If the cells are fixed during metaphase of the 2nd, 3rd, 4th and 5th mitotic div

Question

If the cells are fixed during metaphase of the 2nd, 3rd, 4th and 5th mitotic divisions, determine what pattern(s) of radioactivity (from the picture below) would the chromosomes be expected to exhibit and in what percentage(s)? If a chromosome pattern is NOT present, leave cell BLANK. Place answers IN BOX BELOW. This question is asking for chromosome radioactive patterns after three different mitotic division scenarios. Use fractions for your answers (i.e. 1/2, 1/3, 1/4, 1/8, etc.), and the sum of all fractions should equal 1.

Chromosome Pattern

% after 2nd MITOTIC DIV.

% after 3rd MITOTIC DIV.

% after 4th MITOTIC DIV.

A

B

C

D

E

F

Sum

1

1

1

Note: White chromatids have neither strand labeled with radioactive dTTP.
Striped chromatids have one strand labeled and one strand unlabeled with radioactive dTTP. Black chromatids have both strands labeled with radioactive dTTP.

Chromosome Pattern

% after 2nd MITOTIC DIV.

% after 3rd MITOTIC DIV.

% after 4th MITOTIC DIV.

A

B

C

D

E

F

Sum

1

1

1

A geneticist grows plant root cells for many generations under normal conditions. He then introduces radioactive deoxythymidine triphosphate (dTTP) into the media prior to replication during interphase of the cell cycle. The cells are then grown for several consecutive mitotic divisions in the presence of dTTP, causing newly synthesized strands of DNA to become radioactively labeled. If the cells are fixed during metaphase of the 2nd , 3rd , 4th and 5th mitotic divisions, determine what pattern(s) of radioactivity (from the picture below) would the chromosomes be expected to exhibit and in what percentage(s)? If a chromosome pattern is NOT present, leave cell BLANK. Place answers IN BOX BELOW. This question is asking for chromosome radioactive patterns after three different mitotic division scenarios. Use fractions for your answers (i.e. 1/2, 1/3, 1/4, 1/8, etc.), and the sum of all fractions should equal 1. Note White chromatids have neither strand labeled with radioactive dTTP. Striped chromatids have one strand labeled and one strand unlabeled with radioactive dTTP. Black chromatids have both strands labeled with radioactive dTTP. REMEMBER! Cells in metaphase have the chromosomes in a duplicated format!!! Interphase Prophase Prometaphase Metaphase

Explanation / Answer

2nd mitotic division: 1/3 and 2/3

3rd mitotic division: 1/4, 3/4

4th mitotic division: 1/4, 3/4, 1/8,

5th mitotic division: 1/3 and 2/3

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