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 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 at high lactose levels

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-transcriptional 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 (highly conserved)
Pax6 codes for eye development

Question 10

How is development controlled by mitosis

Answer 10

Mitosis (cell replication) is 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