SCMOA2-B11 Week 1 Lecture 1: Structure of Biological Molecules & DNA Packaging

A set of question-and-answer flashcards covering key points from Week 1 Lecture 1 on biomolecular structure, central dogma, and DNA packaging.

What are the three main information-flow processes in the central dogma of molecular biology?

Replication, transcription, and translation.

In DNA’s backbone, nucleotides are linked together by what type of bond?

Phosphodiester bonds.

Which DNA strand end carries a free phosphate group?

The 5′ end.

Which DNA strand end carries a free hydroxyl group?

The 3′ end.

In what direction is a DNA (or RNA) sequence always read and written?

5′ → 3′ direction.

What type of chemical bond stabilises complementary base pairing in the DNA double helix?

Hydrogen bonds.

The antiparallel nature of DNA refers to what relationship between the two strands?

They run in opposite orientations (one 5′→3′, the other 3′→5′).

Name the two grooves present in B-DNA that are important for protein–DNA interactions.

Major groove and minor groove.

Which DNA secondary structure form is right-handed and predominant in cells?

B-DNA.

Which alternative DNA form is left-handed with a zig-zag backbone?

Z-DNA.

What tertiary structural feature compacts prokaryotic DNA?

Negative supercoiling.

In eukaryotes, what is the fundamental repeating unit of DNA packaging?

The nucleosome.

A nucleosome core contains how many histone proteins and which ones?

Eight histones – two each of H2A, H2B, H3, and H4.

Which histone protein acts as a clamp, securing DNA on the nucleosome?

Histone H1.

Neutralising the positive charges on histones would have what effect on DNA binding?

Histones would bind less tightly to DNA.

How many H3 histone proteins are present in 50 nucleosomes?

100 (two H3 molecules per nucleosome).

Define heterochromatin.

Tightly packed chromatin associated with transcriptional repression.

Define euchromatin.

Loosely packed chromatin associated with active gene expression.

What is the primary structure of RNA?

A linear sequence of ribonucleotides joined by phosphodiester bonds.

Give two functional examples of RNA secondary structures.

tRNA (amino-acid carrier) and ribozymes (catalytic RNAs).

RNA quaternary structure involves interaction with proteins to form which major complexes?

Ribonucleoprotein complexes such as ribosomes and spliceosomes.

What defines the primary structure of a protein?

Its linear amino-acid sequence linked by peptide bonds.

Which secondary structure element is a right-handed coil stabilised by backbone hydrogen bonds?

The α-helix.

β-sheets can be arranged in which two orientations?

Parallel and antiparallel.

Name three major interactions that stabilise protein tertiary structure.

Hydrogen bonds, hydrophobic interactions, and disulfide bridges.

Give an example of a protein that exhibits quaternary structure and state its subunit number.

Haemoglobin; four subunits.

Explain the concept "form fits function" in biomolecules.

The specific three-dimensional structure of a molecule determines its biological activity; alterations at any structural level can impair function.

List three reasons DNA packaging is essential.

Compaction of the genome, maintenance of DNA integrity, and regulation of gene expression.

Approximately how many base pairs of DNA wrap around a histone octamer in a nucleosome?

About 146 base pairs.

What is supercoiling?

The overwinding or underwinding of DNA to help it fit into confined cellular spaces.

Which textbook is prescribed for this module?

“Genetics: A Conceptual Approach” (7th ed.) by Pierce.

What percentage of the course mark is allocated to practicals in Weeks 1–7?

20 %.

What is the required sub-minimum on the summative assessment to pass the module?

40 %.

What are the monomer building blocks for replication, transcription, and translation respectively?

Deoxyribonucleotides, ribonucleotides, and amino acids.

Name the main catalyst for each central dogma process: replication, transcription, translation.

Replication – DNA polymerase; Transcription – RNA polymerase; Translation – the ribosome (rRNA + proteins).

How could a mutation in the histone H3 gene affect many genes at once?

By altering nucleosome stability genome-wide, it changes chromatin compaction and thus gene expression across numerous loci.

Why might a histone H3 mutation disrupt normal cell division?

Abnormal chromatin structure can impair chromosome condensation and segregation, hindering proper cell cycle progression.