A1.2 DNA

Question 1

What are the 4 types of biological molecules upon which life is based?

Answer 1

Lipids
Carbohydrates
Proteins
Nucleic acids

Question 2

What are the two primary functions of nucleic acids?

Answer 2

1. Pass information between generations
   Through DNA replication, the information stored in DNA is passed from cell to cell through generations
2. Code for protein production
   The sequence of nitrogenous bases in nucleic acids forms a code that stores information that is used to make proteins

Question 3

What are the two types of nucleic acids?

Answer 3

DNA - Deoxyribonucleic acid
Passes heredity information between generations of cells
Codes for making RNA during transcription

RNA - Ribonucleic acid
Codes for making proteins during translation-
mRNA, rRNA, and tRNA are the three main types of RNA involved in protein synthesis

Question 4

What are the three parts of a nucleotide?

Answer 4

Phosphate group (negatively charged)
Pentose sugar
A purine or pyrimidine made nitrogenous bases which are:
- adenine
- thymine
- guanine
- cytosine
- uracil

Question 5

H group or OH group one pentose sugar?

When talking about DNA OR RNA

Answer 5

DNA - H group at end as it lacks an oxygen (deoxyribose)

RNA - OH group (ribose)

Question 6

What is the nucleic acid and condensation reaction?

Answer 6

Backbone formed through a condensation reaction, where nucleotides combine to form a single molecule resulting in the loss of a water molecule

DNA and RNA have a “backbone” of phosphate-sugar- phosphate-sugar-phosphate…

The ends of the backbone are identified as 5’ and 3’
5’ end with a phosphate
3’ end with a pentose.

Question 7

How is a DNA molecule adapted to carry out its function?

Answer 7

Stability - can pass through generations without change

Hydrogen bonds - allows easy separation of strands

Large molecule - carries vast amounts of information

Helical cylinder - protection from chemical and physical changes

Question 8

Purines and pyrimidines

Answer 8

Always in a 1:1 ratio. The purines are Guanine and Adrenine. A purine has a double ring structure.

The pyrimidines are cytosine, Thymine and Uracil (only in RNA). Single ring structures

Question 9

Where is DNA and RNA in a eukaryotic and prokaryotic cell?

Answer 9

Eukaryotic
DNA. RNA
nucleus. Nucleus
Mitochondria. Cytoplasm
Chloroplasts

Prokaryotic
DNA. RNA
nucleoid. Cytoplasm
Plasmids

Question 10

How many possible sequences in DNA?

Answer 10

4^n sequences so a stream of DNA with just 15 nucleotide pairs has 1,073,741,824 possibilities

Question 11

What was the Hershey-Chase experiment?

Answer 11

By: Alfred Hershey and Martha Chase

Viruses are made of both DNA and protein and DNA contains phosphorus while protein contains sulfur so they added a radioactive isotope of these elements and the radioactive isotope in the host cell which is affected by the bacteriophage (the virus) is the hereditary component.

Which was DNA.

Question 12

Scientists who found the structure of DNA

Answer 12

Erwin Chargaff - found the pairs are A-T and G-C as they had the ratios of the opposite one for example A had the same ratio as T.

Linus Pauling - came up with a structure which ended up being impossible as there was a clump of phosphates which are all negatively charged so they would repel.

Rosalind Franklin - Took clearest image of DNA after many failed attempts (called photo 51). She also found key things in the structure.

Maurice Wilkens - stole Franklin’s research and gave it to Watson.

Watson and Crick - they out all this research together and came up with a structure which won the Nobel prize

Hershey and Chase - found out DNA is the hereditary and not protein.

Question 13

The Sequence of Bases forms a Code

Answer 13

The order in which the different types of nucleotides are arranged in DNA or RNA serves as a code for storing genetic information in all living organisms