Genetic Information, Variation and Relationships (GENETIC DIVERSITY AND ADAPTION)

Question 1

Define genetic diversity

Answer 1

The number of different alleles of genes in a population
-> this enables natural selection to occur

Question 2

Describe stabilising selection and give an example

Answer 2

2 extreme phenotypes are removed from a population due to selection pressure eg: predation
Therefore, phenotypes close to the mean are favorable and have a selective advantage
These organisms survive and reproduce and pass on the favourable genes on to the next generation which increases the favourable allele frequency
This eventually occurs generation to generation

Eg: human birth weight (both underweight and overweight babies have a lower chance of survival)

Question 3

Describe directional selection and give an example

Answer 3

1 of the extreme phenotypes are favoured due to change in environmental condition
The favoured phenotype survives and reproduces so the favourable allele is passed on and therefore increases in frequency - eventually generation to generation
–> graph shifts either to right or left

Eg: antibiotic resistance in bacteria

Question 4

Explain how antibiotic resistance occurs in bacteria

Answer 4

A random mutation occurs in the DNA of individual bacterial cells.
The mutation protects the bacterial cell from the effects of the antibiotics as it produces an enzyme that breaks antibiotic down.
Bacteria without the mutation die when the antibiotic is present
Antibiotic resistant bacteria survive and can reproduce b binary fission with less competition from non-resistant bacterial strains.
The genes for antibiotic resistance are passed to the offspring
Over time the frequency of bacteria with favourable allele and 1 extreme phenotypes increases example of directional selection)