Chapter 4, Problem 17TYR

Summary Introduction

Introduction:

In cell cycle, a mother cell divides into two daughter cells. The cell cycle mechanism is divided into four stages G₁, S, G₂, and M. G₁, first gap phase within interphase, is also known as growth phase. During the G₁ phase, cell synthesizes proteins and produces more number of mitochondria and ribosomes and increases their size of growth. In the G₁ phase, cell synthesizes and accumulates materials needed for DNA replication in the upcoming phase. In S phase, DNA replicates into two identical copies. In the G₂ phase, cell synthesizes proteins that control cell division and produces more organelles. It detects and repairs the replicated DNA sequence. After nuclear division, cell division has been occurred. Two types of mechanisms are involved in cell division. They are mitosis and meiosis. Meiosis cell division occurs in egg and sperm cells. Mitosis is involved in all somatic cells. Mitosis divides into prophase, metaphase, anaphase, and telophase in the eukaryotic cells. A division of the cytoplasm is known as cytokinesis, which occurs at the end of the mitosis.

DNA is a genetic material consisting of a long stretch of nucleotide sequences with 2 m length. Chromosomes carry genetic information from one generation to the next. A complete set of genetic materials (both coding and non-coding regions of DNA) of an organism is called as a genome. The total human genome consists about 3.1 billion base pairs and nearly 20,000 protein coding genes.