Midterm 2 pt.3

Question 1

Nucleotide?

Answer 1

5-carbons sugar bonded to a nitrogenous base and one or more phosphate groups.

Question 2

Nucleic acid?

Answer 2

polymer consisting of many nucleotide monomers linked by a single phosphate group

Question 3

Nucleoside?

Answer 3

nucleotide without any phosphate group

Question 4

Structure of DNA?

Answer 4

deoxyribonucleic acid
Hydrogen on the second carbon(2’) of the ribose
Nitrogen bases are: Cytosine, Thymine, Adenine and Guanine

Question 5

Structure of RNA?

Answer 5

ribonucleic acid:
Presence of an OH group on the second carbon (2’) of the ribose
Nitrogen bases are: Cytosine, Uracil, Adenine and Guanine

Question 6

Polymerization only occurs…

Answer 6

Polymerization only occurs by the addition of nucleotides on the 3’

Question 7

Sequences are always written from…

Answer 7

5’ to 3’

Question 8

How is DNA oriented/ bonds?

Answer 8

2 polynucleotides: 2 strands organized in a double helix and oriented in opposite direction (antiparallel)
2 hydrogen bonds between A and T
3 hydrogen bonds between C and G

Question 9

Replication is…

Answer 9

Replication is semi-conservative: Each new DNA molecule conserves half of the original molecule

Question 10

What is the replication fork?

Answer 10

The 2 parental DNA strands are unwound by helicases.
Single-strand binding proteins maintain the strands separate.
A topoisomerase relieves the tension ahead of the fork.

Question 11

What is the leading strand?

Answer 11

One strand can be synthesized continuously, in the same direction as the progression of the replication fork and using a single primer: leading strand
The DNA polymerase III synthesizes the new strand

Question 12

elongation can only happen….

Answer 12

Elongation only happens in the 5’ 3’ direction!

Question 13

what is the lagging strand?

Answer 13

One strand has to be synthesized in multiple segments, away from the replication fork, and using multiple primers: lagging strand
Fragments of the lagging strand are called Okazaki fragments
Once all primers have been replaced, a ligase binds the Okazaki fragments together into a continuous DNA stran

Question 14

DNA- Dependant DNA Polymerase:

Answer 14

Synthesizes DNA
Uses DNA as a template to synthesize

Question 15

RNA dependant DNA Polymerase

Answer 15

Synthsizes DNA
Uses RNA as a template to synthesize
Reverse transcriptase
New strand cDNA= complementary DNA

Question 16

DNA-dependant RNA Polymerase

Answer 16

Synthesizes mRNA from DNA

Question 17

RNA Dependant RNA Polymerase

Answer 17

Uses RNA to synthesize RN

Question 18

What is the PCR? (3 steps)

Answer 18

Polymerase chain reaction: A cyclic reaction that makes a large number of copies of a small piece of DNA
1. Denaturation of parental DNA
2. Annealing of DNA primers
3. Extension

Question 19

What is RT-PCR?

Answer 19

Reverse transcriptase–polymerase chain reaction
Technique for determining expression of a particular gene.
1. A reverse transcriptase to synthesize cDNA from an mRNA strand
2. A DNA-dependent DNA polymerase to copy the cDNA (PCR amplification by PCR)

Question 20

What can cause DNA Damage?(5)

Answer 20

Oxygen radicals (O2*)
radiation
UV light
Chemotherapeutics

Question 21

What are mismatch repairs?

Answer 21

Many DNA polymerases proofread each nucleotide added against its template.
Exonucleases remove the mismatched nucleotide that was just added
If the mismatched nucleotide is not removed, other enzymes remove it and replace it
mismatch repair mechanism performed by nucleases, polymerases and ligases

Question 22

What happens when mutations occur?

Answer 22

When a DNA change carries through another round of replication it becomes a mutation:
If the mismatched nucleotide pair is replicated, it becomes permanent in the daughter cell.
In multicellular organisms, if the mutation occurs in germ cells it can be passed on to the next generation.
Most mutations have no phenotypic effect on the organism

Question 23

What are telomeres?

Answer 23

repeated rounds of replication result in the shortening of chromosomes
But… the end of eukaryotic chromosomes DNA molecules have telomeres:
sequences of DNA (TTAGGG in humans) that can be repeated
Telomeres protect the organism’s genes from being eroded during successive rounds of replication

Question 24

Telomerase?

Answer 24

Telomerase: enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells to compensate the shortening that occurs during replication.
The telomerase:
possess its own RNA “primer” molecule complementary to the end sequence of the DNA strand