Inheritance, Selection And Speciation

Question 1

Gene pool

Answer 1

All the alleles of all the genes of a population of a species

Question 2

Species

Answer 2

A group of organisms that share a common gene pool, so they are able to interbreed and produce fertile offspring

Question 3

Hybridisation

Answer 3

A cross between different species. This is rarely successful due to differences in the gene pools. If offspring at produced, they are rarely fertile.

Question 4

Speciation

Answer 4

• selection acts on the gene pool
• alleles that give favourable phenotypes will come to have a higher frequency in the pool because they get passed on more often
• if the environment changes, selection acts differently on the gene pool, and the allele frequencies change
• therefore if the two halves of a population are under different pressures, then speciation will occur

Question 5

Gene

Answer 5

A sequence of bases on a DNA molecule that codes for a polypeptide (protein) which results in a characteristic

Question 6

Allele

Answer 6

A different version of the same gene

Question 7

How many alleles of each gene do most people have?

Answer 7

2 - one from each parent

Question 8

Genotype

Answer 8

The different alleles an organism has

Question 9

Phenotype

Answer 9

The expression of an organisms genes and the effect the environment has had on the genes

Question 10

Dominant allele

Answer 10

An allele whose characteristics appears in the phenotype, even when there’s only one copy

Question 11

Recessive allele

Answer 11

Recessive alleles are those whose characteristics are only expressed if two copies are present

Question 12

Codominant

Answer 12

When both alleles are expressed as neither are recessive

Question 13

Homozygous

Answer 13

Two copies of the same allele

Question 14

Heterozygous

Answer 14

Two different alleles

Question 15

What do genetic diagrams show?

Answer 15

Show the possible genotypes of offspring, so the genotypes and phenotypes can be predicted

Question 16

Monohybrid inheritance

Answer 16

The inheritance of a single characteristic controlled by different alleles

Question 17

Monohybrid crosses

Answer 17

Show the likelihood of alleles being inherited by offspring of particular parents

Question 18

What is a punnet square?

Answer 18

A genetic diagram

Question 19

Example of the monohybrid inheritance of codominant alleles?

Answer 19

Sickle-cell anaemia (caused by a mutation in the haemoglobin cell) if you are codominant for sickle-cell anaemia then some of your haemoglobin will be sickle shaped

Question 20

What is a generic pedigree diagram?

Answer 20

Shows how an inherited trait runs in a group of related individuals

Question 21

What can the Hardy-Weinberg principal be used to work out?

Answer 21

Allele, genotype, and phenotype frequency

Question 22

What conditions allow the H-W principal to be true?

Answer 22

Must be a large population without immigration, emigration, mutations or natural selection
There must be random mating

Question 23

Equation for allele frequency

Answer 23

p+q=1
p = the frequency of the dominant allele
q = the frequency of the recessive allele

Question 24

Genotype frequency

Answer 24

p^2+2pq+q^2=1
p^2 = frequency of homozygous dominant
2pq = frequency of heterozygous
q^2 = frequency of homozygous recessive

Question 25

What is the fundamental prediction of the H-W principal?

Answer 25

Allele frequency of a population won’t change from on generation to the next

Question 26

Differential Reproductive Success

Answer 26

The process of natural selection

Question 27

Stabilising selection

Answer 27

Individuals with alleles for characteristics towards the middle of the range are more likely to reproduce and survive, it occurs when the environment isn’t changing, and it reduces the range of possible phenotypes
Those at the extremes of the range are less likely to survive

Question 28

Example of stabilising selection

Answer 28

Fur length - in a stable environment, animals with long or short fur are less likely to survive

Question 29

Directional selection

Answer 29

This is where animals with alleles for an extreme characteristic are more likely to survive and reproduce, this could be in response to an environmental change

Question 30

Example of directional selection

Answer 30

Cheetahs have become faster, as those with alleles for speed are more likely to survive and reproduce, to cheetahs have become faster over time

Question 31

When does speciation occur

Answer 31

When populations of the same species become reproductively isolated, and often occurs due to geographical isolation

Question 32

Example of geographical isolation

Answer 32

A flood or an earthquake isolating to halves of a population from each other