Microbial Genetics

Question 1

What are the 2 types of nucleic acids?

Answer 1

• Deoxyribonucleic acid (DNA)
• Ribonucleic acid (RNA)

Question 2

What is the monomeric subunit of a nucleic acid?

Answer 2

A nucleotide

Question 3

What are the 3 parts of a nucleotide?

Answer 3

• Phosphate
• Pentose sugar (DNA / RNA)
• Nitrogenous base

Question 4

What are the sugars found in DNA vs. RNA?

Answer 4

• DNA - deoxyribose
• RNA - ribose

Question 5

What are the different nitrogenous bases found in DNA vs. RNA?

Answer 5

• DNA - A, G, C, and T
• RNA - A, G, C, and U

Question 6

How is one nucleotide connected to the next nucleotide in a linear chain of nucleotides?

Answer 6

Phosphodiester bond

Question 7

What is the ‘sugar-phosphate’ backbone?

Answer 7

A linear spine composed of alternating sugars and phosphates

Question 8

The sugar-phosphate backbone is a result of ______

Answer 8

Polymerization

Question 9

What is a phosphodiester bond?

Answer 9

Covalent bond connecting one nucleotide to the next in a linear chain

Question 10

What type of bonding holds the 2 strands of double-stranded DNA together?

Answer 10

Hydrogen bonding

Question 11

Describe the 5’ end of a linear strand of DNA

Answer 11

Terminates with a phosphate group bound to the 5’ carbon of deoxyribose

Question 12

Describe the 3’ end of a linear strand of DNA

Answer 12

Terminates with a hydroxyl group bound to the 3’ carbon of deoxyribose

Question 13

What does the abbreviation “bp” stand for?

Answer 13

Base pairs

Question 14

Describe the base-pairing rules for DNA (2)

Answer 14

• Guanine bonds with cytosine (G-C)
• Adenine bonds with thymine (A-T)

Question 15

Describe the base-pairing rules for RNA

Answer 15

Adenine bonds with uracil (A-U)

Question 16

What term is used to describe 2 DNA strands that are oriented in opposite directions to each other?

Answer 16

Antiparallel

Question 17

What is a nucleoid?

Answer 17

Region in the cytoplasm containing circular molecules of DNA (chromosomes)

Question 18

Most bacterial genomes consist of ______

Answer 18

One or two chromosomes

Question 19

Plasmids are small molecules of ______

Answer 19

Extrachromosomal DNA

Question 20

How do plasmids replicate with respect to the cell chromosome?

Answer 20

Replicate independently of the chromosome

Question 21

What do plasmids contain?

Answer 21

Genes that regulate nonessential life functions

Question 22

How does DNA replication occur? (2)

Answer 22

• A cell separates the two original strands
• Uses each strand as a template for the synthesis of a new complementary strand

Question 23

Biologists claim that DNA replication is ______

Answer 23

Semi-conservative

Question 24

Describe the principle of so-called ‘semiconservative’ DNA replication

Answer 24

Each daughter DNA molecule is composed of one original strand and one new strand

Question 25

Why is DNA replication described as an anabolic polymerization process? (2)

Answer 25

- Allows a cell to make copies of its genome - Polymerization processes require monomers (building blocks) and energy

Question 26

What are molecules with 3 phosphate groups linked together by 2 high-energy bonds called?

Answer 26

Triphosphate deoxyribonucleotides (dNTPs)

Question 27

What are the 2 functions of triphosphate deoxyribonucleotides (dNTPs) during DNA replication?

Answer 27

- Provide energy for polymerization reactions - Link phosphate molecules together

Question 28

What is an ‘origin’ in the context of DNA replication?

Answer 28

Specific sequence of nucleotides where DNA replication begins

Question 29

What role does DNA helicase play in replication?

Answer 29

Unzips the DNA molecule by breaking the hydrogen bonds between the complementary bases

Question 30

When is a replication bubble formed?

Answer 30

When helicase separates two DNA strands

Question 31

What is a replication fork?

Answer 31

A prong-like structure formed within the replication bubble

Question 32

After helicase untwists and separates the DNA strands, ______ binds to each strand

Answer 32

DNA polymerase

Question 33

How does DNA polymerase catalyze the sysnthesis of DNA?

Answer 33

The addition of new nucleotides ONLY to the hydroxyl group at the 3’ end of a nucleic acid

Question 34

How, and in what orientation or direction, do all DNA polymerases ‘read’ and ‘write’ (synthesize) DNA?

Answer 34

5’ to 3’ direction - added one at a time

Question 35

Describe leading strand synthesis

Answer 35

Synthesized continuously (5’ to 3’) as a single long chain of nucleotides

Question 36

Describe lagging strand synthesis

Answer 36

Synthesized in short, discontinuous segments (5’ to 3’) that are later joined together

Question 37

What are the functions of primase in replication? (2)

Answer 37

- Synthesizes a short RNA molecule that is complementary to the template DNA strand - Provides the 3’ hydroxyl group required by DNA polymerase III

Question 38

How is primase activity different between leading and lagging strand synthesis?

Answer 38

The lagging strand requires more primase than the leading strand

Question 39

Describe the movement of DNA polymerase III with respect to the replication fork during leading and lagging strand synthesis

Answer 39

The enzyme moves away from the replication fork as it synthesizes the lagging strand

Question 40

What are Okazaki fragments and where are they found?

Answer 40

Discontinued segments from the synthesis of the lagging strand

Question 41

______ joins Okazaki fragments together

Answer 41

DNA ligase