13.3: A chromosome consists of a DNA molecule packed together with proteins

Question 1

4 levels of packing

Answer 1

1. DNA is wrapped around proteins called histones = nucleosome
2. A string of nucleosomes folds to form a 30nm fiber
3. Further folding of the 30 nm fiber results in looped domains of 300nm
4. As looped domains fold, a metaphase chromosome is formed

Question 2

What kind of chromosomes are not accessible?

Answer 2

Highly packed chromosomes are not accessible to transcription enzymes.

Gene expression is reduced

Question 3

During Interphase _________________

Answer 3

Chromatin is in a form called euchromatin ( spread out)

Question 4

Some parts may be condensed into _______

Answer 4

Some parts may be more condensed into heterochromatin – not accessible to transcription