3 replies to this topic

[krishijones]

I'm totally confused on this problem:

A Gamete has a chromosome complement of 22, X. If this gamete were fertilised by a normal gamete, Would the total number of autosomes present in the somatic cells be 44??

THIS IS WHAT I THOUGHT:

I took as the offsprings would be 45XX or 45 XY but can't guess how we would know the no of autosomes(i.e. non sex cells). Any ideas please help. thanks. In normal offspring, it would be 46XX or 46 XY with 44 autosomes and 2 sex chromosomes. but how to guess/find one for this as we dont know the gamete of the normal gamete here as it could be either 45X or 45Y.

Any help highly appreciated. Thanks.

[swanny]

Hint: for the gamete to be fertilised, the number of chromosomes has to match. Therefore, total autosome numbers are ...

[krishijones]

swanny, on Oct 21 2009, 08:54 PM, said:

Hint: for the gamete to be fertilised, the number of chromosomes has to match. Therefore, total autosome numbers are ...

hey thanks,

so, would the mutated gamete(22,X) be fertilised with another gamete (either 22X or 22Y and NOT 23X or 23Y) meaning the offspring would have 44XX or 44XY, therefore the number of autosome being 42 as there is 2 sex chromosomes? I'm still not sure about this. How do we know that the sex chromosome has been passed from the mutated gamete?

would be grateful if u could help me out please. my uni tutors are rubbish and i get confused with internet!

[swanny]

krishijones, on Oct 23 2009, 03:40 AM, said:

so, would the mutated gamete(22,X) be fertilised with another gamete (either 22X or 22Y and NOT 23X or 23Y) meaning the offspring would have 44XX or 44XY, therefore the number of autosome being 42 as there is 2 sex chromosomes?

Yes. the number refers to the total number of chromosomes, not just the number of autosomes.  So a 22, X gamete being fertilised would lead to an embryo with 44 chromosomes, 2 of which are the sex chromosomes.

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I'm still not sure about this. How do we know that the sex chromosome has been passed from the mutated gamete?

I don't think you can talk about a 'mutated' gamete... unless there's some information in the question that you have omitted. In any case, the loss of a sex chromosome is pretty catastrophic: just think about the human sex chromosome monosomy condition 45X (aka Turner Syndrome); inheritance of a Y chromosome only is embryonic lethal.

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would be grateful if u could help me out please. my uni tutors are rubbish and i get confused with internet!

I just hope your tutors aren't reading this!!!