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biomed > Genetic disorders affecting communication > Flashcards

Genetic disorders affecting communication Flashcards

1
Q

Define gene

A

a region of DNA that codes for a specific protein

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2
Q

What is an exon?

A

a region of coding DNA

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3
Q

What is an intron?

A

a region of non-coding DNA

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4
Q

What is a sequence?

A

the order of bases in a stretch of DNA

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4
Q

How can variants be identified?

A

through genetic sequencing

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4
Q

Define genetic disorder

A

A health problem caused by one or more abnormalities to the genome

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5
Q

What can cause a genetic disorder?

A
  1. mutation in one gene
  2. mutation in multiple genes
  3. chromosomal abnormality
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6
Q

What is a rare disease?

A

occurs in less than 1:2000

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7
Q

How many people in UK have a rare disease?

A

3.5 million

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8
Q

How many rare conditions have been identified?

A

more than 7000

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9
Q

How many rare diseases are caused by genetic change?

A

80%

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10
Q

Define developmental disorder

A
  1. neurologically based condition that can interfere with acquisition, retention, or application of specific skills or sets of information
  2. any disorder that begins at an early age and significantly affects psychological functioning
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11
Q

What are the types of genetic disorder?

A
  1. single gene disorder
  2. chromosomal disorders
  3. mitochondrial disorders
  4. complex multifactoral disorders
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12
Q

What is a single gene disorder?

A

A change in the DNA sequence of a single gene

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13
Q

What are chromosomal disorders?

A

Due to abnormal changes in parts of, or whole chromosomes

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14
Q

What are mitochondrial disorders?

A

due to errors in mitochondrial DNA

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15
Q

What are complex multifactoral disorders?

A

due to errors in several different genes

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16
Q

How is a single gene disorder classified?

A

autosomal or sex-linked

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17
Q

What are the features of single gene disorders?

A
  1. hereditary
  2. affect every cell in the body
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18
Q

What is the inheritance pattern for autosomal dominant disorder?

A

only one copy of dominant allele needed in genotype for disease to be expressed in phenotype

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19
Q

What is the inheritance pattern for an autosomal recessive disorder?

A

two copies of a recessive allele are needed in genotype for disease to be expressed in phenotype

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20
Q

What is a sex linked inherited disorder caused by?

A

a mutation on the X chromosome

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21
Q

What are the different types of chromosomal disorder?

A
  1. chromosomal duplication
  2. aneuploidy
  3. chromosomal fusion
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22
Q

What is aneuploidy?

A

the gain or loss of one chromosome

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23
Q

What is trisomy?

A

the gain of one chromosome

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24
Q

What is monosomy?

A

the loss of a chromosome

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25
Q

Define syndrome

A

A disease or disorder that has numerous symptoms and identifying features

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26
Q

What is fragile X syndrome?

A

A dominant sex linked disorder

27
Q

What gene causes fragile X syndrome?

A

FMR1

28
Q

What are the main presentations of fragile X syndrome?

A
  1. learning dissiculties
  2. autism-like behaviour
  3. hyperactivity
  4. mood disorders
  5. poor eye contact
29
Q

What is the prevalence of fragile X syndrome?

A
  1. most common cause of inherited learning disability in UK
  2. 1 in 4000 males
  3. 1 in 6000 females
  4. males affected more severely than females
30
Q

What protein does FMR1 code for?

A

FMRP

31
Q

What does FMRP do?

A

attaches directly to ribosomes to assist in translation of mRNA

32
Q

What is the FMR1 promoter region made of?

A

CGG repeats

33
Q

Where in the gene does the fragile X mutation occur?

A

in the promoter region

34
Q

What is the normal length of the FMR1 promoter region?

A

15-50 CGG repeats

35
Q

What happens if someone has more than 200 CGG repeats on FMR1?

A

abnormal/no FMRP -> fragile X syndrome

36
Q

What happens if someone has 70-200 CGG repeats on FMR1?

A

premutation, but FMRP is normal

37
Q

How many females have a fragile X syndrome pre-mutation?

A

1 in 130-260

38
Q

How many males have a fragile X syndrome pre-mutation?

A

1 in 250-810

39
Q

What does fragile X syndrome premutation cause in women?

