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CHEM AND BIO HELP AND TIPS HERE

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nid404:
Guys,
        These r my subjects. So if u have any doubts or want to share some tips, pls go ahead. I'll try to answer all ur questions asap........others can join in to help(of course).
There's no common thread for these subjects and so I thought of having one. It'll be easier.

jkiam11:
A question set by my teacher, not sure where he got it and I have no clue about it.

The allele for a normal haemoglobin is In. The allele for a sickle cell haemoglobin production is Is. Explain why under  some circumstances people who are heterozygous for this condition have a greater chance of survival than homozygous people.

nid404:
This is pretty easy. Sickle cell anaemia is caused by a mutation in the blood. When the faulty haemoglobin is present the red blood cells become sickle-shaped, especially when oxygen levels in the blood become low. So these cells r less efficient in transporting oxygen and more likely to get stuck in the capillary, preventing blood flow. The faulty allele is dominated by the normal haemoglobin but has some effect in a heterozygous genotype.(not life-threatening)

Malaria is a life-threatening disease caused by a parasite that invades red blood cells. A person who is heterozygous has a protection from malaria, because the parasite is unable to invade and reproduce in these cells.  A person who is homozygous for sickle cell also has high protection but is likely to die from sickle cell anaemia whereas a person with normal haemoglobin is at a high risk of contracting malaria.

The distributions of malaria and sickle cell on the map coincide in tropical areas because of the selective advantage of the sickle cell allele in providing protection against malaria.

I hope u've understood

jkiam11:
K thanks

nid404:
my pleasure :)

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