6.2.1 Cellular control

Question 1

What are the different types of gene mutation and their effects?

Answer 1

• Substitution (nucleotide(s) replaced) : Not always bad (beneficial, neutral or harmful)
• Insertion (nucleotide(s) inserted) : Causes frameshift (most likely harmful)
• Deletion (nucleotide(s) taken out) : Causes Frameshift (most likely harmful)

Question 2

What are the three places where gene expression can be controlled?

Answer 2

• Transcriptional (genes can be turned on and off)
• post-Transcriptional ( removal of introns to form mature mRNA)
• post-Transational (activation of the protein / addition)

Question 3

Transcriptional level control (in eukaryotes)

Answer 3

• Transcription factors bind to specific DNA sites at the target gene
• RNA polymerase bind to the transcription factor and starts producing mRNA

Question 4

Transcriptional level control in prokaryotes ( E.coli ) (lac operon)

Answer 4

• When glucose is not available the bacteria can respire with LACTOSE
• Lac repressor prevents the binding of RNA polymerase to the operator when LACTOSE is not present
• When lactose is present it binds to the lac repressor changing its structure and making it unbind to the operator
• This allows for RNA polymerase to bind and transcribe the structural genes

Question 5

Post Transcriptional control

Answer 5

• The primary mRNA has its introns spliced and removed
• The mature mRNA only has exons now
• This happens in the nucleus and it is now ready to go on to protein synthesis

Question 6

Post translational level control using cAMP

Answer 6

• Some molecules will bind to the CSM and trigger the production of cAMP
• cAMP activates proteins inside the cells by changing their structure
• This then means the protein can be active or less active

Question 7

What are homeobox genes?

Answer 7

• Regulatory genes that are 180 bp long and are highly conserved/similar between plants animals and fungi

Question 8

What are hox genes?

Answer 8

• Group of homeobox genes only present in animals

- Responsible for body plans

Question 9

How do hox genes control body development?

Answer 9

• Homeobox sequence codes for a homeodomain
• Homeodomain binds to specific sites on the DNA allowing for proteins to work as a transcription factor
• The proteins can activate or repress transcription of proteins that are important in the development of the body

Question 10

What is mitosis?

Answer 10

• Cell division creating new cells for body parts

Question 11

What is apoptosis?

Answer 11

• Programmed cell death where the cell is broken down

- Phagocytes then digest the cell fragments

Question 12

What is the role of mitosis and apoptosis in development?

Answer 12

• Mitosis creates the bulk of the body parts

- Apoptosis removes unwanted structures

Question 13

Examples of Mitosis and Apoptosis in development

Answer 13

• Hands and feet are first connected then apoptosis separates them
• Tadpoles lose their tail when they develop into frogs
• Excess Nerve cells are destroyed

Question 14

What can affect apoptosis and mitosis?

Answer 14

• External factors :
• Stress (lack of nutrient availability)
• DNA damage causes G0 in the cell cycle and apoptosis