DNA, genes and chromosomes

What is a gene?

A base sequence of DNA that codes for the amino acid sequence of a polypeptide or for a functional RNA molecule

Define locus

A fixed position of a particular gene on a chromosome

Define allele

A different version of the same gene

What is a chromosome?

A structure consisting of a long coiled molecule of DNA and its associated proteins (histones)

How many chromosome pairs in humans?

23

What is a homologous chromosome pair?

A pair of chromosomes that are the same size, have the same genes in the same loci, but may have different alleles of those genes

What is DNA

• Deoxyribonucleic acid

• Important information carrying molecule that holds the genetic code for all living organisms

Describe Eukaryotic DNA

• Long

• Linear

• Associated with histone proteins

Describe Prokaryotic DNA

• Short

• Circular

• Not associated with histone proteins

What elements does DNA contain?

• Carbon

• Hydrogen

• Oxygen

• Nitrogen

• Phosphorous

Describe DNA in Mitochondria and Chloroplasts

• Short

• Circular

• Not associated with histone proteins