Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Genetics > More stories from the genetics clinic > Flashcards

More stories from the genetics clinic Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

Genomic Imprinting

A

Inherit only 1 working copy of a gene: maternal or paternal copy is epigenetically silenced.
Silencing occurs through the addition of methyl groups during egg or sperm formation.
In > 75 genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

DNA Methylation

A

Addition of a methyl group to 5 position of pyrimidine ring of a cytosine
Occurs at CpG dinucleotides
Methylation in the promoter of a gene represses gene transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

When X is inactivated it is…

A

Hypermethylated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Methylation patterns

A

vary between tissues and vary depending on age.
are affected by environment.
are potentially heritable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Imprinting disorders

A

Caused by loss of function of 1 of 2 parental chromosomes.

Resulting syndrome depends on whether maternal or paternal chromosome loses function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What happens when a certain part of Chromosome 15 in the paternal chromosome is deleted?

A

Paternal = Prader-Willi Syndrome (PWS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens when a certain part of Chromosome 15 in the maternal chromosome is deleted?

A

Maternal = Angelman Syndrome (AS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

List 7 Symptoms of Prader-Willi syndrome

A 
Hyperphagia: Obesity/Diabetes 
Mental impairment 
Muscle Hypotonia 
Short Stature 
Small Hands and Feet 
Delayed/Incomplete Puberty 
Infertility
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Management of Prader-Willi syndrome

A

Hyperphagia managed by diet restriction
Exercise to increase muscular mass
Growth hormone treatment for short stature
Hormone replacement at puberty

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Genetic Mechanism of Prader-Willi Syndrome

A

Caused by lack of a functional paternal copy of PWS critical region on 15q11- q13

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Causes of Prader-Willi syndrome and their prevalence

A

70% due to deletion of critical region on the paternal chromosome
25% due to inheritance of 2 maternal copies by uniparental isodisomy
5% due to other mechanisms e.g. translocations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Uniparental Isodisomy

A

Zygote gets a pair of chromosomes from 1 parent not both.
Caused by failure to separate chromosomes in meiosis II and failure to remove correct chromosome following non-disjunction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does Uniparental Isodisomy lead to Prader-Willi syndrome?

A

Results in 3 copies of Chr 15, (which would be fine if you deleted 1 copy).
But if paternal copy is deleted
There are only maternal copies
= Prader-Willi Syndrome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How is PWS and AS diagnosed? Which genes near/in the PWS/AS critical region are used?

A

FISH: fluorescently labelling regions on chromosomes
PML (promyelocytic leukaemia) gene is just outside the PWS/AS critical region
snRNP (small nuclear ribonucleoprotein) gene is inside the PWS/AS critical region

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Is there another way to diagnose PWS and AS?

A

methylation-specific PCR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the PWS Critical region

A

Large

Has several genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

As Prader-Willi and Angelman are both caused by loss of function of same region of Chr 15…

A

We expect them to be similar but they are not

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

List 6 Symptoms of Angelman syndrome

A 
Developmental Delay
Speech impairment 
Gait Ataxia 
'Happy Demeanour' 
Microcephaly 
Seizures
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Treatment of Angelman syndrome is symptomatic

A

Anti-Convulsant
Physiotherapy
Communication Therapy
Normal lifespan

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

The Mitochondrial Genome

A

16.6kb, 37 genes
2-10 copies per mitochondrion
~2000 mitochondria per cell
Circular Genome - like bacterial plasmid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Mitochondrial inheritance

A

maternally inherited from egg
Passed to all children regardless of gender
Variable phenotype due to heteroplasmy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Heteroplasmy

A

In a single cell, there’s a mix of mitochondria, some containing mutant DNA and some containing normal DNA.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Threshold of mitochondria at which heteroplasmy begins to cause disease

A

0-3 affected= NO DISEASE
5 affected= MILD DISEASE
9 affected= SEVERE DISEASE

24
Q

List 5 mitochondrial diseases

A 
MELAS 
LHON
MERRF 
DEAF 
NARP
25
Q

What does MELAS stand for?

