During sperm formation in mammals, part of the structure of each chromosome is replaced with proteins called protamines. This replacement allows the DNA to be packaged much more densely than would otherwise be possible.
Which part of the chromosome is replaced by protamines?
centromeres
chromatids
histones
telomeres
The graphs show various distance measurements taken from the start of metaphase of mitosis. The graphs are to scale when compared to one another.
Which row correctly identifies the distance measurement for each graph?
X
Y
distance between poles of spindle
distance of centromeres from poles of spindle
distance between poles of spindle
distance between sister chromatids
distance of centromeres from poles of spindle
distance between sister chromatids
distance of centromeres from poles of spindle
distance between poles of spindle
Which diagrams show roles of mitosis?
1
4
3
1, 2, 3 and 4
1, 2 and 3 only
1 and 2 only
3 and 4 only
Which row correctly shows the behaviour of the nuclear envelope, the centrioles and the spindle during a stage of mitosis?
nuclear envelope
centrioles
spindle
disappears
replicate
spindle microtubules begin to form
not present
begin to move to poles of cell
spindle microtubules fully formed
begins to reform
at opposite poles of the cell
some spindle microtubules shorten
reforms
one beside each nucleus
spindle microtubules break down