Multiple alleles, Biology

MULTIPLE ALLELES

(i)         More than two alternative forms (alleles) of a gene in a population occupying the same locus on a chromosome or its homologue are known as multiple alleles.

(ii)         There are more than two alleles of the same gene.

(iii)        All multiple alleles occupy the corresponding loci in the homologous chromosomes. (iv)  A chromosome or a gamete has only one allele of the group.

(v)         Any one individual contains only two of the different alleles of a gene, one on each chromosome of the homologous pair carrying that gene.

(vi)        Multiple alleles express different alternatives of a single trait.

(vii)        Different alleles may show codominance, dominance - recessive behaviour or incomplete dominance among themselves.

Example :-

Human Blood Groups

(i)         ABO blood group system in human beings is an example of multiple alleles.

(ii)         Human beings have four blood groups or blood group phenotypes - A, B, AB and O.

(iii)        The blood groups are determined by two types of antigens present in the surface coating of red blood cells-A and B.

(iv)        Blood group A persons have antigen A, group B have antigen B, AB have both antigens while blood group O

persons do not carry antigen in the coating of their erythrocytes.

(v)         Presence, absence and type of antigens are determined by three immunogen alleles IA, IB and i. (vi)            IA forms antigen A, IB antigen B while allele i is recessive and does not form any antigen.

(vii)        Both IA and IB are dominant over i, but not over each other.

(viii)       When both IA and IB are present in a person, both the alleles are able to express themselves forming antigens A and B. Such alleles which are able to express themselves in the presence of each other are called codominant. Thus blood group alleles show both codominant and dominant recessive relationships (IA = IB >> i).

(ix)        A human being carries two of the three alleles, one from each parent. The maximum number of possible genotype is six for the four phenotypes. The phenotypes are tested by two antisera, anti-A and anti-B.

1158_multiple alleles.png

S .No.

Blood Group P he notype

Ge notype

Re a ction w ith  Anti-A      Anti-B

1

O

ii

-       -

2

A

IA IA , IA i

+       -

3

B

IB IB, IB i

-       +

4

AB

IA IB

+       +

(x)        Blood groups being a hereditary character, the knowledge of blood groups of the parents can give information about the possible blood groups of children and vice versa.

Posted Date: 10/10/2012 4:31:48 AM | Location : United States







Related Discussions:- Multiple alleles, Assignment Help, Ask Question on Multiple alleles, Get Answer, Expert's Help, Multiple alleles Discussions

Write discussion on Multiple alleles
Your posts are moderated
Related Questions
ONSE T OF PUBERTY IN MALE Puberty is the period when reproductive organs become functional. It is attained at the age of 13-16 yrs. It is stimulated by testasteron. I

State three conditions in a society which could contribute to a reduction in the birth rate. Birth rate might be decreased by (i) later marriages (as smaller families), (

How Pathologic Conditions causing the underweight? Illness can affect weight status in a number of ways. For example, fevers and infections increase the demand for energy, whic

How can i design an experiment to compare the heat output by two different types of germinating seeds?

organisms and their excretory organelles

Why would we evolve so that when we are stressed our immune system is suppressed? How would this increase survival?

Which are the growth tissues of plants? How do they categorize and where can they be found? The growth tissues of the plants are the meristems. Meristems are the tissues that m

Adverse effects of Lactic acidosis- Lactic acidosis and severe hepatomegaly with steatosis have been reported with use of other nucleoside analogs. The most common adverse effe

If one determines the concentration of cortisol in the blood plasma to be 10 ugrams/ml and that in a 24 hour period a person excretes 10 mgs of cortisol, calculate the volume of bl

describe how ulcers can lead to distention and irritation followed by vomiting?