Question Regarding Gamete Formation

[shoehornlettuce]

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In individuals with some form of chromosomal error (say XYY), how does gamete formation work? Would you randomly end up with 2 sex chromosomes in one gamete and 1 in the other (i.e., equal chance of either X and YY or XY and Y)?

 

[MedPR]

In individuals with some form of chromosomal error (say XYY), how does gamete formation work? Would you randomly end up with 2 sex chromosomes in one gamete and 1 in the other (i.e., equal chance of either X and YY or XY and Y)?

XYY specifically would typically be caused by non disjunction in anaphase 2. One sperm would have 2Y and the other would have 0Y

 

[deleted92121]

Non disjunction is the cause. If it occurs in Meiosis I (Anaphase I), all gametes will be abnormal. If it occurs during Meiosis II (Anaphase II), only half of the gametes will be abnormal.

 

[shoehornlettuce]

Thanks for the replies. I should have been a bit more clear in my question. I'm wondering about the gamete formation of the individual who has the condition, not how the condition was brought about in the first place. So say an individual is XXY. When the cell that already contains the XXY undergoes meiosis, after meiosis 1 you have an odd number of replicated chromosomes so how do they divide into gametes? Do you just randomly get 2 in one gamete and 1 in the other? Then after meiosis II you simply have 2 gametes with 1 sex chromosome and 2 gametes with 2 sex chromosomes?

Thanks again

 

[deleted92121]

Thanks for the replies. I should have been a bit more clear in my question. I'm wondering about the gamete formation of the individual who has the condition, not how the condition was brought about in the first place. So say an individual is XXY. When the cell that already contains the XXY undergoes meiosis, after meiosis 1 you have an odd number of replicated chromosomes so how do they divide into gametes? Do you just randomly get 2 in one gamete and 1 in the other? Then after meiosis II you simply have 2 gametes with 1 sex chromosome and 2 gametes with 2 sex chromosomes?

Thanks again

Not sure I understand one hundred percent what you are asking but let me add a little more to my last response in hopes of helping.

If non disjunction occurs during Meiosis I, the gametes that from would be 2 disomic (2 chromosomes per gamete) and 2 nullsomic (no chromosomes per gamete).

If non disjunction occurs at the end of meiosis II, the gametes that form at the end meiosis II would be 2 normal euploid gametes, 1 disomic gamete (2 chromosomes), and 1 nullsomic (no chromosomes).

Hope this helps.

 

[Captain Sisko]

Thanks for the replies. I should have been a bit more clear in my question. I'm wondering about the gamete formation of the individual who has the condition, not how the condition was brought about in the first place. So say an individual is XXY. When the cell that already contains the XXY undergoes meiosis, after meiosis 1 you have an odd number of replicated chromosomes so how do they divide into gametes? Do you just randomly get 2 in one gamete and 1 in the other? Then after meiosis II you simply have 2 gametes with 1 sex chromosome and 2 gametes with 2 sex chromosomes?

Thanks again

Not sure but isn't that person infertile as a result of their condition? I'd think the hormonal issues associated with it would impede sexual development enough to make the issue of gamete formation a moot question. I could be wrong here, never really looked into it.

 

[BB8730]

Thanks for the replies. I should have been a bit more clear in my question. I'm wondering about the gamete formation of the individual who has the condition, not how the condition was brought about in the first place. So say an individual is XXY. When the cell that already contains the XXY undergoes meiosis, after meiosis 1 you have an odd number of replicated chromosomes so how do they divide into gametes? Do you just randomly get 2 in one gamete and 1 in the other? Then after meiosis II you simply have 2 gametes with 1 sex chromosome and 2 gametes with 2 sex chromosomes?

Thanks again

I'm not sure of the exact events that take place during meiosis, but generally XXY males produce normal gametes due to the deletion of the extra sex chromosome early in gametogenesis. They are certainly at an increased risk of producing gametes with abnormalities, though.

Not sure but isn't that person infertile as a result of their condition? I'd think the hormonal issues associated with it would impede sexual development enough to make the issue of gamete formation a moot question. I could be wrong here, never really looked into it.

If two X chromosomes are present, one of them is inactivated and the genes are not expressed. This happens in normal females and XXY males, so most of the genes from the extra chromosome are not expressed and there aren't any huge differences between XXY males and XY males. XXY does cause some hormonal problems, but it can be treated with hormone therapy and people with the XXY karyotype can be fertile.