DNA, genes and chromosomes Flashcards – AQA A-Level Biology - (7402)

What properties do prokaryotic DNA and mitochondrial and chloroplast DNA share?

They are short and circular, and are not associated with proteins.

What are the length and shape of DNA molecules in a eukaryotic nucleus?

They are very long and linear.

What forms a eukaryotic chromosome?

A DNA molecule and its associated proteins, called histones.

Which two organelles contain DNA?

Mitochondria and chloroplasts.

What is a gene?

A sequence of DNA bases that codes for either the amino acid sequence of a polypeptide or a functional RNA.

What is the role of ribosomal RNA?

It forms part of ribosomes.

What is the role of transfer RNA in polypeptide synthesis?

It carries amino acids.

What is a gene's locus?

Its fixed position on a particular DNA molecule, rather than its sequence or product.

What does the genetic code relate?

DNA base sequences to the amino acid sequences of polypeptides.

What is a DNA triplet, and what does it code for?

A sequence of three DNA bases that codes for a specific amino acid.

What does it mean that the genetic code is non-overlapping?

Successive triplets are read as separate groups, with no base shared between adjacent triplets.

What does it mean that the genetic code is degenerate?

More than one triplet can code for the same amino acid.

What does it mean that the genetic code is universal?

The same triplets specify the same amino acids in almost all organisms.

How much DNA in a eukaryotic nucleus does not code for polypeptides?

Much of it does not code for polypeptides.

What kind of non-coding DNA occurs between eukaryotic genes?

Multiple repeats of base sequences.

What are exons in a eukaryotic protein-coding gene?

Sequences containing the information that codes for amino acid sequences.

What are introns in a eukaryotic protein-coding gene?

Non-coding sequences that separate exons.