Chapter 4 : DNA and RNA

Question 1

Why are DNA and RNA so important.

Answer 1

They are able to carry genetic information

Question 2

What are the three components of nucleic acids ?

Answer 2

• 5 carbon sugar
• nitrogenous base
• phosphate group

Question 3

What are the two types of nitrogenous bases ?

Answer 3

• Pyrimidine

- Purine

Question 4

What is the difference between pyrimidines and purines ?

Answer 4

Pyrimidines contain one ring while purines contain two rings

Question 5

What is the similarity between pyrimidines and purines

Answer 5

Both are insoluble in water and have a planar structure

Question 6

Which bases are pyrimidines ?

Answer 6

Cytosine, Uracil and Thymine

Question 7

Which bases are purines ?

Answer 7

Adenine and Guanine

Question 8

What are some other purines not commonly used ?

Answer 8

• hypoxanthine
• xanthine
• uric acid

Question 9

What are nucelosides ?

Answer 9

Contains a nitrogenous base and a sugar ( ribose or deoxyribose )

Question 10

What is the difference between a nuceloside and a nucleotide

Answer 10

Nucleotides contain a phosphate group and nucleosides don’t

Question 11

How are nucelosides named ?

Answer 11

Add - idine to the root name if it’s a pyrimidine an - osine if it is a purine

Question 12

What carbon is the phosphate located on the nucleotide ?

Answer 12

The 5th carbon

Question 13

True or false, nucleotides are weak polyprotic acids

Answer 13

False, nucleotides are strong polyprotic acids. They can dissociate 3-4 protons from their phosphate groups

Question 14

Phosphate anions form stable complexes with divalent cations. Which one is most common?

Answer 14

Complexes with Mg(2+)

Question 15

Nucleic acids are the polymers of ______

Answer 15

nucleotides

Question 16

What kind of bonds connect nucleic acids together ?

Answer 16

phosphodiester bonds

Question 17

Where is a phosphodiester bond created ?

Answer 17

Between the C3 ( OH) of one nucleotide and the C5 phosphate of the next nucleotide

Question 18

What is the difference between the 5’ direction and the 3’ direction

Answer 18

Phosphate on the C5 indicates the 5’ end . -OH on C3 indicates the 3’ end

Question 19

DNA has what type of backbone ?

Answer 19

sugar phosphate backbone

Question 20

Adenine binds with

Answer 20

Thymine

Question 21

Cytosine binds with

Answer 21

Guanine

Question 22

Thymine can bind with either

Answer 22

Adenine or Uracil

Question 23

How many hydrogen bonds are between C and G ?

Answer 23

3

Question 24

How many hydrogen bonds are between A and T

Answer 24

2

Question 25

Why does DNA have a helical structure

Answer 25

DNA is double stranded

Question 26

The sequence of bases also indicates the sequence of

Answer 26

amino acids in proteins

Question 27

How is DNA size indicated

Answer 27

By the number of base pairs

Question 28

True or False, the two strands of DNA have an anti- parallel orientation .

Answer 28

True, one strand has the 5' to 3' end while the other strand is the 3' to 5' end

Question 29

What makes the double helix of DNA so stable ?

Answer 29

- Hydrogen bonding between the bases - Hydrophobic effect from structure of bases - Stacking effect of bases

Question 30

What are the 3 different conformations of DNA?

Answer 30

A , B, and Z

Question 31

B DNA

Answer 31

The most common form of DNA. Termed the right handed helix . The major groove is wide while the minor groove is narrow, both intermediate size.

Question 32

A DNA

Answer 32

- Formed when DNA is dehydrated - found in some DNA- RNA hybrids - Longer right handed helix - Major groove is narrow and deep while minor groove is broad and shallow

Question 33

Z DNA

Answer 33

- biological role is unknown - binds to some viral proteins - Left handed helix - Methylation of C can change Z to B form - Major groove is flattened out and the minor groove is narrow but deep

Question 34

How are stem loop structures formed?

Answer 34

Single stranded nucleic acids fold back on themselves

Question 35

Examples of stem loop structures

Answer 35

ssDNA and RNA

Question 36

What makes up the stem in the stem loop structure

Answer 36

Base pairs

Question 37

What makes up the bulge of the stem loop structure ?

Answer 37

mismatched or unmatched bases

Question 38

How can DNA be denatured?

Answer 38

- Heat or UV radiation | - pH extremes

Question 39

Tm or Melting temperature is dependent on what ?

Answer 39

% of GC content and % of AT content

Question 40

If DNA is removed from denaturing effects, , can the strands renature ?

Answer 40

Yes through a process known as renaturation

Question 41

Renaturation is dependent on what ?

Answer 41

DNA concentration and time

Question 42

The rate of renaturation indicates

Answer 42

How complex the DNA is. The more repeated DNA is , the faster it will reform compared to unique sequences. It also indicates length.

Question 43

Why does DNA have a major groove and a minor groove ?

Answer 43

Since DNA is anti- parallel, the nucleotides are placed at an angle instead of directly across. This can cause the strand's backbone to be closer or father apart from each other

Question 44

When DNA is denatured, what bonds are being broken between the bases ?

Answer 44

Hydrogen bonds

Question 45

Why does DNA with a higher GC content require a higher temperature to be denatured ?

Answer 45

More hydrogen bonds to break

Question 46

What are the three types of RNA

Answer 46

mRNA , rRNA , and tRNA

Question 47

mRNA

Answer 47

Messenger RNA : The RNA copy of the DNA base sequence which is used for protein synthesis. - Also contain a poly A tail an a 5' cap

Question 48

rRNA

Answer 48

Ribosomal RNA : Major component of ribosomes. It contains two subunits of different sizes

Question 49

tRNA

Answer 49

Transfer RNA : carries the appropiate amino acid to the polypeptide chain

Question 50

What kind of secondary structure does tRNA form

Answer 50

Cloverleaf structure that contains acceptor stem, anti-codon loop , D-loop, Tψ loop, and variable loop