6.2.1 Genetic variation

Question 1

Genotype

Answer 1

Genetic makeup of an organism

Question 2

Phenotype

Answer 2

Visible characteristic of an organism

Question 3

Allele

Answer 3

A version of a gene

Question 4

Heterozygous

Answer 4

Not true breeding; having different alleles at a particular gene locus on a pair of homologous chromosomes

Question 5

Homozygous

Answer 5

True breeding: having identical alleles at a particular gene locus on a pair of homologous chromosomes

Question 6

Monogenic

Answer 6

Determined by a single gene

Question 7

Dihybrid

Answer 7

Involving 2 gene loci

Question 8

Codominance

Answer 8

Where both alleles present in the genotype of a heterozygous individual contribute to the individuals phenotype

Question 9

Multiple alleles

Answer 9

Characteristic for which there are 3 or more alleles in the population’s gene pool

Question 10

Sex linked

Answer 10

Gene present on (one of) the sex chromosomes

Question 11

Codominant

Answer 11

Where both alleles present in the genotype of a heterozygous contribute to the individuals phenotype

Question 12

Autosomal linkage

Answer 12

Gene loci present on the same autosome (non sex chromosome) that are often inherited together

Question 13

Epistasis

Answer 13

Interaction of non linked gene loci where one masks the expression of the other

Question 14

Chi-squared test

Answer 14

Statistical test designed to find out if the difference between observed and expected data is significant or due to chance

Question 15

Continous variation

Answer 15

Variation that produces phenotypic variation where the quantitative traits vary by very small amounts between one group and the next

Question 16

Discontinuous variation

Answer 16

Genetic variation producing discrete phenotypes - 2 or more non overlapping categories

Question 17

Directional selection

Answer 17

A type of natural selection that occurs when an environmental change favours a new phenotype so results in a change in the population mean

Question 18

Founder effect

Answer 18

When a small sample of an original population establishes in a new area; its gene pool is not as diverse as the of the parent population

Question 19

Genetic bottleneck

Answer 19

Sharp reduction in the size of a population due to environmental catastrophes such as earthquakes, floods, disease or human activities such as habitat destruction, overhunting or genocide, which reduces genetic diversity. As population expand, becomes less genetically diverse than before

Question 20

Stabilising selection

Answer 20

Natural selection leading to constancy within a population. Intermediate phenotypes are favoured and extreme phenotypes selected against. Alleles for extreme phenotypes may be removed from the population. Stabilising selection reduces genetic variation within the population

Question 21

Population

Answer 21

Members of a species, living in the same place and at the same time, that can interbreed

Question 22

Allopatric speciation

Answer 22

Formation of 2 different species from 1 original species, due to geographical isolation

Question 23

Speciation

Answer 23

The splitting of a genetically similar population into 2 or more populations that undergo genetic differentiation and eventually reproductive isolation, leading to the evolution of 2 or more new species

Question 24

Sympatric speciation

Answer 24

Formation of 2 different species from 1 original species, due to reproductive isolation, while the population inhabit the same geographical location

Question 25

Artificial selection

Answer 25

Selective breeding of organisms; involves humans choosing the desired phenotype and interbreeding these phenotypes individually, therefore selecting the genotypes that contribute to the gene pool of the next generation of these organisms

Question 26

Hybrid vigour

Answer 26

Increased heterozygosity giving increased vigour of fertility, growth and survival

Question 27

Polyploidy

Answer 27

Increase in chromosome number

Either of individual chromosomes or complete sets