Unit 7 Inheritance and Populations

Question 1

Define genotype and phenotype

Answer 1

Genotype
- Genetic constitution of an organism.
Phenotype
- Expression of this genetic constitution and its interaction with the environment.

Question 2

Define Homozygous and heterozygous

Answer 2

Homozygous
- A pair of homologous chromosones carrying the same alleles for a single gene
Heterozygous
- A pair of homologous chromosones carrying 2 different alleles for a single gene

Question 3

Define recessive and dominant allele

Answer 3

Dominant allele
- An allele that is always expressed if present
Recessive allele
- An allele that is only expressed if 2 are present

Question 4

Define codominant and Multiple alleles

Answer 4

Codominant
- Both alleles are equally dominant
Multiple alleles
- More than 2 alleles for a single gene

Question 5

Define sex linkage and autosomal linkage

Answer 5

Sex linkage
- Gene where locus on X chromosone
Autosomal linkage
- Genes that are located on the same chromosones

Question 6

Define Monohybird and Dihybrid

Answer 6

Monohybrid
- Characteristic determined by 1 genes
Dihybrid
- Characteristic determined by 2 genes

Question 7

Define Epistasis

Answer 7

When 1 gene modifies or masks the expression of a different gene at a different locus

Question 8

Outline an example of monohybrid inheritance

Answer 8

Question 9

Outline an example of dihybrid inheritance

Answer 9

Question 10

Outline an example of codominance

Answer 10

Question 11

Outline an example of sex linkage

Answer 11

• Males only have 1 allele

Question 12

Outline an example autosomal linkage

Answer 12

Question 13

Outline an example of multiple alleles

Answer 13

Question 14

Outline an example Epistasis

Answer 14

Question 15

Describe the use of a chi sqaured test

Answer 15

• Chi-squared statistic can be used to see if the ratio you expected was significantly different to the ratio you observed.
• If the number is greater than or equal to the critical value, we conclude there is a significant difference between the observed and expected data and that the results did not occur due to chance.

Question 16

@Define population

Answer 16

A population is a group of the same species in the same habitat at the same time

Question 17

Define gene pool and allele frequency

Answer 17

• Gene pool is all the alleles for all the genes for a population at one time
• Allele frequency is the proportion of each allele within the gene pool

Question 18

@Outline the use if the Hardy–Weinberg principle

Answer 18

Mathematical model which can be used to predict the allele frequencies within a population
p² + 2pq + q² = 1
p+q = 1
p is the frequency of dominant allele
q is the frequency of recessive allele
p2 is the proportion of individuals that are homozygous dominant (AA)
q2 is the proportion of individuals that are homozygous recessive (aa)
2pq is the proportion of individuals that are heterozygous (Aa)

Question 19

@Outline variation and the causes

Answer 19

• There is a wide range of variation in phenotypes due to both genetic and environmental factors.
  The primary source of genetic variation is mutations, meiosis and random fusion of gametes.

Question 20

@What 3 things result in differential survival and reproduction

Answer 20

Predation, disease and competition result in selection pressure

Question 21

Outline process of increasing allele frequency in gene pool

Answer 21

• Organisms with phenotypes giving them a selective advantage are more likely to survive
• Also likely to produce more offspring and pass on their favourable alleles to the next generation.
• The effect of this is a change in the allele frequency (evolution).
• This is differential reproductive success, as not all individuals are equally likely to reproduce, and this results in changes in allele frequencies within a gene pool.

Question 22

Outline Disruptive selection and its effect

Answer 22

• When individuals which contain the alleles coding for either extreme trait are more likely to survive and pass on their alleles.
• Continued disruptive selection can ultimately lead to speciation

Question 23

@Outline effect of stabilising and directional effect

Answer 23

• Effect of stabilising selection is that the range of alleles decreases and most individuals have the modal trait
• Effect of directional selection is that the allele frequency changes and more of one of the extreme trait’s alleles become more frequent.

Question 24

@Define Evolution

Answer 24

Evolution as a change in the allele frequencies in a population.

Question 25

@Outline the process of speciation

Answer 25

• Occurs when one original population of the same species becomes reproductively isolated.
  Then rest of it

Question 26

@Outline allopatric speciation

Answer 26

• Population separated into different groups by geographical isolation
• Seperate groups is exposed to different environments/selection pressures
• Therefore no gene flow between the two groups within the populations. causing a change in frequency of alleles
• Each species cannot interbreed to create fertile offspring
• 2 different species formed

Question 27

@Outline sympatric speciation

Answer 27

• Occurs in the same habitate where mutation causes variation
• Therefore no gene flow between the two groups within the populations. causing a change in frequency of alleles
• Each species cannot interbreed to create fertile offspring
• 2 different species formed

Question 28

@Outline the importance of genetic drift

Answer 28

• The change in the allele frequency within a population between generations.
• Continual, substantial genetic drift results in evolution.
• The smaller a population, the bigger the impact allele frequency changes
• This is why evolution often occurs more rapidly in smaller populations