exam 5 Flashcards
(119 cards)
1
Q
why do cells need to replicate DNA
A
cells replicate DNA in preparation for cell division
2
Q
when during the cell cycle do cells replicate DNA
A
s phase
3
Q
where in the cell is the DNA replicated
A
eukaryotes- nucleus
prokaryotes- nucleoid
4
Q
what will you need to build a new DNA molecule
A
building blocks, pol, blueprint
5
Q
parent strand of DNA is used as template for ___ daughter strand
A
complimentary
6
Q
DNA replication is __
A
semiconservative
7
Q
each helix of DNA consists of a __ strand (used as template) and one ___ strand (complimentary)
A
parent, daughter
8
Q
There are _ billion base pairs in a human haploid genome
A
3
9
Q
there are ___-___ functional genes in human haploid genome
A
20,000-25,000
10
Q
what are the three main components of nucleotides
A
phosphate, deoxyribose sugar, base
11
Q
Describe the phosphodiester linkages in nucleic acids. What is the significance of the 5’ to 3’ phosphodiester bond?
A
they connect the 3’ to 5’. they form ester bonds
12
Q
How are the nitrogenous bases paired in the double helix? What type of bond holds them together?
A
hydrogen bonds
13
Q
What does it mean to say the two strands of DNA they are “anti-parallel?”
A
one runs from 5’ to 3’, while the other runs 3’ to 5’
14
Q
In DNA replication, the two “old” strands of DNA serve as templates for two
new strands. How are the old and new strands paired after replication?
A
the old strands serve as templates of new complementary strands so genetic info is copied and preserved accurately
15
Q
DNA Polymerase is the enzyme that adds nucleotides to the growing chain of DNA that is __ to the template strand
A
complementary
16
Q
step 1 of DNA replication. DNA unwinds at __ __ __
A
origin of replication
17
Q
step 2 of DNA replication. ___ opens the DNA, forming __ __ that will extend bi-directionally.
A
helicase, replication forks
18
Q
step 3 of DNA replication. __ __ ___ __ bind to DNA to precent the helix from reforming
A
single strand binding proteins
19
Q
step 4 of DNA replication. ___ prevents supercoiling of the DNA double helix ahead of the replication fork.
A
topoisomerase
20
Q
step 5 of DNA replication. ___ __ synthesizes RNA primers complementary to the DNA strand
A
RNA primase
21
Q
step 6 DNA replication. __ __ uses the primers 3’ OH to begin adding nucleotides
A
DNA polymerase
22
Q
step 7 of DNA replication. Elongation of both the __ ___ and ___ __ continues.
A
leading strand, lagging strand
23
Q
step 8 DNA replication. An ___ removes the RNA primers
A
exonuclease
24
Q
step 9 DNA replication. The resulting gaps are filled with deoxyribonucleotides by __ __
A
DNA polymerase
25
step 10 of DNA replication. __ __ seals the spaces between the Okazaki fragments, joining the fragments into a single DNA molecule
DNA ligase
26
DNA polymerase always extends __ to __
5' to 3'
27
What is the main enzyme involved in DNA replication? How does it function
DNA polymerase, 3 prime hydroxyl
28
What is the function of the helicase enzyme? How does it accomplish
this task?
separating, breaking the hydrogen bonds
29
What is topoisomerase enzyme? Why is it important? How does it
accomplish its task?
prevents supercoiling, making small cuts ahead of the fork
30
How is the RNA (primer regions) removed from the new strands of
DNA? How are these gaps repaired?
exonuclease, DNA polymerase-3
31
What is the job of DNA ligase?
join the Okazaki fragments to make the lagging strands
32
In which direction does DNA polymerase add nucleotides to the growing chain? Why can it only operate in this direction
5' to 3' it needs a free 3' hydroxyl group
33
What is the problem DNA polymerase encounters when trying to start
the replication process? How is this problem overcome?
it requires a free 3' OH group. it uses primase
34
What are Okazaki fragments? Why are they made? What are the
additional requirements of having to replicate the DNA in this fashion?