A

Mitochondrial myopathy
Encephalopathy
Lactic Acidosis
Stroke

26
Q

Describe MELAS

A

Progressive neurodegenerative disorder

27
Q

List 5 Symptoms of MELAS

A 
Muscle Weakness
Episodic Seizures 
Headache Hemiparesis
Vomiting
Dementia
28
Q

Why does MELAS affect muscles and brain?

A

both have high energy requirements and lots of mitochondria

29
Q

What is treatment like in MELAS?

A

Symptomatic

30
Q

How is MELAS diagnosed?

A

Muscle biopsy

31
Q

MELAS is caused by which single mutations?

A

MTTL1: tRNA translates codon as Phenylalanine instead of Leucine during mitochondrial protein synthesis.
MTND1, MTND5: NADH Dehydrogenase subunits 1 and 5

32
Q

What does LHON stand for?

A

Leber’s Hereditary Optic Neuropathy

33
Q

Which gender is LHON more common in?

A

Males

34
Q

Which age group does LHON affect?

A

20-30s

35
Q

Symptoms of LHON

A

Bilaterial, painless, loss of central vision
Optic Atrophy
Eventually leads to BLINDNESS.

36
Q

What is treatment like in LHON?

A

Symptomatic

37
Q

How is LHON diagnosed?

A

Ophthalmological Findings

Blood Test for mtDNA Mutations

38
Q

Where are the mutations that cause LHON?

A 
NADH dehydrogenase subunits (MTND1, MTND4, MTND5, MTND6)
Cytochrome B (MTCYB)
39
Q

What could potentially be a prevention method for mitochondrial disorders?

A

3 parent babies

40
Q

Inborn errors of metabolism

A 
errors of metabolism, can be hereditary
'1 gene - 1 protein' concept. 
>200 diseases known. 
Mostly autosomal recessive or X-linked
Defective proteins are mainly enzymes.
41
Q

UK newborn screening programme can test for inborn error of metabolism, it involves…

A

Physical exam
Hearing test
Heel prick test

42
Q

What 5 diseases does the ‘heel prick’ test for?

A 
Phenylketonuria 
Congenital Hypothyroidism 
Sickle Cell Disease
Cystic Fibrosis 
MCAD Deficiency
43
Q

What is Phenylketonuria (PKU) ?

A

Phenylalanine Hydroxylase Deficiency

44
Q

What are the symptoms of Phenylketonuria (PKU)?

A

Blonde Hair/Blue Eyes
Eczema
If untreated: Severe Mental Retardation and Convulsions

45
Q

Mechanism of action in PKU

A

Phenylalanine accumulates and is converted to phenylpyruvic acid - excreted in urine.
Phenylalanine isn’t converted into tyrosine (which is then converted into melanin)
Tyrosine Deficiency = reduced melanin (reason for blonde hair and blue eyes)

46
Q

Treatment of PKU

A

Remove phenylalanine from diet (and monitor levels)
Protein supplements to supply other amino acids
Strict diet in pregnancy

47
Q

What does early detection and treatment of PKU result in?

A

No mental retardation
No convulsions
essentially no ill effects at all

48
Q

Problems with the PKU diet

A

Difficult to stick to the diet

Aspartame (artificial sweetener in many diet drinks) contains phenylalanine

49
Q

What is the commonest disorder of fatty acid oxidation?

A

MCAD deficiency

50
Q

Where is the mutation in MCAD?

A

ACADM

51
Q

If MCAD goes undiagnosed

A

25% mortality in 1st episode

52
Q

How does MCAD present in infancy?

A 
Episodic Hypoketotic Hypoglycaemia 
Vomiting
Coma
Metabolic Acidosis
Encephalopathy
53
Q

When is MCAD asymptomatic?

A

At baseline

54
Q

What does fasting/ metabolic stress cause in those with MCAD?

A

Switch to fatty acid oxidation, but this is impaired
Hypoglycaemia
Hypoketosis

55
Q

What is the treatment for MCAD?

A

Avoid fasting

Nutritional supplements at times of increased stress

Genetics (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions