DNA & RNA (DOESN'T INCLUDE PROTEIN SYNTHESIS)

Question 1

DNA

Answer 1

~ Stands for deoxyribonucleic acid
~ Linked by pairs of chemicals called bases

Question 2

What shape is DNA?

Answer 2

Double helix

Question 3

Who discovered DNA is in the form of a double helix?

Answer 3

Watson and Crick

Question 4

Structure of a nucleotide

Answer 4

Contains a phosphate, deoxyribose and a base

Question 4

DNA structure

Answer 4

DNA is made up of nucleotides which are arranged in long chains called polynucleotides

Question 4

Bases

Answer 4

There are four nitrogenous bases two are classified as purines and two are classified as pyrimidines

Question 5

Purine bases

Answer 5

Adenine and guanine

Question 6

Pyrimidine bases

Answer 6

Thymine and cytosine

Question 7

What bases link together?

Answer 7

~ Adenine links with thymine ; two weak hydrogen bonds
~ Guanine links with cytosine ; three hydrogen bonds

Question 8

Double helix

Answer 8

~ Outer two strands of the double helix are composed of deoxyribose and phosphate
~ The base pairs are between these

Question 9

The Genetic Code (code for producing a protein)

Answer 9

~ Genes are made up of DNA which are required for the production of a protein
~ DNA codes for each amino acid by a sequence of three consecutive bases known as a triplet or codon
~ Each triplet forms a specific amino acid
~ A long chain of triplets form a protein1

Question 10

Non-coding / junk DNA

Answer 10

Has no known function

Question 11

RNA (Ribonucleic acid)

Answer 11

~ Needed for protein synthesis
~ One base is different, uracil replaces thymine

Question 12

DNA vs RNA

Answer 12

DNA = longer strand, sugar is deoxyribose, has base thymine, self replicating, found in the nucleus, mitochondria and chloroplast
RNA = shorter strand, sugar is ribose, has base uracil, not self replicating, found in the nucleus, ribosome and cytoplasm

Question 13

Mechanism of DNA replication

Answer 13

1. The double helix unwinds
2. An enzyme breaks the bonds between the base pairs
3. DNA bases that are normally present in the cytoplasm enter the nucleus and attach themselves to exposed complimentary bases
4. Each new strand is half new DNA and half original DNA. It is identical to the original DNA strand and to the other new partner strand
5. Each new piece of DNA rewinds to form a double helix

Question 14

What is the significance of DNA replication?

Answer 14

DNA is able to produce exact copies of itself, this means that the same DNA is passed on to each new generation of cells

Question 15

DNA profiling

Answer 15

Generating a pattern of bands from a DNA sample, which can then be used to distinguish that DNA from another

Question 16

Method of preparation

Answer 16

1. DNA is released
2. DNA is cut into fragments
3. The fragments are separated
4. Patterns are compared

Question 17

1. DNA is released

Answer 17

DNA is released and isolated

Question 18

2. DNA is cut into fragments

Answer 18

The isolated DNA is cut into fragments using restriction enzymes

Question 19

3. The fragments are separated

Answer 19

~ The fragments are separated on the basis of their size by gel electrophoresis
~ The fragments are placed in a tank containing a sugar-based gel, with an electrical current being passed through it
~ The current draws the negatively charged DNA to one end of the end

Question 20

4. Patterns are compared

Answer 20

Pattern is analysed and compared

Question 21

Applications of DNA profiling

Answer 21

~ Crime (Forensic cases)
~ Medical

Question 22

Genetic screening

Answer 22

Testing of DNA for the presence or absence of a gene

Question 23

Methods of genetic screening

Answer 23

1. Adult screening = Some adults might not suffer from a genetic disorder but might be a carrier of a defective gene and could possibly pass this defective gene onto their child
2. Foetal screening = Cells are removed from the placenta or the fluid around the foetus and tested for a number of genetic disorders

Question 24

Ethics of genetic screening

Answer 24

~ Adults: if the results of genetic tests became public, the people concerned may
suffer embarrassment or be treated unfairly.
~ Foetal: it could encourage a termination if a severe defect was found.