Structure and Organization of Nucleic Acids

Question 1

List 4 types of non-coding DNA

Answer 1

1) spacer sequences
2) introns
3) genes encoding non-protein coding RNAs
4) repetitious DNA sequences

Question 2

What’s the difference between exons and introns?

Answer 2

exons - translates into proteins

introns - do not translate into proteins, gets spliced out

Question 3

What’s the characteristics of genes within a gene family? How does it occur?

Answer 3

• similar nucleotide sequences and similar proteins, not identical (most likely isozymes)
• arise from gene duplication events

Question 4

What’s a pseudogene?

Answer 4

duplicated genes that over time become inactivated

Question 5

What’s a chromatin?

Answer 5

DNA and its associated proteins (1/3 DNA and 2/3 proteins)

Question 6

When do condensation of DNA occur?

Answer 6

between cell division

Question 7

What are the three levels of condensation?

Answer 7

1) DNA wraps around histone proteins to form a 11nm wide fiber, known as nucleosomes
2) nucleosomes are associated to form a 30nm wide solenoid fiber
3) 30nm fiber forms a 300nm wide loop domains

Question 8

Number of chromosomes found in diploid human cell

Answer 8

46 chromosomes

Question 9

Number of chromosomes found in haploid cell

Answer 9

23 chromosomes

Question 10

How does mitochondrial genome differ from nuclear genome?

Answer 10

• structurally, mitochondrial genome is circular
• mitochondrial genome has a very high gene density
• mitochondrial genome are not extensively associated with proteins like nuclear genome

Question 11

heterochromatin

Answer 11

• darker in stains

- transcriptionally inactive

Question 12

euchromatin

Answer 12

• lighter in stains
• transcriptionally active
• decondensed DNA

Question 13

What process occurs in nucleolus?

Answer 13

ribosome assembly

Question 14

What are some features of nuclear pore complex?

Answer 14

1) functions to regulate traffic between nucleus and cytoplasm
2) proteins are transported into and out of the nucleus in energy-dependent mechanism
3) small molecules can enter easily (metabollites, ATP, GTP, etc)

Question 15

What are the three main types of molecules that are being transported in and out of the nucleus?

Answer 15

mRNA
proteins
ribosomal subunits

Question 16

Describe how ribosomal subunits are transported and when

Answer 16

ribosomal subunits are synthesized in cytoplasm but assembled in nucleolus, and functions outside the nucleus

1) transport into the nucleus to be assembled
2) transport out to its final destination

Question 17

The energy to drive both import and export mechanisms comes from what?

Answer 17

cytoplasmic hydrolysis of Ran-bound GTP

GTP is loaded onto Ran in the nucleus, then once it goes out to the cytoplasm it gets hydrolyzed

Question 18

What drug acts as a topoisomerase II inhbitor and is used as an anti-cancer agent

Answer 18

doxorubicin

Question 19

What two drugs are bacterial topoismerase II inhibitors that as antibiotics?

Answer 19

nalidixic acid and ciprofloxacin

Question 20

What are the nucleotide donors for DNA synthesis?

Answer 20

dATP, dGTP, dCTP, dTTP

Question 21

What enzyme is this? ATP-dependent enzymes that use free energy from hydrolysis of ATP to power unwinding of DNA double helix

Answer 21

DNA helicase

Question 22

What is enzyme is this? relieves the supercoiling caused by the unwinding

Answer 22

topoisomerase

Question 23

What enzyme synthesize RNA primers?

Answer 23

primase activity of polymerases

Question 24

Which end of the DNA strand does DNA polymerase work at?

Answer 24

3’ end in the direction of 5’ to 3’

Question 25

the strand of DNA being synthesized continuously in the direction of 5’ to 3’
What strand is this? What is the direction of parent strand?

Answer 25

leading strand, parent strand is 3’ to 5’

Question 26

What are Okazaki fragments?

Answer 26

pieces of DNA segments synthesized from the lagging strand

Question 27

What enzymes joins Okazaki fragments together?

Answer 27

DNA ligase

Question 28

What enzyme removes RNA primers?

Answer 28

ribnucleases

Question 29

What is the formula used to calculate number of nucleotide bases?

Answer 29

[adenine]=[thymine] and [guanine]=[cytosine]

[purine]=[pyrimidine]

Question 30

What the name of the class of molecules that fit exactly in between base pairs with the helix, distorting the structure of the double helix?

Answer 30

DNA intercalating agents

- they often cause insertions and deletions

Question 31

Which type of topoisomerase manipulate 2 double helices at the same time, relieving the supercoiling effect?

Answer 31

Topoisomerase II

Question 32

What is the action of topoisomerases?

Answer 32

nick and re-ligate DNA strands

Question 33

What are acridine dyes, ethidium bromide and doxorubicin examples of?

Answer 33

DNA intercalating agents