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Foundations Of Medicine > Genetics > Flashcards

Genetics Flashcards

1
Q

What are the three different types of chromosomal abnormalities

A

Numerical, structural, and mutational

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2
Q

Define trisomy

A

Extra copy of chromosomes

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3
Q

Define monosomy

A

Only 1 chromosome present from a pair is present in cells

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4
Q

What is trisomy 21 known as

A

Down’s Syndrome

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5
Q

What is trisomy 13 known as

A

Patau Syndrome

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6
Q

What is trisomy 18 known as

A

Edward’s Syndrome

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7
Q

What is the result of non-disjunction

A
  1. Two gametes with disomy and 2 dull gametes (meiosis 1)
  2. 1 gamete with disomy, 1 gamete null, and 2 gametes normal (meiosis 2)
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8
Q

What are the features of Down Syndrome

A
  1. Low IQ (less than 50)
  2. Low muscle tone
  3. Short stature
  4. Flat nasal bridge
  5. Protruding tongue
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9
Q

What can Down syndrome cause

A
  1. Alzheimer’s disease in later life
  2. Higher risk of conditions e.g. epilepsy
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10
Q

What increases the risk of Down’s syndrome

A

Advancing maternal age

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11
Q

What are the chromosomal findings of Down’s syndrome

A
  1. Trisomy 21, non-dysjunction (95%), usually maternal origin
  2. Unbalanced Robertsonian translocation (4%)
  3. Mosaicism
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12
Q

What are the features of Patau Syndrome

A

Multiple dysmorphic features and mental retardation

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13
Q

What is the complication of Patau Syndrome

A

5% die within the first month and very few survive beyond first year

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14
Q

What are the chromosomal findings of Patau Syndrome

A
  1. Non-dysjunction (90%), maternal origin
  2. Unbalanced Robertsonian translocation (10%)
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15
Q

What does Edward’s Syndrome cause

A

Severe developmental problems with most patients dying within the first year, many within the first month

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16
Q

What are the features of Edward’s Syndrome

A
  1. Low birth weight
  2. Heart, resp, kidney, and GI conditions
17
Q

What is monosomy 45 X known as

A

Turner’s Syndrome

18
Q

What are the features of Turner’s Syndrome

A
  1. May be born with swollen hands and feet due to excess fluid but will resolve
  2. Neck webbing and widely spaced nipples
  3. Short stature and infertile
  4. Doesn’t affect intelligence or lifespan
19
Q

Who can present with Turner’s Syndrome

A

Females only

20
Q

What condition has 47, XXY

A

Klinefelter Syndrome

21
Q

Who can present with Klinefelter Syndrome

A

Men only

22
Q

What are the features of Klinefelter Syndrome

A
  1. Tall stature, long limbs
  2. Infertile, small testies, about 50% gynaecomastia
  3. Mild learning difficulties
23
Q

What are the different types of structural abnormalities

A
  1. Translocations (reciprocal and Robertsonian)
  2. Deletions
  3. Insertions
  4. Inversions
24
Q

Describe what is balanced translocation

A

2 different chromosomes exchange large sections of information with no DNA missing or any additional DNA

25
Q

What is the outcome of reciprocal translocation

A

Meiosis can create:

  1. Normal gamete (inherit the two normal gametes) which results in a normal zygote
  2. Balanced gamete (inherit the two chromosomes that exhanged information) which results in a balanced carrier zygote
  3. Unbalanced gamete (inherit a normal and a translocated chromosome) which results in a partial trisomy and partial monosomy
26
Q

Describe what Robertsonian translocation is

A

Involves the fusion of acrocenteric chromosomes (long Q arm which has normal coding DNA and a short P arm which has no coding DNA on it)

27
Q

What is the effect of Robertsonian translocation

A

When the two acrocentric chromosomes undergo a fusion, they finish up with a Robertsonian translocation. The two Q arms fuse to present in one chromosome and the short P arms also form a new chromosome

28
Q

What is the outcome of Robertsonian translocation

A
  1. Normal gamete which results in a normal zygote
  2. Balanced robertsonian translocation (only robertsonian translocation is inherited) which results in a balanced carrier
  3. Unbalanced robertsonian translocation (a robertsonian translocation chromosome and a normal chromosome is inherited) which results in trisomy or monosomy (normal chromosome inherited on its own)
29
Q

Describe the structural abnormality of deletion

A

DNA gets broken down in chromosomes which is normal but becomes abnormal if it is not repaired

30
Q

Describe the structural abnormality of inversion

A

A large piece of DNA is reversed (paracentric inversion is away from the centromere and pericenteric inversion is at the centromere)

Foundations Of Medicine (3 decks)

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