Multiple alleles

It includes information regarding multiple allelism

1. 11
June 27, 2020
Multiple Alleles Multiple Alleles
Dr. A. S. WabaleDr. A. S. Wabale
Assistant Professor and Research GuideAssistant Professor and Research Guide
Post Graduate Department of Botany and Research Centre,Post Graduate Department of Botany and Research Centre,
Padmashri Vikhe Patil College of Arts, Science and Commerce,Padmashri Vikhe Patil College of Arts, Science and Commerce,
PravaranagarPravaranagar--413 713413 713
[email protected]@gmail.com

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June 27, 2020
CONTENTSCONTENTS
ÒDefinition, Concept, Characters of multiple alleles,
ÒExamples of multiple alleles
ÒInheritance of blood group in human
ÒSelf-incompatibility in Nicotiana
ÒEye colour in Drosophila
Dr. A. S. Wabale

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June 27, 2020
INTRODUCTIONINTRODUCTION
Dr. A. S. Wabale
Earlier it was considered that a gene has only two alternative forms (alleles),
both influencing the same character alternatively and occupying the same
locusonthehomologouschromosome.
But possibly all the genes change or mutatein several different forms, giving
rise to many alleles .Three or more number of mutantforms-alleles of the
same gene occupying the same locus on the homologous chromosome are
calledmultiplealleles.
All these alleles represent a set or series of multiple alleles. Out of many
allelesonlyoneisdominantandoneisrecessive toallothers.
Irrespective of the number of alleles of a gene only two alleles occur in a
diploid cell (having two homologous chromosomes) and only one allele in a
gamete(havingonlyonechromosomefromeachofthehomologouspair)

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June 27, 2020
HOW ARE MULTIPLE ALLELES WRITTEN ?HOW ARE MULTIPLE ALLELES WRITTEN ?
Dr. A. S. Wabale
In a series of multiple alleles, each gene is dominant to the genes following it and
recessive to those preceding it. Thus, the allele which is dominant to all others
comesfirst and that which is recessive comes last.
Multiple alleles of a series are represented by the same basic latter (preferably the
first letter of the character it represents) and different forms are indicated by the
corresponding small letters with some suitable superscripts which indicate the
characters they represent.
The allele dominant to others is written with capital letters and the recessive one
with small letters.
Example:A series of multiple alleles for coat colour in rabbit is written asC,c
ch
,c
h
,c
where‘C’isdominant and‘c’is recessive.
C c
ch
c
h
c
Full Colour Chinchilla Himalayan Albino

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June 27, 2020
WHAT ARE CHARACTERS OF MULTIPLE ALLELES ?WHAT ARE CHARACTERS OF MULTIPLE ALLELES ?
Dr. A. S. Wabale
üMultiple alleles occupy the same locus on the homologouschromosome
üNo crossing over takes place among themselves due to same loci. When two
alleles are involved in a cross, the same are recovered in the F2
generation.
üMultiple alleles regulate a particular character.
üThe wild type allele is almost always dominant to all others at the same
locus. The other mutant alleles may be either dominant or
intermediate among themselves when two different alleles are
brought together in the same genotype
üWhen any two mutant alleles are crossed, the phenotype of the progeny is
alwaysa mutant type and not the wild type.

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June 27, 2020
HOW BLOOD GROUP IS INHERITED IN HUMAN ?HOW BLOOD GROUP IS INHERITED IN HUMAN ?
Dr. A. S. Wabale
Discovery:
Blood transfusion was first tried in 18
th
century. Some cases were successful, but in others, the recipient
died immediately after he transfusion process. Even, when blood was mixed outside the body, it was
observed that it mixed smoothly in some cases whereas clumping or agglutination of blood cells was found
in others.
Karl Landsteiner,removed blood cells from the plasma and recombined them and noted that smooth
mixing always took place when one’s cells were recombined with one’s own plasma, but when plasma from
one person was mixed with cells from another person, the mixture would be sometimes be smooth but in
other cases resulted in clumping of the cells.
This led to the discovery of blood groups in human. At first, the blood groups were designated by roman
numerals, but today the letter system is used.Karl Landsteiner was awarded with Nobel prize for
Physiology or Medicine in 1930.
Blood groups are distinguished according to the presence or absence of antigens and antibodies
AntigenAntigen AntibodyAntibody
Blood Blood
GroupGroup
Antigenis a substance that form a part of all proteins and is capable of stimulating the production of
specific antibodies.
Antibodyis a substance produced by animals in response to contact with foreign (new to the body)
antigens and react specifically to particular antigens

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June 27, 2020
HOW BLOOD GROUP IS INHERITED IN HUMAN ?HOW BLOOD GROUP IS INHERITED IN HUMAN ?
Dr. A. S. Wabale
Blood GroupsBlood Groups
AA
BB
OO
ABAB
BLOOD TYPES- ABO Blood Group System
According to Landsteiner, the RBC’s of human contain two
naturally occurring antigens. i.e. Antigen-A and Antigen-B.
Depending upon the types of antigens, the blood is classified
into four types or groups
PERSONPERSON
‘A’‘A’
••ANTIGENANTIGEN--AA
PERSONPERSON
’B’’B’
••ANTIGENANTIGEN--BB
PERSON PERSON
‘AB’‘AB’
••ANTIGENANTIGEN--ABAB
PERSONPERSON
‘O’‘O’
••NO ANTIGENNO ANTIGEN
PERSONPERSON
‘A’‘A’
••ANTIBODYANTIBODY--BB
PERSONPERSON
’B’’B’
••ANTIBODYANTIBODY--AA
PERSON PERSON
‘AB’‘AB’
••NO ANTIBODYNO ANTIBODY
PERSONPERSON
‘O’‘O’
••ANTIBODYANTIBODY--A & A &
ANTIBODYANTIBODY--BB
Blood plasma contains antibodies (Anti-A and Anti-B) which
cause clumping of red blood cells containing the
corresponding antigens.

