Unit 3 RNA World of Genetic Information and DNA Replication Flashcards | Quizlet

What is the RNA World Hypothesis?

The theory that RNA was the first genetic material because it can both store information and catalyze chemical reactions.

What is a ribozyme?

An RNA molecule that functions as an enzyme and can catalyze specific biochemical reactions.

In what direction is DNA always synthesized?

DNA is always synthesized in the $5' \rightarrow 3'$ direction.

What does it mean that DNA replication is semiconservative?

Each new DNA molecule consists of one original template strand and one newly synthesized strand.

What is the function of Helicase?

An enzyme that unwinds the DNA double helix at the replication fork by breaking hydrogen bonds between nitrogenous bases.

What is the role of Topoisomerase?

An enzyme that relaxes supercoiling ahead of the replication fork to prevent DNA from overwinding.

What is the function of Primase?

An enzyme that synthesizes short RNA sequences called primers, which serve as starting points for DNA synthesis.

What is the role of DNA Polymerase III?

The primary enzyme that adds DNA nucleotides to the $3'$ end of the growing DNA strand.

What is the role of DNA Polymerase I?

The enzyme that removes RNA primers and replaces them with DNA nucleotides.

What is the function of DNA Ligase?

The enzyme that joins Okazaki fragments on the lagging strand by creating phosphodiester bonds.

What are Okazaki fragments?

Short segments of DNA synthesized discontinuously on the lagging strand.

Define the leading strand.

The DNA strand that is synthesized continuously toward the replication fork.

Define the lagging strand.

The DNA strand that is synthesized discontinuously in short segments away from the replication fork.

What are the three components of a nucleotide?

A five-carbon sugar, a phosphate group, and a nitrogenous base.

Which nitrogenous base is unique to RNA?

Uracil ($U$), which replaces Thymine ($T$) found in DNA.

Which nitrogenous base is unique to DNA?

Thymine ($T$), which is not found in RNA.

What is the structural difference between the sugars in DNA and RNA?

DNA contains deoxyribose sugar, while RNA contains ribose sugar.

How many hydrogen bonds form between Adenine ($A$) and Thymine ($T$)?

There are $2$ hydrogen bonds between $A$ and $T$.

How many hydrogen bonds form between Guanine ($G$) and Cytosine ($C$)?

There are $3$ hydrogen bonds between $G$ and $C$.

What are Purines?

Double-ring nitrogenous bases, specifically Adenine ($A$) and Guanine ($G$).

What are Pyrimidines?

Single-ring nitrogenous bases, specifically Cytosine ($C$), Thymine ($T$), and Uracil ($U$).

What is the function of Single-Strand Binding Proteins (SSBPs)?

Proteins that bind to and stabilize single-stranded DNA to prevent the double helix from re-forming during replication.

What are telomeres?

Protective, non-coding repeating sequences at the ends of eukaryotic chromosomes that prevent the loss of genetic information.

What functional group is found at the $5'$ end of DNA?

A phosphate group.

What functional group is found at the $3'$ end of DNA?

A hydroxyl ($OH$) group.