GENETICS CHAPTER 10

Let's assume that the linker DNA averages 54 bp in length (Nucleosome: ~146 bp of DNA wrapped around a histone octamer). How many molecules of H2A would you expect to find in a DNA sample that is 46,000 bp in length?

460

the chromosomes of eukaryotes typically contain a. a few hundred to several thousand different genes b. multiple origins of replication c, a centromere d. telomeres at their ends e. all of the above

e. all of the above

which of the following is an example of a moderately repetitive sequence? a. rRNA genes b. most protein encoding genes c. both a and b d, none of the above

a. rRNA genes

what are the components of a single nucleosome?

about 146 bp of DNA and eight histone proteins

A bacterial chromosome typically contains

one origin of replication

A segment of DNA had one negative supercoil. If it was given two complete (360 degree) twists in the right-handed direction (overwinding), it would have:

one positive supercoil

Negative supercoiling may enhance activities like transcription and DNA replication because it

promotes DNA strand seperation

in Nolls experiments to test the beads on a string model, exposure of nuclei to a low concentration of DNase 1 resulted in

several bands of DNA in multiples of 200 bp

Origin of replication:

A sequence that is a few hundred nucleotides in length. It functions as an initiation site for the assembly of several proteins required for DNA replication.

What are the components of a single nucleosome?

About 146 bp of DNA and eight histone proteins

Moderately repetitive sequences

Sequences that are found a few hundred to several thousand times in a genome.

Intergenic regions

The nontranscribed regions of DNA located between adjacent genes.

negative supercoiling may enhance activities like transcription and DNA replication because it a. allows the binding of proteins to the major groove b. promotes DNA strand seperation c. makes the DNA more compact d. causes all of the above

b. promotes DNA strand seperation

The compaction leading to a metaphase chromosome does not involve which of the following? a. the formation of nucleosomes b. the formation of 30-nm fiber c. converting its linear DNA to a circular chromosomal DNA d. anchoring and further compaction of the radial loops

c. Converting its linear DNA to a circular chromosomal DNA

the role of cohesion is to a. make chromosomes more compact b. allow for the replication of chromosomes c. hold sister chromatids together d. promote the separation of sister chromatids

c. hold sister chromatids together

a chromosome territory is a region a. along a chromosome where many genes are clustered b. along a chromosome where the nucleosomes are clustered c. in a cell nucleus where a single chromosome is located d. in a cell nucleus where multiple chromosomes are located

c. in a cell nucleus where a single chromosome is located

mechanisms that make the bacterial chromosome more compact include a. the formation of micro and macro domains b. DNA supercoiling c. crossing over d. both a and b

d. a and b

a bacterial chromosome typically contains a. a few thousand genes b. one origin of replication c. some repetitive sequences d. all of the above

d. all of the above

the compaction leading to a metaphase chromosome involves which of the following a. the formation of nucleosomes b. the formation of the 30-nm fiber c. anchoring and further compaction of the radial loops d. all of the above

d. all of the above

Mechanisms that make the bacterial chromosome more compact include a. the formation of loop domains b. DNA supercoiling c. crossing over D. both a and b

d. both a and b

with regard to the 30-nm fiber, a key difference between the solenoid and zigzag models is a. the solenoid model suggests a helical structure b. the zigzag model suggests a more irregular pattern of nucleosomes c. the zigzag model does not include nucleosomes d. both a and b are correct

d. both a and b are correct

DNA gyrase a. promotes negative supercoiling b. relaxes positive supercoils c. cutes DNA strands as part of its function d, does all of the above

d. does all of the above