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Molecular Genetics Flashcards

1
Q

Who were credited with deducing the structure of DNA?

A

James Watson and Francis Crick

They made this discovery in 1953.

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2
Q

What are the components of DNA?

A
  • Deoxyribose sugar
  • Phosphate group
  • Nitrogenous base

These components together form a nucleotide.

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3
Q

What is the structure of DNA?

A

A thread-like molecule twisted in a clockwise direction to form a double helix

DNA consists of two antiparallel strands of nucleotides.

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4
Q

What are the ends of a DNA strand called?

A

5’ end and 3’ end

The two strands run in opposite directions.
‘ means end

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5
Q

What terminates the 5’ end of a DNA strand?

A

Phosphate group

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6
Q

What is the significance of complementary base pairing in DNA?

A

Adenine pairs with Thymine (A-T) and Guanine pairs with Cytosine (G-C)

This pairing is crucial for the structure and function of DNA.

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7
Q

Fill in the blank: DNA is a ______ polymer.

A

nucleotide

This indicates that DNA is made up of repeating units called nucleotides.

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8
Q

True or False: DNA strands are parallel to each other.

A

False

The strands are antiparallel.

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9
Q

What type of molecule is DNA described as?

A

A nucleotide polymer

This means that it is composed of many nucleotides linked together.

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10
Q

What is the direction of the twist in the DNA double helix?

A

Clockwise

This twist is a key feature of the double helix structure.

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11
Q

What are the two types of nitrogenous bases?

A

Adenine and guanine are purines; cytosine and thymine are pyrimidines.

Purines have a double ring structure, while pyrimidines have a single ring structure.

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12
Q

What does complementary base pairing maintain in a DNA molecule?

A

A constant width.

This refers to the consistent distance between the two strands of DNA due to specific pairing of bases.

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13
Q

If the nucleotides of all chromosomes in a genome could be stretched out in one long double helix, how long would they measure?

A

1.8 meters.

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14
Q

What is a nucleosome?

A

A complex of histones supporting coiled DNA.

Nucleosomes are formed by wrapping DNA around histone proteins, facilitating DNA packing.

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15
Q

What is the role of histones in DNA structure?

A

Histones help to coil DNA into nucleosomes.

Histones are positively charged proteins that attract the negatively charged DNA.

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16
Q

What contributes to the molecular stability in a DNA molecule?

A

Three forces:
* Phosphodiester bonds
* Hydrogen bonds
* Hydrophobic interactions.

Each of these forces plays a critical role in maintaining the integrity and stability of the DNA structure.

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17
Q

What do phosphodiester bonds link in a DNA molecule?

A

The sugar-phosphate backbone of one nucleotide to another.

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18
Q

What stabilizes the inner core of the DNA molecule?

A

Hydrogen bonds.

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19
Q

Fill in the blank: The hydrophobic interactions cause bases to remain _______.

A

inside the structure.

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20
Q

True or False: The phosphate group and sugar are hydrophobic.

A

False.

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21
Q

What is the function of supercoiling in chromatin?

A

It helps maintain the compact structure of chromosomes.

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22
Q

What terminates the 3’ end

A

Nitrogenous base

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23
Q

What is the significance of the Meselson and Stahl experiment?

A

Proof of semiconservative replication of DNA

Conducted in 1957 to demonstrate how DNA replicates.

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24
Q

What organism was used in the Meselson and Stahl experiment?

A

E. coli

A type of bacteria used to study DNA replication.

