[BiO BB] whats a haplotype

[Dale Beach]

Carefull there- geneticists get rather irate when you confuse genotype and 
phenoptype.  As a reminder, Genotype is the genetic composition of an 
organism.  Phenotype is the outward expression or result of a genotype. 
For Mendel's peas as an example the genotypes WW and Ww would both produce 
round peas while ww would result in wrinkled peas.  In this case the 
dominant W allele masks the presence of a recessive w allele.

The haplotype is the genotype of the haploid or gamete stage of an 
organism's lifecycle. For most common animals this is hidden.  Human egg 
and sperm do not have thier own lifecycle free of their parents, yet the 
gametes certainly have a genotype.  In contrast budding yeast have a 
haploid lifecycle where the haplotype can be very important. If the 
recessive gene w for instance is required for the cell to live, then any 
haploid cell with only the w allele would be dead. If a diplod yeast of 
unknown genotype at the W locus is sporulated and dissected in such a way 
that each of the 4 resulting spores could be tested, then we could directly 
test the genotype of the diploid parent by assaying the haplotype of the 
progeny as follows:
	WW - all 4 spores live (W W W W)
	Ww - 2 spores live and 2 spores never grow (W W w w)
	ww - well we didn't need to worry its already dead!

So in effect, when we can directly assay the haplotype we can more directly 
and rapidly assess the genotype of a diploid parent. In effect Parthav is 
correct, but the reasoning (at least for a geneticist) is much more 
resticted then his original post.

I hope that this helps, and isn't too long of a reply.

dale


Dale Beach
Department of Biology
University of North Carolina
Chapel Hill, NC



--On Sunday, February 10, 2002 9:27 AM -0800 Parthav Jailwala 
<pajailwala at yahoo.com> wrote:

> hi
> in my view, the term 'haplotype' is just used to suggest a mix of
> phenotype and genotype information used to discover further insights into
> a problem. haplotypic data would suggest data inwhich the information
> content would contain both phenotypic data as well as genotypic data.
> I might be wrong, to wait for other views.
>
> thanks
> Parthav Jailwala
> Research Student
> Marquette University, WI
> ----- Original Message -----
> From: "Ayyagari.Kiran" <ayyagari.kiran at hbh.i-labs.ws>
> To: <bio_bulletin_board at bioinformatics.org>
> Sent: Friday, February 08, 2002 10:05 PM
> Subject: [BiO BB] whats a haplotype
>
>
>> 1)can anyone tell me exactly what is a haplotype?
>>   ( is it just another strain of a species with haploid conditon?or
> results
>> from a internal cross between two strains of any species)
>> 2)how haplotypes are used in studying disease polymorphisms
>> 3)how is it used in cytogenetics studies and genome Maps creation
>>
>> thanks
>>
>> A.S.Kiran
>> i-labs
>>
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