Molecular Genetics

Question 1

Messenger RNA (mRNA)

Answer 1

Varies in length depending on the gene that has been copied.
Acts as the intermediary between DNA and the ribosomes.
Translated into protein by ribosomes.

Question 2

Transfer RNA (tRNA)

Answer 2

Functions as the delivery system of amino acids to ribosomes as they synthesize proteins.
Very short (70 to 90 base pairs long).

Question 3

Ribosomal RNA (rRNA)

Answer 3

Binds with proteins to form the ribosomes.
Varies in length.

Question 4

Point mutations

Answer 4

Small-scale mutations
A change in a specific base pair.
Can have a positive effect (evolution, natural selection), a negative effect (disease) or no effect.

Question 5

Substitution:

Answer 5

The replacement of one base with another.

Question 6

Missense Mutation:

Answer 6

One amino acid is exchanged for another.

Question 7

Nonsense Mutation:

Answer 7

A codon for an amino acid is replaced by a stop codon.

Question 8

Silent Mutation:

Answer 8

A mutation that does not change the amino acid coded for, so there is no phenotypic change.

Question 9

Insertion:

Answer 9

The addition of an extra base pair in a DNA sequence.

Question 10

Deletion:

Answer 10

The elimination of a base pair or group of base pairs from a DNA sequence.

Question 11

Frameshift Mutations:

Answer 11

Causes the reading frame of codons to change.
Causes different amino acids being incorporated into polypeptides.

Question 12

Inversion:

Answer 12

The reversal of 2 adjoining base pairs in a DNA sequence.

Question 13

Chromosomal mutations

Answer 13

Large-scale mutations
Involves multiple nucleotides, entire genes or whole regions of chromosomes.
Insertion/deletion of coding regions may have a negative impact on the organism.

Question 14

Translocation:

Answer 14

Entire genes or sequences move from one chromosome to another, or portions break off and exchange places, resulting in a new gene.

Question 15

Inversion:

Answer 15

The reversal of a large number of base pairs in a DNA sequence.
Entire coding regions may be removed or inverted.
A large loss of genetic material may negatively affect the functioning of the cell.

Question 16

Spontaneous Mutations:

Answer 16

Caused by an error during DNA replication.
For example, if DNA polymerase misses errors in duplicated DNA, a point mutation will be caused.

Question 17

Induced Mutations:

Answer 17

Mutations are caused by the effect of an environment agent (mutagent).
For example, chemicals, UVB radiation or X-rays.

Question 18

TYPES OF INDUCED MUTATIONS

Answer 18

Chemical and electromagnetic radiation.

Question 19

Chemical Mutagens:

Answer 19

A chemical agent enters the nucleus and alters the structure of DNA.
For example, carbon monoxide and tobacco smoke.

Question 20

Electromagnetic Radiation:

Answer 20

Lower energy radiation (UVB) can cause bonds to form between adjacent molecules, creating a kink in the DNA backbone. This complicates replication and transcription.
Higher energy radiation (X-rays) can strip molecules of electrons and break DNA molecule bonds. This may result in deletion or rearrangement of chromosomes.

Question 21

Aminoacyl Site:

Answer 21

Holds the tRNA carrying the next amino acid to be added to the chain.

Question 22

Peptidyl Site:

Answer 22

Holds the tRNA carrying the growing chain.

Question 23

Exit Site:

Answer 23

Where the tRNA that has lost its amino acid is discharged.