CHAPTER 14 DNA STRUCTURE AND FUNCTION Flashcards
1
Q
How many chromosomes in a human cell?
A
23 pairs.
2
Q
DNA stands for?
A
Deoxyribonucliec acid
3
Q
Who reported the first demonstration of bacterial transformation/nucliec acid?
external DNA is taken by cell, changing its morphology & physiology
A
Freidrich Miescher
4
Q
Nuclieotides are the building block of what?
A
DNA
5
Q
Important components of nucleotides?
A
5-carbon sugar ( pentose ), phosphate group, and nitrogenous bases.
6
Q
what are purines? and what nucleotide is a purine?
A
Purines’ are double ringed structure with a six-membered structure fused to a five membered ring.
Adenine and Guanine.
7
Q
what are pyrimidines? and what nucleotide is a pyrimidines?
A
Pyrimidines’ smaller in size; has one six membered ring structure.
Cytosine, Thymine ( DNA ), Uracil ( RNA )
8
Q
How are nucleotides different from nucleosides?
A
Nucleosides contain only sugar and a base.
Nucleotides contain sugar, base and a phosphate group.
9
Q
What is the sugar called in DNA?
A
Deoxyribose.
10
Q
What is the sugar called in RNA?
A
Ribose.
11
Q
In which nucliec acid does the 3’ prime carbon of the sugar deoxyribose attaches to the hydroxyl (OH ) group?
A
DNA
12
Q
What makes DNA and RNA acidic?
A
Phosphate.
13
Q
What did Francis Crick and James Watson discover?
A
Molecular structure of DNA
14
Q
How many hydrogen bonds does adenine and thymine are stablized with?
A
Two hydrogen bonds.
15
Q
How many hydrogen bonds does cytosine and guanine are stablized with?
A
Three hydrogen bonds.
16
Q
What is the backbone of DNA?
A
Phosphate molecules and deoxyribose sugar.
17
Q
What’s stacked inside like rungs of a ladder?
A
NItrogenous bases.
18
Q
a technique used to seperate DNA fragments of different sizes.
A
Gel electrophoresis.
19
Q
RNA and DNA occur in a seperate compartment from protein synthesis.
A
Eukaryotic cells.
20
Q
Both DNA and RNA processes occur together?
A
Prokaryotic cells.
21
Q
What is DNA wrapped around?
A
Histones
22
Q
What are histones functions and what do they form?
A
they bind to DNA,
help give chromosomes their shape and control actvitiy of genes.
nucleosomes
23
Q
Why is DNA negatively charged?
A
Phosphate groups.
24
Q
Heterchromatin contains what? and what region.
A
contains genes that are not expressed and tightly packaged region of the telomeres and centromeres.
25
Euchromatin contains what? and what region.
contains genes that are transcribed with DNA packaged around nucleosomes in a less dense region.
26
Conservative, semi-conservative and, dispersive refer to what?
a. translation
b. transcribing
c. dna replication.
d. dna synthesis
DNA replication
27
The parental DNA remains together, and new formed daughter strands are still together.
a. semi-conservative
b. conservative
c. dispersive
conservative replication.
28
semi-conservative
suggest two parent DNA acts as a template from new DNA to be synthesized after replication each DNA includes a new and old strand.
29
both copies of DNA have double stranded segments of parental dna and newly synthesizied DNA interspersed.
Dispersive
30
What's DNA polymerase?
adds nucleotides 1 by 1 to the growing DNA chain that is complementary strand
31
Where is the energy for the addition of nucleotides obtained from?
The nuceloside triphosphate
ATP GTP CTP TTP.
32
What happens when the bonds between the phosphates is broken?
energy released is used to form phosphodiester bonds between the incoming nucleotide and growing chain.
33
How does the replication machinery know where to begin?
origins of replication
what is it?
34
What process uses ATP hydrolysis?
Helicase to unwind DNA
35
DNA pol 1
Removes RNA primer and replaces new synthesized DNA.
36
DNA POL 3
Main enzyme that adds nucleotides to the 5'-3' direction.