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June 27, 2020
HOW BLOOD GROUP IS INHERITED IN HUMAN ?HOW BLOOD GROUP IS INHERITED IN HUMAN ?
Dr. A. S. Wabale
In humans, blood type antigen is due to agene-I(which stands for isohemagglutinogen). The superscripts ‘A’
and ‘B’ indicate which variation of the allele is represented.
•I
A
represents the gene (allele) that produces theantigen-A.
•I
B
represents the gene (allele) that produces theantigen-B.
•Person heterozygous for these two genes will have bothantigens-AandBand therefore will be classed as
type‘AB’
•I
O
orirepresents the gene that produces none of these antigens.
The blood group character is controlled by a set of these three genes/alleles which is a best example of
multiple alleles.
Genes –I
A
andI
B
are both dominant overgene- I
O
, but not over each other, soI
A
=I
B
Genotypes for the four blood groups are inherited in the simple Mendelian fashion. Offspring with all the
four kinds of blood groups are possible in a cross between two persons heterozygous for blood groups‘A’and
‘B’
Phenotype
(Group)
Genotype Antigen Antibody Can donate blood to
only
Can receive blood of
only
A I
A
I
A
or I
A
I
O
A B A, AB A, O
B I
B
I
B
or I
B
I
O
B A B, AB B, O
AB I
A
I
B
AB - AB A, B, AB, O
(Universal recipient)
O I
O
I
O
i.e. ii - Anti-A and Anti-B A, B, AB, O
(Universal donor)

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June 27, 2020
SELF INCOMPATIBILITY IN SELF INCOMPATIBILITY IN NICOTIANANICOTIANA
Dr. A. S. Wabale
Bisexual plants create functional male and female gametes, however self-pollination
does not lead to fertilization, as a result there is no seed setting. Pollen grain fail to
germinate on the stigma, or even if pollen tube is developed, its growth may be
inhibited.
Such a condition wherepollen grain fail to fertilize the ovule of the same plant is
known as self-incompatibility or self-sterility.Nicotiana(tobacco) was one of the
firstplant in which self-sterility was noticed.
Self-incompatibility is controlled by multiple alleles of a single gene and may be of
two types i.e. gametophytic or sporophytic.Gametophytic self-incompatibility (GSI)
is controlled by the genotype of the pollen grains and is common in families like
Liliaceae, Gramineae and Solanaceae.Sporophytic self-incompatibility (SSI)is
controlled by the somatic or sporophytic cells of the plant which produce pollen
grains, as observed in families Cruciferae and Compositae.
East and Mangelsdorfin 1925 explained the behavior of sterility genes. The gene
controlling incompatibility is designated‘S’and its multiple alleles are represented
by a seriesS
1,S
2,S
3,S
4,S
5,…..and so on. Only two alleles are present in the diploid
cells of a plant.

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June 27, 2020
SELF INCOMPATIBILITY IN SELF INCOMPATIBILITY IN NICOTIANANICOTIANA
Dr. A. S. Wabale
S
1S
2
S
1S
4
S
3S
4
S
1S
2
S
1S
2
S
1S
2
Incompatible Compatible
In the GSI system pollen grains produced by an S
1S
2plant will have either S
1or
S
2allele and are not able to pollinate a pistil with S
1S
2genotype. But if S
1or
S
2pollen grains land on an S
3S
4pistil, fertilization takesplace.
Thus, if the male parent has the genotype S
1S
2it would be incompatible with
plants having S
1S
2,S
1S
4,S
1S
5,S
2S
3,S
2S
4,S
2S
5genotypes, but would be compatible
withS
3S
4,S
3S
5,S
4S
5plants

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June 27, 2020
EYE COLOUR IN DROSOPHILA
Dr. A. S. Wabale
Red eye colourinDrosophilais considered to be normal.White eyedDrosophila
was one of the first mutations discovered inDrosophila.Red and white eye illustrate
simple dominant-recessive relationship.
But, in nature different shades of eye colour inDrosophilaare found. It
means that a number of multiple alleles are responsible for the eye colour in
Drosophila.It is also true that red eye colour is dominant over others.Whenany two
recessivealleles arebroughttogether,intermediate type is obtained.
AllelePhenotype in
homozygous
condition
Heterozygotes
Genotypes Phenotypes
+ Red
W White +/W
W
ch
Cherry +/W
ch
W
h
Blood +/W
h
W
e
Eosin +/W
e
Red Eyes
W
apr
Apricot +/W
apr
W
iv
Ivory +/W
iv
W
cr
Cream +/W
cr
Other HeterozygotesIntermediate
RED CHERRY BLOOD
WHITEBROWN

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SHORTQUESTIONS:
1. Explain multiple alleles with suitable example.
2. Whatarethe charactersof multiple alleles?
3. Explain inheritance of blood group in humans.
4. Define and describe self incompatibility inNicotiana
5. Explain inheritance of Eye ColourinDrosophila
LONGQUESTIONS:
1. Define and explain multiple alleles w.r.t. inheritance of blood group in
humans.
June 27, 2020
ASSIGNMENT
Dr. A. S. Wabale