objective 4

Gene pool

Number of each allele of a gene in a population. Displayed as a percentage.

allele frequency

How often each allele of a gene occurs in a population.

Explain how gene pool allele frequencies can be altered (mutations)

 Introducing new alleles

Explain how gene pool allele frequencies can be altered (Different selection pressures)

Favouring certain alleles

Explain how gene pool allele frequencies can be altered (Random genetic drift)

Random changes in small populations

Explain how gene pool allele frequencies can be altered (Founder effect)

 New populations established by a small group

Explain how gene pool allele frequencies can be altered (Changes in gene flow)

 Movement of alleles between population

Describe the difference between a gene and chromosomal mutation.

A gene mutation affects a single gene, altering the sequence of nucleotides. A chromosomal mutation involves changes to the structure or number of entire chromosomes, affecting many genes

Describe the causes of mutations.

• Mutagenic agents (mutagens): Chemicals like mustard gas, formaldehyde, and radiation (UV light, X-rays)

• Spontaneous mutations: Random errors in biological processes like DNA replication

Describe the difference between somatic and germline mutations.

Somatic mutations occur in non-reproductive cells and are not passed to offspring. Germline mutations occur in reproductive cells and can be inherited by offspring

Describe the effects of mutations.

Missense: Alters amino acid sequence, changing protein function

Nonsense: Introduces a stop codon, truncating the protein

Neutral: Changes amino acid without affecting protein function

Silent: Does not change the amino acid sequence

Describe how migration changes the frequency of alleles in gene pools.

Migration introduces new alleles into a population or removes alleles from it, altering the allele frequencies. This process can increase genetic diversity within a population 

Understand that humans can show multiple variations and how the changing environment can influence the survival of organism with genetic variation.

Environmental changes can influence which genetic variations are advantageous, affecting the survival and reproduction of individuals with those traits

Explain how survival can be enhanced if particular phenotypes are selectively advantageous. Give examples of genetic diseases found in specific populations

Survival can be enhanced when certain phenotypes provide an advantage in a specific environment. For example, Tay-Sachs disease carriers are more resistant to tuberculosis, providing a selective advantage despite the disease being lethal in homozygous individuals

Explain the theory of Evolution using Natural Selection as the key process

Variation: Genetic differences exist within a population

Excess Population: More individuals are born than can survive

Struggle for Existence: Competition for resources

Selection: Individuals with advantageous traits are more likely to survive

Reproduction: Survivors reproduce, passing on favourable traits

Frequency Change: Over time, favourable traits become more common

Describe genetic drift and the founder effect, and how this changes the allele frequency.

Genetic drift is random changes in allele frequencies due to chance events, significant in small populations. The founder effect occurs when a small group establishes a new population, potentially leading to different allele frequencies compared to the original population

Define speciation (including how the gene pool is affected) and explain how isolation plays a factor in its occurrence.

Speciation is the formation of new and distinct species in the course of evolution, involving the splitting of a single gene pool into two or more separate gene pools. Isolation (geographic, reproductive, or behavioural) can prevent gene flow between populations, leading to divergent evolution and the eventual formation of new species