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25
What isotopes were used in the Meselson and Stahl experiment?
Heavy nitrogen (N) and regular nitrogen (N) ## Footnote Heavy nitrogen has a higher atomic mass.
26
What method was used to isolate DNA strands in the experiment?
Centrifugation ## Footnote A technique to separate components based on density.
27
What was the result of the test tube containing heavy DNA?
Produced one discrete band in the low region ## Footnote Indicating the presence of heavy nitrogen-labeled DNA.
28
What was the result of the test tube containing regular DNA?
Produced one discrete band ## Footnote This band was in the region corresponding to regular nitrogen.
29
In the experiment, what was produced after bacteria replicated once in normal nitrogen medium?
One discrete band intermediate between bands in tube 1 and tube 2 ## Footnote Indicated the formation of hybrid DNA.
30
What was the outcome when bacteria from heavy nitrogen medium replicated twice in normal nitrogen medium?
Produced two discrete bands: one at intermediate level, one at regular N level ## Footnote Demonstrated that the initial DNA served as a template.
31
What does the term 'semiconservative replication' mean?
Each new DNA molecule consists of one old strand and one new strand ## Footnote This is the mechanism by which DNA replicates.
32
True or False: The Meselson and Stahl experiment proved that DNA replication is conservative.
False ## Footnote It proved that DNA replication is semiconservative.
33
What type of replication does DNA undergo?
Semi-conservative ## Footnote Each new strand is composed of one parental half and one newly synthesized daughter half.
34
Who conducted experiments that confirmed the semi-conservative nature of DNA replication?
Meselson and Stahl ## Footnote Their experiments provided key evidence for the semi-conservative model.
35
What is the role of proteins at the initiation stage of DNA replication?
Bind to specific sites on DNA, blocking reformation of hydrogen bonds ## Footnote This prevents the strands from re-annealing.
36
What enzymes help relieve tension in DNA strands during replication?
DNA Gyrase and Topoisomerases ## Footnote They cut and reseal DNA strands to allow untwisting.
37
What is the function of DNA Polymerase III?
Builds complementary DNA strands ## Footnote It synthesizes DNA in the 5' to 3' direction.
38
What is required for DNA Polymerase III to start synthesizing DNA?
An existing starting point provided by an RNA primer ## Footnote The RNA primer is inserted on the DNA template by the primase enzyme.
39
What energy source does DNA Polymerase III use to join nucleotides?
Energy from breaking phosphate bonds ## Footnote This energy is derived from the nucleotides themselves.
40
What is the leading strand in DNA replication?
The strand that uses the 5' to 3' template strand and is synthesized continuously ## Footnote It is synthesized in the direction of the replication fork.
41
What is the lagging strand in DNA replication?
The strand using the 3' to 5' template strand, synthesized discontinuously in short fragments ## Footnote These short fragments are called Okazaki fragments.
42
Fill in the blank: DNA Polymerase III synthesizes DNA in the _____ direction.
5' to 3' ## Footnote This is the only direction in which DNA can be synthesized.
43
True or False: The lagging strand is synthesized in the same direction as the replication fork.
False ## Footnote The lagging strand is synthesized in the opposite direction of the replication fork.
44
What is the function of DUA Polymerase I?
Removes RNA primers from the leading strand and fragments of the lagging strand and replaces them with the correct deoxyribonucleotide.
45
What role does DNA ligase play in DNA replication?
Joins Okazaki fragments together via phosphodiester bonds.
46
What happens as DNA strands are built during replication?
They automatically rewind to form a double helix.
47
How do DNA polymerase III and I ensure accuracy in DNA replication?
They recognize whether hydrogen bonding has taken place between base pairs.
48
What occurs if a mismatch is detected by DNA polymerase?
The polymerase excises the incorrect base and inserts the correct one.
49
What are telomeres?
Long sequences of repetitive non-coding DNA.
50
What is the function of telomeres in chromosomes?
They act as buffer zones at the ends of chromosomes, helping guard against loss of valuable genetic material during replication.
51
Fill in the blank: DNA ligase joins Okazaki fragments together via _______.
phosphodiester bond
52
What did Watson and Crick realize about the DNA molecule?
DNA strands must run anti-parallel for stability ## Footnote This was a crucial insight into the structure of DNA.
53
What did Rosalind Franklin discover about DNA?
DNA has a helical structure ## Footnote Her work contributed significantly to understanding DNA's shape.
54
What key concept did Hershey and Chase demonstrate?
DNA is responsible for carrying genetic information ## Footnote Their experiments with bacteriophages provided strong evidence for this.
55
What did Avery, McCarty, and MacLeod discover?
DNA is a transforming substance ## Footnote This finding was pivotal in identifying DNA as the genetic material.
56
What were Chargaff's findings regarding nitrogenous bases?
Nitrogenous bases occur in definite ratios ## Footnote Specifically, adenine pairs with thymine and cytosine pairs with guanine.
57
What did Chargaff discover about the quantities of thymine and adenine?
The quantities always matched ## Footnote This observation was crucial for understanding base pairing in DNA.
58
What role did Hammerling attribute to the nucleus?
Control center of the cell ## Footnote His experiments with algae demonstrated the nucleus's importance in heredity.
59
What did Griffith discover about DNA
the transformation principle
60
What did Meischer discover about DNA
DNA as the hereditary molecule
61

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