Chapter 22

Question 1

Genotype

Answer 1

The genetic makeup of an organism, from the combination of alleles inherited.

Question 2

Phenotype

Answer 2

the observable characteristics of an organism

Question 3

Modifications

Answer 3

Any changes the environment makes to a person’s phenotype, which are not inherited.

Question 4

Dominant allele

Answer 4

The version of the gene that will always be expressed if present.

Question 5

Recessive allele

Answer 5

The version of the gene that will only be expressed if two copies are present.

Question 6

Homozygous

Answer 6

Two identical alleles for a characteristic.

Question 7

Heterozygous

Answer 7

Two different alleles for a characteristic.

Question 8

Monogenic inheritance

Answer 8

A characteristic inherited on a single gene.

Question 9

Codominance

Answer 9

When different alleles of a gene are equally dominant and both are expressed in the phenotype.

Question 10

Multiple alleles

Answer 10

A gene with more than two possible alleles.

Question 11

Sex linked

Answer 11

Genes carried on the sex chromosomes.

Question 12

Carriers

Answer 12

A person who has one copy of a recessive allele coding for a genetically inherited condition.

Question 13

Dihybrid inheritance

Answer 13

A characteristic inherited on two genes.

Question 14

Autosomal linkage

Answer 14

Genes present on the same, non-sex chromosome.

Question 15

Linked genes

Answer 15

Genes inherited as one unit.

Question 16

Recombinant

Answer 16

New combinant of alleles/DNA from two sources

Question 17

Recombination frequency

Answer 17

The amount of crossing over in meiosis.

Number of recombinant offspring/total number of offspring

Question 18

Epistasis

Answer 18

The effect of one gene on the expression of another gene.

Question 19

Epistatic

Answer 19

A gene that affects the expression of another gene.

Question 20

Hypostatic

Answer 20

A gene that is affected by another gene/

Question 21

Evolution

Answer 21

The change in inherited characteristics of a group of organisms over time, due to changes in the frequency of different alleles.

Question 22

Gene pool

Answer 22

Sum total of all the genes in a population.

Question 23

Allele frequency

Answer 23

The relative frequency of a particular allele in a population.

Question 24

Gene flow

Answer 24

The movement of alleles between populations.

Question 25

Genetic drift

Answer 25

A change in allele frequency due to the random nature of mutation.

Question 26

Density-dependent factors

Answer 26

Limit or decrease a population dependent on its size (like competition.)

Question 27

Density-independent factors

Answer 27

Limit or decrease populations of all sizes in the same way (like climate change).

Question 28

Genetic bottleneck

Answer 28

Large reductions in population size lasting for at least one generation.

Question 29

Founder effect

Answer 29

An extreme example of a genetic drift from the establishment of new colonies by a few isolated individuals.

Question 30

Normal distribution

Answer 30

The bell-shaped curve on a graph, showing the variation in a population.

Question 31

Stabilising selection

Answer 31

Natural selection that favours average phenotypes

Question 32

Directional selection

Answer 32

Natural selection that favours one extreme phenotype.