5.5 - Inheritance Patterns

Question 1

Population genetics

Answer 1

Study of genetic variation within a population
i.e. changes in the frequency of alleles and genes, within a population and among populations over time.

Question 2

Factors affecting population genetics

Answer 2

• Mutation
• Population size
• Diversity of the environment
• Migration patterns
• Natural selection

Question 3

Population genetics and conservation management

Answer 3

• Conservation genetics incorporates an understanding how genes are inherited in a population
• Principal aim is to avoid extinction of a species by applying convservation methods

Traditional methods:

• Sampling and statistical analysis
• Field observation
• Focus on distribution of populations
• Abundance of specific organisms

Modern methods:

• DNA analysis, including next-generation analysis methods, use many types of genetic tools including SNPs and haplotypes
• Determining kinship lineages to improve our understanding of microevolution, including selection and mutation

Question 4

Uses of conservation management techniques

Answer 4

• Identifying segments of the genome that are essential for the organism’s adaptation to the environnt
• Can determine relationships and idnetify individuals that could be reintroduced into a population for recovery
• Any deleterious alleles for brain function, immunity, metabolism and other necessary functions can be detected.
• Mutations that may enhance these functions can also be detected, improving the ability of the species to survive in its environment

Question 5

Woolly mammoth extinction case study

Answer 5

The DNA sequence of two historical samples of the wooly mammoth were taken to determine whether there was a reduction in genetic diversity due to inbreeding in the population that had been isolated (on Wrangel island)

Sequencing showed that they had:
- Affected olfactory processes
- Reduced number and variety of the mammoths’ urinary proteins. This would have greatly reduced their ability to mark and recognise territory, hunt, and mate
- 2 mutations were found in the gene known as FOXQ1, which affects hair structure. Mammoths with this gene had translucent, cream-coloured coat that was not good an insulating heat.
- Inbreeding and loss of geneitc diversity made these mammoths more suscpetible to disease and reduced their ability to survive in their environment.

Question 6

Population genetics and disease (black urine disease)

Answer 6

• Alkaptonuria (black urine disease)
• Body cannot process the amino acids phenylalanine and tyrosine, which occur in proteins
• Erchibald Garrod demonstrated this is is a recessive inherited disease
• Caused by a mutation in the HGD gene for the enzyme homgentisate 1,2-dioxygenase on chromosome 3
• It is a monogenic disease (a disease that results from a mutation in a single gene)

Question 7

Monogenic disease

Answer 7

• A disease which results from a mutation in a single gene in all cells of the body. All cells in the individual will have that mutation because monogenic diseases arise from germline mutations
• Around 10,000 monogenic human diseases
• Genetic testing for SNPs that are unique to particular diseases can be carried out quickly and relatively easily.
• In NSW, newborn screening program provides free genetic tests for all newborns for the SNPs associated with the diseases phenlketonuria, cystic fibrosis, urea cycle disorders. Most of these conditions are genetic.

Question 8

Population genetics and human evolution

Answer 8

Combines DNA analysus with historical and archaeological evidence to determine the pathways of human evolution.
Evolutionary forces of:

• Mutation
• Natural selection
• Genetic drift
• Gene flow

are responsible for the patterns of diversity in human populations today.

Question 9

Multiregional hypothesis

Answer 9

Relies on fossil evidence - all human populations can be traced back to when homo erectus first left Africa 2 million years ago.

• There was gene flow between neighbouring populations
• But once they dispersed into other portions of the old world, this stopped and they evolved into modern humans.

Question 10

Replacement hypothesis

Answer 10

“Out of Africa”/”Eve” hypothesis

• Archaic homo sapiens left Africa
• A second migration happened 100,000 years ago, and modern humans of African origin conquered archaic groups and replaced them by inter-breeding with and out-competing them.
• When they first migrated, there were also Neanderthal and Denisovans occupying what is now the Eurasian land mass.
• Genetic evidence suggests that they interbred with Neanderthals. A small amount of Neanderthal DNA persists in the human genome today.
• Scientists have concluded that most Europeans and Asians have 2% Neanderthal DNA.

Question 11

Genomic breakdown

Answer 11

Isolation of woolly mammoths on Wrangel Island, and the resultant inbreeding, caused a loss of genetic diversity. This in turn led to the mammoths’ increased susceptibility to disease and lowered resilience, causing a sever population reduction

Question 12

mtDNA analysis

Answer 12

• Inherited solely through the maternal line and is not subject to recombination → ideal for tracing evolutionary lineages
• Mean rate of mtDNA divergence in humans is 2-4% per million years → population with greatest mtDNA divergence within the group will be the oldest, because it must have had more time to accumulate mutations in the gene pool