Select a research area from the adjacent list Cloning Information: Online Articles Any discussion about cloning needs to begin with careful definitions.
Structure of cytosine with and without the 5-methyl group. Deamination converts 5-methylcytosine into thymine. Base modifications and DNA packaging Further information: DNA methylation and Chromatin remodeling The expression of genes is influenced by how the DNA is packaged in chromosomes, in a structure called chromatin.
Base modifications can be involved in packaging, with regions that have low or no gene expression usually containing high levels of methylation of cytosine bases. DNA packaging and its influence on gene expression can also occur by covalent modifications of the histone protein core around which DNA is wrapped in the chromatin structure or else by remodeling carried out by chromatin remodeling complexes see Chromatin remodeling.
There is, further, crosstalk between DNA methylation and histone modification, so they can coordinately affect chromatin and gene expression.
Mutagens include oxidizing agentsalkylating agents and also high-energy electromagnetic radiation such as ultraviolet light and X-rays. The type of DNA damage produced depends on the type of mutagen.
For example, UV light can damage DNA by producing thymine dimerswhich are cross-links between pyrimidine bases. Because of inherent limits in the DNA repair mechanisms, if humans lived long enough, they would all eventually develop cancer.
Although most of these damages are repaired, in any cell some DNA damage may remain despite the action of repair processes.
These remaining DNA damages accumulate with age in mammalian postmitotic tissues. This accumulation appears to be an important underlying cause of aging.
Most intercalators are aromatic and planar molecules; examples include ethidium bromideacridinesdaunomycinand doxorubicin. For an intercalator to fit between base pairs, the bases must separate, distorting the DNA strands by unwinding of the double helix.
This inhibits both transcription and DNA replication, causing toxicity and mutations. The set of chromosomes in a cell makes up its genome ; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes. Transmission of genetic information in genes is achieved via complementary base pairing.
Usually, this RNA copy is then used to make a matching protein sequence in a process called translationwhich depends on the same interaction between RNA nucleotides. In alternative fashion, a cell may simply copy its genetic information in a process called DNA replication.
The details of these functions are covered in other articles; here the focus is on the interactions between DNA and other molecules that mediate the function of the genome.
Genes and genomes Further information: In eukaryotes, DNA is located in the cell nucleuswith small amounts in mitochondria and chloroplasts. In prokaryotes, the DNA is held within an irregularly shaped body in the cytoplasm called the nucleoid.
A gene is a unit of heredity and is a region of DNA that influences a particular characteristic in an organism. Genes contain an open reading frame that can be transcribed, and regulatory sequences such as promoters and enhancerswhich control transcription of the open reading frame.
In many speciesonly a small fraction of the total sequence of the genome encodes protein. For example, only about 1.Conservative position: "Cloning, even so-called therapeutic or experimental cloning, creates a new life without a father, and reduces a mother to the provider of an almost emptied initiativeblog.comeless, it is a new human life and the determination to destroy it and limit its use to scientific research for therapeutic ends compound further the moral issues rather than protect mankind.
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Conservative position: "Cloning, even so-called therapeutic or experimental cloning, creates a new life without a father, and reduces a mother to the provider of an almost emptied initiativeblog.comeless, it is a new human life and the determination to destroy it and limit its use to scientific research for therapeutic ends compound further the moral .
SCIENTISTS are one step closer to cloning dinosaurs after the discovering the remains of a Tyrannosaurus rex that was pregnant when it died.
Cloning. In biology, the activity of cloning creates a copy of some biological entity such as a gene, a cell, or perhaps an entire organism. This article discusses the biological, historical, and moral aspects of cloning mammals.
The main area of concentration is the moral dimensions of reproductive cloning, specifically the use of cloning in order to .
Any discussion about cloning needs to begin with careful definitions. Cloning can occur at the level of DNA, at the level of the single cell, or at the level of the whole organism.