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Gnetics > Gen > Flashcards

Gen Flashcards

1
Q

What are the single congenital defects

A

Malformation
disruption
Deformation
dysplasia

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2
Q

What are the multiple congenital defects

A

Sequence
syndrome
Association

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3
Q

Define malformation

A

Primary structural defect

As a result of intrinsically abnormal development

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4
Q

Define disruption

A

Defect as a result of extrinsic interference with originally normal development

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5
Q

Define Deformation

A

Mechanical force is causing abnormal shape, form or position

Distorting structure

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6
Q

Define dysplasia

A

Abnormal organisation of cells in a tissue

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7
Q

Define sequence

A

Pattern of multiple abnormalities

Derived single known prior anomaly or factor

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8
Q

Define syndrome

A

Multiple abnormalities
Pathogenically related
Specific underlying cause

Eg. Downs

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9
Q

Define Association

A

Non-random occurrence of abnormality

not explained by syndrome due to unknown cause

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10
Q

What are the three problems that can occur with chromosomes

A

Aneuploidy- loss or gain of chromosomes
Structural- translocations, deletions, insertions, inversions, rings
Mosaicism- different cell lineages

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11
Q

Transfer of genetic material from one chromosome to another is normal in balanced translocations unless…

A

Disruption of a gene

Fusion product

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12
Q

Define monosomy

A

Loss of a single chromosome almost always lethal

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13
Q

Define trisomy

A

Gain of one chromosome can be tolerated for specific chromosomes

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14
Q

Define Mosaicism

A

Where different cells in the same individual have different numbers or arrangements of chromosomes

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15
Q

What type of trisomy is the most common

A

Trisomy 16

Fatal in Utero -miscarriage

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16
Q

What types of trisomies can be viable

A

13, 18, 21

13- patau syndrome
Heart defects, mental retardation

18- Edwards syndrome
Heart defects, kidney malformation, digestive tract defects, mental retardation

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17
Q

What are the clinical features of down syndrome

A

Newborn period
Hypotonia, lethargic, eXcesS nuchal skin

Craniofacial
Macroglossia, small ears, sloping palpebral fissures

Limbs
Single Palmar crease, wide gap between first and second toes

Other
Short stature, douodenal atresia
Low IQ but advanced social skills

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18
Q

What are the three different chromosome aberrations which lead to downs

A

Trisomy 21
90% due extra chromosome from mum
Non-disjunction homologous chromosomes in meiosis 1 (3 copies instead of 2)

Translocation
Break In Acrocentric chromosomes (13,14,15,21,22) and fusion long arms
No. Chroms still 46 but part/full copy chrom 21 attaches another chrom

Mosaicism
Mix of two types of cells some containing 46 chromosomes some containing 47

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19
Q

What is Monosomy X

A

Turner’s syndrome
Loss of X or Y in paternal meiosis
(Other causes: ring chromosome, single arm deletion, Mosaicism)

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20
Q

What are the characteristics of Turner’s

A

Prenatal
Generalised oedema and neck swelling

Newborn/child
Odematous hands and feet, Webbed neck, low set ears, low posterior hairline, broad chest, aortic defects, urinary defects

Adult
Short stature, infertility, diabetes, hypothyroidism

Normal intelligence

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21
Q

What is XXY

A

Klinefelter’s syndrome
Phenotypically male
Learning disability
Tall and infertile

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22
Q

Define dosage compensation

A

Process by which organisms equalise expression of genes between members of different biological sexes

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23
Q

What are the two mechanisms of dosage compensation

A
  1. Random in activation of single X-chromosome in females

2. Increased (2x) expression of X-chromosome genes in males

24
Q

Explain why sex determination is not solely based on sex chromosome karyotype and how it is possible to be chromosomally one gender and phenotypically opposite

A

SRY gene - testes development

This gene can be translated to X-chromosome in SRY recombination

XX males develop testes but are sterile because other Y-chromosome genes important in spermatogenesis

XY females infertile

25
Q

What are the characteristics of a monogenic disorder

List examples

A

Clear inheritance
no environment
individually rare

Eg. Huntington’s cystic fibrosis and haemophilia

26
Q

What are the characteristics of a complex disorder

List examples

A

No clear inheritance
Environment essential
Common

Eg. Type II diabetes, schizophrenia

27
Q

Define polymorphism

A

Mutation at >1%freq. in given population

28
Q

Why are pedigree diagrams important

A 
Identify genetic disease running in family
Identify inheritance patterns
Aid diagnosis
Assist in management of condition
Identify relatives at risk of disease
29
Q

