Lectures 13 - 16

Question 1

Define: Replication, transcription, translation.

Answer 1

Replication - where new identical DNA strand are created.

Transcription - where the DNA is converted into messenger RNA (mRNA).
During transcription, there are three processes that take place. Initiation, elongation, and termination.

Translation - where decoding of the mRNA occurs, decoding it into amino acids, that form proteins that are essential for life functions.

Question 2

Features of Transcription:

Answer 2

• separates the DNA strands
• uses one strand as a template
• sequential addition to growing strand
• new RNA growth is 5’ to 3’

Question 3

What catalyses Transcription

Answer 3

RNA polymerase.

• there is no helicase needed (enzyme that unwinds and separates the two strands of DNA).
• there is no primer needed (a short nucleic acid sequence (RNA) that provides a starting point for DNA synthesis).

Question 4

What is the purpose of primers?

Answer 4

Primers are short stretches of DNA that target/identify unique sequences of genomes (genes). They catalyse the addition of nucleotides to the growing DNA strand.

Question 5

What is asexual reproduction?

Answer 5

when there is one parental cell that develops into two identical daughter cells. Most cells in your body are reproduced asexually.

Question 6

What happens in the G1 phase

Answer 6

Cells grow in size

Question 7

What happens in S phase

Answer 7

DNA synthesis/replication

Question 8

What happens in G2 phase

Answer 8

Chromosomes are now duplicated, but still uncondensed. Centrosomes are also duplicated

Question 9

What is the order of mitosis ( of the stages)

Answer 9

1. Prophase
2. Prometaphase
3. Metaphase
4. Anaphase
5. Telophase
   (6. Cytokinesis)

Question 10

What happens in prophase

Answer 10

Chromosomes condense, nucleolus disappears, mitotic spindle forms

Question 11

What happens during prometaphase

Answer 11

Nuclear envelope fragments, the kinetochores assemble on chromatids

Question 12

What happens during metaphase

Answer 12

Chromatids line up at metaphase plate - pushed/pulled by microtubules

Question 13

What happens during anaphase

Answer 13

Chromatids separate - pulled by kinetochore microtubules
Chromosomes move towards opposite poles
The non-kinetochore microtubules will stretch, resulting in the cell to lengthen

Question 14

What happens during telophase

Answer 14

Events from prophase and prometaphase are undone - meaning that the nuclear envelope and nucleolus form

Question 15

What is cytokinesis

Answer 15

The final division of a cell at the end of mitosis.
Animals = cleavage furrow, cell divides
Plants = vesicles form a cell wall

Question 16

What is a mutation

Answer 16

A mutation is a permanent change in the DNA sequence. It changes a gene from one form (allele) to another. Allele is a particular form of a gene.

Question 17

What is a nonsense mutation

Answer 17

causes the sequence to stop, permanently terminated (substitution)

Question 18

What is a silent mutation

Answer 18

the mutation is not seen in the protein sequence (substitution) - due to the redundancy of the code

Question 19

What is a frameshift mutation

Answer 19

when there is an insertion or deletion of part of the DNA sequence, causing the reading of the sequence to shift (insertion/deletion)

Question 20

What is a missense mutation

Answer 20

a change in one of the codons of the sequence (substitution)

Question 21

What is a spontaneous mutation

Answer 21

mutations that occur during DNA replication.
Examples include:
- DNA polymerase error - when the polymerase doesn’t check its mistakes (1 in 10 million)
- Incorrect pairing due to tautomeric shifts - mistakes from the replication polymerase, but its not its fault. It causes the base pairing rules to change (anomalous arrangement).

Question 22

Nucleotide excision repair of DNA removes thymine dimers using which of the following groups of enzymes?

Answer 22

nuclease, polymerase and DNA ligase

Question 23

Which of the following DNA mutations is most likely to damage the protein it specifies?

Answer 23

A base-pair deletion