Cellular control

Question 1

What are the two main classes of gene mutation?

Answer 1

1. Point mutation

2. Indel mutation

Question 2

What does point mutation mean?

Answer 2

Point mutation is where one of the base nucleotides is altered to another base. Which can cause the amino acid that is produced from the triplet to change.

Question 3

What are the tree types of point mutation?

Answer 3

1. Silent mutation
2. Missense mutation
3. Nonsense mutation

Question 4

Describe what a silent mutation is.

Answer 4

A silent mutation is when there is a change in the base triplet but will still code for the same amino acid and therefore will not have an effect.

Question 5

Describe what a missense mutation is.

Answer 5

A missense mutation is when there is a change in the triplet base sequence but it will code for a different amino acid and change the polypeptide. Can cause issues such as sickle cell anaemia.

Question 6

Describe what a nonsense mutation is.

Answer 6

Nonsense mutation occurs when the base triplet is altered and becomes a termination triplet or stop codon. This mutation will cause proteins to become shorter and therefore wont work as they are meant to. This can cause the genetic disease Duchenne muscular dystrophy.

Question 7

What does indel mutation mean?

Answer 7

Is the insertion or deletion of a base nucleotide to the DNA sequence.

Question 8

What is Deletion?

Answer 8

Deletion is a type of mutation involving the loss of genetic material. It can be small, involving a single missing DNA base pair, or large, involving a piece of a chromosome.

Question 9

What is Insertion?

Answer 9

A type of genetic change that involves the addition of a segment of DNA. It may be as small as a single base but can vary significantly in size.

Question 10

What does the term frameshift mean?

Answer 10

Causing a mutation in which a number of nucleotides not divisible by three is inserted or deleted so as to change the reading frame of some triplet codons during genetic translation.

Question 11

Give an example of a condition that is caused by a frameshift mutation.

Answer 11

Some forms of Thalassaemia, a haemoglobin disorder resulting from frameshift due to deletion

Question 12

What is the cause of Huntington disease?

Answer 12

Results from an expanding nucleotide repeat. If the number of repeating CAG sequences goes above a certain number, then the person with that genotype will develop the symptoms of Huntington disease later in life.

Question 13

Explain how mutation may be beneficial.

Answer 13

They lead to new versions of proteins that help organisms adapt to changes in their environment. Beneficial mutations are essential for evolution to occur. They increase an organism’s changes of surviving or reproducing, so they are likely to become more common over time.

Question 14

Describe how the presence of lactose intolerance induces the production of two enzymes in the bacteria.

Answer 14

A repressor protein is produced by the regulator gene if there is lactose the lactose will bind to the repressor and change its shape so it is unable to bind to the operator and therefor is not blocking the promotor. This means that the when RNA polymerase is produced it can bind to the promotor which then allows transcription and translation to occur for the enzymes. Lactose permease and beta galactose are made.

Question 15

What are transcription factors?

Answer 15

A protein or non - coding short RNA that bind to DNA to inhibit or activate transcription.

Question 16

Explain the role of transcription factors in gene expression.

Answer 16

Transcription factors are vital molecules in the control of gene expression, directly controlling when, where and the degree to which genes are expressed. They bind to specific sequences of DNA and control the transcription of DNA into mRNA.

Question 17

Explain the sequence of events that demonstrate how the removal of introns produces functional mRNA.

Answer 17

1. All DNA of a gene is transcribes.
2. Primary mRNA is produced.
3. The introns are edited out and removed (using endonuclease)
4. The remaining mRNA exons are joined together again using endonuclease by slicing. Forming a continuous strand again.

Question 18

What is post transcription gene regulation?

Answer 18

Post-transcriptional regulation is the control of gene expression at the RNA level. It occurs once the RNA polymerase has been attached to the gene’s promoter and is synthesising the nucleotide sequence.

Question 19

What is post translational gene regulation?

Answer 19

Post-translational regulation refers to the control of the levels of active protein.

Question 20

Explain how cAMP acts a second messenger to activate intracellular enzymes to stimulate transcription.

Answer 20

1. A signalling molecule binds to the receptor.
2. Activation of G protein which activates adenyl cyclase.
3. Catalysis of cAMP from ATP.
4. cAMP activates protein kinase A
5. PKA can phosphorylate cAMP response element binding (CREB) protein - enters the nucleus and acts as a transcription factors.

Question 21

How does ATP convert into cAMP.

Answer 21

The alpha subunit with GTP binds to cyclase. This converts ATP to cyclic AMP

Question 22

What is a cAMP molecule?

Answer 22

A secondary messenger released inside cells to activate a response.

Question 23

What is gene expression?

Answer 23

The transcription of DNA in preparation for translation.

Question 24

What is a homeotic gene?

Answer 24

Homeotic gene, any of a group of genes that control the pattern of body formation during early embryonic development of organisms.

Question 25

What is a homeobox gene?

Answer 25

Homeobox genes are a group of genes that regulate development in multicellular organisms; this includes cell differentiation and morphogenesis.

Question 26

What do Hox genes do?

Answer 26

One group of animal genes containing homeobox sequences is specifically referred to as Hox genes. This cluster of genes is responsible for determining the general body plan, such as the number of body segments of an animal, the number and placement of appendages, and animal head-tail directionality.

Question 27

In which organism were Hox genes discovered.

Answer 27

Hox genes are found in bilateral animals, including Drosophila.

Question 28

What is the result of a mutation of the Hox genes?

Answer 28

The result of a mutation of the Hox gene could lead to an abnormality

Question 29

Why are Hox genes called ‘master homologous structures’?

Answer 29

Because they control all the characteristics of organisms.

Question 30

What is meant by Hox genes being highly conserved gene?

Answer 30

A highly conserved sequence is one that has remained relatively unchanged far back up the phylogenetic tree, and hence far back in geological time.

Question 31

Name the stages in the control of apoptosis.

Answer 31

1. Normal cell
2. Condensation
3. Fragmentation
4. Apoptic bodies

Question 32

What is the role of apoptosis in plant and animal tissue development.

Answer 32

Removes harmful or ineffective T lymphocytes.

Question 33

What happens at the normal cell stage?

Answer 33

Enzymes break down cytoskeleton.

The cytoskeleton becomes dense and tightly packed.

Question 34

What happens at the condensation stage?

Answer 34

Cell surface membrane changes and forms blebs.

Question 35

What happens at the fragmentation stage?

Answer 35

Chromatin condenses and nuclear envelope breaks and the DNA breaks into fragments.

Question 36

What happens at the apoptic bodies stage?

Answer 36

The debris is disposed of and the whole process happens very quickly.
The cell breaks into vesicles that are taken up by phagocytosis.

Question 37

What can happen if there is too much apoptosis?

Answer 37

Too much can cause degeneration.

Question 38

What can happen if there is too little apoptosis?

Answer 38

Not enough can cause tumours.