Variation and Inheritance

Question 1

Name the two types of variation that exists amongst members of a species

Answer 1

Discrete variation

Continuous variation

Question 2

Discrete variation traits

Answer 2

Blood groups 
Earlobes attachment
Tongue rolling
Fingerprint shape
- a characteristic shows discrete variation if it can be used to divide the species into two or more distinct groups

Question 3

Describe continuous variation traits

Answer 3

Weight
Birth weight
Skin colour
- a characteristic shows continuous variation if members of the species vary in a smooth continuous manner over a range of values- there are no distinct groups

Question 4

Define the term polygenic inheritance

Answer 4

Continuous variation traits are controlled by many genes this is shown by polygenic inheritance

Question 5

Number of genes that control discrete variation

Answer 5

Single gene

Question 6

Define phenotype

Answer 6

The physical appearance of an organism

Question 7

Define genotype

Answer 7

The genes (alleles) that an organism possesses. Usually written as letters e.g. BB

Question 8

Define alleles

Answer 8

Different forms of the same gene

Question 9

Define dominant

Answer 9

An allele that always expresses itself whether it is partnered by a recessive allele or by another like itself

Question 10

Define recessive

Answer 10

An allele that will only be expressed in the phenotype if it is paired with another recessive allele

Question 11

Define homozygous

Answer 11

This describes a genotype in which the two alleles for the characteristics are identical e.g. BB or bb

Question 12

Define heterozygous

Answer 12

This describes a genotype in which two alleles for a particular characteristics are different e.g. Bb

Question 13

Define true breeding

Answer 13

An organism possessing two identical alleles for a particular trait i.e. They are homozygous for a trait