2. TRANSCRIPTOME The initial product of genome expression is the transcriptome, a collection of RNA molecules derived from those protein-coding genes whose biological information is required by the cell at a particular time .
8. Duplication of Entire Chromosome Sets Accidents in meiosis can lead to one or more extra sets of chromosomes, a condition known as polyploidy The genes in one or more of the extra sets can diverge by accumulating mutations; these variations may persist if the organism carrying them survives and reproduces
9. Alterations of Chromosome Structure Humans have 23 pairs of chromosomes, while chimpanzees have 24 pairs Following the divergence of humans and chimpanzees from a common ancestor, two ancestral chromosomes fused in the human line Duplications and inversions result from mistakes during meiotic recombination Comparative analysis between chromosomes of humans and 7 mammalian species paints a hypothetical chromosomal evolutionary history
11. Duplication and Divergence of Gene-Sized Regions of DNA Unequal crossing over during prophase I of meiosis can result in one chromosome with a deletion and another with a duplication of a particular region Transposable elements can provide sites for crossover between nonsisterchromatids
12. Evolution of Genes with Related Functions Human Globin Genes The genes encoding the various globin proteins evolved from one common ancestral globin gene, which duplicated and diverged about 450–500 million years ago After the duplication events, differences between the genes in the globin family arose from the accumulation of mutations
14. Evolution of Genes with Novel Functions For example the lysozyme gene was duplicated and evolved into the α lactalbumin gene in mammals Lysozyme is an enzyme that helps protect animals against bacterial infection α-lactalbumin is a nonenzymatic protein that plays a role in milk production in mammals
Accessing the genome. This involves various processes that influence chromatin structure and nucleosome positioning in the parts of the genome that contain active genes, ensuring that these genes are accessible and are not buried deep within highly packaged parts of the chromosomes.Assembly of the transcription initiation complex, which comprises the set of proteins that work together to copy genes into RNA. Synthesis of RNA, during which the gene is transcribed into an RNA copyProcessing of RNA involves a series of alterations that are made to the sequence which must occur before the RNA molecules can be translated into proteinRNA degradation is the controlled turnover of RNA molecules. Degradation is not simply a means of getting rid of unwanted RNAs: it plays an active role in determining the make up of the transcriptome and hence is an integral step in genome expression.Assembly of the translation initiation complex occurs near the 5′ termini of coding RNA molecules, and is a prerequisite for translation of these molecules.Protein synthesis is the synthesis of a protein by translation of an RNA molecule.Protein folding and protein processing may occur together. Processing involves modification of the protein by addition of chemical groups and, for some proteins, removal of one or more segments of the protein.Protein degradation has an important influence on the composition of the proteome and, like RNA degradation, is an integral component of genome expression.
