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 base sequence
More likely to be either 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 (no effect) meaning no changes occur in the base sequence

Question 4

How is gene expression regulated at the transcriptional level ?

Answer 4

Transcription factors, which are proteins that can either turn on or off 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 concentration

Answer 5

Prokaryotes 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 unattached from the gene. Allows RNA polymerase to bind to 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 activities 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, animails 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’s highly controlled and keeps cell division at a constant rate so as to prevent cancer

Question 12

Explain Lac Operon

Answer 12

When lactose is absent, the regulatory gene is transcribed and translated
The repressor protein binds to the operator
Preventing RNA polymerase from binding to the promoter so the structural genes cannot be transcribed
However when lactose is present, it binds to the repressor protein, causing it to undergo a conformational change, unable to bind to the operator. The RNA polymerase binds to the promoter. Transcription of structural genes can now occur. Enzyme lactase is produced

Question 13

What control occurs as post-translational level ?

Answer 13

After translation, they undergo modifications in the Golgi, non-protein group is added.

Question 14

What is a homeobox

Answer 14

A DNA sequence that codes for a transcription factor, turns on and off different genes

Question 15

What are Homeobox genes responsible for ?

Answer 15

Genetic control of the development of body plans, basic body pattern of organisms
E.g. polarity of the organism (Head & Tail)

Question 16

How has an animails become deformed ?

Answer 16

Perhaps there has been a mutation in the box gene, this is because the hox gene regulates body development, so a mutation may result in a different arrangement, as a transcription factor cannot be formed