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The expression of genes encoded in DNA begins by transcribing the gene into RNA, a second type of nucleic acid that is very similar to DNA, but whose monomers contain the sugar ribose rather than deoxyribose. RNA also contains the base uracil in place of thymine. RNA molecules are less stable than DNA and are typically single-stranded.
A graphical representation of the typical human karyotype The human mitochondrial DNA. Human genetic variation is the genetic differences in and among populations. There may be multiple variants of any given gene in the human population , a situation called polymorphism. No two humans are genetically identical.
Since traits come from the genes in a cell, putting a new piece of DNA into a cell can produce a new trait. This is how genetic engineering works. For example, rice can be given genes from a maize and a soil bacteria so the rice produces beta-carotene, which the body converts to vitamin A. [19] This can help children with Vitamin A deficiency.
Since humans have many more genes on the X than the Y, there are many more X-linked traits than Y-linked traits. However, females carry two or more copies of the X chromosome, resulting in a potentially toxic dose of X-linked genes. [4] To correct this imbalance, mammalian females have evolved a unique mechanism of dosage compensation.
Genetic variation can be identified at many levels. Identifying genetic variation is possible from observations of phenotypic variation in either quantitative traits (traits that vary continuously and are coded for by many genes, e.g., leg length in dogs) or discrete traits (traits that fall into discrete categories and are coded for by one or a few genes, e.g., white, pink, or red petal color ...
The Neanderthal DNA found in modern human genomes has long raised questions about ancient interbreeding. New studies offer a timeline of when that occurred and when ancient humans left Africa.
Genes → Gene expression → Proteins → Metabolic pathways → Sub-cellular structures → Cells → Tissues → Organs → Organisms. Even at the small scale, the relationship between genes and proteins (once thought of as "one gene, one polypeptide") [13] is more complicated, because of alternative splicing.
Human DNA recovered from remains found in Europe is revealing our species’ shared history with Neanderthals. The trove is the oldest Homo sapiens DNA ever documented, scientists say.