Reproduction is the process by which new offspring are produced by the involvement of male and female sex cells which involves transferring of genetic information. In the event of fertilization, the male sex cell i.e, the sperm and the female sex cell i.e, the egg fuse to form the zygote. Through stages of meiosis and mitosis(cell division), DNA is split and transferred to the child. The new offspring inherits exactly half the DNA from each of their parents, while each parent passes half their DNA to each of their children.
During sexual fertilization, DNA from both the parents combine. This assures that the families pass on and maintain the genetic identity, but there is a genetic difference either with their parents or their paternal and maternal grandparents so much so that they are also different genetically from their own sisters and brothers unless it is a case of identical twins.
Human DNA has a history of our ancestors. The mix of the DNA is unique to an individual as we receive 50% of the DNA from each of the parent, who received 50% of their DNA from their parents and so on which keeps reducing over generations. Genes are a series of letters and forms the blueprint of our body that is preserved in the nucleus of the cells. These letter sequences contain genetic information to build specific molecules.
The letters that get passed down to each generation are random, and not all letters get passed. Our siblings can have different combinations of letters. The genes are duplicated ‘letter for letter’ to a related substance called the RNA(ribonucleic acid). The functional components of the cell read the RNA to create the hormone or protein as per the instructions. Each gene codes the instruction for one protein only, and this one protein can have different roles in the human body. One characteristic can be influenced by many genes. Variation in the gene code sometimes leads to the disruption of the coded messages of the genes. These variations are referred to as mutations, which can lead to numerous medical conditions.
The table below shows the percentage of DNA that is shared with each generation on average.
|Percentage of DNA||Generation|
|6.25||Great great grandparents|
|3.125||Great great great grandparents|
Recombination causes chunks of DNA from distant relatives to eventually weaken away. The above table depicts the percentage of DNA that we obtain from our great-great-great-grandparents which is a mere 3%. As swapping in recombination is arbitrary, the percentage can slightly vary and hence we might obtain more DNA from one chromosome in a pair than the other.
Take This Quiz
Q.1. Is it possible to inherit chromosomal disorders?
A.1. It is possible to inherit some chromosomal abnormalities, while most of the disorders are not passed from one to another generation. For example, Down Syndrome.
Q.2. What is DNA testing?
A.2. It is a test that analyses the DNA of a person, whose application can be extended to know one’s parents or even in identifying a criminal.
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