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Genetics and Evolution

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Genetics

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Genetics is a branch of science which deals with the study of genes, genetic variations, and heredity in organisms. Genes are made up of DNA and are a kind of genetic guidance. These instructions are used to make molecules and to regulate the chemical reactions of life. We are transferred from parent to offspring.


What is Genetics ?

We have studied in earlier classes about the DNA present inside the nucleus of the cell. DNA of male and female gametes combine and form a new DNA during the fertilization and gamete formation. This DNA gets transferred in the cells of the offspring and is responsible for the transfer of biological information required for the growth of the organism. This particular substance is known as gene in the common language and Biology as well. Gene is formed out of DNA molecules arranged in a helical structure. The study of all these genes is known as Genetics. Though the term is a very recent development, as a concept it has been used by mankind since prehistoric times for breeding and developing crop species.


Evolution

It is a process of hereditary changes in the population of organisms over several generations. The inherited traits are the expression of genes that are copied and transmitted to the offspring during reproduction. Heritable traits that are useful for survival and reproduction become more common, while harmful traits are uncommon.


What is Evolution ?

It is said that life originated 3.6 billion years ago. It started with unicellular organisms or prokaryotic bacteria. Later it developed into more structured cellular organisms called eukaryotic organisms. These eukaryotic organisms in turn developed into multicellular organisms and gradually into more bigger and complex organisms. But the diversity we see today resembles nothing like those during the origin of life on the history of earth. plants and animals have changed substantially over their ancient predators with time. This phenomenon is known as evolution.


The evolutionary biology describes how the organisms get adapted to the ever changing natural environment by the process of natural selection. Charles Darwin was the pioneer of this theory. He drew this conclusion by observing the similarity between two or more distant species of animals or birds of the same family. He also discovered the modification of body parts of the same species living in different environments or habitats. 


Evolutionary Genetics

Evolutionary genetics is a study of how genetics leads to evolutionary changes. It involves studying the evolution of the structure of the genome. This is the sum of population genetics and evolution. Genome evolution is the process by which the size and structure of the genome change over time. The prokaryote genome develops through mutation, transduction, and horizontal gene transfer.


What is Evolutionary Genetics?

Evolutionary genetics is known as how genetic variation contributes to evolutionary changes. This includes the evolution of the genome structure, the genetic basis of adaptation and specification, and genetic changes in response to population selection. Evolutionary genetics is the sum of the genetics and evolution of the population.


Evolution of Structure of Genome

Genome evolution is defined as the process by which the genome changes its structure and size over time. The evolution of the prokaryotic genome happens by a number of methods-mutation, horizontal gene transfer, and transduction. The mutation is any permanent change in the body's nucleotide sequence. Horizontal gene transfer is a method of transferring genetic material from donor to recipient that is different from the vertical transfer (from parent to offspring).


Example of Genome Evolution - Bacteria

Transduction is another mode that takes evolution into the structure of the genome. It is defined as the transfer of genetic material via the virus to the cell. Figure 2 below: shows the evolutionary methods of prokaryotes. The eukaryotic genome is larger and more complex than the procaryotes. They 're evolving through sexual reproduction. This introduces a wide genetic diversity in eukaryotes compared to prokaryotes.


Mechanism of Genome Evolution

1.Duplication of Gene 

This is the duplication of a particular DNA region. It occurs by recombination, aneuploidy, transposition, polyploidy, and error in DNA replication. 


2.Transposable Components 

This refers to a DNA region that can be inserted anywhere in the genome. Ty elements in Drosophila, for example. Sequence Alu is the most common transposable element found in humans. 


3.Mutation  

Spontaneous mutations are responsible for genome changes. The nucleotide sequence changes resulting in a frameshift mutation that alters the genome. This is most common in prokaryotes.


4.Exon's Shuffling 

During this time, two exons from different genes come together. This process is created by new genes. As a result, a new gene is inserted in the genome.


What are the Different Mechanisms of Genome Evolution?

  • Gene Duplication- When a particular DNA region is duplicated. Gene duplication can occur through recombination, transposal, aneuploidy, polyploidy, and replication of the slippage (DNA replication error). Gene replication via recombination occurs when there is an irregular crossing at the time of meiosis. 

  • Transposable Elements – A region of DNA that can be inserted anywhere in the genome either by "cutting and paste mechanism" or by "copy and paste mechanism." For example, "Ty elements in Drosophila." The most common transposable element found in humans is the Alu sequence.

  • Mutation - Spontaneous mutations often cause changes in the genome. Mutations induce changes in the nucleotide sequence that induce the mutation of the frameshift, thereby altering the genome. It is also one of the processes of adaptation of the genome. Most common in prokaryotes. 

  • Exon Shuffling - During exon shuffling, two exons of two different genes come together to form exon or repeat the same exon. This is the process by which new genes are being created. This adds a new gene to the genome. This plays an important function in the evolution of the genome.


Are Chimps Closer to Humans than Gorillas?

Earlier human species have been kept in the Hominidae family and apes have been kept in Pongidae. This separation was based on certain features, such as the more advanced human brain and bipedal locomotion. Yet recent work has indicated that chimpanzees are nearest to the man followed by gorillas. The genetic material of primates and humans is closely linked to each other. The genetic material of chimpanzees and man differ by 1.2 percent, while the difference between gorillas and man is about 1.6 percent. This difference in genetic material confirms that chimpanzees are closer to humans than gorillas.


Terms to Remember 

  • Exon is the coding part of the gene, i.e. exon is a part of gene expression. The mature RNA messenger consists only of exons, which are later translated into protein. 

  • Aneuploidy is a deletion or addition of chromosome number, which in normal humans contains 46 chromosomes, but aneuploidy results in either 45 or 47 chromosomes. 

  •  Polyploidy consists of more than two sets of chromosomes. 

  • Transposition is a process in which the segment of the chromosome is transferred to a new position.

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FAQs on Genetics and Evolution

1. Explain Genetics

During fertilization the formation of new gene or DNA takes place by the process of transcription. It is the copying and pasting of the previous DNA sequence of the parents. Because this is natural there occurs some error in this process and the new DNA carries slightly from that of parents. This change in turn imparts different characteristics in the offspring altogether. This phenomenon is studied in biology under the name of mutation. Some external factors are also responsible for mutation in genes such as UV radiation or radiation of gamma rays.

2. Which Ape is Genetically Closest to Humans?

Chimpanzees are considered to be the closest living ape to the animal kingdom. The genome of the chimpanzee was sequenced by the researchers and it was found that they share 99 percent of DNA with humans, making them similar to each other.

3.What is mutation ?

During fertilization the formation of new gene or DNA takes place by the process of transcription. It is the copying and pasting of the previous DNA sequence of the parents. Because this is natural there occurs some error in this process and the new DNA carries slightly from that of parents. This change in turn imparts different characteristics in the offspring altogether. This phenomenon is studied in biology under the name of mutation. Some external factors are also responsible for mutation in genes such as UV radiation or radiation of gamma rays.

4.What is Mendel's Law ?

As we very clearly understand, the offspring inherit the characteristics of their parents by passing genes. Gregor Mendel was the first researcher to establish this fact. He suggested that every species contains two copies of every gene inherited from each parent in sexual reproduction. If the two copies are same then it is termed as homozygous otherwise heterozygous. In a heterozygous organism having two dissimilar genes or alleles one gene is dominant over another and dictates the phenotype of the organism. Sometimes incomplete dominance is also observed in some cases. This phenomenon was termed as Mendel's law by him.

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