Chromosomes, Genes and DNA

Question 1

Examples of mutagens:

Answer 1

• Ionising radiation
• Chemicals including mustard gas and nitrous oxide
• Chemicals in cigarette smoke
• The tar from cigarettes

Question 2

Define homologous pairs

Answer 2

Pair of chromosomes that carry genes controlling the same features at the same positions on each chromosome.

The members of each homologous pair are the same size and shape

Question 3

Define haploid cells

Answer 3

Cells containing half the normal number of chromosomes.

Haploid cells contain one chromosome from each homologous chromosome

Question 4

Define genome

Answer 4

The entire DNA of an organism

Question 5

What are structural genes?

Answer 5

Genes coding for a protein

Question 6

Where does gene regulation occur?

Answer 6

In regions of the DNA called operons

Question 7

Explain how gene regulation takes place?

Answer 7

The structural genes are headed by a non-coding length of DNA called operator along with a promoter

The promoter starts transcription by binding to RNA polymerase

Regulatory genes code for a protein called a repressor

The repressor can bind to the operator which prevents RNA polymerase from binding to the promoter and therefore stopping transcription