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Biology Honors Cambridge > C6: Nucleic Acids & Protein Synthesis > Flashcards

C6: Nucleic Acids & Protein Synthesis Flashcards

1
Q

What was considered the genetic material until 1940 and why?

A

Proteins were considered to be the genetic material because they were very complex in structure.

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2
Q

Describe Griffith’s experiment and his conclusion.

A

Griffith tested 4 cases with an S strain (virulent) and an R strain (nonvirulent):
1. Living S strain (mouse dies)
2. Living R strain (mouse lives)
3. Dead S strain (mouse lives)
4. Dead S strain & living R strain (mouse dies)
Conclusion: a substance from one cell is capable of genetically transforming another cell

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3
Q

Describe Avery, MacLeod, and McCarty’s experiment and their conclusion.

A

They tested 4 cases with a dead S strain (virulent) and a living R strain (nonvirulent):
1. The control group -> nothing removed (mouse dies)
2. remove proteins (mouse dies)
3. remove polysaccharides (mouse dies)
4. remove RNA (mouse dies)
5. remove DNA (mouse lives)
Conclusion: DNA is the molecule responsible for carrying genetic information

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4
Q

What are the two features of a molecule that stores genetic information?

A
  1. the ability to store information
  2. the ability to copy itself accurately
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5
Q

Describe Hershey and Chase’s experiment and their conclusion.

A

They tested 2 cases with the T2 bacteriophage (bacteriophage infects bacterial cells):
1. protein coats labeled with radioactive sulfur -> after centrifugation, there was radioactivity in the supernatant (bacterial cells form the pellet and other surrounding liquids including bacteriophages form the supernatant)
2. DNA labeled with radioactive phosphorous -> after centrifugation, there was radioactivity in the pellet
Conclusion: the genetic material is DNA, not proteins

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6
Q

What polymers do nucleotides create?

A

nucleic acids / polynucleotides

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7
Q

What does DNA and RNA stand for?

A

DNA -> deoxyribonucleic acid
RNA -> ribonucleic acid

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8
Q

Describe Wilkins and Franklin’s experiment and the conclusion that Watson made.

A

They used X-ray crystallography to study the structure of DNA:
- the X-rays are diffracted as they pass through purified, crystallized DNA
- the diffraction pattern can be used to deduce the 3D shape of molecules
Watson’s conclusion: DNA is helical in shape

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9
Q

What is the width of DNA?

A

2 nm

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10
Q

How far apart are the nitrogenous bases?

A

0.34 nm apart

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11
Q

How many base pairs are there per turn in DNA?

A

10 base pairs (3.4 nm)

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12
Q

What did Watson and Crick do?

A

they constructed a model for DNA structure

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13
Q

What happened to Franklin that many people view as “unfair”?

A

Franklin’s work was essential for Watson and Crick to determine the structure of DNA, but Franklin died of cancer (due to X-ray overexposure) and did not get a Nobel Prize.

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14
Q

What three subunits is each nucleotide made up of?

A
  1. a sugar molecule
  2. a phosphate group (PO₄³⁻)
  3. an organic nitrogenous base
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15
Q

What is deoxyribose and what is its molecular formula?

A

deoxyribose is a pentose sugar (C₅H₁₀O₄)

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16
Q

What is ribose and what is its molecular formula?

A

ribose is a pentose sugar (C₅H₁₀O₅)

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17
Q

What is the difference between deoxyribose and ribose?

A

deoxyribose has one less oxygen atom than ribose (ribose has a hydroxyl group attached to carbon 2 while deoxyribose has just one hydrogen molecule attached to carbon 2)

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18
Q

What are the nitrogenous bases in DNA and RNA?

A

DNA:
- Adenine(A), Guanine(G), Cytosine(C), Thymine(T)
RNA:
- Adenine(A), Guanine(G), Cytosine(C), Uracil(U)

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19
Q

What is the bond that forms between two nucleotides?

