6.1.1: Cellular control

Question 1

What is a mutation?

Answer 1

An alteration to the DNA base sequence.
Often arise spontaneously during DNA
replication.

Question 2

What are addition and deletion mutations?

Answer 2

● Where one or more nucleotides (bases) are
either inserted or deleted from the DNA
sequence.
● More likely to be either harmful or beneficial,
due to frame shift which means the entire
amino acid sequence will be different

Question 3

What is a substitution mutation?

Answer 3

● When a nucleotide in the DNA
sequence is replaced by another.
● More likely to be a neutral mutation,
meaning no change occurs in the
amino acid sequence

Question 4

How is gene expression regulated at the

transcriptional level?

Answer 4

Transcription factors. These are proteins
that can either initiate or inhibit the
transcription of genes, so that only
certain parts of the DNA are expressed

Question 5

Describe the function of the lac operon in low lactose

concentrations.

Answer 5

● E.coli can use lactose as a respiratory
substrate, via use of an enzyme.
● When lactose concentration is low, the lac
operon binds to the gene that makes this
enzyme and inhibits its expression

Question 6

Describe the function of the lac operon in high

lactose concentrations.

Answer 6

Lactose binds to the operon, causing it to
change shape and unattach from the
gene. Allows RNA polymerase to bind
and the gene to be expressed.

Question 7

How is gene expression regulated at the

post-transcriptional level?

Answer 7

Splicing. Primary mRNA contains both coding
regions (exons) and non-coding regions
(introns). The introns are removed to produce
mature mRNA ready for translation.

Question 8

How is gene expression regulated at the

post-translational level?

Answer 8

Activation of proteins, such as adrenaline.
When adrenaline binds to a receptor, an
enzyme is activated which converts ATP to
cyclic AMP. Prompts further enzyme reactions,
which activates the protein.

Question 9

How is development controlled by homeobox genes?

Answer 9

Code for transcription factors that activate
genes when they’re needed during
development of a zygote. Their sequences
are similar in plants, animals, and fungi.

Question 10

How is development controlled by mitosis?

Answer 10

Mitosis (cell replication) is the primary
mechanism of growth. Genes regulating
mitosis respond to various stimuli, both
internal and external, in order to control
rate of growth.

Question 11

How is development controlled by apoptosis?

Answer 11

Programmes the death of cells. It is
highly controlled and keeps cell division
at a constant rate so as to prevent
cancer