Biology by

Cell division

29hayesbenjamin — 2014-02-26 10:04:05 UTC

Chromosomes are made from DNA. Genes are short sections of DNA. Genetically identical cells are produced by a type of cell division called mitosis. In sexual reproduction, a male gamete fuses with a female gamete to produce a new cell. This is called fertilisation. Gametes are produced by a type of cell division called meiosis. They contain a single set of chromosomes, whereas body cells contain two sets of chromosomes.

Meiosis is a special type of cell division necessary for sexual reproduction in eukaryotes, such as animals, plants and fungi. The number of sets of chromosomes in the cell undergoing meiosis is reduced to half the original number, typically from two sets to one set.

Mitosis is the process, in the cell cycle, by which a cell duplicates into two genetically alike daughter cells. In mitosis, chromosomes in the cell nucleus are separated into two identical sets of chromosomes, each in its own nucleus. It is a form of nuclear division.

Made by Daniel Stark and Ben Hayes

29starkdaniel — 2014-02-26 10:10:47 UTC

Inheritance

29hayesbenjamin — 2014-02-26 10:22:37 UTC

Alleles are different forms of a gene. They can be dominant or recessive. Genetic diagrams help us to understand the possible outcomes when parents produce offspring. Huntington’s disease for example, is a disorder of the nervous system that is caused by a dominant allele. Cystic fibrosis is an inherited disorder that affects the cell membranes, causing the production of thick and sticky mucus. It is caused by a recessive allele. This means that it must be inherited from both parents. The genetic diagram shows how this can happen. is a disorder of the cell membranes caused by a recessive allele.

Recessive and Dominant genes can be shown using a genetic diagram. In a genetic diagram, you show all of the possible alleles for a particular characteristic. There will be two alleles from one parent, and two from the other parent, making four altogether. You then draw lines to show all the possible ways that these alleles could be paired in the offspring. There will be four possible ways, but some or all of them could be repeated.

Photosynthesis

29starkdaniel — 2014-02-26 11:45:22 UTC

The process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water.

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