(4) Chapter 16

Question 1

What are the two types of nucleic acids?

Answer 1

Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA).

Question 2

What does DNA provide directions for?

Answer 2

DNA provides directions for its own replication.

Question 3

How does DNA control protein synthesis?

Answer 3

DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis.

Question 4

Where does protein synthesis occur?

Answer 4

Protein synthesis occurs on ribosomes.

Question 5

What is the lagging strand?

Answer 5

The lagging strand is the other new strand that DNA polymerase synthesizes away from the replication fork.

Question 6

What are Okazaki fragments?

Answer 6

Okazaki fragments are segments synthesized by DNA polymerase III on the lagging strand.

Question 7

What must happen to RNA primers during DNA replication?

Answer 7

RNA primers must be replaced with DNA.

Question 8

What is the role of DNA polymerase I?

Answer 8

DNA polymerase I can remove RNA nucleotides and fill in the gap with DNA nucleotides.

Question 9

What does DNA ligase do?

Answer 9

DNA ligase can join the 5’ end of one DNA molecule with the 3’ end of another.

Question 10

What type of genome do bacteria have?

Answer 10

Bacteria have a circular genome with a single DNA molecule and 1 origin of replication.

Question 11

What type of genome do humans have?

Answer 11

Humans have a linear genome with multiple linear chromosomes and multiple origins of replication on each chromosome.

Question 12

What are telomeres?

Answer 12

Telomeres are special repetitive, non-coding nucleotide sequences at the ends of eukaryotic chromosomal DNA molecules.

Question 13

What is the function of telomeres?

Answer 13

Telomeres postpone the erosion of genes near the ends of DNA molecules.

Question 14

How does telomere shortening relate to aging?

Answer 14

Telomeres in somatic cells are generally shorter in older individuals.

Question 15

What is the role of telomerase in germ cells?

Answer 15

Telomerase is expressed in germ cells to maintain telomeres at their original length.

Question 16

How might telomeric shortening be protective against cancer?

Answer 16

Telomeric shortening may limit continuous cell division, which can be protective against cancer.

Question 17

What is the error rate of DNA polymerase?

Answer 17

About once every 100,000 nucleotides, DNA polymerase will mistakenly add the wrong nucleotide.

Question 18

What exonuclease activity do DNA Pol I and DNA Pol III have?

Answer 18

Both have 3’ to 5’ exonuclease activity to remove mistaken nucleotides.

Question 19

What is the rate of nucleotide incorporation for human polymerase?

Answer 19

The rate is 50 nucleotides/sec for human polymerase.

Question 20

What is the rate of nucleotide incorporation for bacterial polymerase?

Answer 20

The rate is 500 nucleotides/sec for bacterial polymerase.

Question 21

What is the function of helicase?

Answer 21

Helicase unwinds DNA to create two single strands.

Question 22

What does Single Strand Binding Protein (SSB) do?

Answer 22

SSB binds to and stabilizes the single stranded DNA.

Question 23

What is the role of primase?

Answer 23

Primase provides an RNA primer to start new DNA strand synthesis.

Question 24

What does topoisomerase do?

Answer 24

Topoisomerase travels ahead of helicase, ‘nicking’ and swiveling the DNA to relieve torsional strain.

Question 25

What does Polymerase III do?

Answer 25

Polymerase III assembles new DNA strand in the 5’ - 3’ direction.

Question 26

What does Polymerase I do?

Answer 26

Polymerase I can remove RNA nucleotides as it adds new DNA in a 5’ – 3’ direction.

Question 27

What is the function of ligase?

Answer 27

Ligase joins two DNA strands together at their ends.

Question 28

What is the role of telomerase?

Answer 28

Telomerase maintains telomere length in germline cells to protect the health of gametes.