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Molecules to Cells > DNA Structure and Function > Flashcards

DNA Structure and Function Flashcards

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1
Q

Is DNA positively or negatively charged? How does this affect stability?

A

Negative

Enhances stability

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2
Q

How many H bonds between C and G?

A

3

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3
Q

How many H bonds between A and T?

A

2

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4
Q

Which carbon on a ribose contains the hydroxyl group?

A

C2

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5
Q

What are the purines?

A

Adenine

Guanine

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6
Q

Describe the appearance of guanine

A

Bulky, carbonyl

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7
Q

Describe the appearance of adenine

A

Bulky, amine

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8
Q

Describe the appearance of cytosine

A

Not bulky, amine

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9
Q

Describe the appearance of thymine

A

Not bulky, carbonyl

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10
Q

You always read a DNA sequence __’ to __’

A

5’ to 3’

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11
Q

How does the A form helix appear?

A

Bases appear twisted and larger/stretched

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12
Q

What are the stabilizing factors of DNA?

A

H bonds between bases

Van der Waals forces

Positively charged ions

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13
Q

Does single or double stranded DNA absorb light better?

A

Single stranded due to openness/exposure of bases

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14
Q

What is the melting temperature of DNA?

A

When 50% of the DNA is separated

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15
Q

Does AT-rich or GC-rich DNA require higher melting temps?

A

GC-rich

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16
Q

What are nucleoside reverse transcriptase inhibitors (NRTIs)?

A

Block HIV RNA from being reverse transcribed

lacks a 3’ hydroxyl

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17
Q

What is AZT?

A

an NRTI to fight HIV

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18
Q

What is acyclovir?

A

An anti-HIV drug that is converted by (virus-encoded) thymidine kinase into a nucleoside (gGTP) analog similar to AZT

(lacks a 3’ OH)

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19
Q

What is ciprofloxacin?

A

A quinolone (fluoroquinolone)

Used to treat a wide variety of infections agents (gram-negative AND gram-positive)

20
Q

How does ciprofloxacin work?

A

Binds to DNA gyrase topoisomerase II (or IB) via a water metal ion (Mg2+) bridge

Inhibits the topoisomerase ligase activity leading to DNA fragmentation

21
Q

Does DNA have to be cut and re-ligated to be supercoiled?

A

Yes

22
Q

Type I topoisomerases can only work on DNA that is ______.

A

Strained

23
Q

Do type II topoisomerases require ATP?

A

Yes

24
Q

Does type I topoisomerase require ATP?

A

No, uses the energy of the strained DNA

25
Q

What type of organisms use type II topoisomerases?

A

Bacteria, which is why Cipro only attacks bacterial not human DNA!

26
Q

What are Type I topoisomerases used for?

A

Ovarian, colorectal, cancer (since type I will attack human DNA, this is the only useful purpose)

27
Q

Which four histones make up the nucleosome core?

A

H2A, H2B, H3, H4

28
Q

What is the function of H1 histone?

A

Holds the tertiary structure of the nucleosome together by binding to the linker DNA

29
Q

Histones are ______ charged.

A

Positively

30
Q

What is a solenoid?

A

6 nucleosomes per turn coiled with DNA to form a long fiber

31
Q

mRNA is created based off the ______ strand and is thus the ___’ to ___’ strand.

A

Template 3’ to 5’

32
Q

What type of mRNA/DNA is colinear? Why?

A

Prokaryotic mRNA/DNA because there are no introns/exons and thus the sequences are nearly identical

33
Q

What are 3 traits of prokaryotic genes?

A
  1. DNA and protein are colinear
  2. Gene sequences are unique/not repeated
  3. Size of genome corresponds to number of genes
34
Q

What are 3 traits of eukaryotic genes?

A
  1. Size of genome does not correspond to number of genes
  2. Most eukaryotic DNA is non functional or not unique
  3. About 10% of genome codes for proteins
35
Q

How many repeats must genes have be to be considered a “highly repetitive sequence”?

A

> 300,000 copies/genome

36
Q

What are some attributes of highly repetitive sequence?

A

Not transcribed

Usually short tandem AT rich repeats

Make up 10% or less of the genome

37
Q

What is a prime example of a highly repetitive sequence?

A

Telomeres!

38
Q

What are some attributes of moderately repetitive sequences?

A

Derived from transposons

Usually transcribed usually not translated

Make up 25%-45% genome

Code for highly used genes such as histones, rRNA, tRNA but mostly nonfunctional

Separates highly transcribed single copy DNA (i.e. LINES and SINES)

39
Q

How many repeats are “moderately repeated sequences”?

A

2-300,000

40
Q

What are unique or single copy sequences?

A

Make up 40-60% of genome - coding and noncoding

Only 1% of the genome is made into protein in any one cell

Some unique sequences can be related/grouped after a duplication and divergence (e.g. globulins, tubulins, actins) These are often tissue or developmentally regulated and can be clustered or dispersed

41
Q

What are housekeeping genes?

A

Universally required genes

42
Q

What are pseudogenes?

A

Non-functional unique sequences that arise by gene duplication

43
Q

What is myotonic dystrophy type 1?

A

An autosomal dominant trinucleotide (CTG) repeat in which increased repeat-element copy number results in increased severity.

Age at onset decreases and the severity increases in successive generations (anticipation)

44
Q

Trinucleotide repeats _____ than 49 are ______.

A

less than 49 = asymptomatic

45
Q

What mistake leads to trinucleotide repeats?

A

Slippage during replication

46
Q

What are some triplet repeat diseases?

A

Fragile X
Friedrichs Ataxia
Huntingtons
Myotonic dystrophy

Molecules to Cells (34 decks)

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