6.1.1 Cellular Control COMPLETE

Question 1

DEFINITION- Mutation

Answer 1

A random mistake that causes a change in the structure of DNA, or the structure/ number of chromosomes.
Occur when DNA is replicating prior to mitosis or meiosis.
They’re spontaneous but rate is increased by mutagens such as radiation.

Question 2

Types of Mutation

Answer 2

Substitution
Deletion
Insertion

Question 3

Substitution

Answer 3

Swapping one or more base for another base, this causes a change in one triplet and may change the amino acid

Question 4

Deletion

Answer 4

The loss of one or more base causing a frame shift, all the following base triplets are disrupted

Question 5

Insertion

Answer 5

The addition of a new base/ bases which also causes frame shift

Question 6

Effects of mutation

Answer 6

• No effect
• Harmful Missense mutation
• Harmful Nonsense mutation
• Beneficial mutation

Question 7

No effect mutations

Answer 7

Single base mutations often have no effect because the DNA code is degenerate
A mutation may also code for a different amino acid which is chemically similar to the original amino acid and away from an active site meaning theres not functional effect

Question 8

Missense Mutation- Harmful

Answer 8

A change in the amino acid may lead it to becoming less effective or not function at all, this decreases chance of survival likelihood.
A single change in the amino acid may affect the tertiary structure meaning the active site is no longer complementary to the substrate

Question 9

Nonsense Mutation- Harmful

Answer 9

Mutations may cause a stop codon to be introduced part way along the gene, leads to a short non functioning polypeptide.
May mean that RNA polymerase is unable to bind properly meaning transcription can’t take place

Question 10

Beneficial Mutation

Answer 10

Occasionally a change in the amino acid in protein can lead to it being more effective, increasing the chance of survival.
i.e. antibiotic resistant bacteria

Question 11

Somatic Mutation

Answer 11

Not inherited but can cause ageing and cancer, result of mutation in normal diploid cells

Question 12

Germline Mutation

Answer 12

Due to mutation during gamete formation, can cause genetic diseases and are passed onto the next generation.
When beneficial it begins about evolution

Question 13

Gene Expression

Answer 13

Different genes are switched on and off in different cells so that they’re specialised to perform different functions and not make proteins we don’t want.

Question 14

Transcriptional Level Regulation of Gene Expression

Answer 14

To produce a protein a gene is transcribed into mRNA, the RNA polymerase must bind to the DNA near the start of the gene called the promotor.

Question 15

DEFINITION- Operon

Answer 15

Structural genes that code for proteins that work together, are sometimes found in groups together with a single promoter.

Question 16

The Lac Operon

Answer 16

• Collection of genes responsible for lactose digestion and their regulation.
• If glucose is unavailable the E.Coli can also absorb and hydrolyse lactose.
• To save resources it only produces the enzymes needed when lactose is available
• When Lactose is present both Lactose Permease and Beta Galactosidase

Question 17

Lactose Permease

Answer 17

Transports lactose into the cell acting as a carrier protein

Question 18

Beta Galactosidase

Answer 18

Hydrolyses Lactose into glucose and galactose

Question 19

Process when no lactose is available

Lac Operon

Answer 19

1. Regulator gene transcribes mRNA which translates a repressor protein
2. Repressor protein binds to operator site and blocks the transcription of structural genes
3. RNA polymerase cannot bind to the promotor region which blocks the transcription of Lactose Permease and Beta Galactosidase

Question 20

Process when lactose is available

Lac Operon

Answer 20

1. Regulator gene transcribes and translates a repressor protein
2. Lactose binds to the allosteric site so it no longer bins to the operator site
3. RNA polymerase can therefore bind properly to the promotor region
4. Beta Galactosidase and Lactose Permease can be transcribed and translated

Question 21

Transcriptional Level Regulation of Gene Expression in Eukaryotes

Answer 21

In eukaryotes, proteins or non coding pieces of RNA called Transcription Factors can bind to the DNA at promotor regions.
These either allow RNA polymerase to bind (Activators)
or prevent them binding (Repressors)
When DNA is tightly wound around histone proteins during mitosis or meiosis, it is not able to be used for protein synthesis.

Question 22

Post transcriptional Level control

Answer 22

Eukaryote genes contain Exons and Introns
Primary mRNA must be edited in the nucleus to remove the introns, this produces mature mRNA corresponding to DNA exons
Endonuclease enzymes must be used

Question 23

Introns

Answer 23

Post transcriptional level Control
Non coding DNA within genes
Interruptions

Question 24

Exons

Answer 24

Post transcriptional level Control
DNA that codes for amino acids
Expressed

Question 25

Post Translational Level Control

Answer 25

Proteins that have been transcribed and translated may need to be activated.
This could be modification in the Golgi apparatus, e.g. add carbohydrate
Many enzymes need to be phosphorylated which alters the charge, tertiary structure and hence function.
Catalysed by Protein kinases, may need to activated by cyclic AMP

Question 26

Homeobox Genes

Answer 26

• Control the development of a zygote to a complete organism
• The genes switch a whole set of other genes on or off affecting the organisms overall body plan
• Code for the production of transcription factors which can bind to certain sections of DNA causing it to be transcribed
• Very little mutation across species

Question 27

DEFINITION- Hox Genes

Answer 27

Homeobox genes found only in animals, responsible for the correct positioning of body parts, thalidomide disrupted this

Question 28

Maternal Effect Genes

Answer 28

Determines the embryo polarity, which end will be the head and which will be the tail

Question 29

Segmentation Genes

Answer 29

Specify the polarity of each segment

Question 30

DEFINITION- Apoptosis

Answer 30

Programmed cell death

e.g. the tail of a tadpole

Question 31

Process of Apoptosis

Answer 31

1. Cell receives internal and external signals including cytokines, hormones ect.
2. Cytoskeleton broken down by enzymes, cell shrinks and membrane blebs
3. Nucleus begins to disintegrate, chromatin condenses and DNA breaks down into fragments
4. Cell fragments made with intact plasma membranes containing organelles
5. Cell fragments are ingested and digested by phagocytic cells

Question 32

Problems linked to apoptosis

Answer 32

• Not enough leads to the formation of tumours
• Too much leads to degeneration of tissue
• Cell signalling usually monitors the correct balance