iPad 911 PM thestudentroomcouk Answer 2 A different set of r

iPad 9:11 PM thestudentroom.co.uk Answer (2) A different set of results was obtained when the count was repeated on (ii) another occasion with a different garlic root tip. Give two reasons for the difference in results. (2) Total 7 marks) (a) Nucleus A and nucleus B come from the same organism. The diagram shows these nuclei immediately before division and the nuclei formed immediately after their division. The table gives information about some of the nuclei shown in the diagram. Nucleus C Nucleus A Mitosis Nucleus B Meiosis Nucleus D Nucleus Number of chromosomes Mass of DNA arbitrary units 600 B 600 Complete the table for nuclei C and D (2) A student investigated the process of meiosis by observing cells on a microscope slide

Solution

5.
a) Mitosis produces the same number of chromosomes in daughter cells and meiosis halves the chromosomes in daughter cells (after fertilization, it doubles and becomes normal again)
so in case of Nucleus C there will be 8 chromosomes and in case of Nucleus D there will be 4 chromosomes.
Assuming that the mass of DNA is 600 is after DNA replication, just before the cell division.
The mass of DNA in Nucleus C would be 300 and in Nucleus D would be 150
As in case of Nucleus A which undergoes mitosis, the DNA mass would be halved after cell division.
And in case on Nucleus B which undergoes meiosis, the DNA mass would be halves twice (divided by four).

b)

i) Meiosis is used by organisms to reproduce sexually and the process can be observed in sex cells, which is sperm for males and eggs for females. Sperm can be obtained from testes of a male and eggs can be obtained from the ovaries of a female.

ii) Staining in cases of sex cells is primarily used to differentiate between life and dead cells.

Nucleus	No. of Chromosomes	Mass of DNA/arbitrary unit
A	8	600
B	8	600
C	8	300
D	4	150