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Bio Exam 2 > Lecture 14- DNA > Flashcards

Lecture 14- DNA Flashcards

1
Q

What is DNA composed of?

A

Nucleotides

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2
Q

What are nucleotides composed of?

A

Nitrogenous base, pentose sugar (deoxyribose/ribose), & phosphate group

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3
Q

What was the significance of Griffith’s experiment?

A

Hypothesized transformation (experiment with mice and streptococcus pneumoniae)

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4
Q

How many common amino acids are there?

A

20

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5
Q

What was the significance of the experiments conducted by Avery, MacLeod, & McCarty?

A

Lysed smooth (S) cells-> separated contents into biological macromolecules-> tested each macromolecule for transforming ability-> discovered that only DNA could transform

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6
Q

What was the significance of the Hershey-Chase experiment?

A

discovered that bacteriophages are composed of just DNA and protein (via radioactive tracers)

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7
Q

What are the main classifications of nitrogenous bases?

A

Purines & pyrimidines

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8
Q

What is the difference between purines and pyrimidines?

A

Pyrimidines are composed of a single ring whereas purines are composed of two rings

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9
Q

Which nitrogenous bases are considered purines?

A

Adenine and guanine

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10
Q

Which nitrogenous bases are considered pyrimidines?

A

Thymine, cytosine, and uracil

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11
Q

What was the significance of Rosalind Franklin’s experiment?

A

Discovered the helical structure of DNA via x-ray crystallography

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12
Q

What was the significance of Erwin Chargaff’s experiment?

A

Discovered that there are approximately equal amounts of purines and pyrimidines in DNA

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13
Q

What was the significance of the discovery made by Watson & Crick?

A

Using Rosalind Franklin’s DNA model, Watson & Crick were able to explain how DNA could carry genetic information and how information could be replicated. Found that each rung in DNA is composed of a purine and a pyrimidine

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14
Q

What type of bond occurs between the sugar-phosphate backbone?

A

Phosphodiester linkages

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15
Q

What type of bonds occurs between the nitrogenous bases?

A

Two hydrogen bonds between adenine and thymine & three hydrogen bonds between guanine and cytosine

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16
Q

How does dehydration synthesis occur to form bonds between the sugar-phosphate backbone?

A

Occurs between the free 3’ hydroxyl (OH) and the free 5’ phosphate

17
Q

Which nitrogenous bases pair with each other?

A

Adenine with thymine in DNA or uracil in RNA & cytosine with guanine (in both DNA/RNA)

18
Q

What does it mean that DNA replication follows a semi-conservative model?

A

A parental strand is used to synthesize a daughter strand

19
Q

What are the steps of transcription in order?

A

Initiation-> elongation-> termination

20
Q

Which events marks the start of transcription initiation?

A

Separation of strands & formation of replication bubble (origin of replication)

21
Q

How do single-stranded binding proteins (SSBPs) aid in DNA replication?

A

SSBPs keep DNA strands apart

22
Q

Relative to the replication bubble, in which direction does replication proceed?

A

Replication proceeds towards the replication forks

23
Q

Which protein is responsible for unwinding the DNA helix during replication?

A

Helicase

24
Q

What is the function of topoisomerase?

A

Relaxes DNA helix (provides stability to unwound DNA)

25
Q

What is the function of RNA primase?

A

Synthesize RNA primers which allow DNA polymerase to proceed with replication

26
Q

What is the end result of transcription?

A

Pre-mRNA

27
Q

How are DNA strands oriented relative to one another?

A

Antiparallel

28
Q

What are the modifications pre-mRNA undergoes before it is considered a mature mRNA?

A

Introns snipped out by spliceosome and exons are joined together. Also a 3’ poly-adenine tail and 5’ guanosine cap are added to the ends of the mRNA

29
Q

What is added to the growing molecule during the elongation stage of DNA replication?

A

Nucleoside triphosphates added-> forms new phosphodiester bond-> releases pyrophosphates

30
Q

Which enzyme is responsible for combining DNA strands back together at the end of replication?

A

DNA ligase

31
Q

What is the lagging strand composed of?

A

Okazaki fragments

Bio Exam 2 (9 decks)

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