for the continuous synthesis of DNA, exonuclease and ligase
35
DNA polymerase can __
proofread
36
in eukaryotic organisms there are __ origins of replication
multiple
37
the rate of replication is much slower in eukaryotes- approximately ___ nucleotides per second
100
38
DNA replication in eukaryotic cells have a problem with the lagging strand in the end. DNA is synthesized in Okazaki fragments and requires many separate RNA primers. At the end of a linear strand of DNA, there is no place for ___ to be made
primer
39
The ends of linear chromosomes are called__. They consist of repetitive sequences that do not code for a particular gene
telomeres
40
the telomeres protect __ from getting deleted as cells continue to divide
genes
41
in addition there is an enzyme called __ that contains built in template strand made of RNA
telomerase
42
The enzyme telomerase attaches to the 3' end of the original template strand so that one more ___ fragment can be made
Okazaki
43
telomerase is active in __ cells and __ stem cells
germ, adult
44
telomerase is not active in __ ___ cells
adult somatic
45
if telomerase is not present, ___ shorten
telomeres
46
in dividing somatic cells when telomerase is not made, the telomeres __
shorten
47
many cancer cells have dysregulation or mutation that reactivates expression of the __ gene
telomerase
48
How many origins of replication are in eukaryotes (humans)?
multiple
49
How do the rates of DNA replication compare in prokaryotes vs. eukaryotes? What cellular features account for some of the
difference?
faster in prokaryotes, eukaryotic is wrapped around histones
50
what cells in eukaryotes are vulnerable?
the ones that are replicating
51
What is the name of the enzyme that can extend the ends of the
chromosomes?
telomerase
52
the two step process of expressing protein from genes is called __ __ of molecular biology
central dogma
53
DNA makes RNA, and RNA makes protein
what the central dogma states
54
the synthesis of RNA using the genetic template of DNA
transcription
55
the synthesis of protein based on the sequence of nucleotides encoded in RNA
translation
56
___ produces an RNA copy of the DNA by generating mRNA
transcription
57
is the molecular copy of one or more genes
mRNA
58
__ the conversion of the mRNA nucleotide template into a protein product
translation
59
proteins are macromolecules consisting of various polypeptide sequences of the __ __ __ monomers
20 amino acids
60
linking of amino acids called:
peptide bonds
61
what gives rise to the diverse structure and function of proteins
variation in amino acid sequence
62
How can information for 20
different amino acids be stored
using only 4 different monomers?
the sequences of these nucleotides in genes that determine how the proteins are assembled
63
each amino acid is defined by a three nucleotide mRNA sequence called
codon
64
the nuclear code is __ meaning a given amino acid can be encoded by more than one nucleotide triplet
degenerate
65
the way the nucleotide sequence is divided into triplets to be read as codons is __
reading frame
66
AUG is the __ __ to initiate translation
start codon
67
AUG sets the ___ ___ for translation near the 5' end of the mRNA
reading frame
68
AUG also always specifies the amino acid __
methionine
69
three of the 64 codons do not represent amino acids, these are called nonsense codons or ___ ___
stop codons
70
what are the three stop codons
UAA, UAG, UGA
71
There are __ __ __ that could each each code for any amino acid, but in all species, the __ -_ code for each of the amino acids
64 triplet codons, same 3
72
What is mRNA? What is its function?
messenger, delivering instructions from DNA to create proteins
73
How many possible nucleotide triplets are there?
64
74
What does the
term degenerate mean in this sense?
multiple codons coding for multiple amino acids
75
Three of the codons do not strictly code for amino acids. Which three are unique and what are their special functions?
end protein synthesis
76
the strand of DNA that is used to make mRNA is called the __ __
template strand
77
transcription uses the principle of __
complementarity (being different but fitting together/aligning)
78
The non-template strand is also called the __ __
coding strand
79
what is the enzyme that performs transcription
RNA polymerase
80
like DNA polymerase RNA polymerase synthesizes in a __ __ __ direction
5' to 3'
81
Step 1 of transcription: __. ___ ___ recognizes and bind to the DNA at the
start of a gene sequence. The helix is opened, and transcription begins
initiation, RNA polymerase
82
What enzyme pulls apart DNA strands?
