Biology Lecture 1: DNA and RNA Structure

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Questions and Answers

What is the primary function of deoxyribonucleic acid (DNA) in cells?

Synthesizing proteins directly

Facilitating cellular respiration

Serving as the primary energy source for cellular functions

Transmitting genetic material from cell to cell (correct)

Which component of a nucleotide is responsible for varying the identity of the nucleotide?

Nitrogenous base (correct)

Phosphate group

Covalent bond

Five-carbon sugar

In the structure of DNA, the two strands are held together primarily by which type of bond?

Ionic bonds

Covalent bonds

Van der Waals forces

Hydrogen bonds (correct)

What type of RNA is primarily involved in protein coding?

Messenger RNA Signup and view all the answers

What role do histone proteins play in the structure of chromatin?

Packaging DNA into a compact structure Signup and view all the answers

Which of the following best describes a chromosome?

A compact structure of DNA and proteins Signup and view all the answers

What is a key characteristic of the nucleotide structure of RNA compared to DNA?

RNA has ribose sugar, while DNA has deoxyribose sugar Signup and view all the answers

The order of nucleotides in a DNA strand determines what?

The genetic information and instructions Signup and view all the answers

Which modification of histone tails is associated with the loosening of chromatin structure?

Acetylation Signup and view all the answers

What primarily determines whether chromatin is active or inactive?

Post-transcriptional modifications of histone tails Signup and view all the answers

What type of chromatin is typically associated with condensed and less accessible DNA?

Heterochromatin Signup and view all the answers

Which of the following bonds are responsible for holding the two strands of DNA together?

Hydrogen bonds Signup and view all the answers

What type of bond joins nucleotides in a single strand of DNA?

Phosphodiester bonds Signup and view all the answers

Which modification can lead to a more condensed chromatin structure?

Methylation Signup and view all the answers

Which structural characteristic defines DNA?

Antiparallel double-stranded helix Signup and view all the answers

What is the role of histone protein tails in chromatin regulation?

To undergo modifications that regulate chromatin structure Signup and view all the answers

What is the function of histone proteins in DNA packaging?

To bind and coil DNA into nucleosomes Signup and view all the answers

How many histone proteins make up the core of a nucleosome?

8 Signup and view all the answers

In which direction can nucleic acids be synthesized?

5’ to 3’ direction Signup and view all the answers

What role does the N terminal tail of core histones play in chromatin structure?

They can be modified to influence chromatin packing Signup and view all the answers

What best describes the structure of DNA?

An antiparallel double helix Signup and view all the answers

What type of bond links nucleotides together in a DNA strand?

3’, 5’ phosphodiester bonds Signup and view all the answers

What term describes the packaging of DNA into structures that allow for gene expression?

Chromatin Signup and view all the answers

Which of the following correctly describes the composition of a chromosome?

A long piece of DNA and associated proteins Signup and view all the answers

What process allows for transient carriers of molecular instructions from DNA?

RNA synthesis Signup and view all the answers

Which of the following statements about the ends of DNA strands is true?

The 3’ end can attach new nucleotides during synthesis Signup and view all the answers

Study Notes

Structure and Function of DNA and RNA

DNA (Deoxyribonucleic acid) serves as the genetic material, inherited during cell division and from generation to generation through reproductive cells.
Information within DNA is stored in the nucleus of every dividing cell.
RNA (Ribonucleic acid) converts genetic instructions from DNA; it functions primarily in protein synthesis and gene regulation.

Nucleotide Composition

DNA and RNA are polymers made up of nucleotides, which consist of:
- A five-carbon sugar
- A phosphate group
- One of four nitrogenous bases:
  - DNA: Adenine (A), Guanine (G), Cytosine (C), Thymine (T)
  - RNA: Adenine (A), Guanine (G), Cytosine (C), Uracil (U) instead of Thymine.

DNA Structure

DNA has two long chains of nucleotides that form a double helix, resembling a spiral staircase.
Each nucleotide is connected to the next via strong covalent bonds, forming a linear backbone of alternating sugar and phosphate.
Base pairing is specific: A pairs with T, and C pairs with G; this non-random base pairing is crucial for replication and gene expression.
DNA strands are antiparallel and have a chemical polarity, written from 5’ to 3’ direction.

Function of DNA

Transmits genetic information and requires precise copying to ensure fidelity.
Stores instructions via the sequence of nucleotides, directly influencing gene expression.

RNA Function and Types

Acts as a transient carrier of information from DNA to the sites of protein synthesis.
Includes several forms of RNA:
- Protein-coding RNA
- Non-coding RNA
Essential in regulating gene expression through mechanisms like splicing, editing, and translation.

Chromosome Structure and DNA Packaging

Each human cell contains approximately 2 meters of DNA, which is highly compacted into structures called chromosomes.
Chromosomes consist of DNA wrapped around histone proteins forming nucleosomes, which resemble a “string of beads.”
Nucleosomes are combined into further organized structures through the binding of H1 proteins, creating 30nm chromatin fibers.

Nucleosome and Chromatin Structure

A nucleosome is the basic unit comprised of eight histone proteins around which 147 base pairs of DNA are coiled.
Modifications to histone tails (e.g., acetylation and methylation) can affect chromatin structure, influencing whether chromatin is active (euchromatin) or inactive (heterochromatin).
The state of chromatin is crucial in regulating gene expression and is influenced by post-transcriptional modifications.

Summary of Differences between DNA and RNA

DNA is double-stranded, while RNA is single-stranded.
The sugar in DNA is deoxyribose; in RNA, it is ribose.
DNA contains thymine, while RNA contains uracil.
DNA primarily serves the role of information storage, while RNA plays a more active role in protein synthesis and regulation.

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Description

This quiz covers the fundamental concepts of DNA and RNA, including their chemical structures and functions in genetics. You will also learn about the processes of DNA replication and the significance of accurate genetic information storage. Test your knowledge on these essential biological macromolecules!