22

d. Has a poly(A) tail

Question 23

Which of the following reactions are known to be carried out by a ribozyme?

a. DNA synthesis
b. Transcription
c. RNA splicing
d. Protein hydrolysis
e. Polysaccharide hydrolysis

Answer 23

c. RNA splicing