Question

A couple Molecular Biology questions

1) Human somatic cells have 46 chromosomes.
a) How many daughter cells are formed when a somatic cells undergoes mitosis? b) What is the chromosome number of each daughter cell? c) How many chromatids are present at anaphase of mitosis, G2 of mitosis, anaphase I of meiosis, anaphase II of meiosis, G1 just prior to meiosis I and prophase of meiosis?

2)You digested pBR322 with both EcoRI and BamHI enzymes and purified the large EcoRI- BamHI fragment. You also digest cellular DNA from your favourite organism with EcoRI and BamHI. After mixing the large plasmid vector fragment and the cellular DNA and ligating them you transform an ampicillin sensitive strain of E. coli, and select for ampicillin resistant colonies. If you test all your ampicillin resistant colonies (transformants) for tetracycline resistance, what result do you expect? Please justify your answer.

Answer 1

1.

A. Two diploid daughter cells

B. 2n = 46

C. 92, 46 at each pole of the cell in anaphase of mitosis

92, there will be 46 chromosomes and each chromosome will have 2 chromatids in G2

92 chromatids in 46 chromosomes in anaphase 1

46 chromatids, 23 at each pole of the cell in anaphase 2

46 chromosomes and each chromosome with single chromatid (so, 46 chromatids in total) at G1

46 chromosomes (92 chromatids) in prophase 1

2.

We know that our plasmid was having ampicillin resistance. It means it was able to grow in the presence of ampicillin but not in the presence of any other antibiotic. So if we will use tetracycline for testing the presence of resistance, then none of the colonies will grow because the colonies do not contain any resistance for tetracycline.

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