Question

1) determine the Haploid numberrs of the following Diploid organisms from per cell observations given below

a) 12 tetrads at metaphase 1 of meiosis: ____

b) 80 chromatids at metaphase 1 of meiosis: ____

c) 24 centromeres at metaphase 2 of mitosis: ____

d) 18 chromosomes at metaphase of mitosis:____

Answer 1

a) 12 tetrads at metaphase 1 of meiosis: 12.

Each tertad has two chrmosomes, so, the hapoloid number is equals to tetrad number. Say for example during meiosis we can observed 23tetrads in human cells.

b) 80 chromatids at metaphase 1 of meiosis: 20.

As the metaphase I of meiosis occurs after S phase of interphase, each chromosomes has two chromatids. So, the number of chromsomes = 80/2 = 40, so, the haploid number is 20.

c) 24 centromeres at metaphase 2 of mitosis: 24

As the chromosome segragation occurs in Anaphase I of meiosis, the chromosome number reduced to half. So, the chromosome number in phases II of meiosis is equals to haploid chrmosome number.

d) 18 chromosomes at metaphase of mitosis: 09

During metaphase as chromotid segreatation only occurs, it maintains the diploid chromosome number, so the haploid chromosome number is 18/2 = 9.