SCSA Human Biology Science as a Human Endeavour

The evolutionary mechanism is the founder effect/genetic drift.

The original population contains variation and a wide variety of phenotypes.

A small group of individuals moves to a new area and establishes a new population. This new group is not genetically representative and has a different allele frequency to the original population, resulting in decreased genetic variation in the new population.

There is no breeding between populations as the populations are isolated from each other. Over many generations, the ratio of allele frequency will differ to that of the original population, and these changes in allele frequency are non-directional or by chance.

Comparative genomics involves comparing the genome sequence of different species to determine relatedness.

DNA is sequenced to determine the order of nucleotides or bases. Over time, populations accumulate more and more differences in their genome. More similar DNA suggests species are more closely related and have a more recent common ancestor.

Nuclear DNA is found in the nuclei of cells and is inherited from both parents. Due to recombination, migration is difficult to track; hence, it is used to trace evolutionary relationships between species.

Mitochondrial DNA (mtDNA) is found in the mitochondria and is only inherited from the mother. It has a high mutation rate; hence, it is used to trace migration routes between populations within a species.

The purpose of PCR is to create more copies of a DNA sequence, whereas gel electrophoresis is used to separate DNA strands based on size.

In terms of process, PCR uses a thermal cycle while gel electrophoresis uses an electric current in an agarose gel. Also, PCR uses enzymes to copy DNA, while gel electrophoresis uses enzymes to break DNA into fragments.

For the end products, PCR creates large amounts of copied DNA, whereas gel electrophoresis provides a visual representation of DNA fragments.

DNA sequencing determines the order of nucleic acids in the DNA.

It is used to (any 5 of the following):

• identify the degree of genetic variations in a population
• identify the degree of genetic similarity between species
• quantify the degree of genetic diversity between species
• establish molecular clocks or determine the time since organisms shared a common ancestor
• help construct phylogenetic trees
• identify how genes derived from common ancestors have changed over time
• and use comparative genomics to help understand the process of evolutionary changes over time.

Bioinformatics allows for large scale computerised analysis of genetic data. This allows the determination of the degree of similarity. The higher the degree of similarity, the more recent the separation from a common ancestor, which helps determine where species are placed in phylogenetic trees.

Any 1 of the following:

• Degenerative neurological disease
• Caused by deficiency of the HexA enzyme
• Disorder of lipid metabolism
• Autosomal recessive disease

There was a r migration of a small group to Australia, with some or one individual/s carrying the allele for Tay-Sachs disease. Due to restricted breeding within the gene pool, the frequency of the allele increases over time.

Denaturing separates complementary base pairs.

Annealing involves adding a primer, which is a small single strand of DNA, to bind to complementary base sequences.

Extension involves DNA polymerase making a copy of DNA strands through a repeated series.

Individuals are heterozygous for Tay-Sachs. There is isolation of the gene pool. Individuals that are heterozygous are more likely to survive. Suitable genes are passed onto offspring, while individuals that do not possess suitable genes die off.