37
Helicase
Opens the DNA helix by breaking hydrogen bonds in between nitrogenous bases,
38
Ligase
Seals gaps between okazaki fragments to create oen continous DNA strand.
39
Primase
Synthesizes RNA primers needed to start replication.
40
Sliding camp
Helps hold the DNA polymerase in place when nucleotides are being added.
41
Topoisomerase
Helps relieve the strain on DNA when unwinding by causing breaks and then resealing the dna
42
SSB
binds to single stranded dna to prevent DNA from rewinding back.
43
Two restrictions of DNA polymerase?
1. able to add nucleotides only in the 5'-3' direction(new dna can only be extended this way)
2. requires at free 3' -OH group to add nucleotides by forming a phosphodiester bond between 3'-OH end and the 5'phosphate of the next nucleotide.
* cannot add nucleotides if a free -OH group is not available.
44
Why DNA template strand have opposing orientations?
1. polymerase can only extend in the 5' to 3' direction and DNA double helix is antiparallel.
45
What can be synthesized continously towards the replication fork.
only one new dna strand that is complementary to the 3' to 5' parental DNA strand.
46
Okazaki fragments
the short lengths of DNA that are produced by the discontinuous replication of the lagging strand.
47
The process of DNA replication can be summarized as follows: Whats the correct order.
1.DNA unwinds at the origin of replication.
2.Single-strand binding proteins coat the DNA around the replication fork to prevent rewinding of the DNA.
3.Primase synthesizes RNA primers complementary to the DNA strand.
9.DNA polymerase III starts adding nucleotides to the 3'-OH end of the primer.
4.Topoisomerase binds at the region ahead of the replication fork to prevent supercoiling.
5.Gaps are filled by DNA pol I by adding dNTPs.
6.Helicase opens up the DNA-forming replication forks; these are extended bidirectionally.
7.The gap between the two DNA fragments is sealed by DNA ligase, which helps in the formation of phosphodiester bonds.
8.Elongation of both the lagging and the leading strand continues.
10. RNA primers are removed by exonuclease activity.
1, 6, 2, 4,3,9, 8,10, 5, 7
48
Major roles of DNA replication in DNA polymerase
pol α, pol β, pol γ, pol δ, and pol ε.
49
What is Eukaryotic DNA bound to?
Histones that form nucleosomes
50
Difference between replication in Prokaryotic and Eukaryotic replication.
Prokaryotes have single orgin of replication, rate of 1000 nucleotides/s, 5 DNA polymerase types, DNA pol 1 primer removal, DNA Pol 3 elongation, Sliding camp
Eukaryotes have multiple origin of replication, rate of 50 to 100 nucleotides/s, 14 Dna Polymerase types, Telomerase present, RNase H as removal primer, Pol a,o,e as elongation and PCNA as sliding camp.
51
Which is the leading/lagging strand in DNA poly in Eukaryotes
leading is enzyme pol e, lagging pol o
52
telomeres
genomic portions at the ends of linear chromosomes.
53
Proof reading
DNA pol reads the newly added base before adding the next one, so correction can be made.
54
What happens in an incorrect base is added, and what is it performed by.
the enzyme makes a cut at the phosphodiester bond and releases wrong bond
does this by 3' exonuclease.
55
Mismatch pair
error corrected after replication.
56
how do mismatch repair enzymes recognize which of the two bases is the incorrect one?
they detect the non-methylated strand
In E. coli, after replication, the nitrogenous base adenine acquires a methyl group; the parental DNA strand will have methyl groups, whereas the newly synthesized strand lacks them
57
Xeroderma pigmentosum in human is associated with an error in what repair mechanism?
nucleotide excision repair
58
Which of the following are true statements concerning telomeres?
1. telomere shortening is associated with aging
2. telomeres contain repetitive sequences that do not code for a particular gene
59
Nucleotide excision repair
used to remove damaged bases.
replaces abnormal bases by making a cut on both 3'to5' ends of damaged base
60
Induced mutations
those that result from an exposure to chemicals, UV rays, x-rays, or some other environmental agent.
