Gene

2008-06-27T02:12:55Z

SThewise: /* Mutation */

The '''gene''' is the fundamental unit of [[heredity]].

A section of [[DNA]] that codes for the production of an [[RNA]] molecule. In most cases that RNA molecule codes for the production of a [[protein]], but in some cases (most notably the transfer RNA ([[tRNA]]) and ribosomal RNA ([[rRNA]]) genes) the RNA molecule is the end product.

Gene expression refers to all the processes involved in converting [[gene]]tic information from a [[DNA]] sequence, or [[protein]]. In [[prokaryote]]s, there are just two processes required: [[transcription]] and [[translation]]. In [[eukaryote]]s, there is an additional step [[RNA]] processing (splicing), which intervenes.
The synthesis of a single-stranded RNA molecule using DNA as a template is referred to as transcription. The enzyme that catalyzes this reaction is known as RNA polymerase. Although the subunit structure and details of the process differ significantly in prokaryotes and eukaryotes, the chemical reaction is identical.

==History==

By 1900 scientists knew that cells were the building blocks of living things. All living things start as a single fertilized cell which keeps dividing. Scientists identified tiny threads in the nucleus of the cells. Because they could stain the threads with colored dyes to study them under a microscope, they called the threads [[chromosome]]s, from the [[Greek]] words for colored bodies. They could see that chromosomes came in pairs, and that human cells all contained 23 matching pairs. American biologist [[Walter Sutton]] knew [[Mendel's principles of genetics|Mendel's]] work on peas, and suggested that chromosomes held the secret of inheritance.

Another American biologist, [[Thomas Hunt Morgan]], developed the idea that chromosomes were made up of linked groups of factors called [[genes]]. He experimented with red-eyed [[fruit fly|fruit flies]] and found that sometimes a white-eyed fly appeared. When he mated them, he found that as he expected there were three red-eyed flies to every white-eyed fly, but that all the white-eyed flies were male. He concluded that the gene for white eyes must be on a chromosome that was related to being male. Later workers found that this is why some hereditary diseases such as [[hemophilia]] and [[muscular dystrophy]] only show in males, though women can carry the gene for the disease without showing it.

Once Crick and Watson had unraveled the structure of [[DNA]], the function of genes became clearer.

One strand of [[DNA]] contains many genes. DNA is made of four [[nucleotide]]s, [[guanine]], [[adenine]], [[thymine]] and [[cytosine]]. G always pairs with C, and A with T. Different combinations of GC and AT join together in different orders along the strands of DNA coiled up along our [[chromosome]]s to give our cells instructions for making the different kind of protein of which our bodies are made. These groups of instructions are called genes. Our bodies are made up of about 100 trillion cells, each of which is responsible for a specific function. The thousands of different proteins in the cells work together like a machine to make the [[cell]] function as it should. If the genes are normal, the body part will function well. If a change (mutation) has happened in a gene, the protein may be faulty, as for example in sickle cell anemia where the instructions for making [[blood]] cells are abnormal.

==Mutation==

Changes of a species from its normal state are called [[mutation]]s. Sometimes they happen on their own, but they can also happen when a parent is exposed to something that will affect the way they reproduce. High doses of [[X-rays]] can produce mutations, and so can some chemicals. According to the [[theory of evolution]], most mutations are neutral, some are deleterious (harmful), and a very small proportion are beneficial such that they improve the individual's chance of survival and reproduction, thus passing on to the next generation. Some mutations can be both helpful and harmful. For example, people from some [[Africa]]n countries carry a gene for an illness called [[sickle-cell anemia]]. This illness causes health problems, but people who have the gene for sickle-cell anemia are also less likely to catch [[malaria]], a serious illness common in Africa.

==References==
<references/>

[[Category:Genetics]]

Dominant gene

2008-06-27T02:07:53Z

SThewise:

A '''Dominant gene''' is a gene that more often results in a specific [[physical]] characteristic, for example, a hereditary [[disease]], even though the patient's [[genome]] possesses only one copy. If one partner has a dominant gene, the chance of passing on the gene to children is 50-50 in each pregnancy, if both partners possess it, the chance increases to 75%, as a recessive gene will only show if paired with a recessive gene.

[[Category:Genetics]]

Allele

2008-06-27T02:06:51Z

SThewise:

An '''allele''' is one of the variant forms of a [[gene]]. They produce variation in inherited characteristics such as hair color or blood type.

In the case of simple inheritance, one form of the allele (the [[dominant gene]]) may be ''expressed'' more than another form (the [[recessive gene]]).



[[Category:Genetics]]

Conservapedia - User contributions [en]

Gene

Dominant gene

Allele