Microbial Genetics Flashcards
What are the 2 types of nucleic acids?
- Deoxyribonucleic acid (DNA)
- Ribonucleic acid (RNA)
What is the monomeric subunit of a nucleic acid?
A nucleotide
What are the 3 parts of a nucleotide?
- Phosphate
- Pentose sugar (DNA / RNA)
- Nitrogenous base
What are the sugars found in DNA vs. RNA?
- DNA - deoxyribose
- RNA - ribose
What are the different nitrogenous bases found in DNA vs. RNA?
- DNA - A, G, C, and T
- RNA - A, G, C, and U
How is one nucleotide connected to the next nucleotide in a linear chain of nucleotides?
Phosphodiester bond
What is the ‘sugar-phosphate’ backbone?
A linear spine composed of alternating sugars and phosphates
The sugar-phosphate backbone is a result of ______
Polymerization
What is a phosphodiester bond?
Covalent bond connecting one nucleotide to the next in a linear chain
What type of bonding holds the 2 strands of double-stranded DNA together?
Hydrogen bonding
Describe the 5’ end of a linear strand of DNA
Terminates with a phosphate group bound to the 5’ carbon of deoxyribose
Describe the 3’ end of a linear strand of DNA
Terminates with a hydroxyl group bound to the 3’ carbon of deoxyribose
What does the abbreviation “bp” stand for?
Base pairs
Describe the base-pairing rules for DNA (2)
- Guanine bonds with cytosine (G-C)
- Adenine bonds with thymine (A-T)
Describe the base-pairing rules for RNA
Adenine bonds with uracil (A-U)
What term is used to describe 2 DNA strands that are oriented in opposite directions to each other?
Antiparallel
What is a nucleoid?
Region in the cytoplasm containing circular molecules of DNA (chromosomes)
Most bacterial genomes consist of ______
One or two chromosomes
Plasmids are small molecules of ______
Extrachromosomal DNA
How do plasmids replicate with respect to the cell chromosome?
Replicate independently of the chromosome
What do plasmids contain?
Genes that regulate nonessential life functions
How does DNA replication occur? (2)
- A cell separates the two original strands
- Uses each strand as a template for the synthesis of a new complementary strand
Biologists claim that DNA replication is ______
Semi-conservative
Describe the principle of so-called ‘semiconservative’ DNA replication
Each daughter DNA molecule is composed of one original strand and one new strand
Why is DNA replication described as an anabolic polymerization process? (2)
- Allows a cell to make copies of its genome
- Polymerization processes require monomers (building blocks) and energy
What are molecules with 3 phosphate groups linked together by 2 high-energy bonds called?
Triphosphate deoxyribonucleotides (dNTPs)
What are the 2 functions of triphosphate deoxyribonucleotides (dNTPs) during DNA replication?
- Provide energy for polymerization reactions
- Link phosphate molecules together
What is an ‘origin’ in the context of DNA replication?
Specific sequence of nucleotides where DNA replication begins
What role does DNA helicase play in replication?
Unzips the DNA molecule by breaking the hydrogen bonds between the complementary bases
When is a replication bubble formed?
When helicase separates two DNA strands
What is a replication fork?
A prong-like structure formed within the replication bubble
After helicase untwists and separates the DNA strands, ______ binds to each strand
DNA polymerase
How does DNA polymerase catalyze the sysnthesis of DNA?
The addition of new nucleotides ONLY to the hydroxyl group at the 3’ end of a nucleic acid
How, and in what orientation or direction, do all DNA polymerases ‘read’ and ‘write’ (synthesize) DNA?
5’ to 3’ direction - added one at a time
Describe leading strand synthesis
Synthesized continuously (5’ to 3’) as a single long chain of nucleotides
Describe lagging strand synthesis
Synthesized in short, discontinuous segments (5’ to 3’) that are later joined together
What are the functions of primase in replication? (2)
- Synthesizes a short RNA molecule that is complementary to the template DNA strand
- Provides the 3’ hydroxyl group required by DNA polymerase III
How is primase activity different between leading and lagging strand synthesis?
The lagging strand requires more primase than the leading strand
Describe the movement of DNA polymerase III with respect to the replication fork during leading and lagging strand synthesis
The enzyme moves away from the replication fork as it synthesizes the lagging strand
What are Okazaki fragments and where are they found?
Discontinued segments from the synthesis of the lagging strand
______ joins Okazaki fragments together
DNA ligase