For example, Charlotte Auerbach and J.M Robson discovered the mutation-inducing effects of mustard gas.
61
Spontaneous mutations
occur without any exposure to any environmental agent; they are a result of natural reactions taking place within the body.
62
Transition subsitution
refers to a purine or pyrimidine being replaced by a base of the same kind; for example, a purine such as adenine may be replaced by the purine guanine.
63
tranversion subsitution
refers to a purine being replaced by a pyrimidine, or vice versa;
for example, cytosine, a pyrimidine, is replaced by adenine, a purine. Some point mutations are not detectable in the final product; these are known as silent mutations.
64
silent mutations
due to a substitution in the third base of a codon, which often represents the same amino acid as the original codon.
65
Mutations can be..
the result of the addition of a base, known as an insertion, or the removal of a base, also known as deletion.
66
A frameshift mutation that results in the insertion of three nucleotides is often less deleterious than a mutation that results in the insertion of one nucleotide. Why?
If three nucleotides are added, one additional amino acid will be incorporated into the protein chain, but the reading frame won't shift
67
frameshift mutation
a gene refers to the insertion or deletion of nucleotide bases in numbers that are not multiples of three.
68
the cellular process of transcription generates what?
mRNA - messenger RNA
a mobile molecular copy of one or more genes with an alphabet of A, C, G, and uracil (U).
69
Central dogma
the flow of genetic information DNA mRNA TO Protiens
70
How is the copying DNA straight forward?
with one nucleotide being added to the mRNA strand for every nucleotide read in the DNA strand.
71
Translation to protein is what
systematic and colinear
nucleotides 1 to 3 correspond to amino acid 1, nucleotides 4 to 6 correspond to amino acid 2, and so on.
72
Triplet codon
three nuceotide sequence
73
What did Francis crick and Sydney brenner experiment?
used the chemical mutagen proflavin to insert one, two, or three nucleotides into the gene of a virus.
which demonstrated that amino acids must be in groups of three of specified nucleotides.
74
Nucleotides triplets
Codons
75
Reading frame
one of three possible ways of reading a nucleotide sequence
76
Start Codon
AUG: Methionine
77
Stop Codon
UAA,UAG,UGA
78
Nonsense codons
stop codons ; one of the three mRNA codons that specifies termination of translation
79
Degeneracy
specification of a single amino acid by multiple similar codons
Degeneracy is believed to be a cellular mechanism to reduce the negative impact of random mutations.
80
* something to know*
that some amino acids get a block and a half-block for a total of six codons.
81
Baterial chromosomes
a closed circle that is not wrapped around histone proteins
82
Plasmids
shorter circular DNA that may contain one or a few genes
83
Central region of the cell in prokaryotes resides is called
Nuclieod Region
84
Transcription in Pro. and Euk. requires ?
requires the DNA double helix to partially unwind in the region of mRNA synthesis.
85
The region of unwinding
Transcription bubble
86
Transcription always proceeds from the same DNA strand for each gene,
Template strand
87
Non template strand or coding strand
The mRNA product is complementary to the template strand and is almost identical to the other DNA strand,
88
Nucleotide Difference in mRNA
all of the T nucleotides are replaced with U nucleotides
89
Nucleotide difference in DNA
A can bind U via two hydrogen bonds, just as in A–T pairing in a DNA double helix.
90
+1 site, or the initiation site.
nucleotide from which mRNA synthesis proceeds in the 5' to 3' direction; denoted with a “+1”
The site on the DNA from which the first RNA nucleotide is transcribed
91
_______ doesn't have a membrane enclosed nuclei
Prokaryotes
92
sigma factor (σ). This enzyme consists of only two alpha (2α), one beta (β), one beta prime (β') and one omega (ω).
sigma factor (σ). This enzyme consists of only two alpha (2α), one beta (β), one beta prime (β') and one omega (ω).
93
Holoenzyme
Polymerase consisting of all five subunits
94
Promoter
a DNA sequence where the RNA polymerase binds to initiate transcription.
upstream of the DNA
