Chromosomes

Question 1

What is a chromosome?

Answer 1

DNA molecule that is coiled around proteins called histones to form a super coiled helix.

Question 2

What is a gene?

Answer 2

1. A base sequence of DNA that codes for:
   - the amino acid sequence of a polypeptide
   - a functional RNA molecule
2. Located along chromosomes

Question 3

What is a genome and what is a proteome?

Answer 3

Genome = a complete set of genes in a cell

Proteome = the full range of proteins that a cell is able to produce

Question 4

What are alleles and what is a locus?

Answer 4

Alleles = different forms of the same gene

Locus = position of a gene on a chromosome

Question 5

What are homologous chromosomes?

Answer 5

A pair of chromosomes that are identical:

1. Are the same length
2. Have the same genes (but different alleles)
3. Genes have the same loci
4. Have centromeres in the same position

Question 6

Describe the difference between introns, exons and multiple base repeats.

Answer 6

Introns = do not code for amino acids

Exons = code for a sequence of amino acids

Multiple base repeats = non coding base repeat sequences found between genes

Question 7

When do chromosomes appear as X shapes?

Answer 7

• chromosomes replicate during cell division where a genetically identical copy is made
• the replicated chromosomes are joined together by the centromere and are called sister chromatids

Question 8

What is the difference between diploid and haploid cells?

Answer 8

Diploid cell = contains pairs of homologous chromosomes eg. A fertilised egg cell

Haploid cell = contains half of the diploid number of chromosomes (one from each homologous pair) eg. Gamete cells