Difference btwn autosomal recessive and autosomal dominant

A

At least one parent affected in autosomal dominant whereas no affected parent in autosomal recessive

30
Q

Example of autosomal dominant disease

A 
Huntington’s disease
Cell death in Basal ganglia
Unstable CAG triplet repeats
10-35 unaffected
27-35 unaffected, risk affected kid
35-40 sometimes affected
40+ affected
31
Q

What is example of an autosomal recessive disease

A

Cystic fibrosis
Mutation CFTR gene chrom 7
Coding chloride channel

32
Q

What is special about X-linked recessive diseases

A

No affected parents
Transmitted by carrier female
Only male affected

33
Q

Example of an ex-linked recessive disease

A

Haemophilia
Blood clotting disorder causing easy bruising and heavy bleeding
A and B (rarer) types

Haemophilia A -F8
Haemophilia B -F9
Both genes are on the X-chromosome

34
Q

What are the three types of genetic heterogeneity

A

Same gene, different mutations leading to different symptoms

Same disease, different genes

Same disease, different genes, different inheritance patterns

35
Q

Define incomplete penetrance

A

Symptoms are not always present in an individual with a disease causing mutation

36
Q

Define variable expressivity

A

Disease severity may vary between individuals with the same disease causing mutation

37
Q

Define phenocopy

A

Having the same disease but with a different underlying cause

38
Q

Explain mechanisms of dominant conditions

A

Mutations leading to toxic protein effects of mutated gene which mask normal copy

39
Q

Explain mechanisms of recessive conditions

A

Mutations cause an absence of a functional protein so the normal copy is absent

40
Q

How can you treat dominant conditions

A

Neutralise the toxic protein effects or switch off the mutant gene

41
Q

What is Genomic imprinting

A

You inherit two copies of genes
one from mother one father usually both copies of the each gene active but sometimes one copy is turned on

which copy is made active depends on parent of origin some genes and only active only when inherited from father etc.

42
Q

What is uniparental disomy

A

A person receives two copies of chromosome or part of a chromosome from one parent and no copies from the other parent

43
Q

Two examples of uniparental dysomy

A

Prader Willi syndrome and Angelman syndrome

44
Q

What are the symptoms of Prada Willi syndrome

A

Due loss Paternal chr15

Hyperphagia leading to obesity
Mental impairment
Behavioural problems
Muscle hypotonia
Short stature small hands and feet
Delayed or incomplete puberty
Infertility
45
Q

What are the symptoms of Angelman syndrome

A

Due loss maternal chr15

Developmental delay and speech impairment
Movement disorder
Behavioural uniqueness e.g. happy demeanours, excitable, short attention span
Seizures

46
Q

List examples of mitochondrial disorders

A

MELAS

LHON

47
Q

Describe symptoms LHON

A

More common in males
Degeneration of retinal ganglion cells
Loss of central vision
Most become blind

48
Q

Describe symptoms MELAS

A

Progressive and ultimately fatal
Muscle weakness vomiting headache dementia

Single mutation in several genes

49
Q

List two examples of inborn errors of metabolism currently included in UK national neonatal screening programs

A

Phenylketonuria PKU

MCADD DEFICIENCY

50
Q

Describe what PKU is

A

Inborn errors of metabolism and included in the UK national neonatal screening programs

Blonde hair/blue eyes no melanin
eczema and must Odour

51
Q

Describe what MCADD Deficiency is

A

Inborn errors of metabolism and currently included in UK national neonatalscreening program

Most common disorder of fatty acid oxidation
Medium chain acyl CoA dehydrogenase

52
Q

Treatment of PKU

A

Remove Phenylalanine from diet
Protein supplements to supply other AAs
Strict diet in preg
Early detection

53
Q

Treatment of MCADD deficiency

A

Avoid fasting

Nutritional supplements at times of increased stress

54
Q

What is the difference between somatic and germline mutations

A

Somatic occurs in body cells and cannot be passed on to offspring

Germline mutations in gametes which can be passed on to offspring

55
Q

What is the difference between driver and passenger mutations

A

Passengers are mutations that don’t contribute to the development of cancer but have occurred during growth cancer

Drivers contribute to cancer development

56
Q

What are oncogenes

A

Promotes growth and proliferation in cells

Signal in cascades and mitogenic pathway activation

E.g..growth factors, transcription factors, tyrosine kinases

57
Q

What are tumour suppressor is

A

Regulate cell division, DNA damage checkpoints, Apple ptosis, DNA repair

Gnetics (1 decks)

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