How can we write allele?

[lizaaudacious]

salaam........can v write that allele is composed of two genes?OR
is it the way in which a gene expresses itself in either of the ways like dominant or ressesive?
tell me ftaft
REGARDS

[tx_ned]

Originally Posted by lizaaudacious

salaam

Wasalam

can v write that allele is composed of two genes?

In my personal opinion, you cannot write so in general as "An allele is an alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome."

A gene is the basic instruction, a sequence of nucleic acid (DNA or, in the case of certain viruses RNA), while an allele is one variant of that gene. Thus, when the mainstream press refers to "having" a "gene" for a specific trait, this may be incorrect. In many cases, all people would have the gene in question, but certain people will have a specific allele of that gene, which results in the trait.

Please go through following links:


http://en.wikipedia.org/wiki/Gene


http://www.biology-online.org/biolog...about2650.html


http://wiki.answers.com/Q/Difference...ene_and_allele


http://www.differencebetween.net/sci...ne-and-allele/


http://library.thinkquest.org/28751/...eredity/2.html


http://qwickstep.com/search/allele-vs-gene.html

OR is it the way in which a gene expresses itself in either of the ways like dominant or ressesive?

Please go through the following link:

http://askville.amazon.com/makes-all...uestId=4617963


http://www.biology-online.org/biolog...minant%20trait


http://answers.yahoo.com/question/in...2124700AA3wsZC


http://www.microbiologyprocedure.com...tions-13-3.htm


http://www.blurtit.com/q2976706.html

tell me ftaft

In my opinion, you need to solidify the concept and deeply go through the difference of a gene and allele so that you cannot mix them up.

REGARDS

[lizaaudacious]

thanx a lot ov u 4 such a detailed analysis of my question 1st n then 4 the hierarchy of answers.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.
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.
tell me aram aram sy

[tx_ned]

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.

My pleasure, you are always welcome !

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.

"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

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.

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.

tell me aram aram sy

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

[lizaaudacious]

yup i got it.thanx a lot.
next thing is how many past papers do v have to prepare?like mostly seniors advise to prepare papers of past 10 years na,so is it sufficient 4 just objective portion?if not then Encyclopedia by Faridi publishers fulfills the same purpose or not?
REGARDS

[tx_ned]

Originally Posted by lizaaudacious

yup i got it.thanx a lot.

That s really great if I could be helpful. You are welcome !

next thing is how many past papers do v have to prepare?like mostly seniors advise to prepare papers of past 10 years na,so is it sufficient 4 just objective portion?if not then Encyclopedia by Faridi publishers fulfills the same purpose or not?

Sadly reporting, I don't have enough knowledge as the context of this query is purely related to CSS.

I think some other senior member will definitely respond you soon.

I do apologise to not advise you as I don't have sufficient knowledge and background of CSS preparation.

REGARDS

[goswamiraaj]

Genetics
The scientific study of heredity and of the mechanism by which characteristics are transmitted from one generation to the next dates back to the earliest attempt at selected breeding
Variation
Any change in hereditary characters
Hereditary
The transfer of characters from generation to generation
Gene
Gene is a basic unit of hereditary information and consists of a sequence of DNA bases. Each gene occupies a specific position called locus on a chromosomes.
Gene Locus
It is the specific location of a particular gene along the length of a certain chromosome. In other words it is the position of alleles on homologous chromosomes.
Alleles
Alleles are alternative forms of teh same gene, controlling a give trait. Alleles of a gene are present on the same relative locus on a homologous pair of chromsomes. Each individual inherits two alleles for a given trait, one form each parent.
Example
in pea plant, the gene for seed coat has two alleles; one for smooth seed and the other for wrinkled seeds.
Homozygous
When a diploid organism contains two identical alleles for a particular character, it is said to be homozygous for that character.
Example
Genes TT and tt are homozygous for length of stem.
Heterozygous
When a diploid organism contains two different alleles for a particular character, it is termed as heterozygous for that character.
Example
Genes Tt are heterozygous for length of stem.
Dominant
In a heterozygous condition, the allele which expresses itself morphologically and masks the appearance of other allele is said to be dominant.
Example
In pea plant allele for tall stem is dominant over allele for dwarf stem.
Recessive
In a heterozygous condition, the allele which does not express itself morphologically and remains masked by the other allele is called recessive.
Example
Allele for dwarf stem is recessive in pea plant.
Genotype
The description of genetic make up of an organism for a particular trait.
Example
In pea plant genotype for tall stem can be TT (homozygous) or Tt (heterozygous).
Phenotype
It is the visible expression of genes, both physical and physiological.
Example
Phenotype for both TT and Tt genotype will be tall stem.
Hybrid
The product obtained as a result of crossing two pure breeding varieties of an organism with contrasting characters is known as hybrid.
Example
Individuals obtained as a result of crossing a pure breeding tall pea plant with dwarf pea plant will be a hybrid.