4.1 DNA, Genes + Chromosomes

What is a Chromosome?

• Long, linear DNA + its associated with histone proteins

• Located in the Nucleus of eukaryotes

What is a Gene?

A sequence of DNA (nucleotide) bases that codes for:

• The amino acid sequence of a polypeptide

• Or a functional RNA (eg. rRNA or tRNA

What is a Locus?

Fixed position a gene occupies on a particular DNA molecule

Triplet code

A sequence of 3 DNA bases, called a triplet, codes for a specific amino acid

Universal

The same base triplets code for the same amino acids in all organsims

Non-overlapping

Each base is part if only 1 triplet so each triplet is read as a discrete unit

Degenerate

An amino acid can be coded for by more than 1 base triplet

Non-coding base sequence

DNA that doesn’t code for amino acid sequences/ polypeptides

List 2 places where non-coding base sequence are found

1. Between genes - e.g. non-coding multiple repeats

2. Within genes - introns

Intron

Base sequence of a gene that doesn’t code for amino acids, in Eukaryotes

Exon

Base sequence of a gene coding for amino acid sequences (in a polypeptide)