A
  1. repeats tend to lengthen in final stage of egg gamete -> increased risk of child having fragile X syndrome
  2. 20% have primary ovarian insufficiency
40
Q

What does fragile X syndrome pre-mutation cause in males?

A
  1. repeats do not lengthen in fertilisation
  2. increased risk of ataxia
41
Q

Which cells are affected by fragile X syndrome?

A
  1. CNS neurons
  2. Cells which synthesise connective tissue
42
Q

What happens when CNS neurons are affected by fragile X syndrome?

A
  1. slower speech and language development
  2. intellectual disability
  3. around 1/3 males show autism spectrum disorders
43
Q

What happens when cells synthesising connective tissue are affected by fragile X syndrome?

A
  1. elongation of craniofacial bones
  2. hyper-reflexion of joints
44
Q

How does fragile X syndrome affect speech and language?

A
  1. most boys develop language half rate of normal
  2. complicated by hypotonia
  3. expressive delayed more than receptive
  4. excessive self-repetition
  5. difficulties turn-taking
  6. unpredictable speaking (slow to fast)
45
Q

What is life expectancy for fragile X syndrome?

A

normal

46
Q

What is Down’s syndrome?

A
  1. neurodevelopmental syndrome
  2. chromosomal disorder
47
Q

What causes down syndrome?

A

trisomy 21 - extra chromosome 21

48
Q

What are the main presentations of Down’s syndrome?

A
  1. mild to moderate cognitive impairment
  2. almond-shaped upward slanting eyes
  3. flattened face and/or nose bridge
  4. protruding tongue
  5. shorter neck
49
Q

What is the prevalence of Down’s syndrome?

A

around 1 in 1000 live births

50
Q

What is the life expectancy of Down’s syndrome?

A

can lead active, healthy, independent lives into 60s, 70s and beyond

51
Q

When does trisomy 21 occur?

A

during meiosis, when two chromosome 21s don’t separate (non-dysjunction) usually in egg gametes

52
Q

What percentage of Down’s syndrome is caused by chromosome non-dysjunction?

A

95%

53
Q

What causes the other 5% of Down’s syndrome?

A

translocation - segment of chromosome 21 transferred to 14 or 15 - can be inherited

54
Q

Which cells are affected by Down’s syndrome?

A

Massive overexpression in many genes causing:
1. excess RBCs
2. smaller frontal & parietal lobe and cerebellum
3. delayed myelination
4. changes in astrocytes and glial cells
5. changes in mitochondria

55
Q

What are the effects of Down’s syndrome on speech and language?

A
  1. difficulty remembering sounds and putting them into words
  2. hearing problems may delay speech
  3. low muscle tone in muscles of mouth
  4. changes in jaw, tongue, and teeth can affect articulation
56
Q

What is muscular dystrophy?

A

A severe, progressive, muscle wasting disease leading to difficulties with movement, assisted ventilation, and premature death

57
Q

What causes muscular dystrophy?

A

mutation on X chromosome (recessive)

58
Q

What is DMD?

A

Duchenne’s muscular dystrophy

59
Q

What is the prevalence of DMD?

A
  1. 8 in 100,000
  2. more common in males
60
Q

Which type of muscular dystrophy is most common?

A

DMD

61
Q

What protein does the DMD gene code for?

A

Dystrophin

62
Q

Where is dystrophin found?

A
  1. skeletal muscle cells
  2. cardiac muscle cells
  3. merve cells in brain
63
Q

What is the function of dystrophin?

A
  1. part of a protein complex
  2. strengthens muscle fibres
  3. protects fibres from injury during contraction/relaxation
64
Q

What types of mutations is DMD?

A
  1. 60-70% are deletions
  2. 5-15% are duplications
  3. 20% are point mutations/small deletions/insertions
65
Q

What is the inheritance of DMD?

A

sex linked recessive

66
Q

What is the presentation of DMD?

A

2-3 = difficulties climbing stairs, waddling gait, frequent falls
10-12 = wheelchair dependent
20 = may need assisted ventilation
20-40 = death from cardiac and/or respiratory failure

67
Q

What are the effects of DMD on speech and language?

A
  1. slower language development
  2. delayed comprehension of complex verbal info
  3. poor phonological comprehensions
  4. dysarthria in muscles of tongue and mouth
  5. EDS difficulties

biomed (30 decks)

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