Cell division is the process by which one organic cell divides in half to create a copy of itself. This copying procedure is made possible by the presence of genetic material. Tiny structures called chromosomes store genetic coding inside the nucleus of a cell. Each chromosome contains proteins and DNA (deoxyribonucleic acid). Genes are the parts of DNA that communicate inheritable traits. DNA is made of two strands of a chain of nucleotides that come together to form a double helix. The whole sequence of DNA is known as an organism's genetic code. This code contains instructions for building the proteins required for all the biological functions of the organism. To make these proteins, the DNA is transferred to RNA (ribonucleic acid). If a gene is missing or contains an error, then a birth defect or genetic disease may occur.
Regular body cells (also known as "somatic" cells) divide by mitosis. In this process, each chromosome is copied, and an exact duplicate goes into the nucleus of each new cell. This creates an exact copy of the original cell.
However, sexual reproduction involves the combination of genetic material from two specialized cells known as gametes - - one from each parent. A gamete has half as many chromosomes as a somatic cell. The reduction in the number of chromosomes is the result of meiosis. This process involves two cell divisions, known as the first and second meiotic divisions. Diploid cells, like cells in the testes and ovaries, go through meiosis. Parental chromosomes are copied, and afterwards, homologous parental chromosomes pair up and connect during synapsis. In the first meiotic division, a cell divides into two diploid cells with a mixture of chromosomes from each parent. In the second meiotic division, each diploid cell divides into two cells. Finally, there are four haploid cells known as gametes. Sexual recombination occurs at the union of male and female gametes, and the resulting fertilized egg is called a zygote.
How are genes turned off and on?
Answered by Science Channel
What's the connection between telomeres and long life?
Answered by Discovery Channel
What is the future of tissue engineering?
Answered by Shameema Sarker PhD and Nina Tandon