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Biochemistry > Chapter 4 : DNA and RNA > Flashcards

Chapter 4 : DNA and RNA Flashcards

1
Q

Why are DNA and RNA so important.

A

They are able to carry genetic information

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2
Q

What are the three components of nucleic acids ?

A
  • 5 carbon sugar
  • nitrogenous base
  • phosphate group
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3
Q

What are the two types of nitrogenous bases ?

A
  • Pyrimidine

- Purine

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4
Q

What is the difference between pyrimidines and purines ?

A

Pyrimidines contain one ring while purines contain two rings

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5
Q

What is the similarity between pyrimidines and purines

A

Both are insoluble in water and have a planar structure

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6
Q

Which bases are pyrimidines ?

A

Cytosine, Uracil and Thymine

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7
Q

Which bases are purines ?

A

Adenine and Guanine

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8
Q

What are some other purines not commonly used ?

A
  • hypoxanthine
  • xanthine
  • uric acid
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9
Q

What are nucelosides ?

A

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

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10
Q

What is the difference between a nuceloside and a nucleotide

A

Nucleotides contain a phosphate group and nucleosides don’t

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11
Q

How are nucelosides named ?

A

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

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12
Q

What carbon is the phosphate located on the nucleotide ?

A

The 5th carbon

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13
Q

True or false, nucleotides are weak polyprotic acids

A

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

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14
Q

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

A

Complexes with Mg(2+)

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15
Q

Nucleic acids are the polymers of ______

A

nucleotides

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16
Q

What kind of bonds connect nucleic acids together ?

A

phosphodiester bonds

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17
Q

Where is a phosphodiester bond created ?

A

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

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18
Q

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

A

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

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19
Q

DNA has what type of backbone ?

A

sugar phosphate backbone

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20
Q

Adenine binds with

A

Thymine

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21
Q

Cytosine binds with

A

Guanine

22
Q

Thymine can bind with either

A

Adenine or Uracil

23
Q

How many hydrogen bonds are between C and G ?

A

3

24
Q

How many hydrogen bonds are between A and T

A

2

25
Q

Why does DNA have a helical structure

A

DNA is double stranded

26
Q

The sequence of bases also indicates the sequence of

A

amino acids in proteins

27
Q

How is DNA size indicated

A

By the number of base pairs

28
Q

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

A

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

29
Q

What makes the double helix of DNA so stable ?

A
  • Hydrogen bonding between the bases
  • Hydrophobic effect from structure of bases
  • Stacking effect of bases
30
Q

What are the 3 different conformations of DNA?

A

A , B, and Z

31
Q

B DNA

A

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.

32
Q

A DNA

A
  • 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
33
Q

Z DNA

A
  • 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
34
Q

How are stem loop structures formed?

A

Single stranded nucleic acids fold back on themselves

35
Q

Examples of stem loop structures

A

ssDNA and RNA

36
Q

What makes up the stem in the stem loop structure

A

Base pairs

37
Q

What makes up the bulge of the stem loop structure ?

A

mismatched or unmatched bases

38
Q

How can DNA be denatured?

A
  • Heat or UV radiation

- pH extremes

39
Q

Tm or Melting temperature is dependent on what ?

A

% of GC content and % of AT content

40
Q

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

A

Yes through a process known as renaturation

41
Q

Renaturation is dependent on what ?

A

DNA concentration and time

42
Q

The rate of renaturation indicates

A

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

43
Q

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

A

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

44
Q

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

A

Hydrogen bonds

45
Q

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

A

More hydrogen bonds to break

46
Q

What are the three types of RNA

A

mRNA , rRNA , and tRNA

47
Q

mRNA

A

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

48
Q

rRNA

A

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

49
Q

tRNA

A

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

50
Q

What kind of secondary structure does tRNA form

A

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

Biochemistry (8 decks)

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