M6C20 - Patterns of inheritance and variation Flashcards

Question

What is epistasis?

Answer 1

The interaction between genes at different loci, where one gene can mask or modify the expression of another gene.

Answer 2

-Inhibiting allele codes for a repressor protein -Protein binds to mRNA -Stops transcription

Answer 3

When a recessive allele at one locus prevents the expression of an allele at another locus, resulting in a 9:3:4 phenotype ratio.

Answer 4

When a dominant allele at one locus completely masks the alleles at a second locus, resulting in a 12:3:1 phenotype ratio.

Answer 5

Natural selection that favours average stereotypes e.g. babies with average birth weights are more likely to survive than overweight babies.

Answer 6

Occurs when there is a change in the environment and the normal phenotype is no longer the most advantageous e.g. peppered moths.

Answer 7

Change in allele frequency due to the random nature of mutation

Answer 8

When a random event means the size of a population is significantly reduced so therefore the number of alleles in the population also decreases.

Answer 9

Many alleles were lost when population dropped. Population is descended from few survivors.

Answer 10

When a few individuals of an area colonise a new area, meaning there is a small gene pool for reproduction.

Answer 11

The movement of alleles between populations

Answer 12

The formation of a new species due to evolution.

Answer 13

Speciation caused by a physical barrier that isolates populations, leading to different selection pressures and reproductive isolation.

Answer 14

Seasonal changes – individuals develop different flowering or mating seasons, or become sexually active at different times of the year. Mechanical changes – changes in genitalia prevent successful mating. Behavioural changes – a group develops a different courtship ritual that isn’t attractive to the rest of the population.

Answer 15

Speciation without a physical barrier, often due to chromosomal errors or ecological niches, leading to reproductive isolation.

Answer 16

The process where humans select individuals for specific traits to breed, to get desirable characteristics, creating selection pressures.

Answer 17

Dairy cows, where cows with the highest milk yields are bred to increase milk production.

Answer 18

Modern bread wheat, which is hexaploid and was created by hybridizing wild and domesticated wheat species.

Answer 19

Similar genes in generations means: -Some diseases are more dangerous as all the organisms would be affected. -Increased risk of genetic disease caused by -recessive genes. -Inbreeding leads to a reduction in the size of the gene pool, making it more difficult to produce new varieties in the future.

Answer 20

Dachshund backs and necks have been bred to be longer, and legs have become smaller. They have the highest risk of any breed for intervertebral disc disease which can result in paralysis.

Answer 21

The frequency of alleles in a population and whether allele frequencies are changing over time.

Answer 22

p + q = 1, where p is the frequency of the dominant allele and q is the frequency of the recessive allele.

Answer 23

The expansion p² + 2pq + q², which gives the frequencies of the three genotypes: p² for homozygous dominant, 2pq for heterozygous, and q² for homozygous recessive.

Answer 24

Sexually reproducing organisms Diploid Organisms Large populations Randomly-mating populations No migration into or out of population No mutations occur