Cellular Controll 6.1

Question 1

two main types of mutation …

2

Answer 1

• point mutations

- indel (insertion , deletion )

Question 2

whats the lac operon ? 1

Answer 2

-used in respiration if glucose is unavailable , then lactose is broken down

Question 3

outline the structure of the lac operon …

4

Answer 3

From left to right :

1. Regulatory gene (i) =codes fro repressor protein (laci)
2. Promotor region= RNA polymerase binds here to begin the transcription of the lacZ and lacY.
3. Operator region=repressor protein (laci) binds here
4. lacZ and LacY = structural genes =codes fro enzymes such as B galactosidase and lactose permease .

Question 4

what does a regulatory gene do in the lac operon ? 
-name 
-function 
-explanation , when expressed 
4

Answer 4

• name is i
• codes for repressor protein = laci
• when expressed repressor protein is made - (Laci) protein binds to the operator
• this means that the lacZ and LacY genes aren’t transcribed.
• enzymes for lactose metabolism aren’t made so genes are OFF

Question 5

what does the promotor region do in lac operon ?

1

Answer 5

-RNA polymerase binds here to begin transcription

Question 6

What does the Operator region do in lac operon ?

operator+promoter are know as …

Answer 6

• REPRESSOR protein binds here and stops RNA polymerase binding to Promoter region .
  = operator + promotor===>controll sites

Question 7

what do the structural genes do in lac operon ?
4
explain what the enzymes do …

Answer 7

lacZ and lacY :

• lacZ = B galactosidase=> turns lactose –>glucose + galactose
• lacY = Lactose Permease —> allows lactose to enter the bacterial cell.

Question 8

what molecule is the inducer in the lac operon ?1

Answer 8

lactose

Question 9

what happens when lactose is present ?

4

Answer 9

• Lactose binds to repressor protein (lacI)
• This causes a conformational change meaning that it can no longer bind to the operator region
• RNA polymerase now can transcribe the lacZ and lacY
• enzymes produced for lactose metabolism …

Question 10

what’s a transcription factor ? 3

Answer 10

• proteins or short non coding parts of RNA
• act in the nucleus
• controll what’s turned on or off

Question 11

why is mRNA shorter than the gene is was transcribed from ? 3

Answer 11

• whole gene= introns and exons
• primary RNA = introns and exons
• mRNA = only EXONS hence it is shorter

Question 12

whats a homeobox gene ? 2

Answer 12

sequence of 180 base pairs ( without introns), found in genes that regulate ANATOMICAL DEVELOPMENT = animals , plant and fungi

Question 13

whats a HOX gene ? 3

Answer 13

subset of homeobox genes ,

• found only in animals ,
• involved in formation of anatomical features in correct location of body plan .

Question 14

why is it important that homeobox sequence is high;y conserved ?
2

Answer 14

• means we all had common ancestor (plant and animals and fungi )
• still present today so it must be important !

Question 15

How is Hox gene different form Homeobox genes ?

2

Answer 15

• Hox is only in animals and it controls cell differentiation mitosis, apoptosis , regulates cell cycle,cell migration

Question 16

Whats colinearity ? 2

Answer 16

-genes that control anterior and posterior axis , develop in same order as organs ( head , shoulders , knees and toes )

Question 17

why doesn’t apoptosis damage surrounding cell tissue ?

Answer 17

• no hydrolytic enzymes involved

Question 18

why should the rate of apoptosis = the rate of mitosis ?

2

Answer 18

• tumour will occur if rate of apoptosis is too slow

- Degeneration will occur if the rate of apoptosis is too fast

Question 19

why should pregnant mothers not eat liver?

3

Answer 19

• liver has a lot of RENTINOL
• body converts this to RETANOIC ACID
• this interfere with HOX genes
• leads to abnormalities in child

Question 20

whats the difference between RNA polymerase and DNA polymerase …
4

Answer 20

RNA POLYMERASE : used to make mRNA and tRNA , used in transcription ,and only small part of one strand of DNA used …
DNA POLYMERASE : used in DNA replication, whole length used ,2 strands formed

Question 21

why do stop codons stop the translation ? 1

Answer 21

• no matching Amino Acid present …

Question 22

whats the sequence of apoptosis ?

Answer 22

1- enzymes break down cell cytoskeleton
2-cytoplasm = dense with tightly packed organelles
3-small protusions called BLEBS form
4-Chromatin condenses , nucleur envelope breaks and DNA breaks into fragments
5-Cells = vesicles that are ingested by phagocytic cells
(no hydrolytic enzymes involved )