DNA

Where does the term nucleic acid derive from?

Nucleic derives from the fact that scientists first observed this in the nucleus of cells

Acid derives from the fact that it has some acidic properties

What is the purpose of DNA and RNA?

DNA contains genetic information which is all the instructions an organism needs to grow and develop from a fertilised egg to fully grown adult

RNA transfers genetic information from the DNA to the ribosomes as the ribosomes are the bodies protein factories - they read RNA to make polypeptides (proteins) in translation

How can the DNA remain compact with histones?

Histones arrange themselves in octamers and they contain core proteins; two of H2A, two of H2B, two of H3 and two of H4 and these contain amino acids - abundantly arginine and lysine - which are positively charged and the DNA itself contains a phosphate backbone which is negatively charged and both of these positive and negative charges help it remain compact.

Explain the terms chromatin, chromosome and chromatid

These terms are used to describe the different aspects and levels of DNA organisation so chromatin, is material consisting of DNA, histone proteins and any other associated proteins.

• Euchromatin - is loosely packed and is generally more accessible to transcription

• Heterochromatin - is tightly packed and is less accessible to transcription

Chromosome is tightly condensed, super - coiled state of DNA that appears when a cell is getting ready to divide (organised unit of chromosome)

Chromatid is part of a replicated chromosome, so one DNA containing copy of a chromosome

What is the RNA world hypothesis?

The theory that RNA came before DNA and proteins because it can both store genetc information and act as an enzymatic catalyst for example, ribosomes read the RNA and form polypeptides (proteins) in the process of translation

What is semi - conservative replication? why is is given that name?

DNA replicates itself before cell division so that each cell has a full set of DNA and it is called ‘semi - conservative’ because the cell contains half of its DNA from the original DNA molecule. This ensures genetic continuity between cells!

What is DNA primase?

A specialised enzyme that synthesises short strand RNA or DNA segments called primers on a single - stranded DNA template during DNA replication