One mother (Dougherty family) discussed how others (a) speak of the ' risky relations' created by genetic tales of. The aims of intermarrying are often to bolster family unity and keep wealth within the family. A relationship between related people is called consanguinity. The first study to investigate the genetic influence on jealousy was recently feels at some point, and a major cause of relationship problems.
How we inherit characteristics We can inherit characteristics in many different ways. Variations in the gene for that characteristic cause these different forms. We can inherit different alleles of the gene pair one from each parent in different ways.
Dominant and recessive genes The two copies of the genes contained in each set of chromosomes both send coded messages to influence the way the cell works. Generally, for example, the coded message from the genes that tells the eye cells to make brown colour is dominant over blue eye colour. However, a number of different genes together determine eye colour and so blue-eyed parents can have a child with brown eyes.
Dominant and recessive blood-group inheritance Dominant inheritance is when one allele of a gene is dominant within the pair. For blood groups, the A allele is dominant over the O allele, so a person with one A allele and one O allele has the blood group AO. Another way of saying this is that the O group is recessive — a person needs two O alleles to have the blood group O.
So a child may have blood group A because the blood group A gene inherited from their mother is dominant over the blood group O gene inherited from their father. The father has two O alleles OOso he has the blood group O. Each one of their children has a 50 per cent chance of having blood group A AO and a 50 per cent chance of having blood group O OOdepending on which alleles they inherit.
Co-dominant genes Not all genes are either dominant or recessive. Sometimes, each allele in the gene pair carries equal weight and will show up as a combined physical characteristic.
So someone with one copy of A and one copy of B has the blood group AB.
Gene family - Wikipedia
Continuing the example of blood groups, a person with the alleles AO will have the blood group A. The observable trait — blood group — is known as the phenotype. The genotype is the genes that produce the observable trait. Chemical communication Although every cell has two copies of the 23, genes, each cell needs only some specific genes to be switched on in order to perform its particular functions.
The unnecessary genes are switched off. Genes communicate with the cell in chemical code, known as the genetic code. The cell carries out its instructions to the letter. A cell reproduces by copying its genetic information then splitting in half, forming two individual cells.
Occasionally, a mistake is made, causing a variation genetic mutation and the wrong chemical message is sent to the cell. Genetic mutations are permanent. Some of the causes of a spontaneous genetic mutation include exposure to radiation, chemicals and cigarette smoke. Genetic mutations also build up in our cells as we age.
Coefficient of relationship
For example, skin cancer can be caused by a build-up of spontaneous mutations in genes in the skin cells caused by damage from UV radiation. Sometimes, a parent may have one copy of a gene that is faulty and the other copy containing the correct information.
The correct copy of a gene overrides the faulty copy. For example, the gene controlling red—green colour recognition is located on the X chromosome.
A mother who carries the faulty gene causing red—green colour blindness on one of her X chromosome copies will have perfectly normal vision, as she still has a functioning gene copy for red—green colour recognition on her other X chromosome. However, her sons have a 50 per cent chance of being colourblind.
This is because there is a 50 per cent chance that they will inherit the X chromosome from their mother that contains the faulty gene. There is also a 50 per cent chance that they will inherit the X chromosome containing the correct copy of the gene and so will have normal vision.
Genetic conditions To date, scientists have identified around 1, conditions caused directly or indirectly by changes in the genes.
- Gene family
- Genes and genetics explained
Around half of all miscarriages are caused by changes in the total number of genes in the developing baby. Similarly, about half of the Australian population will be affected at some point in their life by an illness that is at least partly genetic in origin.
The three ways in which genetic conditions can happen are: The variation in the gene that makes it faulty a mutation happens spontaneously in the formation of the egg or sperm, or at conception.
The faulty gene is passed from parent to child and may directly cause a problem that affects the child at birth or later in life.
The faulty gene is passed from parent to child and may cause a genetic susceptibility. Environmental factors, such as diet and exposure to chemicals, combine with this susceptibility to trigger the onset of the disorder.
Coefficient of relationship - Wikipedia
It simply means you are at increased risk of developing the condition. Many conditions involving genetic susceptibility, such as some types of cancer, need to be triggered by environmental factors such as diet and lifestyle.
For example, prolonged exposure to the sun is linked to melanoma. Avoiding such triggers means significantly reducing the risks. Genes and genetics — related parents Many cultures approve of marriage between relatives such as first cousins. The aims of intermarrying are often to bolster family unity and keep wealth within the family.
Consanguinity is often associated with factors such as: Related parents are more likely than unrelated parents to have children with health problems or genetic disorders. This is because the two parents share one or more common ancestors and so carry some of the same genetic material. If both partners carry the same inherited altered mutated gene, their children are more likely to have a genetic disorder. Related couples should seek advice from a clinical genetics service if their family has a history of a genetic condition.
Processed pseudogenes are genes that have lost their function after being moved around the genome by retrotransposition. For example, a single gene in the ancestor of humans and chimpanzees now occurs in both species and can be thought of as having been 'duplicated' via speciation. As a result of duplication by speciation, a gene family might include 15 genes, one copy in each of 15 different species.
Duplication[ edit ] In the formation of gene families, four levels of duplication exist: Exon duplication and shuffling gives rise to variation and new genes.
Genes are then duplicated to form multigene families which duplicate to form superfamilies spanning multiple chromosomes. Whole genome duplication doubles the number of copies of every gene and gene family. Autopolyploidization is the duplication of the same genome and allopolyploidization is the duplication of two closely related genomes or hybridized genomes from different species.
The expansion of a gene cluster is the duplication of genes that leads to larger gene families. Transposable elements play a role in the movement of genes. Transposable elements are recognized by inverted repeats at their 5' and 3' ends. When two transposable elements are close enough in the same region on a chromosome, they can form a composite transposon.
The protein transposase recognizes the outermost inverted repeats, cutting the DNA segment. Any genes between the two transposable elements are relocated as the composite transposon jumps to a new area of the genome. This new DNA copy of the mRNA is integrated into another part of the genome, resulting in gene family members being dispersed.
The LINEs contain a sequence that encodes a reverse transcriptase protein.
Due to the highly repetitive nature of these elements, LINEs and SINEs when close together also trigger unequal crossing over events which result in single-gene duplications and the formation of gene families. Duplication gives rise to multiple copies of the same gene, giving a level of redundancy where mutations are tolerated. With one functioning copy of the gene, other copies are able to acquire mutations without being extremely detrimental to the organisms.
Mutations allow duplicate genes to acquire new or different functions. The process by which gene families maintain high homogeneity is Concerted evolution. Concerted evolution occurs through repeated cycles of unequal crossing over events and repeated cycles of gene transfer and conversion.
Unequal crossing over leads to the expansion and contraction of gene families. Gene families have an optimal size range that natural selection acts towards.
Contraction deletes divergent gene copies and keeps gene families from becoming too large. Expansion replaces lost gene copies and prevents gene families from becoming too small. Repeat cycles of gene transfer and conversion increasingly make gene family members more similar. Mutant alleles spreading in a gene family towards homogeneity is the same process of an advantageous allele spreading in a population towards fixation.
Gene conversion also aids in creating genetic variation in some cases.