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Biology 120 > DNA Structure And Replication > Flashcards

DNA Structure And Replication Flashcards

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1
Q

What theory linked chromosomes to Mendel’s principles?

A

Chromosomal theory of inheritance

Developed in the early 1900s.

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2
Q

Who demonstrated sex-linked traits confirming the chromosomal theory?

A

Thomas Morgan Hunt

His work provided evidence for the chromosomal basis of inheritance.

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3
Q

What did Griffith’s experiments identify in bacteria?

A

The ‘transforming principle’

Conducted in the 1920s.

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4
Q

Which experiment confirmed DNA as the ‘transforming principle’?

A

Avery’s work

Conducted in the 1940s.

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5
Q

What was the purpose of the Hershey-Chase experiment?

A

To confirm DNA as the hereditary molecule

Used radio-labeled DNA and proteins in bacteriophages.

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6
Q

Who revealed DNA’s helical structure through X-ray diffraction?

A

Rosalind Franklin and Maurice Wilkins

Their work was crucial in understanding DNA structure.

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7
Q

What model of DNA did Watson and Crick propose?

A

The double helix model

Proposed in 1953 based on X-ray data.

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8
Q

What is DNA composed of?

A

A polymer of nucleotides

Each nucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base.

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9
Q

What are the nitrogenous bases found in DNA?

A
  • Adenine
  • Thymine
  • Guanine
  • Cytosine

These bases pair to form the genetic code.

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10
Q

What is the structure of the DNA backbone?

A

Sugar-phosphate backbone with bases inside

Nucleotides form this backbone.

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11
Q

What structural feature of DNA involves strands running in opposite directions?

A

Antiparallel strands

This arrangement is critical for replication and function.

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12
Q

What base pairs complementarily in DNA?

A
  • A-T (2 hydrogen bonds)
  • G-C (3 hydrogen bonds)

These pairs are essential for the stability of the DNA molecule.

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13
Q

What does Chargaff’s rule state?

A

Equal amounts of purines and pyrimidines

It provides evidence for complementary base-pairing: A and G are purines, T and C are pyrimidines.

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14
Q

What is the primary model of DNA replication proposed by Watson and Crick?

A

Semiconservative replication: each new DNA molecule contains one parental strand and one newly synthesized strand.

This model was confirmed by Meselson and Stahl’s experiment using isotope-labeled DNA.

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15
Q

What are the three proposed replication mechanisms that could lead to different experimental results?

A

Conservative, semiconservative, and dispersive replication.

Each mechanism proposes a different way in which DNA strands could be replicated.

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16
Q

What initiates DNA replication at the origins of replication?

A

Formation of replication bubbles.

These bubbles allow for the simultaneous replication of DNA in both directions.

17
Q

What is the leading strand in DNA replication?

A

The strand that is synthesized continuously.

It is synthesized in the same direction as the replication fork.

18
Q

What is the lagging strand in DNA replication?

A

The strand that is synthesized in fragments (Okazaki fragments).

This occurs because DNA polymerase can only add nucleotides to the 3’ end.

19
Q

What is the direction of DNA polymerase activity during replication?

A

5’ to 3’ direction.

DNA polymerase adds nucleotides only to the 3’ end of the growing strand.

20
Q

What is the role of helicase in DNA replication?

A

Unwinds DNA.

This enzyme is crucial for separating the two strands of DNA.

21
Q

What do single-stranded binding proteins (SSBs) do during DNA replication?

A

Stabilize unwound DNA.

They prevent the strands from re-annealing or forming secondary structures.

22
Q

What is the function of topoisomerase in DNA replication?

A

Prevents supercoiling ahead of the fork.

It helps relieve the tension that builds up as DNA unwinds.

23
Q

What does primase do in the context of DNA replication?

A

Synthesizes RNA primers.

These primers are necessary for DNA polymerases to initiate synthesis.

24
Q

What is the role of DNA polymerase III in DNA replication?

A

Extends the DNA strand from primers.

It is the primary enzyme responsible for synthesizing new DNA.

25
Q

What is the function of DNA polymerase I?

A

Replaces RNA primers with DNA.

This is critical for completing the DNA strand after primer synthesis.

26
Q

What does ligase do during DNA replication?

A

Joins Okazaki fragments.

This enzyme is essential for linking the short pieces of DNA synthesized on the lagging strand.

27
Q

What happens to the ends of linear DNA molecules during replication?

A

They shorten with replication.

This shortening occurs because DNA polymerase cannot fully replicate the ends of linear DNA.

28
Q

What is the role of telomerase in DNA replication?

A

Extends telomeres in certain cells.

Telomerase helps maintain the length of telomeres, which protect the ends of chromosomes.

Biology 120 (24 decks)

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