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

Chapter 15: DNA and the Gene Flashcards

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Biology 101 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
Q

Occurs continuously and only requires one primer

A

Leading strand

26
Q

What does primate provide?

A

The initial chain, in the form of an RNA primer, so replication can proceed (new nucleotides can be added to it)

27
Q

How does topoisomerase relieve tension?

A

It cuts DNA, lets it unwind a little, then seals it back up ahead of helicase

28
Q

Where does DNA replication begin?

A

Specific sites called origins of replication

29
Q

What do enzymes which synthesize DNA need to start making a strand and why?

A

They need an -OH group bc they cant start a new chain on their own and can only add to an existing strand

30
Q

What are dNTPs?

A

Nucleotide triphosphate added by DNA polymerases to create a replicated strand of DNA

31
Q

What is xeroderma pigmentosum?

A

Disorder caused be inherited defect in NER that causes a hypersensitivity to light

32
Q

When else can errors arise other than replication?

A

Environment (sun, smoke, carcinogens, etc)

33
Q

What is mismatch repair similar to?

A

Tumor suppressors. They stop the cell from leaving incorrect pairs

34
Q

Untwists the double helix and separates the strands of DNA

A

Helicase

35
Q

Discontinuous. A new fragment cannot be started until the fork moves forward and exposes template

A

Lagging strand

36
Q

Joins all of the fragments (Okazaki fragments) of the lagging strand into a continuous strand

A

DNA ligase

37
Q

Consists of a short nucleotide sequence (TTAGGG) in humans that is repeated 100-1000x times

A

Telomeres

38
Q

Which way does replication proceed from the origin of replication?

A

It proceeds in both directions

39
Q

Lays down an RNA primer which is complementary to the template strand

A

Primase

40
Q

Synthesized toward the replication fork

A

Leading strand

41
Q

How long does it take to copy DNA and how often do errors occur?

A

Only takes a few hours to copy with about 1 error in every 1 billion nucleotides

42
Q

The ends of chromosomes that don’t encode any genes

A

Telomeres

43
Q

What is the RNA component of telomerase?

A

Telomerase RNA (TERC)

44
Q

What happens if DNA polymerases miss a mistake?

A

Mismatch repair (MMR) kicks in

45
Q

What are defects in mismatch repair enzymes linked to?

A

Cancer

46
Q

Is the leading strand on top or bottom? What about the lagging strand?

A

They are both on top and bottom bc the DNA strands run antiparallel

47
Q

What direction must DNA polymerase add dNTPs in?

A

5’ to 3’ (this is the direction of the strand being made)

48
Q

What happens when telomeres reach a critical limit? How long does it take to get there?

A

The cell enters senescence (no longer divides). Cells can usually divide about 50 times before they hit this point

49
Q

Who found that DNA was the genetic material and not protein?

A

Hershey and Chase (1952). Phage transferred DNA to bacteria that was dyed and showed up in bacteria

50
Q

A large macromolecule machine formed by the many enzymes involved in DNA replication

A

Replisome

51
Q

What links the sugar-phosphate groups of the DNA backbone?

A

Phosphodiester bonds

52
Q

Adds a nucleotide to the RNA primer and then keeps adding complementary nucleotides to the growing strand

A

DNA polymerase III

53
Q

Where must DNA polymerases add nucleotides?

A

The free 3’ end (they need the free OH to attach the next base)

54
Q

Enzymes which catalyze the synthesis of DNA by adding nucleotides to an existing chain

A

DNA polymerases

Bio 1113 (22 decks)

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