Have you encountered people comparing your looks to your parents or to your siblings? Your eyes look like your father while the texture of your hair is that of your mother. Whereas your sibling is opposite to you with eyes like that of your grandmother and hair texture like your father. Confused? Well, all these mixtures and variations come from genes. Genes are functional units of heredity. These transfer characteristics or traits from parents to the children. the chromosomes are composed of DNA while the DNA is made of genes. To define a gene, “a gene is a sequence of DNA”. Mendel, the father of genetics, used to call these genes as ‘factors’.
Humans possess 23 pairs of chromosomes, that is, all together 46 chromosomes. 23 received from the mother whereas the another 23 received from the father. thus, this is how characters or traits are transferred from parents to their offspring.
The term gene was coined by Wilhelm Johannes. There are about 30000 genes in each cell of a human body. DNA present in the gene comprises of only 2% of the genome.
FUNCTIONS OF A GENE –
· Genes control the DNA and RNA, both structurally and functionally.
· Protein synthesis in any organism is controlled by the genes
· Genes also work specifically, i.e., the globin gene produces haemoglobin
Coming to the second part of your question, genetic drift –
To quote, “Genetic drift is an evolutionary change in allelic frequencies of a population as a matter of chance.
· It occurs in small populations
· It occurs due to an error in selecting the alleles for the next generation from the gene pool of the current generation.
· There are two types of genetic drifts –
(i) Bottleneck effect
(ii) Founders effect
Let’s consider an example of genetic drift –
Consider a bird having 2 types of alleles for its beak. Through genetic drift one of the types might get eliminated, thus reducing the gene pool and variations for the bird’s population.
I hope this answer helps you.