Question

QUESTION 1

If an organism has 24 tetrads, how many chromosomes will its gametes have?

		12
		24
		6
		48

QUESTION 3

In an organism with five pairs of homologous chromosomes, how many different ways can the tetrads align at the metaphase I plate and how many different combinations of chromosomes will be present in this organism’s gametes?

Different alignments: ____________________

Different chromosome combinations: ___________________

QUESTION 4

1. How many different alleles can exist for a specific gene on a chromosome?

   		1
   		2
   		3
   		no limit to the number of alleles for a gene

   QUESTION 5

2. In what stage of meiosis does chromosome crossing over occur?

   		S phase
   		Prophase I
   		Metaphase I
   		Metaphase II

Answer 1

Answer 1) 24

There are 24 tetrads in the cell. There are 4 chromatids arm in one tetrad. And two chromosome in one tetrad. Hence there is found 48 chromosome in the cell in prophase 1.

The gametes is haploid in number. That's why the gametes have 48/2=24 chromosomes.

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2) The different alignment in metaphase is calculated by 2^(n-1) = 2^(5-1) = 2^4 = 16

There are five pairs of homologous chromosomes in the cell. It means n= 5

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Differnet chromosomes combination in gametes is 2× 16= 32

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4) answer is 1.

The single allele of a gene is found on one chromosomes. That's why there is found only one allele.

In diploid organism, there is found two allele because of two chromosome.

5) Prophase 1.

The pachytene stage of prophase 1 has the crossing over event between the non sister chromatids of homologous chromosome. This leads to swap the genes between non sister chromatids.

Crossing over is not found in metaphase 1 and 2. The chromosome are arranged at equatorial plate. Whereas the DNA duplication occurs in S phase.

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