2.7.2 Genetic variation

Question 1

Why does sexual reproduction give variation?

Answer 1

Sexual reproduction gives rise to variation
because, when gametes fuse, one of each
pair of alleles comes from each parent.

Question 2

How many pairs of chromosomes are there?

Answer 2

In human body cells, one of the 23 pairs of

chromosomes.

Question 3

What are the male chromosomes and female chromosomes?

Answer 3

In females the sex chromosomes are the
same (XX); in males the sex chromosomes are
different (XY).

Question 4

What are alleles?

Answer 4

Some characteristics are controlled by a single
gene. Each gene may have different forms
called alleles.

Question 5

What is a dominant allele?

Answer 5

An allele that controls the development of a
characteristic when it is present on only one
of the chromosomes is a dominant allele

Question 6

What is DNA?

Answer 6

Chromosomes are made up of large molecules
of DNA (deoxyribo nucleic acid) which has a
double helix structure.

Question 7

What is a gene?

Answer 7

A gene is a small section of DNA.

Question 8

What does each gene do?

Answer 8

Each gene codes for a particular combination

of amino acids which make a specific protein.

Question 9

What is the process to indentify individuals?

Answer 9

Each person (apart from identical twins) has
unique DNA. This can be used to identify
individuals in a process known as DNA
fingerprinting.