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Nucleotides and nucleic acids Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What does DNA

stand for?

A

Deoxyribonucleic acid

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2
Q

What does RNA

stand for?

A

Ribonucleic acid

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3
Q

What is the
monomeric unit for
nucleic acids?

A

Nucleotides

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4
Q

What are the 3
components of a
nucleotide?

A

-phosphate group
-pentose (5 carbon
sugar) either
deoxyribose or ribose
-nitrogenous base

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5
Q

Name the 5

nitrogenous bases

A
  • thymine
  • quanine
  • adenine
  • cytosine
  • uracil
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6
Q

Name the 4 bases

present in DNA

A
  • thymine
  • adenine
  • guanine
  • cytosine
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7
Q

Name the 4 bases in RNA

A
  • uracil
  • adenine
  • guanine
  • cytosine
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8
Q

Which base is never

found in DNA?

A

Uracil

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9
Q

Which base is never

found in RNA?

A

Thymine

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10
Q

How are
polynucleotides
formed?

A 
-condensation
reactions occur
-between the
phosphate on carbon
5 of one nucleotide
and the hydroxyl
group on carbon 3 of
another nucleotide
-water is released
-phosphodiester
bond formed
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11
Q

What sort of bond is
formed between
nucleotides?

A

Phosphodiester

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12
Q

How are sequences of

RNA/DNA given?

A

From the 5’ end to

3’ end

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13
Q

What are the two

types of bases?

A

Purines and pyrimidines

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14
Q

What is the structure

of purines?

A

Double ringed

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15
Q

What is the structure

of pyrimidines?

A

Single ringed

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16
Q

Which bases

are purines?

A

Adenine and guanine

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17
Q

Which bases are

pyrimidines?

A

Cytosine, thymine,

and uracil

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18
Q

What does
complementary base
pairing allow?

A

-DNA to be copied

and transcribed

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19
Q

What type of bonds

hold bases together?

A

Hydrogen bonds

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20
Q

How many hydrogen
bonds form between
Adenine and Uracill
Thymine?

A

2

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21
Q

How many hydrogen
bonds form between
Guanine and
Cytosine?

A

3

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22
Q 
In order to allow for
the bases to form
hydrogen bonds what
must happen to one
of the polynucleotide
chains?
A

It must be rotated

through 180 degrees

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23
Q

How does the sugar
phosphate backbone
run on one of the polynucleotide chains? How does the other polynucleotide chain run? What is
this called?

A

From 5’ to 3’ and the other from 3’ to 5’

The antiparallel nature of DNA

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24
Q

Describe the steps
involved in extracting
DNA

A 
-sample ground up
using pestle and
mortar
-sample mixed
with detergent
-salt is added
-protease is added
-ice cold ethanol is
added down the side
of the test tube
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25
Q

Why is the sample
ground in the
extraction of DNA?

A

it breaks down the

cell walls

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26
Q

Why is detergent
added to the sample
in the extraction of
DNA?

A

breaks down the cell
membrane, releasing
the cell contents into
solution

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27
Q

Why is salt added to
the sample in the
extraction of DNA?

A 
neutralises charges
on phosphates in
sugar phosphate
backbone
breaks the hydrogen
bonds between DNA
and water
makes DNA
less soluble
28
Q

Why is protease
added to the sample
in the extraction of
DNA?

A

breaks down the
proteins associated
with DNA

29
Q

Why is ethanol added
to the sample in the
extraction of DNA?

A 
Causes the DNA to
form a white
precipitate between
the layer of the
sample and the
ethanol
30
Q 
Why is a low
temperature
maintained
throughout the
process of DNA
extraction?
A

Reduces rate of
enzyme controlled
reactions that break
down DNA

31
Q

Why should the

ethanol be ice cold?

A

Helps to make DNA

more insoluble

32
Q

At what point in the
cell cycle does DNA
replication occur?

A

S phase

33
Q 
Why is it important
that DNA replication
results in 2 genetically
identical molecules of
DNA?
A 
-ensures the
continuation of
species
-ensures cells and
structures in a
species are
maintained
34
Q

Why is DNA
replication described
as being semi-
conservative?

A 
-Each one of the two
daughter molecules
contains one original
strand of DNA and
one newly
synthesised strand
-the original strand
acts as a template for
a new strand
35
Q

What is the
relationship between
the two daughter
molecules?

A

They are genetically

identical

36
Q 
What is the
relationship between
the daughter
molecules and the
original DNA
molecule?
A

they are identical

37
Q

Which two enzymes
are used in DNA
replication?

