Fruit flies normally have eight chromosomes. The diagram below shows the results of meiosis in three fruit flies to produce gametes with the number of chromosomes indicated. The male then mates with both female A and female B to produce three zygotes (1, 2 and 3)
http://tinypic.com/r/wwgakh/7
In which parent did non disjunction take place? Explain.
How many chromosomes would be in zygote 1, 2, and 3?
Which zygote, if any, would be most likely to be healthy? Explain.
Name the conditions the non-healthy zygotes have.
http://tinypic.com/r/wwgakh/7
In which parent did non disjunction take place? Explain.
How many chromosomes would be in zygote 1, 2, and 3?
Which zygote, if any, would be most likely to be healthy? Explain.
Name the conditions the non-healthy zygotes have.
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In which parent did non disjunction take place? Explain.
I think it's obvious right now that the non-disjunction took place in the male parent.
If you need an explanation for non-disjunction, it simply means that the chromosomes are separated unevenly during cell division (during anaphase). In the case of meiosis, it will result in gametes with differing number of chromosomes. That's your male parent.
How many chromosomes would be in zygote 1, 2, and 3?
This is simple. Your resultant embryo will have a chromosome number that's an addition of the chromosome number of your gametes.
Zygote 1: add 4 & 3, that's 7 chromosomes.
Zygote 2: 5 + 4 = 9 chromosomes.
Zygote 3: 5 + 4 = 9 chromosomes.
Which zygote, if any, would be most likely to be healthy? Explain.
They mentioned the normal fruit flies have 8 chromosomes. Therefore, none of them are likely to be healthy. Do also note that normal zygotes have an even number of chromosomes (2n), therefore they will be able to form gametes of haploid number (n).
Name the conditions the non-healthy zygotes have.
Apart from what emucompboy mentioned, the resultant offsprings are also likely to be sterile because of the odd number of chromosomes.
Hope it helps! email me if you have any problems.
I think it's obvious right now that the non-disjunction took place in the male parent.
If you need an explanation for non-disjunction, it simply means that the chromosomes are separated unevenly during cell division (during anaphase). In the case of meiosis, it will result in gametes with differing number of chromosomes. That's your male parent.
How many chromosomes would be in zygote 1, 2, and 3?
This is simple. Your resultant embryo will have a chromosome number that's an addition of the chromosome number of your gametes.
Zygote 1: add 4 & 3, that's 7 chromosomes.
Zygote 2: 5 + 4 = 9 chromosomes.
Zygote 3: 5 + 4 = 9 chromosomes.
Which zygote, if any, would be most likely to be healthy? Explain.
They mentioned the normal fruit flies have 8 chromosomes. Therefore, none of them are likely to be healthy. Do also note that normal zygotes have an even number of chromosomes (2n), therefore they will be able to form gametes of haploid number (n).
Name the conditions the non-healthy zygotes have.
Apart from what emucompboy mentioned, the resultant offsprings are also likely to be sterile because of the odd number of chromosomes.
Hope it helps! email me if you have any problems.
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> In which parent did non disjunction take place?
"Male." With eight chromosomes, normal meiosis would produce gametes with four chromosomes. You can see that "Male" produced gametes with three, and with five.
> How many chromosomes would be in zygote 1, 2, and 3?
Zygote 1 has 4 + 3 = 7 chromosomes (you add the contributions from the parents).
Zygote 2 has 5 + 4 = 9 chromosomes
Zygote 3 has 5 + 4 = 9 chromosomes
> Which zygote, if any, would be most likely to be healthy? Explain.
None of those listed. None of them have the normal chromosome number (which is eight).
> Name the conditions the non-healthy zygotes have.
I can't be specific here, but generally,
Zygote 1 has a monosomy (missing one chromosome from a pair)
Zygote 2 has a trisomy (has a third chromosome in a pair)
Zygote 3 has a trisomy (has a third chromosome in a pair)
"Male." With eight chromosomes, normal meiosis would produce gametes with four chromosomes. You can see that "Male" produced gametes with three, and with five.
> How many chromosomes would be in zygote 1, 2, and 3?
Zygote 1 has 4 + 3 = 7 chromosomes (you add the contributions from the parents).
Zygote 2 has 5 + 4 = 9 chromosomes
Zygote 3 has 5 + 4 = 9 chromosomes
> Which zygote, if any, would be most likely to be healthy? Explain.
None of those listed. None of them have the normal chromosome number (which is eight).
> Name the conditions the non-healthy zygotes have.
I can't be specific here, but generally,
Zygote 1 has a monosomy (missing one chromosome from a pair)
Zygote 2 has a trisomy (has a third chromosome in a pair)
Zygote 3 has a trisomy (has a third chromosome in a pair)