The significance of recognizing multigene families is that the members may have related functions. Genes that are identical or nearly identical in sequence and regulation can be considered to encode isoforms rather than members of a multigene family.
A multigene family is a group of genes that have descended from a common ancestral gene and therefore have similar functions and similar DNA sequences. A group of related multigene families is sometimes called a supergene family.
What features characterize gene families? A group of genes that have related sequences, believed to have been derived from repeated duplication. Eukaryotic protein-coding genes differ from their prokaryotic counterparts in that only eukaryotic genes: contain introns.
how can transposable elements contribute to the evolution of the genome? They can promote recombination, disrupt cellular genes or control elements, and carry entire genes or individual exons to new locations.
the locations that correspond to most genetic diseases, the areas of a genome that most often mutate due to enviromental effects, and the locations that most often correspond with chromosomal breakpoints.
Pseudogenization is an evolutionary phenomenon where-by a gene loses its function by disruption to its regulatory or. coding sequence. Such loss of function is generally thought. to be detrimental to an organism and selectively disadvan-
Gene families are groups of related genes that share a common ancestor.
The density of DNA is a function of its base and sequence, and satellite DNA with its highly repetitive DNA has a reduced or a characteristic density compared to the rest of the genome. Thus, the name 'satellite DNA' was coined.
A gene is the basic physical and functional unit of heredity. Genes are made up of DNA. Some genes act as instructions to make molecules called proteins. However, many genes do not code for proteins.
Regulatory protein gene families
- 14-3-3 protein family.
- Achaete-scute complex (neuroblast formation)
- FOX proteins (forkhead box proteins)
- Families containing homeobox domains. DLX gene family. Hox gene family. POU family.
- Krüppel-type zinc finger (ZNF)
- MADS-box gene family.
- NOTCH2NL.
- P300-CBP coactivator family.
The C value paradox is that the amount of DNA in a haploid genome (the 1C value) does not seem to correspond strongly to the complexity of an organism, and 1C values can be extremely variable. The organism thus has the final say in the C value, and selfish DNA does not explain the paradox.
C-value is the amount, in picograms, of DNA contained within a haploid nucleus (e.g. a gamete) or one half the amount in a diploid somatic cell of a eukaryotic organism.
What is the difference between a "copy and paste" transposon and a "cut and paste" transposon? Retrotransposons move by means of an RNA intermediate. Transposons and retrotransposons comprise 20-50% of most mammalian genomes.
Multigene families are formed through a variety of evolutionary events that generate gene paralogs (i.e., duplicate nonhomologous gene copies). Such events may include a single gene amplification event or series of sequential duplications involving individual genes or entire genomes.
Table 1
| Chimp | Human |
|---|
| Total # of Families | 9,693 | 10,349 |
| Total # of Genes | 20,947 | 22,763 |
| Annotation Artifacts | 94 | 612 |
| Creations | 2 | 20 |
Repetitive DNA: DNA sequences that are repeated in the genome. These sequences do not code for protein. One class termed highly repetitive DNA consists of short sequences, 5-100 nucleotides, repeated thousands of times in a single stretch and includes satellite DNA.
The immunoglobulin heavy variable (IGHV) and T cell beta variable (TRBV) loci are among the most complex and variable regions in the human genome.
Each new gene must have arisen from an already existing gene.†Gene duplication occurs when errors in the DNA-replication process produce multiple instances of a gene. Over generations, the versions accrue mutations and diverge, so that they eventually encode different molecules, each with their own function.
Operon: A set of genes transcribed under the control of an operator gene. More specifically, an operon is a segment of DNA containing adjacent genes including structural genes, an operator gene, and a regulatory gene. An operon is thus a functional unit of transcription and genetic regulation.
A trait that is controlled by more than one gene is called polygenic which translates to "multiple genes". The genes work together to make one trait. Examples are skin, eye and hair color.
Genetic testing can reveal changes (mutations) in your genes that may cause illness or disease. Although genetic testing can provide important information for diagnosing, treating and preventing illness, there are limitations.
A gene related to a second gene by descent from a common ancestral DNA sequence. The term, homolog, may apply to the relationship between genes separated by the event of speciation (see ortholog) or to the relationship betwen genes separated by the event of genetic duplication (see paralog).
Currently, over 60,000 protein families have been defined, although ambiguity in the definition of protein family leads different researchers to highly varying numbers.
