8.2 DNA and chromosomes

Question 1

What is the difference between DNA in prokaryotes and eukaryotes?

Answer 1

Prokaryotes- DNA molecules are shorter, form a circle and are not associated with protein molecules. Prokaryotes therefore do’t have chromosomes. (same with DNA of mitochondria and chloroplast)

Eukaryotes- DNA molecules are longer, form a line (linear) rather than a circle and occur in association with proteins (histones) to form chromosomes.

Question 2

What holds the DNA in the chromosomes?

Answer 2

Histones

Question 3

Define homologous pair

Answer 3

a pair of chromosomes, one maternal and one paternal, that have the same gene and therefore the same features. They are not necessarily identical, however, as individual alleles of the same gene may vary (e.g gene for hair colour but one carries allele for long hair and the other carries allele for brown hair)

Question 4

Define allele

Answer 4

one of a number of alternative forms of a gene

Question 5

What creates a mutation?

Answer 5

Any changes in the base sequence of a gene producing a new allele of that gene