Genetic Variation and Change

Question 1

Allele

Answer 1

An alternative form of a gene.

Question 2

Chiasma

Answer 2

The point at which paired chromosomes contact during crossing over.

Question 3

Co-dominance

Answer 3

A condition in which an individual who is heterozygous will express the phenotypes associated with both alleles.

Question 4

Crossing over

Answer 4

A process occurring during meiosis wherein two chromosomes pair up and exchange segments of their genetic material.

Question 5

Diploid

Answer 5

A cell that contains two complete sets of chromosomes, one from each parent. (In humans somatic cells are diploid as they contain 46 chromosomes.)

Question 6

Evolution

Answer 6

A gradual process in which something changes into a different and usually more complex or better adapted form.

Question 7

Founder effect

Answer 7

The reduced genetic diversity that results when a population is descended from a small number of colonising ancestors.

Question 8

Gamete

Answer 8

A reproductive cell having the haploid number of chromosomes, especially a mature sperm and egg.

Question 9

Gene

Answer 9

A section of DNA that codes of a particular amino acid.

Question 10

Gene pool

Answer 10

The total sum of different alleles in an interbreeding population.

Question 11

Genetic biodiversity

Answer 11

Refers to to the total number of genetic characteristics in the genetic make-up of a species.

Question 12

Genetic drift

Answer 12

The process of change in the genetic composition of a population due to chance or random events rather than by natural selection.

Question 13

Genetic variation

Answer 13

Variation in the allele frequency or genome between members of species or between groups of species.

Question 14

Genotype

Answer 14

The set of alleles that determines the expression of a particular characteristics or trait.

Question 15

Haploid

Answer 15

A cell that contains a single set of unpaired chromosomes. In humans this means 23 unpaired chromosomes.

Question 16

Heterozygous

Answer 16

An individual two different alleles for a specific trait.

Question 17

Homozygous dominant

Answer 17

An organism or cell that contains two dominant alleles for a single trait.

Question 18

Homozygous recessive

Answer 18

An organism or cell that contains two recessive alleles for a single trait.

Question 19

Incomplete dominance

Answer 19

A relationship between alleles of a single gene in which one allele masks the phenotypic expression of another allele at the same gene locus.

Question 20

Independent assortment

Answer 20

The process of random segregation and assortment of chromosomes during meiosis resulting in the production of genetically unique gametes.

Question 21

Lethal alleles

Answer 21

Alleles that cause an organism to die when present in homozygous condition.

Question 22

Linked genes

Answer 22

Genes that are inherited together with other gene (s) as they are located close together on the same chromosome.

Question 23

Locus

Answer 23

The position that a given gene occupies on a chromosomes.

Question 24

Meiosis

Answer 24

The process of cell division in sexually reproducing organisms that reduces the number of chromosomes in reproductive cells from diploid to haploid.

Question 25

Multiple alleles

Answer 25

Three or more alleles for a particular gene. The presence of multiple alleles is best illustrated by the ABO blood groups of humans.

Question 26

Mutagen

Answer 26

An agent, such as a chemical, ultraviolet light or a radioactive element that induce or increase the frequency of mutation in an organism.

Question 27

Mutation

Answer 27

A permanent change in the base sequence of DNA.

Question 28

Natural selection

Answer 28

The process whereby organisms better adapted to their environment tend to survive and produce more offspring.

Question 29

Phenotype

Answer 29

The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.

Question 30

Population bottleneck

Answer 30

A sharp reduction in size of a population due to environmental events (such as fires, earthquakes and floods) or human activities.

Question 31

Pure breeding

Answer 31

When two organisms with identical genotypes produce offspring with the same traits (e.g. both parents are homozygous for a particular trait).

Question 32

Segregation

Answer 32

The separation of paired alleles or homologous chromosomes, especially during meiosis so that the members of each pair appear in different gametes.

Question 33

Somatic cells

Answer 33

Any cell of the body that is not a sexually reproductive cell.

Question 34

Test cross

Answer 34

A cross between an organism whose genotype for a certain trait is unknown and an organism that is homozygous recessive for that trait.

Question 35

Trait

Answer 35

A genetically determined characteristic or condition.