A1.2

Question 1

Nucleic Acids

Answer 1

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.

Question 2

DNA vs RNA

Answer 2

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

Question 3

RNA base composition

Answer 3

adenine
thymine
guanine
uracil

Question 4

DNA base composition

Answer 4

adenine
thymine
guanine
cytosine

Question 5

DNA structure

Answer 5

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.

Question 6

purine and pyrimidine

Answer 6

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

Question 7

Genetic Code

Answer 7

codes for specific amino acid sequence

Question 8

triplet codon

Answer 8

3 bases codes for one specific amino acid without overlapping

Question 9

Degenerative

Answer 9

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

Question 10

universal

Answer 10

Coding system is common in most organism

Question 11

Chromosome

Answer 11

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

Question 12

describe how DNA associate with histone proteins

Answer 12

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

Question 13

Hershey-Chase Experiment

Answer 13

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

Question 14

procedure of Hershey-Chase Experiment

Answer 14

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_

Question 15

results of Hershey-Chase Experiment

Answer 15

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

Question 16

Chargaff’s Rule

Answer 16

Aim: to falsify the tetranucleotide hypothesis

Question 17

Chargaff’s rule definition

Answer 17

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

Question 18

Tetranucleotide hypothesis

Answer 18

The proportion of all the nitrogenous bases are equal.

Question 19

how did Chargaff conduct research

Answer 19

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

Question 20

Results of Chargaff’s research

Answer 20

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.