Mendel and the rediscoverers of genetics Correns dc Vries an

Mendel and the re-discoverers of genetics Correns, dc Vries and Tschermak identified discrete traits whose patterns of inheritance followed interpretable rules. But most traits found in animals and plants were continuous, not discrete, and tended to mix in offspring - when you cross a Labrador and a poodle (two breeds of dogs), you get a labradoodle, not Labradors that give a 3:1 ratio of Labradors and poodles in the next generation. Explain the concept of a gene resulting from the work of Mendel, and use it to explain the appearance of labradoodles. Keep in mind not all dogs are Labradors or poodles.

Solution

Mendel and the re-discoverers of genetics Correns,de Vries and Tschermak identified discrete traitswhose patterns of inheritance followed interpretablerules.But most traits found in animals and plantswere continuous, not discrete, and tended to mix in offspring – when you cross a Labrador and a poodle(two breeds of dogs), you get labradoodles, not Labradors that give a 3:1 ratio of Labradors and poodles in the next generation. Explain the concept of a gene resulting from the work of Mendel, and use it to explain the appearance of labradoodles. Keep in mind that many dogs are neither poodles nor Labradors

ANSWER :

Labrador + Poodle = Labradoodle

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COLOR IS DETERMINED BY

ALLELE AT LOCI B AND E

AND EPISTATIC NATURE OF ALLELES OF COLOR

labrador genotype

at B locus;

black gene dominant over the chocolate gene which is called recessive.

BB = black Lab, no chocolate gene

Bb = black Lab, carries chocolate gene

bb = chocolate Lab, no black gene

Two black genes (BB) gives ------------à black Labrador

One of each (Bb)also give ----------àblack Labrador

Two brown genes (bb) gives ----------àchocolate Labrador

Alleles at locus E, influences the color of ----------à

Genotype

Phenotype

EEBB

Black

EEBb

Black

EEbb

Brown

EeBB

Black

EeBb

Black

Eebb

Brown

eeBB

Yellow

eeBb

Yellow

eebb

Yellow

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Labradoodle=

A black labradoodle can have one of 4 different genotypes.

BBEE

BBEe
or

The yellow labradoodle with the genotype

BB ee

, because of the two dominant alleles BB
, means that it does not carry the recessive brown gene b
. So this dog cannot produce brown (chocolate/cafe/parchement) puppies.

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The yellow labradoodle with the genotype Bb ee ; because of the recessive allele       b

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Because of epistatic nature of allele in Labrador , which doesnot give 3:1 ratio in next generation

Genotype	Phenotype
EEBB	Black
EEBb	Black
EEbb	Brown
EeBB	Black
EeBb	Black
Eebb	Brown
eeBB	Yellow
eeBb	Yellow
eebb	Yellow