Genetics | Definition of Genetics by Merriam-Webster

Genetics is biological study of how some inherited traits are transmitted and how they differ from each other and in particular chromosomes and DNA. Different individuals might differ in terms of their structure or their reasoning capacity and all these information is contained in the DNA. Different traits are inherited from parents to offspring and this promotes diversity. This article provides information on some key areas of genetics involving how traits are passed from parents to offspring.

Assuming that the purple flower is represented by letter P since it is dominant and the white flower represented by w, it is possible to identify the offspring expected using the punnet square.

The probability of having a white flower is ½ (half)

In case of homozygous recessive and homozygous dominant it is possible to identify the first and the second generation by use of a punnet square.

This form the first generation of offspring’s. The first generation will only consist of purple flowers since the gene for purple flower is dominant. The probability of having a white flower is zero. The second generation will consist of Pw and Pw as the genotypes. Using the punnet squire it is possible to establish the second generation as follows.

The phenotype for the second generation will be; PP, Pw, Pw, ww.

Individual one (Ee) might be a result of a cross between EE and ee or a cross between Ee and ee. The phenotypes as a result of the cross between EE and ee are; Ee, Ee, Ee and Ee while the phenotype as a result of cross between Ee and ee are; Ee, Ee, ee, ee. Individual two (EE) might be as a result of a cross between genotype Ee and EE. The phenotypes in this case will be; EE, Ee, EE, Ee. Individual three (ee) might be as a result of a cross between genotype ee and ee or a cross between genotype Ee and ee. The phenotypes will be ee, ee, ee, ee and Ee, Ee, ee, ee respectively.

Testcross helps to determine whether an individual is homozygous dominant or heterozygous. The genotype to be used is the parent’s and this is in order to predict to genotype of the offspring. The phenotype of the parent genotype becomes the genotype of the offspring. Crossing organisms with distinct phenotypes results to formation of offspring with a third phenotype that blends with the parental traits and this is referred to as incomplete dominance while codominance crossing organisms with two distinct phenotypes and produces an offspring with the third phenotype that has both the parental traits appearing together.

In humans, male children inherit the Y chromosome from the father. The X chromosome is inherited from the mother’s side. The X chromosome is inherited by the girl from both parents and this is how chromosomes determine the gender of individuals. A fruit fly with color being a sex-linked gene and red eye being dominant and white alleles being recessive, it is possible to identify the probability of having red eyed males using the punnet square. Assuming that the red eye allele is represented by R and white alleles represented by h.

Males and females do not have the same color eyes. The probability of having the red eyed males is ½ (half)

During meiosis one, physical crossing over may occur and this leads to the rearrangement of heterozygous homologous chromosomes into new combinations in a process referred to as recombination. Based on how genes are close to each other will determine the amount crossing over that occurs. The determination of the number of gametes that are recombinant is made possible by establishing the gametes in the lowest frequency. The distance from one gene to another determines the rate of recombination taking place. It is possible to establish the distance between two genes by identifying how fast genes cross over.

In human, the males have the X Y chromosomes. In female XX chromosomes are present. Males only inherit one X chromosome from parents as opposed to female who have two X chromosomes. Sex linked disorders are the kind that are determined by the sex chromosomes alone. In some cases, one X chromosome might be inactivated. This disadvantage the male since they will inherit this kind of gene the way it is without having an alternative X chromosome. Since most sex-linked disorders are carried on the X chromosome, once it is inherited from the parent it brings a disability to the male child. These defective genes might exist in the body of the mother as being inactive and reveals itself once it is inherited by a male child.

Assuming a situation where there is a red flower RR, a white flower rr, and a pink flower Rr, the probability of getting a pink flower by crossing a pink flower and a white flower can be established by use of a punnet square as follows.

Genotypes in this case are Rr and rr while the phenotype include; Rr, Rr, rr, rr. The probability of getting as red flower is equal to the probability of getting white flower which is ½ (half)

The knowledge of genetics helps individuals to know and understand why most sexual related disorders are associated with the boy child. The acquisition of this knowledge makes people to appreciate diversity and respect the differences among different people in the society.