DNA Packaging
DNA is wound around the outside of the nucleosome, _____ turns comprising ___ bp.
1.75 turns 146 base pairs
How many histone proteins make up the nucleosome core?
8
How many total polypeptide chains would be present in a single nucleosome core particle?
8
About how many base pairs are there between nucleosomes?
About 50-100 bp
What are the histones?
H1, H2a, H2b, H3, and H4.
The nucleosome is comprised of four proteins called...
Histones and DNA.
The ends of the chromosomes are called
Telomeres
When the sister chromatin are attached at one point this is called...
The centromere.
What happens to the two copies each of the histones?
They assemble into a short, cylindrical particle 11 nm in diameter and 5.7 nm high.
What are some examples of heterochromatin?
centromeric DNA repetitive DNA telomeric DNA Barr body
What does the backbone of the DNA consists of?
the negatively charged phosphates which repel each other making the DNA rather stiff.
What makes up the protein component of a nucleosome?
two tetramers of histone proteins
What is karotype ?
when identifying the pairs of chromosomes when they are visible during mitosis. This pairing is called the karotype.
When does the second order of chromatin packing occurs?
when nucleosomes coil together to form a solenoid fiber that is 30 nm in diameter.
Which technique identifies specific areas of a chromosome composed of heterochromatin?
C-banding
What is the first order of chromatin packing?
Coiling around nucleosomes
Heterochromatin
For DNA that is not accessible, the nucleosomes associate to take on a higher order, more condensed structure.
Euchromatin
Genes that are readily accessible for expression, the DNA is in an uncondensed state with the nucleosomes bound, but not associated with each other.
A single chromosome at the beginning of cell division appears as a doublet and each member of the doublet is a _______.
Sister chromatid.
What is the most basic structure of a chromosome?
The nucleosome
What is Cell ploidy?
The number of copies of each chromosome each cell has. (haploid/diploid/triploid)
Assume that the DNA associated with a nucleosome core particle plus the DNA in the linker adds up to 200 bp. Approximately how many base pairs are found in the linker region?
about 54
What chromosome can not be discerned by light microscopy
interphase chromosomes