A

phosphodiester bond (phosphate group connects with a nucleotide on carbon 3 and another nucleotide on carbon 5)

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20
Q

Draw the structure of adenine.

A
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21
Q

Draw the structure of guanine.

A
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22
Q

Draw the structure of cytosine.

A
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23
Q

Draw the structure of thymine.

A
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24
Q

Draw the structure of uracil.

A
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25
Q

What is a nucleoside?

A

nitrogenous base + sugar molecule

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26
Q

What three components is ATP made up of?

A

3 phosphates, ribose sugar, and adenine base

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27
Q

What bonds occur between two nitrogenous bases?

A

hydrogen bonds

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28
Q

What is Chargaff’s Rule?

A
  • adenine bonds with thymine/uracil (2 hydrogen bonds)
  • cytosine bonds with guanine (3 hydrogen bonds)
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29
Q

What nitrogenous bases are purines and what nitrogenous bases are pyrimidines?

A
  • Purines: Adenine (A), Guanine (G)
  • Pyrimidines: Cytosine (C), Thymine (T), Uracil (U)
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30
Q

What does it mean by the two DNA strands being antiparallel?

A

one DNA strand runs in the 5’ to 3’ direction while the other DNA strand runs in the 3’ to 5’ direction.

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31
Q

What shape is DNA? (include direction)

A

double right-handed helix

32
Q

What is the role of helicase?

A

helicase “unzips” the DNA double helix by breaking hydrogen bonds between the base pairs to form two single polynucleotide DNA strands

33
Q

Why is DNA semi-conservative?

A

the two DNAs created from replication have half original DNA and half new DNA

34
Q

Describe Meselson and Stahl’s experiment and their conclusion.

A

They first put E.coli in nitrogen-15 (0th generation):
- 1st generation (after putting fully nitrogen-15 DNA into nitrogen-14) -> 100% hybrid DNA
- 2nd generation -> 50% hybrid and 50% light DNA
- 3rd generation -> 25% hybrid and 75% light DNA
Conclusion: DNA replication is semi-conservative

35
Q

What are the two incorrect mechanisms of DNA replication? (describe them as well)

A
  1. Conservative
    - the original DNA is conserved and an entirely new DNA is synthesized
  2. Dispersive
    - the original DNA is broken into smaller fragments and each fragment serves as a template for the synthesis of a new DNA fragment
36
Q

What do you call the location at which DNA replication starts/begins?

A

origin/point of replication

37
Q

What is the function of DNA polymerase III?

A

the enzyme adds complementary free nucleotides to each separated DNA strand (moves from 5’ to 3’ direction of the strand being synthesized)

38
Q

What is the function of DNA polymerase I?

A

the enzyme digests RNA primers and replaces it with DNA

39
Q

What is the function of DNA ligase?

A

the enzyme joins neighboring fragments together (“the glue”)

40
Q

What are Okazaki fragments and which strand do they form in? (why)

A

Okazaki fragments are fragments of DNA that appear in the lagging strand due to the DNA polymerase having to move from 5’ to 3’. DNA polymerase has to wait for more unwinding to happen before it can go back and synthesize new strands again.

41
Q

What is the function of RNA primers?

A

the enzymes provide a starting point for the DNA polymerase in the lagging strand by having a 3’ end (DNA polymerase can only add new bases to a 3’ end)

42
Q

What is the function of RNA primase?

A

the enzyme synthesizes short RNA primers

43
Q

What is the function of single-stranded binding proteins (SSBPs)?

A

the proteins prevent the separated DNA strands from re-forming the double helix by holding it in place

44
Q

What is the function of topoisomerase?

A

the enzyme regulates the winding and unwinding of DNA

45
Q

What is a group of three DNA bases called?

A

a triplet

46
Q

What is a group of three mRNA bases called?

A

a codon

47
Q

What is the start codon and what amino acid does it code for?

