Multiple alleles, Biology

Assignment Help:

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.


Related Discussions:- Multiple alleles

Explain the energy requirements during sepsis, Explain the Energy Requireme...

Explain the Energy Requirements during Sepsis? Patients suffering from septicemia with or without MODS are generally hyper-metabolic which results in weight loss. Critically il

What is aortic enlargement, Q. What is Aortic Enlargement ? Ascending ...

Q. What is Aortic Enlargement ? Ascending Aorta: The ascending aorta, along with the SVC forms a portion of the right cardiac border on the PA view. After the age of about 40

Deficiency diseases-copper deficiency, Copper deficiency Copper deficie...

Copper deficiency Copper deficiency may be primary or secondary (conditional). Primary copper deficiency occurs due to its inadequate dietary intake; whereas secondary copper d

Types of insulin, There are different types of insulin available and prescr...

There are different types of insulin available and prescribed by the doctor according to the need of the patient. Insulin is grouped according to the speed of action in the body i.

What are the vitamins which make up the b complex, Q. What are the vitamins...

Q. What are the vitamins which make up the B complex? Which problems does the lack of these vitamins cause? Vitamins of the B complex are: vitamin B1 or thiamin, riboflavin, or

Name some emulsifiers which are present in nature, Name some emulsifiers wh...

Name some emulsifiers which are present in nature? There are many emulsifiers which are present in nature such as phospholipids e.g. lectin which is present in egg yolk which a

How do genetic mutations influence biological diversity, How do genetic mut...

How do genetic mutations influence biological diversity? Too frequent or too extensive genetic mutations usually are deleterious for individuals and species. These mutations fr

Why the depicted food web is not complete, The depicted food web is not com...

The depicted food web is not complete, mainly because:  a. The number of producers is less than the number of consumers. b. There are no decomposers. c. Only secondary co

What is hdls, HDLs have the opposite function to that of LDLs in which they...

HDLs have the opposite function to that of LDLs in which they deleted cholesterol from the tissues.  The HDLs are synthesized in the blood mainly from components derived from the d

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd