A1.2 Nucleic Acid Flashcards

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1
Q

Nucleic Acids

A

Nucleic acids are composed of monomers called nucleotides, which join to form polynucleotide chains

Each nucleotide consists of 3 components – a pentose sugar, a phosphate group and a nitrogenous base

The type of sugar and composition of bases differs between DNA and RNA.

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2
Q

DNA vs RNA

A

DNA (deoxyribonucleic acid) is a more stable double stranded form that stores the genetic blueprint for cells

RNA (ribonucleic acid) is a more versatile single stranded form that transfers the genetic information for decoding

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3
Q

RNA base composition

A

adenine
thymine
guanine
uracil

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4
Q

DNA base composition

A

adenine
thymine
guanine
cytosine

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5
Q

DNA structure

A

Made up of monomers called _nucleotides

There are _hydrogen bonds_between the _complementary base pairs

2 hydrogen bonds between Adenine (A) and Thymine (T)

3 hydrogen bonds between Guanine (G) and Cytosine (C)

The two strands are arranged in _anti-parallel

Winded into a double helix structure

There is 3’ - 5’ linkage between the nucleotide of the same strand, known as phosphodiester bonds

The end with phosphate group attached to the C5 of the deoxyribose is known as the 5’ end_. And the ends with phosphate group that attached to the C3 of the deoxyribose is known as the 3’ end.

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6
Q

purine and pyrimidine

A

hydrogen bond_between purine_ and pyrimidine

Purine is a nucleotide with a two-ring nitrogenous base. (One 5 ring and one 6ring) For DNA, it’s Adenine and Guanine.

Pyrimidine is a nucleotide with a one-ring nitrogenous base. For DNA, it’s cytosine and _thymine

Only purine will pair with pyrimidine, this is described as complementary base pairing

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7
Q

Genetic Code

A

codes for specific amino acid sequence

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8
Q

triplet codon

A

3 bases codes for one specific amino acid without overlapping

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9
Q

Degenerative

A

20 amino acids existed in nature
(4 bases and 3 bases are being read one at a time, 43 = 64 combination)

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10
Q

universal

A

Coding system is common in most organism

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11
Q

Chromosome

A

DNA associate with histone proteins

DNA molecules wrapped around a core of eight histone proteins_held together by an additional histone protein attached to linker DNA

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12
Q

describe how DNA associate with histone proteins

A

eight histones make up the nucleosome core

DNA wraps twice around the eight histones of the nucleosome core

linker DNA extending from the previous nucleosome

linker DNA going to the next chromosome

histone maintaining the shape of the nucleosome

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13
Q

Hershey-Chase Experiment

A

Aim : to find out whether DNA or protein was the genetic material of the cell

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14
Q

procedure of Hershey-Chase Experiment

A

1) Viruses (T2 bacteriophage) were grown in an isotopic medium:
Viruses grown in radioactive sulfur (35S) had radiolabeled _proteins
Viruses grown in radioactive phosphorus (32P) had radiolabeled DNA

2) Viruses were then allowed to _infect a bacterium (E. coli)

3) Then the virus and bacteria were separated via centrifugation

4) The larger bacteria formed a solid pellet_ while the smaller viruses remained in the __supernatant_

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15
Q

results of Hershey-Chase Experiment

A

The radioactivity appears to be in the bacterial pellet when infected by the 32P-viruses

But the radio activity appears to be in the supernatant when infected by the 35S - viruses

This demonstrated that DNA was the genetic material as DNA was transferred to the bacteria

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16
Q

Chargaff’s Rule

A

Aim: to falsify the tetranucleotide hypothesis

17
Q

Chargaff’s rule definition

A

DNA molecule contain the same number of adenine and thymine nucleotides, and the same number of guanine and cytosine nucleotides

18
Q

Tetranucleotide hypothesis

A

The proportion of all the nitrogenous bases are equal.

19
Q

how did Chargaff conduct research

A

In the late 1940s a researcher named _Erwin Chargaff developed a research technique designed to show the proportion of nitrogenous base found in various sources of DNA.

His separation and identification technique involves paper chromatography

20
Q

Results of Chargaff’s research

A

There is sound shows that there is almost the same ratio of adenine and thymine, and the same ratio of guanine to cytosine.

The idea became the foundation of complementary base pairing.