A

DNA helicase

DNA polymerase

38
Q

What is the role of

DNA helicase?

A 
-unwinds DNA
from histones
-unzips DNA by
breaking Hydrogen
bonds betwem
complementary base
pairs
39
Q

What is the role of

DNA polymerase?

A 
-catalyses the
reaction to form
phosphodiester
bonds between the
free nucleotides to
form a sugar
phosphate backbones
40
Q

Outline how DNA

is replicated

A 
-DNA helicase
unwinds DNA from
histones and unzips
DNA by breaking
Hydrogen bonds
between
complementary base
pairs
-free nucleotides are
attracted to the
exposed nucleotides
on the strand of DNA
by base
complementarity
-DNA polymerase
forms phosphodiester
bonds between
nucleotides
-two genetically
identical molecules of
DNA are formed
41
Q

What does the
unzipping mean for
DNA nucleotides?

A

They are exposed

42
Q

Due to the
nucleotides being
exposed, what
happens?

A 
Free nucleotides are
attracted to the
exposed nucleotides
by base
complementarity and
form hydrogen bonds
43
Q

Where do the free
nucleotides come
from?

A

Our diet

44
Q

How do free
nucleotides enter the
nucleus?

A

From the cytoplasm
through the nuclear
pores

45
Q

What is a primer?

A 
A short piece of RNA
or DNA with a
complementary
sequence to part of
the DNA template
46
Q

What direction does

DNA synthesis occur?

A

5’ to 3’

47
Q

What is the difference
between the leading
strand and lagging
strand?

A 
The leading strand is
built continuously
whereas the lagging
strand is built
discontinuously
48
Q

Why is there a leading
strand and a lagging
strand?

A

The antiparallel nature

of DNA

49
Q

Why are primers

needed in DNA

A

DNA polymerase
requires them in order
to bond to the 3’ OH
group

50
Q 
What does the
discontinuous
building of the lagging
strand lead to the
production of?
A

Okazaki fragments

51
Q

Which experiment
was used to prove
that DNA replication is
semi-conservative?

A

The Meselsohn and

Stahl experiment

52
Q

Which two techniques
did the Meselsohn
and Stahl experiment
use?

A

Mass labelling and

density centrifugation

53
Q 
Which isotope was
used for mass
labelling in the
Meselsohn and Stahl
experiment?
A

N- 15

54
Q

Why was N-15 used in
the Meselsohn and
Stahl experiment?

A 
It could be
incorporated into the
nitrogenous bases
and therefore track
the movement of
them
55
Q

Which part of the
nucleotide was
labelled in mass
labelling?

A

The nitrogenous

bases

56
Q

What was observed in
the key Meselsohn
and Stahl experiment?

A

band of DNA was
formed inbetween the
N-15 and N-14 bands

57
Q 
How did the key
Meselsohn and Stahl
experiment prove
DNA replication is
semi-conservative?
A 
-the initial molecule of
DNA contained only
N-15 nucleotides
-as DNA replication is
semi-conservative the
DNA which was newly
synthesised in the
N-14 growth media
would contain one
strand with N-15
nucleotides and one
strand with N-14
nucleotides
-so the band would
be in the middle
58
Q 
If DNA replication was
conservative what
would have been
observed in the key
Meselsohn and Stahl
experiment?
A

band of DNA at the
N-14 and N-15
positions

59
Q 
If the E.coli were
allowed to divide
twice in the key
Meselsohn and Stahl
experiment in N-14
what would be seen?
A

A band at N-14 and in
the middle in the ratio
1:1

60
Q 
If the E.coli were
allowed to divide
three times in the key
Meselsohn and Stahl
experiment in N-14
what would be seen?
A

band at N-14 and in
the middle in the ratio
3:1

61
Q

Explain why
complementary base
pairing is important in
DNA replication

A 
-reduces occurrences
of mutation
-allows for formation
of hydrogen bonds
-DNA is replicated
without error
62
Q

What is a mutation?

A

A change in the
sequence of DNA
bases within a gene

63
Q

How do mutations

Occur?

A

A base changing

64
Q

What are 2 possible
consequences of
mutations?

A

evolution

genetic disorders

65
Q

Give 3 differences
between DNA and
RNA?

A 
-DNA has a double
stranded structure
whilst RNA has a
single stranded
structure
-In DNA A bonds to T
and G bonds to C, in
RNA A bonds to U and
G bonds to C
-DNA is too big to
leave the nucleus,
RNA is small enough
to leave the nucleus

Biology (11 decks)

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