6.1.2 Inheritance Key Terms

Question 1

Genotype

Answer 1

The genetic constitution of an organism (the alleles it has for a gene)

Question 2

Phenotype

Answer 2

The expression of the genes and its interaction with the environment

Question 3

Homozygous

Answer 3

A pair of homologous chromosomes carrying the same alleles for a single gene

Question 4

Heterozygous

Answer 4

A pair of homologous chromosomes carrying two different alleles for a single gene

Question 5

Recessive allele

Answer 5

An allele only expressed if no dominant allele is present

Question 6

Dominant allele

Answer 6

An allele that will always be expressed in the phenotype

Question 7

Codominant

Answer 7

Both alleles are expressed in the heterozygous resulting in a different phenotype

Question 8

Multiple alleles

Answer 8

More than two alleles coding for a single gene

Question 9

Sex linkage

Answer 9

A gene whose locus of on the X (or Y) chromosome

Question 10

Autosomal linkage

Answer 10

Genes that are located on the same chromosome (not sex-chromosomes)

Question 11

Epistasis

Answer 11

When one gene modifies or masks the expression of a different gene at a different locus

Question 12

Monohybrid

Answer 12

Genetic inheritance cross of characteristics determined by one gene

Question 13

Dihybrid

Answer 13

Genetic inheritance cross for characteristics determined by two genes

Question 14

Chi squared conclusion

Answer 14

The x^2 value (…) is more/less than the critical value at the 5% level (…) at (…) degrees of freedom
Therefore the null hypothesis can be accepted/rejected
The difference between what we expected and observed is statistically significant/insignificant- the differences are/aren’t due to chance

Question 15

Continuous variation

Answer 15

A characteristic with continuous values.
Due to genetics and the environment, many genes are involved (polygenic)
E.g mass and height of organisms

Question 16

Discontinuous variation

Answer 16

A characteristic with categorical (discrete) values.
Due to genetics only.
One or two genes involved.
E.g. blood group

Question 17

Directional selection

Answer 17

One of the extremes has the selective advantage.
Occurs when there’s a change in the environment.
The modal trait changes.
E.g, antibiotic resistance in bacteria

Question 18

Stabilising selection

Answer 18

The modal trait has the selective advantage.
Occurs when there’s no change in the environment.
Modal trait remains the same
Standard deviation decreases as individuals with the extreme trait decrease.
E.g. human birth weight

Question 19

Genetic drift

Answer 19

Change in allele frequency I thin a population between generations.
The smaller the population, the bigger the impact allele frequency changes have proportionally-occurs more rapidly.

Question 20

Genetic bottlenecks

Answer 20

Caused by events that kill almost all of the population, leaving only a few individuals left.
Results in a very small gene pool.
Many alleles for genes are lost, the remaining breeding population pass on the same alleles.
Lack in genetic diversity, genetic diseases that exist are more likely to be passed on.

Question 21

Founder effect

Answer 21

When a few individuals from an existing population relocate to an isolated area.
This results in a small population breeding together-small gene pool.

Question 22

Natural selection

Answer 22

Wide range of variations in a phenotype within a population. Due to genetic and environmental factors
Primary source of genetic variation is mutation.
Predation, disease, competition result in selection pressures.
Organisms with phenotypes providing advantages are likely to survive.
Also likely to produce more offspring and pass on their favourable alleles to the next generation.
Effect is a change in allele frequency (evolution)

Question 23

Artificial selection

Answer 23

Humans select plats or animals with favourable characteristics and deliberately breed them together.
Manipulates the gene pool so the favourable alleles become more common than the less favourable.
Prevalent in creating dog breeds with popular features.
Ethical issues, due to certain selected features, health problems are likely to arise and affect their lives.

Question 24

Gene banks

Answer 24

A way of maintaining genetic material for use in selective breeding.
Stores of biological samples (plant seeds, animal semen or eggs).
Used to help increase genetic diversity by outbreeding (breeding unrelated individuals)
Reduces the frequency of homozygous recessive disease in the offspring.