Cellular Control

Question 1

How are different cells made? (3)

Answer 1

• Activation and deactivation of genes (1)
• Activated genes transcribed to mRNA and translated to proteins (1)
• Cell becomes specialised as proteins modify the cell (1)

Question 2

What are transcription factors? (3)

Answer 2

• Proteins that carry out the activation and deactivation of genes (1)
• Activators bind to the promotor region and help RNA polymerase to bind and transcribe the gene (1)
• Repressors block the RNA polymerase from binding (1)

Question 3

What are operons? (2)

Answer 3

• What transcription factors bind to in prokaryotes (1)
• Cluster of genes controlled by a single promoter (1)

Question 4

What’s the structure of operons (from left to right)? (3)

Answer 4

Regulatory gene = Codes for TF (1)

Control elements = contains promotor and operator regions where RNA polymerase and TF can bind (1)

Structural genes = Codes for useful proteins such as enzymes (1)

Question 5

What happens when lactose is absent? (2)

Answer 5

• Regulator gene produces lac repressor (1)
• Binds to operator region and blocks RNA polymerase from transcribing structural genes

Question 6

What happens when lactose is present? (4)

Answer 6

• Lactose binds to the lac repressor and changes its shape (1)
• Lac repressor no longer binds to the operator region allowing RNA polymerase to transcribe structural genes as it binds to the promotor region(1)
• LacZ codes for enzymes to break lactose glycosidic bonds (1)
• LacY codes for lactose permease to transport lactose into the cell (1)

Question 7

What is splicing? (2)

Answer 7

• Introns are removed from mRNA before translation (1)
• As introns don’t code for amino acids (1)

Question 8

Where does splicing occur? (2)

Answer 8

• Only in eukaryotes (1)
• Prokaryotes don’t contain introns (1)

Question 9

What is cyclic AMP? (3)

Answer 9

• Secondary messenger (1)
• Changes 3D structure (1)
• Activates proteins synthesised inactively (1)

Question 10

What are hox genes? (2)

Answer 10

• Controls the arrangement of organisms body parts (1)
• Highly conserved meaning DNA barely changes through evolution (1)

Question 11

Explain how hox genes work? (3)

Answer 11

• Hox genes transcribed and translated into hox proteins (1)
• Binds to DNA at homeodomain binding site (1)
• Hox proteins act as a transcription factor, activating and repressing genes (1)

Question 12

What is apoptosis? (1)

Answer 12

• Where cells annihilate themselves (1)

Question 13

What are types of mutations? (4)

Answer 13

Substitution = Base replaced will affect one amino acid unless degenerate (1)

Insertion/Deletion = Adding/Removing base causes frameshift and affects all following codons (2)

Inversion = ATC/CTA affects one amino acid (1)

Question 14

Why would mutation have a neutral effect? (2)

Answer 14

• Different triplets code for the same amino acids (1)
• Different amino acid is chemically similar (1)