Question

Describe the mechanisms of dynamic evolution that have shaped the human genome? (2 pages )

Answer 1

The human body contains hundreds of different cell types with diverse forms and functions, yet each cell contains (essentially) the same genome. There are certain typesof gene modifications that take place across the human genome like methylation and acetylation. These gene modifications can be influenced by environmental factors and in some cases inherited across generations.
The majority of human phenotypes of clinical and evolutionary interest are specified by multiple loci across the human genome.
Genome evolution is the process by which a genome changes in structure (sequence) or size over time.
The human genome has been shaped by evolutionary pressures.
Prokaryotic genomes have two main mechanisms of evolution. They are mutation and horizontal gene transfer. There is another mechanism of genome evolution in eukaryotes, i.e., sexual reproduction.
Eukaryotic genomes are generally larger than that of the prokaryotes. The eukaryotic genome is linear and can be composed of multiple chromosomes, packaged in the nucleus of the cell. The non-coding portions of the gene, known as introns. These introns are removed by RNA splicing before translation of the protein can occur.
Eukaryotic genomes evolve over time through many mechanisms including sexual reproduction which introduces much greater genetic diversity to the offspring than the prokaryotic process of replication in which the offspring are theoretically genetic clones of the parental cell.
The number of genes that make up the genome does not correlate with genome size.

There are various mechanisms of dynamic evolution that have shaped human genome. They are: gene duplication, whole genome duplication, mutations, exon shuffling and genome reduction and gene loss.
Gene duplication: It is the process by which a region of DNA coding for a gene is duplicated. This can occur as the result of an error in recombination or through a retrotransposition event.
Whole genome duplication: It is the process by which an organism's entire genetic information is copied, once or multiple times, which is known as polyploidy. This may provide an evolutionary benefit to the organism by supplying it with multiple copies of a gene thus creating a greater possibility of functional and selectively favored genes.
Mutations: the changes that occur in the sequence of DNA either by natural factors or by artificial factors are known as mutations. Spontaneous mutations occur oftenly, which can cause various changes in the genome. Mutations can either change the identity of one or more nucleotides, or result in the addition or deletion of one or more nucleotide bases.
Exon shuffling: It is a mechanism by which new genes are created. This can occur when two or more exons from different genes are combined together or when exons are duplicated. Exon shuffling results in new genes by altering the current intron-exon structure. This can occur by any of the following processes: transposon mediated shuffling, sexual recombination or non-homologous recombination.
Genome reduction and gene loss: It happens when organisms adapt to a parasitic life style, e.g. when their nutrients are supplied by a host. As a consequence, they lose the genes needed to produce these nutrients.