L14-15: Chromosomes

1.

1 point

Where would you find HU proteins, which are small, positive 2-subunit proteins that do not have stable binding?

Prokaryotic chromosomes

Eukaryotic chromosomes

Linker regions

Areas of the eukaryotic genome containing genes that are frequently expressed

2.

1 point

I am attached to the inner membrane by scaffold protein complexes, which organize DNA into ~500 dynamic loops that can move through protein complexes. WHO AM I?

Prokaryotic chromosome

Eukaryotic chromosome

Mitochondrial DNA

Extrachromosomal plasmids

3.

1 point

You are a scientist in a post-apocalyptic wasteland. You are trying to determine why your antibiotic for the zombie bacteria is not working. You discover a structure that is up to 10^5 base pairs in size, has antibiotic resistance genes, and its gene for beta lactamase degrades penicillin. What is this structure?

HU proteins

Topoisomers

Extrachromosomal plasmids

Mitochondrial DNA

4.

1 point

What is TRUE for mitochondrial chromosomes?

They are linear structures.

They can be replicated by a polymerase encoded by nuclear DNA.

They are only found in prokaryotes.

They have 99,973 genes.

5.

1 point

Topoisomers:

Break, underwind and seal 1 DNA strand without ATP.

Break, underwind and seal 2 DNA strands with ATP.

Have the same number of nucleotide pairs, but different link numbers.

Change the winding status of DNA by cutting the strand and then religating it.

6.

1 point

What is NOT true for Type I topoisomerases?

They underwind relaxed DNA.

They relax underwound DNA.

They change Lk by 1.

They relax overwound DNA.

7.

1 point

Which is NOT true for gyrase?

It changes Lk by 1.

It can relax overwound DNA.

It is a prokaryotic topoisomerase II.

It can cut both DNA strands ahead of the replication fork, underwind, and then religate DNA.

8.

1 point

Histones bind to:

C-G preferentially.

N-beta-glycosidic bonds.

The minor groove.

The major groove.

9.

1 point

A nucleosome has (a) ____ base pairs of DNA from mid-linker to mid-linker, and 146 base pairs are bound to the histone core. Histones are basic as they consist of 25% lysine and (b) ________.

(a) 200 (b) arginine

(a) 216 (b) threonine

(a) 146 (b) aspartic acid

(a) 146 (b) serine

10.

1 point

Which statement is NOT true for histones?

They bind to the minor groove using 142 hydrogen bonds and electrostatic interactions.

Modification such as acetylation, methylation and phosphorylation can influence their charge and shape.

They are assembled using histone chaperones such as chromosome assembly factor-99.

A 10 nm fibre strand of double helix DNA is wound around its core.

11.

1 point

You are fiddling with E. Coli in the lab and accidentally change the Lk number of the DNA you were working on from 243, to 240. WHAT HAVE YOU DONE?

Created a positive supercoil.

Overwound the DNA.

CREATED AN ABOMINATION.

Underwound the DNA.

12.

1 point

Eukaryotes do not have (a) _______ to underwind DNA. Instead they have nucleosomes with underwound DNA, with a Lk number of (b) ___ . The adjacent regions are overwound in compensation, and relaxed by topoisomerase. This allows nucleosomes to be relaxed and stable. Therefore, when histones are removed during DNA synthesis, DNA is left underwound and can be separated quickly.

(a) topoisomer (b) +1

(a) nuclease (b) - 1

(a) nuclease (b) +1

(a) gyrase (b) – 1

13.

1 point

Which is NOT true for the condensation of DNA during mitosis?

Nucleosomes compact DNA 7-fold.

Nucleofilaments compact DNA a further 100-fold.

Higher order packaging compacts DNA a further 15-fold.

DNA is compacted a total of 40,000 fold during mitosis.

14.

1 point

Which of the following is NOT true?

E.Coli DNA has ~4.4k genes, codes for ~4.3k proteins, and produces 115 RNAs.

E.Coli DNA contains 4.6 x 10^6 base pairs.

Most chromosomes are organized into nucleofilaments, but regions with frequently expressed genes are bound to non-histone proteins.

Histones are formed with the help of two types of SMC proteins.