Problem Set 1
This problem set covers material from January 9
through January 18
From Griffiths et al. 9
edition, (# in parentheses = same question found in the10
Chapter 2, problems 2(16), 3(17), 9(23), 11(25), 13(27)
Chapter 3, problems 7(18), 15(26), 16(27)
Chapter 7, problems 1(6), 2(7), 3(8), 5(10), 18(24), 19(25), 26(30), 27(31)
2.2(16) PFGE separates DNA molecules by size.
When DNA is carefully isolated from
Neurospora (which has seven different chromosomes) seven bands should be produced using this
Similarly, the pea has seven different chromosomes and will produce seven bands
(homologous chromosomes will co-migrate as a single band).
2.3(17) There is a total of 4 m of DNA and nine chromosomes per haploid set.
On average, each
is 4/9 m long.
At metaphase, their average length is 13
m, so the average packing ratio is 13 x
m: 4.4 x10
or roughly 1:34,000.
This remarkable achievement is accomplished through the
interaction of the DNA with proteins.
At its most basic, eukaryotic DNA is associated with
histones in units called nucleosomes and during mitosis, coils into a solenoid.
As loops, it
associates with and winds into a central core of nonhistone protein called the scaffold.
2.9(23) As cells divide mitotically, each chromosome consists of identical sister chromatids that
are separated to form genetically identical daughter cells.
Although the second division of
meiosis appears to be a similar process, the “sister” chromatids are likely to be different.
Recombination during earlier meiotic stages has swapped regions of DNA between sister and
nonsister chromosomes such that the two daughter cells of this division typically are not
It could work but certain DNA repair mechanisms (such as postreplication
recombination repair) could not be invoked prior to cell division.
There would be just two cells
as products of this meiosis, rather than four.