Molecular inheritance

Question 1

What is the structure of DNA?

Answer 1

Double helix composed of two antiparallel strands of nucleotides.

Question 2

What are the two classes of nitrogenous bases?

Answer 2

Purines (adenine, guanine) and pyrimidines (cytosine, thymine).

Question 3

Which bases pair together in DNA?

Answer 3

Adenine pairs with thymine (A–T); guanine pairs with cytosine (G—C).

Question 4

What type of bonds hold base pairs together?

Answer 4

Hydrogen bonds.

Question 5

What does semiconservative replication mean?

Answer 5

Each new DNA molecule has one old strand and one newly synthesized strand.

Question 6

Where does DNA replication begin?

Answer 6

At the origin of replication.

Question 7

What enzyme unwinds the DNA helix?

Answer 7

Helicase.

Question 8

What enzyme relieves strain ahead of the replication fork?

Answer 8

Topoisomerase.

Question 9

What are single-strand binding proteins (SSBPs)?

Answer 9

Proteins that stabilize unwound DNA strands and prevent reannealing. Keep Fork Open

Question 10

What is the replication fork?

Answer 10

Y-shaped region where DNA is unwound and new strands are synthesized.

Question 11

What enzyme synthesizes the RNA primer?

Answer 11

Primase.

Question 12

What is the function of an RNA primer?

Answer 12

Provides a short RNA segment with a free 3′-OH group for DNA polymerase to extend.

Question 13

Which enzyme adds new nucleotides during replication?

Answer 13

DNA polymerase III.

Question 14

In what direction does DNA replication occur?

Answer 14

Always in the 5′ to 3′ direction.

Question 15

What is the leading strand?

Answer 15

The DNA strand synthesized continuously toward the replication fork.

Question 16

What is the lagging strand?

Answer 16

The strand synthesized discontinuously away from the fork in short Okazaki fragments.

Question 17

What are Okazaki fragments?

Answer 17

Short segments of DNA formed on the lagging strand.

Question 18

Which enzyme removes RNA primers and replaces them with DNA?

Answer 18

DNA polymerase I.

Question 19

What enzyme seals gaps between fragments?

Answer 19

DNA ligase.

Question 20

DNA Ligase

Answer 20

Connects Sugar Phosphate Backbone

Question 21

What is the rate of DNA replication?

Answer 21

≈500 bp/sec in bacteria; ≈50 bp/sec in eukaryotes.

Question 22

How many origins of replication are found in prokaryotes and eukaryotes?

Answer 22

Prokaryotes: one origin per chromosome; eukaryotes: multiple origins per chromosome.

Question 23

What enzymes proofread DNA for errors?

Answer 23

DNA polymerases.

Question 24

What enzyme removes damaged sections during DNA repair?

Answer 24

Nuclease.

Question 25

Which enzymes fill in the gap after nuclease excision?

Answer 25

DNA polymerase and DNA ligase.

Question 26

What are mutations?

Answer 26

Permanent changes in the DNA sequence.

Question 27

What are telomeres?

Answer 27

Protein bind single standed section protects genes near end of chromosome(human repeat = TTAGGG).

Question 28

What is the function of telomerase?

Answer 28

Extends telomeres to compensate for shortening during replication.

Question 29

Which cells have active telomerase?

Answer 29

Germ cells, stem cells, and some cancer cells.

Question 30

Define nucleosome.

Answer 30

DNA wrapped around histone protein cores.

Question 31

What is chromatin?

Answer 31

Complex of DNA and proteins forming chromosomes.

Question 32

What is heterochromatin?

Answer 32

Tightly packed, transcriptionally inactive chromatin.

Question 33

What is euchromatin?

Answer 33

Loosely packed, transcriptionally active chromatin.