helicase
83
What protein prevents rebinding?
single stranded binding protein
84
What enzyme prevents supercoiling?
topoisomerase
85
Step 2 of transcription: __. RNA polymerase transcribes at a rate of about 40
nucleotides per second. The transcribed DNA is rewound with the passing of RNA polymerase.
elongation
86
Step 3 of transcription: __. Once the gene is transcribed, terminator sequences signal the
polymerase to stop. RNA polymerase releases the DNA and the DNA rewinds.
termination
87
Transcription occurs from which strand of the
double-stranded DNA?
template, noncoding
88
What is the term used to describe the strand of DNA that does not function as the template during
transcription? What is its relationship with mRNA?
non template, coding, same as DNA A just has U
89
Name the enzyme that performs transcription in prokaryotes and eukaryotes.
RNA polymerase
90
proteins account for more __ than any other component of living organism
mass
91
in translation, amino acid monomers are covalently linked via __ __ in lengths ranging from 50 to over 1000 amino acids
peptide bonds
92
The general machinery required in translation is similar in __ and __
prokaryotes and eukaryotes
93
ribosomes are the site of __ __. they are found in the __ and __ __
protein synthesis, cytoplasm, rough ER
94
in translation the small subunit of ribosomes is responsible for __ __ __
binding mRNA template
95
tRNAs are called __ __ because they are complementary to the codons
anti codons
96
The amino acid each tRNA carries corresponds to the sequence of the __ it interacts with
codon
97
each tRNA is linked to its correct amino acid in the cytoplasm. This process is called __
charging
98
a group of enzymes called __ __ __ perform the charging of the tRNAs
aminoacyl tRNA synthetases
99
How many different
aminoacyl tRNA
synthetases are there?
20
100
In translation tRNA brings with it the amino acid corresponding to the codon and adds it to the growing __ __
polypeptide chain
101
What are the 4 cellular components responsible for actual protein synthesis?
mRNA, tRNA, ribosome, aminoacyl tRNA synthetases
102
What is tRNA? Where does it perform its job?
transfer RNA, amino acid to growing polypeptide chain.
103
What is the anti-codon region of tRNA and why is this region so important in translation?
binds to codon
104
What is tRNA “charging?” Which enzyme performs this task?
linked to amino acid, aminoacyl tRNA synthetases
105
How is the genetic code physically turned into a chain of amino acids?
DNA to mRNA to tRNA
106
what compartment binds incoming charged tRNA moleulces
A (aminoacyl) site
107
what compartment binds tRNAs carrying amino acid that have formed peptide bonds with the growing chain
P (peptidyl) site
108
what compartment releases dissociated tRNAs so they can be recharged with free amino acids
E (exit) site
109
The formation of each peptide bond is catalyzed by an enzyme called __ __
peptidyl transferase
110
Termination of translation occurs when a nonsense (__ __) is encountered
stop codon
111
What are the three binding sites or compartments on the large ribosomal unit that advance the growing amino acid chain?
Exit, Peptide, Amino Acid
112
Which enzyme is responsible for forming the peptide bonds in the growing chain of amino acids?
peptidyl transferase
113
The stop codons signal for termination of translation. How does this occur?
there is no corresponding tRNA with those corresponding amino acids
114
What happens to the cellular components when translation is finished? What happens to the mRNA?
primary structure of protein chain, mRNA, tRNA, ribosomal subunits. The mRNA is recycled.
115
Eukaryotic mRNA must undergo __ before being translated
processing
116
mRNA processing removes __ from the mRNA which are sequences that do not code for functions proteins. Remaining sequences are called __
introns, exons
117
What are the two main ways that
transcription/translation differ between
prokaryotes and eukaryotes?
different locations, processing of mRNA
118
Why are transcription and translation able to
be coupled in prokaryotes, but must be
performed independently in eukaryotes
locations and processing of mRNA
119
What are exons and introns?
introns do not code for proteins and exons do
