Topic 21 - Inheritance Definitions

Question 1

Gene

Answer 1

A section of DNA coding for the formation of a protein controlling a specific characteristic of the organism.

Question 2

Allele

Answer 2

An alternative form of a gene.

Question 3

Chromosome

Answer 3

A thread of DNA, made up of genes

Question 4

Haploid nucleus

Answer 4

A nucleus containing a single set of unpaired chromosomes (I.e. in gametes)

Question 5

Diploid nucleus

Answer 5

A nucleus containing pairs of chromosomes, I.e in somatic (body) cells.

Question 6

Genotype

Answer 6

The genetic make-up of an organism, e.g. Bb, where B and B are alleles of a gene

Question 7

Phenotype

Answer 7

The characteristics visible in an organism, controlled by the genotype (e.g. blue eyes or brown eyes)

Question 8

Homozygous

Answer 8

Having a pair of identical alleles controlling the same characteristic, e.g. BB, where B = brown eyes

Question 9

Heterozygous

Answer 9

Having a pair of dissimilar alleles for a characteristic, e.g. Bb

Question 10

Dominant

Answer 10

A gene that always shows in the phenotype of an organism (e.g. B)

Question 11

Recessive

Answer 11

A gene that only shows in the phenotype of an organism when the organism is homozygous (bb)