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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
What is trisomy?
the gain of one chromosome
24
What is monosomy?
the loss of a chromosome
25
Define syndrome
A disease or disorder that has numerous symptoms and identifying features
26
What is fragile X syndrome?
A dominant sex linked disorder
27
What gene causes fragile X syndrome?
FMR1
28
What are the main presentations of fragile X syndrome?
1. learning dissiculties 2. autism-like behaviour 3. hyperactivity 4. mood disorders 5. poor eye contact
29
What is the prevalence of fragile X syndrome?
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
What protein does FMR1 code for?
FMRP
31
What does FMRP do?
attaches directly to ribosomes to assist in translation of mRNA
32
What is the FMR1 promoter region made of?
CGG repeats
33
Where in the gene does the fragile X mutation occur?
in the promoter region
34
What is the normal length of the FMR1 promoter region?
15-50 CGG repeats
35
What happens if someone has more than 200 CGG repeats on FMR1?
abnormal/no FMRP -> fragile X syndrome
36
What happens if someone has 70-200 CGG repeats on FMR1?
premutation, but FMRP is normal
37
How many females have a fragile X syndrome pre-mutation?
1 in 130-260
38
How many males have a fragile X syndrome pre-mutation?
1 in 250-810
39
What does fragile X syndrome premutation cause in women?
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
What does fragile X syndrome pre-mutation cause in males?
1. repeats do not lengthen in fertilisation 2. increased risk of ataxia
41
Which cells are affected by fragile X syndrome?
1. CNS neurons 2. Cells which synthesise connective tissue
42
What happens when CNS neurons are affected by fragile X syndrome?
1. slower speech and language development 2. intellectual disability 3. around 1/3 males show autism spectrum disorders
43
What happens when cells synthesising connective tissue are affected by fragile X syndrome?
1. elongation of craniofacial bones 2. hyper-reflexion of joints
44
How does fragile X syndrome affect speech and language?
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
What is life expectancy for fragile X syndrome?
normal
46
What is Down's syndrome?
1. neurodevelopmental syndrome 2. chromosomal disorder
47
What causes down syndrome?
trisomy 21 - extra chromosome 21
48
What are the main presentations of Down's syndrome?
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
What is the prevalence of Down's syndrome?
around 1 in 1000 live births
50
What is the life expectancy of Down's syndrome?
can lead active, healthy, independent lives into 60s, 70s and beyond
51
When does trisomy 21 occur?
during meiosis, when two chromosome 21s don't separate (non-dysjunction) usually in egg gametes
52
What percentage of Down's syndrome is caused by chromosome non-dysjunction?
95%
53
What causes the other 5% of Down's syndrome?
translocation - segment of chromosome 21 transferred to 14 or 15 - can be inherited
54
Which cells are affected by Down's syndrome?
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
What are the effects of Down's syndrome on speech and language?
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
What is muscular dystrophy?
A severe, progressive, muscle wasting disease leading to difficulties with movement, assisted ventilation, and premature death
57
What causes muscular dystrophy?
mutation on X chromosome (recessive)
58
What is DMD?
Duchenne's muscular dystrophy
59
What is the prevalence of DMD?
1. 8 in 100,000 2. more common in males
60
Which type of muscular dystrophy is most common?
DMD
61
What protein does the DMD gene code for?
Dystrophin
62
Where is dystrophin found?
1. skeletal muscle cells 2. cardiac muscle cells 3. merve cells in brain
63
What is the function of dystrophin?
1. part of a protein complex 2. strengthens muscle fibres 3. protects fibres from injury during contraction/relaxation
64
What types of mutations is DMD?
1. 60-70% are deletions 2. 5-15% are duplications 3. 20% are point mutations/small deletions/insertions
65
What is the inheritance of DMD?
sex linked recessive
66
What is the presentation of DMD?
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
What are the effects of DMD on speech and language?
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

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