Genes are made up of two alleles that can come from either one or both parents. Recombination is a process during which a chromosome randomly combines genetic material from counterparts.
The frequency of recombination between two genes is always less than 50% because the chromosomes have to have been separated for this process to take place, and the probability that one particular chromosome will break in half and reattach to another is less than 50%.
In other words, there will always be an underdog gene on each chromosome. Genes are not split evenly so the probability of recombination between any two genes is often lower than 50%.
In the case of a pair of genes which have been separated for many generations, the recombination rate between them has decreased to the point where there is almost no chance of these two genes being joined together again.
It is most likely that one copy will be inherited from only one parent, and the other from another. This means that unless mistakes are made by humans, or by plants or animals, there will be a tendency for one allele to become ‘dominant’ and a second to ‘recessive’.
This kind of complex inheritance is best explained by the idea that every cell in an organism carries half of its DNA with it from its mother and half from its father.
Each chromosome carries a pair of alleles.
1.Meiosis is a form of cell division.
In which a single chromosome becomes separated from its pair.
2.Recombination occurs more frequently between two genes.
Which have been separated for a short period of time. Which is true of members of the same chromosome pair.
3.Chromosomes contain a pair of genes on each side of a pair of centromeres .
Which must be broken to separate the chromosomes into two distinct pieces.
Each chromosome is made up from a set of one or more pairs called homologous chromosomes, meaning that each member from the homologous pair comes from the same genetic parent.
Each homologous pair is held together by a centromere and has its own independent DNA sequence.
4.The difference between the two alleles in each gene pair .
Is the result of variation and changes that occur during recombination.
5.A diploid cell.
It has one complete set of homologous chromosomes and the individual genes that make up two separated pairs are called alleles.
Genes determine what traits an organism will show; these traits are passed down to its offspring (with some minor alterations, such as mutations).
Genes can be dominant or recessive, meaning if a dominant trait is inherited from both parents, it will be stronger than a recessive trait that comes from only one parent.
6.In a dihybrid cross.
Four different alleles are inherited from a cross between two heterozygous parents.
7.The X and Y chromosomes determine whether a cell is male or female.
A male has two X chromosomes, while a female has one X and one Y chromosome.
At fertilization, each parent contributes one chromosome for each pair to the embryo.
Both chromosomes are on the same individual at fertilization, but are not expressed on the same cell in an individual.
8.A dominant trait is expressed .
When it appears on all of the homologous chromosomes in an individual’s body, a recessive trait is not expressed in all if its cells or not expressed at all in some but not the others.
9.A chromosome carries two alleles.
Which are two different forms of a gene..Parental chromosomes come together during fertilization, and exchange genetic material between them.
This results in different genes being passed between each chromosome.
10.Recombinant chromosomes are formed when chromosomes break during meiosis.
The homologous chromosomes contain two alleles, or different forms of one gene, and are said to be heterozygous for that gene..
Can occur when homologous chromosomes come apart during meiosis and recombine.
Because the resulting offspring has the potential to change into one of the original parents, these recombinant individuals can be called hybrids or cross-pollinated plants or animals.
11.Most cases of inheritance
Each of the alleles from a heterozygous pair is inherited from one parent only. In most situations, only one allele will be dominant over the other.
In some situations, there can be a situation where both alleles are dominant over the other.
This situation is known as codominance and it results in the occurrence of an intermediate phenotype between two phenotypes that can be seen in dihybrid crosses between these two parents.
(For Example: a heterozygote cross hybridizes exhibiting a stronger phenotype than either homozygote.)