Week 1 - Nucleic Acid Structure

Question 1

What is the hereditary molecule shared by all life?

Answer 1

deoxyribonucleic acid (DNA)

DNA has been present since the common ancestor of all known species, dating back to microscopic organisms 3.7 billion years ago.

Question 2

Who proposed the idea that nucleotide sequences differ between species?

Answer 2

Chargaff

Chargaff also found that the amounts of Adenine = Thymine and Guanine = Cytosine.

Question 3

What are the three basic subunits of DNA?

Answer 3

• bases
• sugar
• phosphate

Question 4

What are the two types of nitrogenous bases in DNA?

Answer 4

• purines
• pyrimidines

Question 5

Name the purines found in DNA.

Answer 5

• Guanine (G)
• Adenine (A)

Question 6

Name the pyrimidines found in DNA.

Answer 6

• Cytosine (C)
• Thymine (T)

Question 7

What sugar is found in DNA?

Answer 7

deoxy-ribose

Deoxy-ribose is a ribose sugar that lacks a hydroxyl group (OH) on carbon 2 (C2).

Question 8

What type of bond links sugar and phosphate in DNA?

Answer 8

phosphodiester bonds

These are strong covalent bonds that form the sugar-phosphate backbone.

Question 9

What is the structure of a double-stranded DNA molecule?

Answer 9

A double helix

It consists of two sugar-phosphate backbones running in opposite directions with complementary bases.

Question 10

How do purines pair with pyrimidines in DNA?

Answer 10

• Guanine (G) with Cytosine (C) forming three hydrogen bonds
• Adenine (A) with Thymine (T) forming two hydrogen bonds

Question 11

True or False: The sequence of bases in DNA can generate a vast number of combinations.

Answer 11

True

For example, with three bases, there are 64 possible sequences (4^3).

Question 12

What is the minimum number of bases required to generate enough combinations for all 20 amino acids?

Answer 12

four bases

With four bases and three-base codons, it provides enough combinations for 20 amino acids.

Question 13

What is the significance of the angle at which the bases are offset in the DNA structure?

Answer 13

It allows the DNA molecule to be helical

The offset angle is approximately 32 degrees.

Question 14

What is the maximum number of amino acids that can be coded by two-base codons?

Answer 14

four amino acids

Question 15

Calculate the number of base pairs required for a protein composed of 142 amino acids using a 4-base sequence with 3-base codons.

Answer 15

426 base pairs

This is more efficient than using a 2-base sequence with 5-base codons, which would require 710 base pairs.

Question 16

What is the role of uracil in nucleic acids?

Answer 16

Uracil is a base found in RNA molecules.

Question 17

Fill in the blank: The combined work of Rosalind Franklin and Maurice Wilkins, along with Crick and Watson, led to the discovery of the _______ structure of DNA.

Answer 17

double helical

Question 18

Who discovered DNA in 1869?

Answer 18

Friedrich Miescher

Question 19

What did Stanley Miller contribute to the understanding of the origin of life?

Answer 19

He conducted experiments related to the primordial soup theory.

Question 20

What is the function of the sugar-phosphate backbone in DNA?

Answer 20

It provides structural support to the DNA molecule.