Genetic Variation Glossary

Question 1

Allele

Answer 1

Different forms of a gene due to slightly different order of bases eg. brown eyes and blue eyes

Question 2

Allele frequency

Answer 2

Is a measure of the relative frequency of an allele on a genetic locus in a population

Question 3

Asexual reproduction

Answer 3

Reproduction involving only one parent. Doesn’t produce genetic variation

Question 4

Chiasma

Answer 4

Point of contact, the physical link, between two (non-sister) chromatids belonging to homologous chromosomes during crossing over

Question 5

Co-dominance

Answer 5

Heterozygous individuals have a phenotype that shows the phenotype of both parents

Question 6

Complete dominance

Answer 6

A form of dominance in heterozygous condition wherein the allele that is regarded as dominant completely masks the effect of the allele that is recessive

Question 7

Crossing over

Answer 7

Occurs during meiosis, when the homologous chromosomes line up at the equator, sometimes they tangle, snap and exchange genetic information.

Question 8

Diploid

Answer 8

A cell or an organism consisting of two sets of chromosomes: usually, one set from the mother and another set from the father.

Question 9

Evolution

Answer 9

Is the change in the characteristics of a species over several generations and relies on the process of natural selection.

Question 10

Fertilisation

Answer 10

A process in sexual reproduction that involves the union of male (sperm) and female (ovum) gametes (each with a single, haploid set of chromosomes) to produce a diploid zygote

Question 11

Fi

Answer 11

The parental generation (P) is the first set of parents crossed. The F1 (first filial) generation consists of all the offspring from the parents

Question 12

Founder effect

Answer 12

Is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.

Question 13

Gamete

Answer 13

Sex cell of an organism e.g. sperm, egg, pollen or ova

Question 14

Gametic cells

Answer 14

Sex cells, e.g. sperm, egg, pollen and ova, cells with half the chromosome number. If a mutation occurs in one of these cells and that cell results in a zygote, all cells in the offspring will have that mutation

Question 15

Gene

Answer 15

A length of DNA that holds the instructions for a characteristic

Question 16

Gene pool

Answer 16

Refers to the total number of genes of every individual in a population.

Question 17

Genetic diversity

Answer 17

The total number of genetic characteristics in the genetic makeup of a species.

Question 18

Genetic drift

Answer 18

Is the change in the frequency of an existing gene variant (allele) in a population due to random chance alone and not natural selection.

Question 19

Genotype

Answer 19

The genetic make-up of the organism

Question 20

Haploid

Answer 20

When a cell has half the usual number of chromosomes.

Question 21

Heterozygous

Answer 21

Different forms of the allele is present in the genotype eg. HH

Question 22

Homologous chromosome

Answer 22

Chromosome pairs (one from each parent) that are similar in length, gene position, and centromere location. They contain. The position of the genes on each homologous chromosome is the same. However, the genes may contain different alleles.

Question 23

Homozygous

Answer 23

The same form of the allele is present in the genotype e.g. HH

Question 24

Incomplete dominance

Answer 24

Heterozygous individuals have a phenotype that is intermediate between the two homozygous phenotypes (like a bland)

Question 25

Independent assortment

Answer 25

The way the homologous chromosomes line up at the equator maternal and paternal, is completely random

Question 26

Lethal genes

Answer 26

Alleles that produce a gene product that kills the offspring

Question 27

Linked genes

Answer 27

Genes located on the same chromosome that tend to be inherited together

Question 28

Meiosis

Answer 28

The type of cell division which produces gametes

Question 29

Migration

Answer 29

Movement of organisms into (immigration) and out (emigration)of a population.

Question 30

Multiple alleles

Answer 30

When three or more alternative forms of a gene (alleles) that can occupy the same locus. e.g. ABO blood types

Question 31

Mutation

Answer 31

A permanent change in the bases on the DNA. It is the only way of creating new alleles

Question 32

Natural selection

Answer 32

The process by which heritable traits increase an organism’s chances of survival and reproduction. These traits are favoured than less beneficial traits

Question 33

Pedigree chart

Answer 33

Is a diagram that depicts the biological relationships between an organism and its ancestors

Question 34

Phenotype

Answer 34

The physical appearance of the organism

Question 35

Population bottleneck

Answer 35

Is an event that drastically reduces the size of a population, may be caused by various events, such as an environmental disaster. The population bottleneck produces a decrease in the gene pool of the population because many alleles, or gene variants, that were present in the original population are lost.

Question 36

Pure breeding

Answer 36

A group of identical individuals that only produce one type of gamete due to the fact they are homozygous

Question 37

Segregation

Answer 37

The process that occurs during meiosis where pairs of alleles are separated when the homologous chromosomes split

Question 38

Selective pressure

Answer 38

Can take many forms, including environmental conditions, availability of food and energy sources, predators, diseases, and even direct human influence. The selective pressure means that animals that don’t have these characteristics are less likely to survive and reproduce due to natural selection.

Question 39

Sexual reproduction

Answer 39

Reproduction involving two parents. Produces genetic variation.

Question 40

Somatic cells

Answer 40

Body cells, e.g. skin cells, if a mutation occurs in these cells it will not be passed on to offspring.

Question 41

Test cross

Answer 41

A genetic cross between a homozygous recessive individual and a corresponding suspected heterozygote to determine the genotype of the latter.