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Section 4 > Structure and Organization of Nucleic Acids > Flashcards

Structure and Organization of Nucleic Acids Flashcards

1
Q

What are 4 noncoding DNA Sequences?

A
  1. spacer sequences
  2. Introns
  3. genes encoding non-coding RNA
  4. repetitious DNA
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2
Q

Where is most of satellite dna confined?

A

teleomeres and centromeres

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3
Q

What is the most abundant class of repetitious DNA? What percentage? What does it consist of?

A

interspersed repeats; account for about 45% of DNA..

transposons and retrotransposons

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4
Q

What are spliced out of primary RNA?

A

introns

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5
Q

The DNA sequence that is transcribed to yield a protein or a functional RNA is called a what?

A

gene

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6
Q

Gene families arise from what?

A

gene duplications

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7
Q

What is a pseudogene?

A

when mutations inactivate the duplicate created when a gene family is made

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8
Q

The B-globin gene is an example of what?

A

gene families clustered at one chromosomal locus

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9
Q

DNA + histone = ?

A

chromatin

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10
Q

Explain the 3 levels of condensation in a chromosome.

A

Dna is wrapped around histone proteins to form an 11 nm wide fiber (H2A, H2B, H3, H4)

The histones with DNA wrapped around them are called nucleosomes. a fifth histone H1 attaches to the nucleosomes and seals the structure.

Nucleosomes associated to form a 30 nm wide fiber

30 nm wide fibers forms a 300 nm wide loop domain

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11
Q

What phases does each chromosome consist of two identical DNA strands called chromatids?

A

G2 and M

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12
Q

What are the 3 types of molecules that must be actively transported into the nucleus?

A

mRNA, proteins, and ribosomal subunits

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13
Q

What 2 proteins assist in the important and export of molecules into and out of the nucleus?

A

importin or exportion

Ran-GTP

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14
Q

What are the key points to DNA replication?

A
  1. semi-conservative
  2. replication is initiated at specific origins (multiple ones are found on each chromosome)
  3. replication origins are activated in clusters
  4. replication is bidirectional from each origin
  5. nucleosomes are also replicated
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15
Q

What are 4 properties of DNA polymerases?

A
  1. RNA primers are required
  2. template directed
  3. 5’ –> 3’
  4. dATP, dGTP, dCTP, and dTTp are nucleotide donors
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16
Q

DNA replication steps.

A
  1. DNA helicases unwind DNA.
  2. single-stranded binding proteins bind to expose DNA strand
  3. super-coiling results and topoisomerases received to relieve strain
  4. DNA poly alpha synthesizes short RNA primer and generates a primase with a free 3=OH
  5. DNA poly alpha switches to DNA poly delta
  6. accessory proteins are loaded adjacent to the primer to allow the enzyme to synthesize more DNA before falling off
  7. 5 prime to 3 prime direction; leading strand synthesized and lagging strand is synthesized and generates an Okazaki fragment
  8. RNA primers removed by specific rubonucleases and gaps filled in by DNA polymerase
17
Q

What is TTAGGG?

A

telomere sequence

18
Q

What is the telomere sequence?

A

TTAGGG

19
Q

What are the 3 components of a nucleotide?

A
  1. pentose sugar (ribose or 2’ deoxyribose)
  2. phosphate group
  3. purine/pyrimidine base
20
Q

How would you find the amount of a nucleotide?

A 
Adenine = Thymine
Guanine = Cytosine

Purine = Pyrimidine

So if Adenine is equal to 20%, that means
T= 20. So, A+T = 40% and G+T must equal 60%

21
Q

How many hydrogen bonds from between g and c?

A

3

22
Q

The helical structures of DNA are stabilized by what 3 things?

A
  1. hydrogen bonding
  2. hydrophobic and stakcing interactions between the bps in teh center
  3. interactions of polyanionic backbone with cations
23
Q

How many hydrogen bonds between A and T?

A

2

24
Q

How are base pairs assembled on top of each other?

A

stacked on top of each other like rungs on a ladder

25
Q

What is a class of molecules that fit exactly on the rungs of the ladder, distorting the structure of the double-helix?

A

intercalating agents

26
Q

What are 3 types of intercalating agents?

A

acridine orange, ethiudium bromide and doxorubicin

27
Q

Intercalating agents are mutagenic because they do what?

A

interfere with DNA replication (cause insertions and deletions)

28
Q

What are the two types of topoisomerases?

A

Top 1: cut backbone of one strand, allowing the other strand to rotate. They religate.

Top II: double strand break introduced.

29
Q

What acts on teh human top II and is used as an anticancer agent?

A

doxorubicin

30
Q

What act on bacterial top II enzymes and function as antibiotics?

A

Nalidixic acid and ciproflaxin

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