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Bio 1113 > Chapter 15: DNA and the Gene > Flashcards

Chapter 15: DNA and the Gene Flashcards

1
Q

How many origins of replication do bacteria have? Eukaryotes?

A

Bacteria only have 1 origin of replication on their circular chromosome while eukaryotes have multiple along their chromosomes

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2
Q

Synthesized away from the replication fork

A

Lagging strand

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3
Q

Relieves strain/stress ahead of replication fork caused by unwinding by breaking, swiveling, and rejoining DNA strands

A

Topoisomerase

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4
Q

What did the Meselson-Stahl experiment prove?

A

DNA is replicated semiconservatively

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5
Q

What allows cells to continue to divide without shortening their chromosomes?

A

Telomerase

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6
Q

What are the parts of DNA structure?

A

5’ and 3’ ends, phosphate group, sugar, and nitrogenous bases

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7
Q

Bind to separated DNA strands to prevent repairing (keeps bases from snapping back together)

A

Single-strand DNA-binding proteins (SSBPs)

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8
Q

What is telomerase made of?

A

Protein and RNA

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9
Q

Who found that genes are located on chromosomes?

A

Morgan with his fruit flies and X linked traits

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10
Q

Enzymes (not DNA polymerases) that remove and replace incorrectly paired nucleotides

A

Mismatch repair (MMR)

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11
Q

Creates Okazaki fragments

A

Lagging strand

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12
Q

Why do eukaryotes have multiple origins of replication?

A

It speeds up the process of DNA replication

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13
Q

When is telomerase active?

A

During embryonic development but shut off in most somatic cells at later stage. Also in male germ cells, activated lymphocytes, some stem cells, and 90% of tumors

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14
Q

What are Okazaki fragments?

A

Chunks of the replicated DNA strand that consist of a primer and DNA. There are many created on the lagging strand

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15
Q

What is the problem that occurs at the end of DNA replication?

A

The end fragment of the chromosome is not replicated bc the lagging strand is too short. This causes the chromosome to shorten

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16
Q

How are DNA strands oriented?

A

Antiparallel

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17
Q

How are errors between incoming bases and the template strand corrected?

A

DNA polymerases proofread each base as soon as it is added and if it is incorrectly paired, it is removed and synthesis resumes

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18
Q

What is the location where DNA is unwound at called (the place where open DNA meets double stranded)?

A

Replication fork

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19
Q

When are replication errors most common?

A

Between incoming bases and the template strand

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20
Q

What does lagging strand synthesis require?

A

Multiple primers. One for each fragment

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21
Q

What is the protein component fo telomerase?

A

Telomerase reverse transcriptase (TERT)

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22
Q

How is DNA constantly monitored and repaired?

A

DNA polymerases, mismatch repair (MMR), and nucleotide excision repair (NER)

23
Q

Replaces the RNA primer with DNA nucleotides

A

DNA polymerase I

24
Q

This cuts out a damaged DNA segment using a nuclease and the gap is filled by DNA polymerase and ligase using the undamaged strand as a template

A

Nucleotide excision repair (NER)

25
Occurs continuously and only requires one primer
Leading strand
26
What does primate provide?
The initial chain, in the form of an RNA primer, so replication can proceed (new nucleotides can be added to it)
27
How does topoisomerase relieve tension?
It cuts DNA, lets it unwind a little, then seals it back up ahead of helicase
28
Where does DNA replication begin?
Specific sites called origins of replication
29
What do enzymes which synthesize DNA need to start making a strand and why?
They need an -OH group bc they cant start a new chain on their own and can only add to an existing strand
30
What are dNTPs?
Nucleotide triphosphate added by DNA polymerases to create a replicated strand of DNA
31
What is xeroderma pigmentosum?
Disorder caused be inherited defect in NER that causes a hypersensitivity to light
32
When else can errors arise other than replication?
Environment (sun, smoke, carcinogens, etc)
33
What is mismatch repair similar to?
Tumor suppressors. They stop the cell from leaving incorrect pairs
34
Untwists the double helix and separates the strands of DNA
Helicase
35
Discontinuous. A new fragment cannot be started until the fork moves forward and exposes template
Lagging strand
36
Joins all of the fragments (Okazaki fragments) of the lagging strand into a continuous strand
DNA ligase
37
Consists of a short nucleotide sequence (TTAGGG) in humans that is repeated 100-1000x times
Telomeres
38
Which way does replication proceed from the origin of replication?
It proceeds in both directions
39
Lays down an RNA primer which is complementary to the template strand
Primase
40
Synthesized toward the replication fork
Leading strand
41
How long does it take to copy DNA and how often do errors occur?
Only takes a few hours to copy with about 1 error in every 1 billion nucleotides
42
The ends of chromosomes that don't encode any genes
Telomeres
43
What is the RNA component of telomerase?
Telomerase RNA (TERC)
44
What happens if DNA polymerases miss a mistake?
Mismatch repair (MMR) kicks in
45
What are defects in mismatch repair enzymes linked to?
Cancer
46
Is the leading strand on top or bottom? What about the lagging strand?
They are both on top and bottom bc the DNA strands run antiparallel
47
What direction must DNA polymerase add dNTPs in?
5' to 3' (this is the direction of the strand being made)
48
What happens when telomeres reach a critical limit? How long does it take to get there?
The cell enters senescence (no longer divides). Cells can usually divide about 50 times before they hit this point
49
Who found that DNA was the genetic material and not protein?
Hershey and Chase (1952). Phage transferred DNA to bacteria that was dyed and showed up in bacteria
50
A large macromolecule machine formed by the many enzymes involved in DNA replication
Replisome
51
What links the sugar-phosphate groups of the DNA backbone?
Phosphodiester bonds
52
Adds a nucleotide to the RNA primer and then keeps adding complementary nucleotides to the growing strand
DNA polymerase III
53
Where must DNA polymerases add nucleotides?
The free 3' end (they need the free OH to attach the next base)
54
Enzymes which catalyze the synthesis of DNA by adding nucleotides to an existing chain
DNA polymerases

Bio 1113 (22 decks)

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