Friday, October 29, 2010
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Join Date: Feb 2010
Location: Manchester
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Quote:
Originally Posted by lizaaudacious
thanx a lot ov u 4 such a detailed analysis of my question 1st n then 4 the hierarchy of answers.
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My pleasure, you are always welcome !
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1 more confuzing thing iz here that plz read this statement n then tell me is it right ?
Recessiveness is a pattern of inheritance in which a child receives identicak allees 4m parents.
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"A Recessive" can be defined as following 2 ways:
1) Genetics Of, relating to, or designating an allele that does not produce a characteristic effect when present with a dominant allele.
2) Of or relating to a trait that is expressed only when the determining allele is present in the homozygous condition.
Let me make it more simple "Tending to go backward or recede" is recessiveness.
A recessive (of a gene) is capable of producing its characteristic phenotype in the organism only when its allele is identical.
In genetics, the failure of one of a pair of genes (alleles) present in an individual to express itself in an observable manner because of the greater influence, or dominance, of its opposite-acting partner. Both alleles affect the same inherited characteristic, but the presence of the recessive gene cannot be determined by observation of the organism; i.e., although present in the organism’s genotype, the recessive trait is not evident in its phenotype.
The term recessive is applied both to the trait in the organism having the alleles of a gene pair in the recessive condition and to the allele whose effect can be masked by another allele of the same gene.
Please go through the following link:
http://www.genetics.com.au/pdf/factsheets/fs08.pdf
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I think 4 any trait 2 b recessive it iz not necessary that it should receive identical alleles.like if Hh is genotype of a child n he is short so recessiveness is here.
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With the birth of a child, it gets its genes from both parents. Some genes 'override' other genes. Using hair colour as example:
If one parent is blond (Pb) and one parent is black hair (Pd), blond would be the recessive gene, and dark would be the dominant gene. Meaning:
Pb x Pb = Blond Pd x Pd = Dark Pb x Pd = Dark Pd x Pb = Dark
Recessive genes basically occur in the genotype (inside the body, disease, disorder) or phenotype (appearance, blue eyes brown eyes). When both parents have them. In all other cases the dominant gene will override recessive gene.
How to determine the genotype ratio and the phenotype ratio?
for Heterozygous short-hair (Hh) X heterozygous short-hair (Hh), after you put it in the Punnet square, you get HH, Hh, Hh, and hh. So the genotype is simply the different combinations you see here. So HH = homozygous dominant. Hh=heterozygous and hh is homozygous recessive.
You have 1 HH, 2 Hh, and 1 hh. So genotypic ratio would be 1:2:1 for homozygous dominant: heterozygous: homozygous recessive
Phenotypic ratio here would be 3:1 since HH and the two Hh's have a big H and show the dominant trait. Only 1 (hh) shows the recessive trait.
Quote:
tell me aram aram sy
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Ab iss se ziada aaraam aaraam se aik engineer typical biology (Genetics) kaisay bata sakta hay
Some useful links are:
http://www.accessexcellence.org/RC/VL/GG/recessive.php
http://medical-dictionary.thefreedic...ecessive+trait
http://www.wisegeek.com/what-is-a-recessive-trait.htm
http://library.thinkquest.org/C01180..._recessive.htm
Regards
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