The Cell Cycle and Cellular Reproduction

Cellular Reproduction - Overview

In biology, reproduction is the creation of a new organism or germ cells by the duplication of an organism's genetic material and the subsequent differentiation of this material into a new organism. It is the basis for growth and evolution. There are two forms of reproduction: asexual and sexual.

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The Cell Cycle and Cellular Reproduction

The Genome

In biology, the genome is the entire set of hereditary instructions encoded in the DNA of a single cell of an organism. The genome of a single cell contains all of the DNA present in the germ line cells of the organism and thus the complete genetic information necessary to pass on to successive generations. In human beings, the genome is composed of 23 chromosomes, containing a total of about 3.2 billion nucleotide pairs. The human genome was the first of all vertebrate genomes to be completely sequenced. As of 2012, thousands of human genomes have been completely sequenced, and many more have been mapped at lower levels of resolution.

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The Cell Cycle and Cellular Reproduction

Asexual Reproduction

In biology, asexual reproduction is a type of reproduction that does not involve the union of two gametes (i.e. sperm and egg). Asexual reproduction is found in single-celled organisms and also in some multicellular organisms.

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The Cell Cycle and Cellular Reproduction

Mitosis

In cell biology, mitosis is a part of the cell cycle when replicated chromosomes are separated into two new nuclei. Mitosis and cytokinesis together define the phase known as mitotic cell division. Mitosis occurs only in eukaryotic cells. Prokaryotic cells undergo a different process of division, known as binary fission. Mitosis occurs only in the nucleus of the cell, while binary fission can occur in the cytoplasm, and both processes involve the formation of a cell plate at the center of the cell.

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The Cell Cycle and Cellular Reproduction

Regulation of Mitosis

The cell cycle is the series of events that take place in a cell leading to its division and duplication. The cell cycle is essential to the process of cellular division, involving the duplication of genetic material and the preparation of the cell for division.

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The Cell Cycle and Cellular Reproduction

Sexual Reproduction

In biology, sexual reproduction is a type of reproduction where two specialized sex organs (called gametes), fuse during sexual intercourse to produce an offspring that inherits genes from both parents. Sexual reproduction is a fundamental feature of all known life; each individual organism exists as the result of sexual reproduction. Two gametes fuse to form a single cell called a zygote, which develops into a new organism.

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The Cell Cycle and Cellular Reproduction

Chromosomal Ploidy

The number of sets of chromosomes in a cell. A diploid cell has two sets of chromosomes, a haploid cell has one set, and a polyploid cell has three or more sets.

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The Cell Cycle and Cellular Reproduction

Meiosis

In biology, meiosis (from Greek ??????? "method of preparation", from ????? "to drink, imbibe") is a specialized type of cell division that reduces the chromosome number by half (from diploid to haploid) in order to produce gametes (sex cells) that are genetically different from other cells of the organism. Meiosis results in the production of gametes via the reduction division process of nuclear division, leading to cell division with half the normal number of chromosomes (see also anaphase). Meiosis begins with one diploid cell (2N) and results in four haploid cells (N).

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The Cell Cycle and Cellular Reproduction

Mitosis vs. Meiosis

In cell biology, mitosis (from Greek mitos, thread) is a part of the cell cycle when replicated chromosomes are separated into two new nuclei. During mitosis, the nuclear envelope disassembles, and the chromosomes condense and become visible under a light microscope. The entire process is also called karyokinesis. Mitosis and meiosis are together known as cell division. Meiosis produces haploid cells, usually eggs or sperm, from diploid cells, usually germline cells. Mitosis produces diploid daughter cells from a parent cell that has duplicated its chromosomes.

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The Cell Cycle and Cellular Reproduction

Sexual Reproduction and Genetic Variation

In biology, sexual reproduction is a type of reproduction where an organism creates offspring that contain both of the sexes' genes. Most species that reproduce sexually are also able to reproduce asexually through parthenogenesis, budding, or cloning. Sexual reproduction requires the production of relatively few offspring, compared with asexual reproduction, which produces many copies of itself. The gametes produced by sexual reproduction are the male sperm cells (spermatozoa) and female eggs (or ova). In sexual reproduction, the many sperm cells produced by males and females in sexual intercourse carry either an X or a Y chromosome, and unite to form a new individual. The male and female gametes carry half the number of chromosomes. The chromosomes in the sperm and the egg are each divided in two, and combine to form a new individual. This fertilized egg cell then divides and grows into a new organism.

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