Final: Chapter 10 - DNA and RNA

Question 1

What are nitrogenous bases?

Answer 1

aromatic nitrogen containing heterocycles

Question 2

What is a nuceloside?

Answer 2

a nitrogenous base linked to a pentose sugar

Question 3

What are two examples of nucelosides?

Answer 3

D-ribose and 2-Deoxy-D-ribose

Question 4

What is a nucleotide?

Answer 4

A phosphate ester of a nucleoside

Question 5

What is a nucleic acid?

Answer 5

linear polynucleotides linked by phosphodiester bridge

Question 6

What are pyrimidines? Which?

Answer 6

smaller nitrogenous bases; cytosine, uracil, and thymine

Question 7

What are purines? Which?

Answer 7

larger nitrogenous bases; adenine guanine

Question 8

What are three properties of nitrogenous bases?

Answer 8

1) electron rich because aromatic with N and O
2) strong UV absorption
3) water insoluble b/c aromatic

Question 9

What is the difference between uracil and thymine?

Answer 9

one methyl group on carbon 5

Question 10

Which bases are pyrimidines? are they smaller or larger?

Answer 10

cytosine, uracil, and thymine; smaller

Question 11

Which bases are purines? Are they smaller or larger

Answer 11

Adenine and Guanine; larger

Question 12

What kind of bond connects nitrogenous bases and sugars?

Answer 12

glycosidic bond

Question 13

What are the two possible confirmations of a glycosidic bond?

Answer 13

beta and alpha

Question 14

Does a beta glycosidic bond point up or down?

Answer 14

up

Question 15

What configuration are nucleoside glycosidic bonds typically found in?

Answer 15

beta

Question 16

What does anti and syn rotation describe

Answer 16

Rotation around a glycosidic bond?

Question 17

Does syn confirmation mean that nitrogenous base and sugar are stacked or staggered?

Answer 17

stacked

Question 18

Does anti confirmation mean that nitrogenous base and sugar are stacked or staggered?

Answer 18

staggered

Question 19

What is the function of nucleosides?

Answer 19

Typically no function besides adenosine

Question 20

What is the function of adenosine?

Answer 20

Produced as a byproduct of ATP usage for energy, accumulates and promotes sleepiness

Question 21

How does caffeine prevent feeling tired?

Answer 21

Blocks adenosine receptors because it has a similar structure

Question 22

What is a nucelotides?

Answer 22

nucleoside with a phosphate attached at carbon 5

Question 23

What is the name of a nucleoside containing cytosine?

Answer 23

cytidine

Question 24

What is the name of nucleoside containing adenine?

Answer 24

adenosine

Question 25

What is the name of a nucleoside containing uracil?

Answer 25

uridine

Question 26

What is the name of a nucleoside containing guanine?

Answer 26

guanosine

Question 27

Do nucleosides typically reside in anti or syn conformation and why?

Answer 27

anti because there is less steric strain

Question 28

Why do nucleotides link to 5' hydroxyl rather than 2' or 3' hydroxyls?

Answer 28

Because 5' is a primary alcohol which is more accessible than a secondary alcohol

Question 29

What are cyclic nucleotides used for?

Answer 29

signaling pathways

Question 30

How are cyclic nucleotides formed?

Answer 30

Oxygen on phosphate forms ring with 3' hydroxyl on sugar

Question 31

What are three types of nucleotide reactions?

Answer 31

1) hydrolysis 2) functional group transfer 3) nucleic acid synthesis

Question 32

What is a phosphoryl group transfer?

Answer 32

transfer of a phosphate group

Question 33

What is a pyrophosphoryl group transfer?

Answer 33

transfer of two phosphate groups

Question 34

What is a nucleotide group transfer?

Answer 34

transfer of a sugar, phosphate, and nitrogenous base

Question 35

What are three characteristics of nucleic acids?

Answer 35

1) Always linked 3' to 5' by phosphodiester bonds between phosphates and sugars 2) Highly repetitive sugar phosphate backbone 3) Nitrogenous bases give unique identify to nucleic acids

Question 36

What are Chargaff's rules?

Answer 36

1) cytosine amount should be equal to guanine amount 2) adenine amount should be equal to thymine amount 3) purines amount should be equal to pyrimidine amount

Question 37

What is the Watson and Crick model?

Answer 37

Describes DNA as two stranded complementary DNA helix with antiparallel strand that have H-bonding between base pairs

Question 38

How many H-bonds d guanine and cytosine have between them?

Answer 38

3

Question 39

How many H-bonds to adenine and thymine have between them?

Answer 39

2

Question 40

Why do guanine and cytosine form more H-bonds than adenine and thymine?

Answer 40

guanine has a carbonyl that provides an extra H-bond acceptor; adenine does not

Question 41

What is rRNA?

Answer 41

A complex secondary structure of RNA that is the primary component of a ribosome

Question 42

How is rRNA characterized?

Answer 42

sedimentation coefficients; measure sedimentation velocity in response to centrifugation

Question 43

What is tRNA

Answer 43

clover leaf shaped RNA that carries AAs to the ribosome during protein synthesis

Question 44

Why is rRNA structure complex?

Answer 44

there is typically base pairing within the strand

Question 45

What is siRNA?

Answer 45

short interfering RNA that is complimentary to known RNA and creates double stranded RNA to silence translation

Question 46

Why doesn't DNA contain uracil?

Answer 46

cytosine is likely to deaminate to uracil; if uracil was part of DNA code it would be more difficult to proofread

Question 47

What is the benefit of DNA contain 2-deoxy-D-ribose instead of D-ribose?

Answer 47

it is more resistant to alkaline hydrolysis

Question 48

Why does RNA hydrolysis occur? (3 steps)

Answer 48

1) in basic conditions the 3' is deprotonated making it a good nucleophile 2) nucleophilic O attacks electrophilic phosphorus of phosphate 3) phosphate cleaved from 5' carbon

Question 49

What are two enzymes that perform enzymatic hydrolysis of nucleic acids?

Answer 49

1) nucleases 2) restriction endonucleases

Question 50

How can nuclease cleavage vary?

Answer 50

Either hydrolyzes 3' or 5' side of phosphodiester bond

Question 51

How do endonucleases cleave DNA?

Answer 51

identifies specific sequences of DNA and cleaves bond and specific site