Genes
(Gene is the basic physical and functional units of heredity)
(Gene is the basic physical and functional units of heredity)
-Traditionally : A gene is the portion of a DNA molecule which codes for one protein.
-Genes are lengths of DNA that code for particular proteins (
gives a transcript/ non-coding genes).
-Each DNA molecule contains many genes.
-There are estimated to be between 20,000 and 25,000 human
protein-coding genes.
-The estimated number of human genes has been repeatedly
revised down
-Earlier predictions estimated that human cells have as much
as 200,000 genes. However, human cells make extensive use of alternative
splicing to produce several different proteins from a single gene, and the
human proteome is thought to be much larger than other organisms.
-Most human genes have
multiple exons, and human introns are frequently much longer than the flanking
exons. Human genes are distributed across the chromosomes.
-Each chromosome
contains various gene-rich and gene-poor regions, which seem to be correlated
with chromosome bands and GC-content.
-In addition to protein coding genes, the human genome
contains thousands of RNA genes, including tRNA, ribosomal RNA, microRNA, and
other non-coding RNA genes.
Types of genes
• genes cllassified into three kinds:
1 - Regulatory Genes
A gene governing the work of many other genes
2 - Operator Genes
It is working genes play a role as a phone that control the opening and closing a large number of other genes, called Structural Genes
3 - Structural Gene
A gene responsible for the installation on protein or enzyme.
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