FunMed: PBL 2 (Peroxisomal/Mitochondrial Division Abnormality)

Question 1

Define ‘gyrus’

Answer 1

Fold between two clefts of cerebral brain surface (outer protrusion)

Question 2

Define ‘sulci’

Answer 2

Indent between two clefts of cerebral brain surface

Question 3

What is the sylvian fissure?

Answer 3

Fissure which separates the frontal and parietal lobes from the temporal lobes

Question 4

What is the role of peroxisomes?

Answer 4

Metabolism of fatty acids and detoxification of free radicals in liver and kidney

Question 5

Describe basic binary fission

Answer 5

Replication of circular DNA molecule inside the cell, replicated DNA then moves to poles of cell, the cell lengthens and the equatorial plate of the cell constricts and separates the plasma membrane (two daughter cells/organelles)

Question 6

How do mitochondria and peroxisomes divide?

Answer 6

Binary fission

Question 7

Describe mitochondrial/peroxisomal division

Answer 7

Replication of circular DNA inside cell, replicated DNA moves to poles of cell, cell lengthens and DRP1 protein is used to ‘pinch’ off the membrane stalk between the two cells, and this is activated by mitochondrial fission factor (MFF) binding to DRP1 to promote fission

Question 8

How may peroxisomes be produced?

Answer 8

Growth by importing proteins and lipids into existing peroxisomes or binary fission

Question 9

What are the 5 stages of grief?

Answer 9

Denial, anger, bargaining, depression and acceptance

Question 10

What is the role of mitochondria?

Answer 10

Production of ATP by oxidative phosphorylation

Question 11

What is the difference between euchromatin and heterochromatin?

Answer 11

Euchromatin - lightly packed and involved in transcription

Heterochromatin - responsible for gene regulation and protects chromosomal integrity

Question 12

What is DRP1/DLP1?

Answer 12

dynamin-like protein 1 (involved in separation of mitochondria/peroxisomes in fission)

Question 13

How does mitochondrial abnormality cause these symptoms?

Answer 13

Inability to produce sufficient ATP (too few mitochondria due to ineffective division) –> muscle hypotonia due to inability to respire –> muscle wastage

Question 14

How does peroxisomal abnormality cause these symptoms?

Answer 14

Usually break down very long chain fatty acids (beta oxidation) to medium-chain ones, which go to mitochondria to be used in respiration, without enough, fat energy not respired –> hypotonia. First reactions to produce plasmalogen (phospholipid in myelin) occurs in peroxisomes, without –> dysmyelination and abnormal gyral patterns. Involved in bile acid production for absorption of fat and some vitamins –> malnourishment

Question 15

What are the main ways in which mutations occur in cells?

Answer 15

Errors in replication (unrepaired), ionising radiation, UV light, mutagens, inherited mutations from germ cells

Question 16

What is a frameshift mutation?

Answer 16

insertion/deletion of number of bases (not multiple of 3), changing reading frame of protein

Question 17

What are the 3 types of point mutation?

Answer 17

Silent, nonsense, missense

Question 18

Describe missense mutations

Answer 18

Change in base –> changes codon to different amino acid

Question 19

Describe nonsense mutations

Answer 19

Change in base –> changes codon to stop codon

Question 20

Describe silent mutations

Answer 20

Change in base –> still codes for same amino acid

Question 21

What are the bases for the start codon?

Answer 21

AUG –> codes for methionine

Question 22

What are the bases for stop codons?

Answer 22

UAA, UAG and UGA

Question 23

What does bereavement counselling involve?

Answer 23

talking through emotions with counsellors, and finding incentive to distract someone from life event (sport or hobby)

Question 24

What does genetic counselling involve?

Answer 24

Education about implicated health condition, assessment of risk of reproductive transmission, family tree to assess personal risk, genetic tests performed/recommended (risks, benefits and limitations), interpretation of results, and info about support groups

Question 25

How do cells know when they have enough cell organelles prior to mitosis?

Answer 25

Checkpoints decipher this, at the restriction point (G1-S) number appropriation is checked, and this is repeated at G2

Question 26

How could Lorenzo’s oil potentially be used as a treatment?

Answer 26

Normalises accumulation of very long chain fatty acids in the brain so can prevent damage to white matter

Question 27

Is a DLP1 mutation dominant or recessive?

Answer 27

Dominant

Question 28

What may be the cause of the dysmorphic face?

Answer 28

Elevated serum fatty acids damage the white matter of the brain (due to peroxisomes not converting it for use)