6.1 Cellular Control

Question 1

What is a Mutation?

Answer 1

An random alteration to the DNA base sequence.

Question 2

When are Mutations most likely to arise and why

Answer 2

Often arise spontaneously during DNA replication, Most likely here due to exposed bases or base sequence errors

Question 3

What are Insertion and Deletion Mutations?

Answer 3

• Where one or more nucleotides (bases) are either inserted or deleted from the DNA sequence.
• More likely to be either harmful or beneficial, due to frame shift which means the entire amino acid sequence will be different

Question 4

What is a Substitution Mutation?

Answer 4

• When a nucleotide in the DNA sequence is replaced by another.
• More likely to be a neutral mutation, meaning no change occurs in the amino acid sequence.

Question 5

How is gene expression regulated at the transcriptional level?

Answer 5

Transcription factors. These are proteins (or no coding RNA pieces) that can either initiate or inhibit the transcription of genes, so that only certain parts of the DNA are expressed.

Question 6

What are Introns and Exons

Answer 6

Introns are NON coding pieces of DNA

Exons are coding pieces of DNA

Question 7

What is the function of the Lac operon

Answer 7

a group of genes in E.coli that allows it to metabolise lactose instead of glucose as a respiratory substrate(if no glucose, but lactose present)

Question 8

What is the function of

Lactose permease

Answer 8

Lactose permease allows lactose to pass through the bacterial cell wall(permeate)

Question 9

What is the function of B-galacotsidase

Answer 9

B galacotsidase hydrolyses lactose to its monomers, glucose and galactose

Question 10

What does Lac I code for

Answer 10

Lac I codes for repressor protein that binds to lac o and prevents lac Z&Y being transcribed

Question 11

What does Lac O do

Answer 11

O for operator, is where repressor protein binds to, preventing trancription

Question 12

What do Lac Z, and Lac Y code for

Answer 12

code for B-galactosidase(Z)

and lactose permease(Y)

Question 13

How does Lactose Induce the Lac Operons activity

Answer 13

Lactose binds to Lac I altering the shape of the represor protein it produces and preventing it binding to the operator, allowing lac Z&Y to be made

Question 14

Describe the function of the Lac Operon in low lactose concentrations.

Answer 14

When lactose concentration is low, the repressor proteins bind to the the operator preventing transcription of genes(Z&Y)

Question 15

Describe the function of the Lac Operon in high lactose concentrations.

Answer 15

Lactose binds to the repressor protection, causing it to change shape and unattach from the operator. Allows RNA polymerase to bind and the genes (Z&Y) to be transcribed

Question 16

How is gene expression regulated at the Post-Transcriptional level?

Answer 16

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 17

How is gene expression regulated at the Post-Translational level?

Answer 17

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 activates the protein.

Question 18

What’s a Homeobox sequence?

Answer 18

180 base pairs(exons) that regulate patterns of development in animals,fungi &plants

Question 19

How is development controlled by Homeobox genes?

Answer 19

They code for transcription factors that activate genes when they’re needed during development of a zygote.

Question 20

What’s a Hox gene?

Answer 20

subset of homebox genes ONLY found in animals(bilaterians) that are involved in formation of body parts in the correct locations

Question 21

How is development controlled by Mitosis?

Answer 21

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 22

What is Apoptosis, what does it do?

Answer 22

Programmed cell death. It is highly controlled and keeps cell division at a constant rate so as to prevent cancer.

Question 23

What’s a Nonsense mutation

Answer 23

a mutation where a stop codon is made and the strand is cut off early resulting in a truncated, non-functional protein

Question 24

What’s a Missense mutation?

Answer 24

a codon change which results in the production of a different amino acid, thus resulting in altered tertiary structure of the protein

Question 25

What’s a Silent mutation?

Answer 25

due to DNA’s degenerative code multiple codons make the same amino acid so this base change has NO effect on the final protein

Question 26

What does it mean to “Sequence” a genome?

Answer 26

to read the order of base sequences

Question 27

Why must Apoptosis be highly controlled?

Answer 27

too much leads to cell loss & degeneration.

Not enough can lead to tumors and Cancer

Question 28

Briefly summarize the cAMP Post translation regulation example

Answer 28

1.signalling molecule binds to target cells plasma membrane receptors
2. activates trans membrane protein which activates G protein which activates adenyl cyclase enzymes
3. enzymes catalyse formation of cAMP from ATP
4 cAMp activate protein kinase which may phosphyrlate another protein that enters the nucleus and acts as a transcription factor

Question 29

What does ‘Frame shift’ mean

Answer 29

The whole DNA sequence is moved by space(s) and can result in a new sequences

Question 30

Define operon

Answer 30

a group of genes under the same regulatory mechanism, transcribed as a single unit

Question 31

How might cells diffrentiate/specialise

Answer 31

transcription factors bind to sections of DNA, activating or supressing gene transcription leading to differential expression