6.1.1 Cellular Control

Question 1

What is a mutation ?

Answer 1

•An alteration to the DNA base sequence
•They often arise spontaneously during DNA replication

Question 2

What are addition and deletion mutations ?

Answer 2

•Where one or more nucleotides are inserted into the DNA sequence or removed
•They are likely to be entirely harmful or beneficial due to frameshift, which means the entire amino acid sequence is different

Question 3

What is a substitution mutation ?

Answer 3

•When a nucleotide in a DNA sequence is replaced with another
•More likely to be a neutral mutation, resulting in no significant change occurs in the sequence

Question 4

How is gene expression regulated on 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 functions of the lac operon in low lactose concentrations

Answer 5

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

Question 6

Describe the functions 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 that turns ATP into cAMP
*This prompts further enzyme reactions, which activates the protein.

Question 9

How is development controlled by homeobox genes ?

Answer 9

•They code for transcription factors that activate genes when they are needed during a zygotes development
•Their sequences are similar in plants, animals and fungi.

Question 10

How is development controlled by mitosis ?

Answer 10

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

Question 11

How is development controlled by apoptosis ?

Answer 11

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