6.1 CELLULAR CONTROL

Question 1

Define mutation

Answer 1

• A random change in DNA base sequence which may create a non functioning protein or give advantage to the organism

Question 2

State four mutagenic agents

Answer 2

• UV
• Gamma
• X-ray
• Carcinogens

Question 3

State the two types of mutation

Answer 3

1) Substitution mutation
2) Insertion or deletion/indel mutation

Question 4

State the three forms of substitution mutations

Answer 4

1) silent
2) nonsense
3) missense

Question 5

Define silent mutation

Answer 5

• When the altered base triplet still codes for the same amino acid as before
• Protein structure not altered

Question 6

Define nonsense mutation

Answer 6

• When the altered base triplet codes for a different amino acid than before
• Protein structure altered

Question 7

Define missense mutation

Answer 7

• When the altered base triplet codes for a stop codon
• Protein structure altered and shortened

Question 8

State and explain what type of insertion or deletion/indel mutations cause a frameshift

Answer 8

• A single base insertion/deletion
• Because genetic code is non overlapping and read in groups of three bases

Question 9

Describe expanding triple nucleotide repeats

Answer 9

• number of repeat triple nucleotides increases during meiosis from generation to generation
• (-CAG CAG CAG-)

Question 10

State the cause of huntingtons disease

Answer 10

• Expanding triple nucleotide repeats

Question 11

State the regulatory mechanism at transcriptional level gene expression

Answer 11

• Lac operons for prokaryotes and eukaryotes
• Transcription factors ONLY for eukaryotes

Question 12

State the regulatory mechanism at post-transcriptional level gene expression

Answer 12

• The editing of primary mRNA and removal of introns to produce mature mRNA

Question 13

State the regulatory mechanism at post-translational level gene expression

Answer 13

• Protein activation by cyclic AMP

Question 14

Define operon

Answer 14

• a group of genes that function as a single transcription unit

Question 15

Draw a lac operon section of DNA

Answer 15

Question 16

State the function of lacZ and lacY section on the lac operon

Answer 16

• Structural genes that code for the enzymes lactose permease and B-galactosidase

Question 17

State the function of promotor region on the lac operon

Answer 17

• Where the enzyme RNA polymerase attaches to begin transcription for lacZ and lacY

Question 18

State the function of operator region on the lac operon

Answer 18

• Where the repressor protein lacL attaches to prevent RNA polymerase from attaching to the promoter to inhibit transcription

Question 19

State the function of regulatory gene next to the lac operon

Answer 19

• Codes for the repressor protein lacL

Question 20

Explain what E.coli does as part of transcriptional level gene expression

Answer 20

• E.coli metabolises glucose as a respiratory substrate
• If glucose is absent and the disaccaride lactose is present, then lactose induces the production of the enzymes lactose permease and B-galactosidase

Question 21

State the two enzymes that lactose induces

Answer 21

1) Lactose permease
2) β-galactosidase

Question 22

State the function of the enzyme lactose permease

Answer 22

• Allows lactose to enter the bacteria cell

Question 23

State the function of the enzyme B-galoactosidase

Answer 23

• Hydrolyses the dissacaride lactose into glucose and galactose

Question 24

Explain how the expression of the regulatory gene (I) inhibits transcription

Answer 24

• When regulatory gene (I) is expressed, it produces a repressor protein
• This repressor protein then binds to the operator region (lacO)
• This prevents RNA polymerase from binding to the promotor region (P)
• Therefore, inhibiting transcription of lacZ and lacY
• Thus, the two eznymes for lactose metabolism are not made, genes are “off”