Genetic Terms

Question 1

Define gene.

Answer 1

A sequence of DNA that occupies a specific locus on a chromosome and codes for a polypeptide, or a sequence of DNA coding for a characteristic.

Question 2

Define allele.

Answer 2

Alleles are variant nucleotide sequences for a particular gene at a given locus coding for an altered phenotype. A single gene may have one or many alleles, and they always occupy the same locus.

Question 3

Define homozygous.

Answer 3

Both chromosomes in a homologous pair have the same allele. Homozygous dominant = dominant allele, homozygous recessive = recessive allele

Question 4

Define heterozygous.

Answer 4

The alleles on the chromosomes of a homologous pair are different. The individual has a dominant and recessive allele and is ‘carrying’ the recessive characteristic.

Question 5

Define dominant allele

Answer 5

If it is present, the characteristic shows.

Question 6

Define recessive allele.

Answer 6

The individual only shows this characteristic of both chromosomes in a homologous pair have the recessive allele.

Question 7

Define genotype

Answer 7

The alleles possessed by an organism

Question 8

Define phenotype

Answer 8

The physical characteristics of an organism, controlled by the genotype.

Question 9

Define F1.

Answer 9

The first filial generation (offspring of the parents of the cross)

Question 10

Define F2

Answer 10

The second filial generation. It is the offspring of a self fertilised F1 plant or a cross between members of the F1 generation, ie the grandchildren of the original parents