A

AUG codes for methionine

48
Q

What is the Central Dogma

A

DNA -> RNA -> protein
- DNA to RNA is transcription
- RNA to protein is translation

49
Q

One gene, one ________

A

protein / RNA

50
Q

What are the two stages of protein synthesis?

A

transcription and translation

51
Q

Where does transcription occur and how does the synthesized mRNA exit?

A

transcription occurs in the nucleus and the mRNA exits through the nuclear pores

52
Q

What is the function of RNA polymerase?

A

the enzyme synthesizes mRNA using free RNA nucleotides and unwinds the DNA

53
Q

Where does RNA polymerase first attach?

A

it attaches to the promoter region of the gene on DNA

54
Q

What are the three main steps of transcription?

A
  1. Initiation (promoter region)
  2. Elongation (mRNA grows)
  3. Termination (RNA polymerase detaches)
55
Q

What is the sequence of DNA when signals termination during transcription?

A

continuous adenine bases

56
Q

What are exons and introns?

A

exons are the coding sequences of DNA and introns are the non-coding sequences of DNA

57
Q

How do introns get removed as they are not needed?

A

After transcription, a process called “splicing” removes introns and fuses the exons together

58
Q

What is the main function of mRNA, tRNA, and rRNA?

A
  • mRNA: carries the code from the nucleus to a ribosome
  • tRNA: matches the codon in mRNA with the correct amino acid
  • rRNA: makes up some parts of ribosomes
59
Q

What do the two ends of tRNA have?

A

one end has an anticodon loop and the other end has an amino acid attachment site

60
Q

What subunits does a ribosome consist of?

A
  • large subunit (50S)
  • small subunit (30S)
61
Q

Where in the ribosome does mRNA bind to?

A

an mRNA binding site in the small subunit

62
Q

What are the three tRNA binding sites in ribosomes?

A
  1. A (aminoacyl) site
  2. P (peptidyl) site
  3. E (exit) site
63
Q

When does the large ribosomal subunit bind to the small ribosomal subunit and form a functional ribosome?

A

after the mRNA binds to the small subunit and the initiator tRNA binds to the start codon (AUG)

64
Q

What are the three steps in the elongation process during translation?

A
  1. codon recognition
  2. peptide bond formation
  3. translocation (ribosome shifts along the mRNA)
65
Q

When does elongation in translation stop?

A

once a stop codon reaches the ribosome’s A (aminoacyl) site

66
Q

What is a mutation?

A

a mutation is a random change in the nucleotide sequence in DNA (gene mutation) or in the structure and/or number of chromosomes (chromosome mutation)

67
Q

What two things can mutations be caused by?

A
  1. errors during DNA replication
  2. mutagens
68
Q

What is the DNA strand that does not get used during transcription called?

A

non-template/coding/sense strand

69
Q

What is the DNA strand that gets used during transcription called?

A

template/antisense strand

70
Q

What is the error in sickle cell disease?

A

a base on chromosome 11 that is part of a gene coding for the β-chain of hemoglobin is changed from T to A.

71
Q

Why are insertions and deletions more dangerous than substitutions?

A

Insertions and deletions cause a frame-shift mutation because they shift the position of every base that follows (alters the reading frame)

72
Q

What is mutagenesis and what is it caused by?

A

mutagenesis is the process by which DNA is changed or mutated
- mutagenesis is caused by spontaneous error or a physical or chemical mutagen

73
Q

What are the three types of substitution mutations?

A
  1. missense (the mutation changes the amino acid that gets made)
  2. silent (the mutation does not change the amino acid produced)
  3. nonsense (the mutation creates a stop codon to be formed)
74
Q

How many hydrogen bonds form between adenine and thymine/uracil?

A

2 hydrogen bonds

75
Q

how many hydrogen bonds form between guanine and cytosine?

A

3 hydrogen bonds

Biology Honors Cambridge (7 decks)

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