Genes & Transcription

Questions and Answers

What type of bond holds nucleotides together within an individual DNA strand?

Hydrogen bond

Peptide bond

Glycosidic bond

Phosphodiester bond (correct)

What is the characteristic of the DNA strands in the double helix structure?

They run in the same direction

They are perpendicular to each other

They run in opposite directions (correct)

They are parallel to each other

How many nucleotide pairs of DNA are present in chromosome 22?

48 million (correct)

4.8 million

4.8 billion

480 million

What is the diameter of the nucleus that holds all the chromosomes?

6 μm Signup and view all the answers

What is the length of chromosome 22 if it were laid out in one long perfect double helix?

1.5 cm Signup and view all the answers

Which of the following base pairs is correct?

Guanine pairs with cytosine Signup and view all the answers

What is the main function of histone modification in chromatin structure?

To influence the accessibility of DNA for gene expression Signup and view all the answers

During DNA replication, what is the property that allows the double-stranded DNA to be 'pulled apart'?

Weak bonds between bases between strands Signup and view all the answers

What is the mechanism by which DNA replication occurs?

Semi-conservative Signup and view all the answers

What is the role of base complementarity in DNA replication?

To recognise individual nucleotides Signup and view all the answers

What is the significance of histone modification in gene expression?

It influences DNA accessibility for gene expression Signup and view all the answers

What is the purpose of DNA replication?

To ensure the accurate copying of genetic information Signup and view all the answers

What is the term for the process by which DNA is wrapped around histone proteins?

Nucleosome formation Signup and view all the answers

What is the result of histone modification on chromatin structure?

Relaxation of chromatin Signup and view all the answers

What is the basic structural unit of a chromosome, composed of DNA wrapped around a protein core?

Nucleosome Signup and view all the answers

Which of the following is NOT a type of histone protein found in a nucleosome?

Histone H1 Signup and view all the answers

How does histone modification contribute to the regulation of gene expression?

By changing the accessibility of DNA to transcription factors Signup and view all the answers

What is the approximate ratio of DNA to protein in a chromosome?

1:2 Signup and view all the answers

What is the role of non-histone proteins in chromosome structure?

They help regulate gene expression and chromosome organization Signup and view all the answers

What is the primary function of the nucleosome?

To compact and organize DNA into a more manageable form Signup and view all the answers

Study Notes

Protein-DNA Interactions

Specialised proteins bind to and fold DNA, creating several levels of organisation, such as coils and loops.
Chromatin refers to a mixture of DNA and proteins that form chromosomes, with each contributing equally to the mass of the chromosome.

Histone Proteins and Nucleosome Structure

Histone proteins are responsible for the nucleosome, the basic level of chromosome packaging, which has a "bead-like" structure.
Each nucleosome consists of two of each of the following histones: H2A, H2B, H3, and H4, forming an octamer.
Double-stranded DNA winds around the octamer.

Base Pairing and DNA Structure

Guanine pairs with cytosine, and adenine pairs with thymine.
Nucleotides within an individual strand are bonded by strong covalent bonds (phosphodiester bonds).
Nucleotides between individual strands are held together by weaker hydrogen bonds.
The famous double helix structure is formed by the two strands running in opposite directions (anti-parallel).
DNA is highly condensed in chromosomes, with about 48 million nucleotide pairs in chromosome 22, which would stretch out to about 1.5 cm in length if laid out in a perfect double helix.

Histone Modification and DNA Accessibility

Histones can be modified through post-translational mechanisms (e.g. acetylation, phosphorylation) to alter the accessibility of DNA, influencing gene expression and protein production.

DNA Replication and Genetic Inheritance

All cells replicate their DNA through templated polymerisation, ensuring the accurate copying of genetic information.
DNA replication relies on base complementarity (e.g. G-C and A-T) and occurs in a semi-conservative manner, with new strands synthesised against a template (old strand).
The separation of the double-stranded DNA allows each individual nucleotide on each individual strand to be recognised by a free (unpolymerised) nucleotide.

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Description

Learn about the proteins that bind to and fold DNA, creating different levels of organization such as coils and loops, and the role of histone proteins in chromosome packaging.