7 - Genetic and Pediatric Disease (Exam 2) Flashcards

1
Q

What are the three major categories of human disease determined by?

A
  1. Environmental factors
  2. Genetics
  3. Combination of environmental factors and genetics
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2
Q

Are humans diploid or haploid, and what does that mean?

A

Diploid

Have pairs of each chromosome

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3
Q

How many pairs of chromosomes do humans have, and what is the total number of chromosomes?

A

23 pairs of chromosomes

46 total chromosomes

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4
Q

What is karyotyping?

A

The study of number, size and shape of somatic chromosomes

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5
Q

How many pairs of autosomes do humans have?

A

22 pairs

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6
Q

How many pairs of sex chromosomes do humans have?

A

1 pair

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7
Q

What do the sex chromosomes of a female present as?

A

XX

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8
Q

What do the sex chromosomes of a male present as?

A

XY

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9
Q

What percent of newborns possess a gross (physical) chromosomal abnormality?

A

1%

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10
Q

About what percent of pregnancies end in miscarriage?

A

33%

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11
Q

What are mutations?

A

Permanent changes in DNA structure

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12
Q

What are the two major types of mutations?

A
  1. Genome mutations

2. Chromosome mutations

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13
Q

What are two types of genome mutations?

A
  1. Point mutations

2. Frameshift mutations

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14
Q

What are point mutations?

A

Substitution of a single nucleotide

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15
Q

What are frameshift mutations, and what do they cause?

A

Insertion/deletion of one or two base pairs of an allele

Cause alteration in reading frame of DNA

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16
Q

How do chromosome mutations differ from genome mutations, and how do they occur?

A

Usually numerical errors (chromosome compliment not a multiple of 23) resulting from faulty disjunction during meiosis
Results in extra chromosome/ extra copy of genes
Example: Down’s syndrome - trisomy 21

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17
Q

What is aneuploidy?

A

Numerical errors in chromosomes

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18
Q

What is of primary importance with chromosomal aberrations?

A

Karyotype analysis

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19
Q

With sex chromosome aberration, most traits are lethal. What is frequent in survivors?

A

Mental retardation

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20
Q

Do sex chromosome aberrations typically have a family history?

A

No

Therefore pedigree analysis is difficult and not practical

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21
Q

What are 3 categories of genetic disease?

A
  1. Single gene inheritance
  2. Multifactorial or polygenic inheritance
  3. Chromosomal aberrations/ cytogenic disorders
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22
Q

What are individuals with single gene inheritance carriers of?

A

5-8 deleterious genes

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23
Q

What are the majority (80-85%) of single gene inheritances?

A

Familial

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24
Q

What are the 4 patterns of single gene inheritance?

A
  1. Autosomal dominant
  2. Autosomal recessive
  3. X-linked dominant
  4. X-linked recessive
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25
Q

What are X-linked chromosome related disorders also known as?

A

Sex linked chromosome related disorders

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26
Q

Will autosomal dominant disorders manifest in a heterozygous state?

A

Typically yes

However don’t always manifest

27
Q

What percent of offspring will be affected if one parent is affected with an autosomal dominant disorder?

A

Equal risk for boys and girls
50% of boys
50% of girls

28
Q

What may cause skipping of generations with autosomal dominant disorders?

A

Reduced penetrance

29
Q

How are autosomal dominant disorders expressed, and does expressivity vary?

A

As a production of an abnormal protein
Can be structural or enzymatic
Expressivity varies from mild to severe

30
Q

Can the onset of an autosomal dominant disorder be delayed?

A

Yes

May not present until later on in life

31
Q

What is the largest category of Mendelian disorders?

A

Autosomal recessive disorders

32
Q

What gives an increased risk to offspring with autosomal recessive disorders?

A

Incest

33
Q

What is the risk to children of expressing an autosomal recessive disorder if both parents are carriers?

A

Equal for boys and girls
25% of boys
25% of girls

34
Q

Is there a risk that offspring of one autosomal recessive disorder carrier parent will express the disorder?

A

No

There is a chance they will be a carrier

35
Q

Does expressivity vary with autosomal recessive disorders?

A

No

Often very severe

36
Q

With what chromosome are ALL sex chromosome related disorders linked to?

A

X chromosome

37
Q

What is the chance female carrier will pass an X-linked condition to male offspring?

A

50%

38
Q

What is the chance a male with an X-linked disorder passes the condition to female offspring? To male offspring?

A

Female - 100% will be carriers
Male - 0% will be affected
Assuming mother is not a carrier

39
Q

What are 2 common features common to all sex chromosome disorders?

A
  1. Subtle, chronic problems related to sexual development, therefore difficult to diagnose at birth
  2. Higher number of X chromosomes results in higher likelihood of mental retardation
40
Q

Are there any carriers for X-linked dominant disorders?

A

No

Genotype always shows the phenotype

41
Q

What percent of offspring of heterozygous females will be affected with an X-linked dominant disorder?

A

Same chance for boys and girls
50% of boys
50% of girls
Assuming father does not have trait as well

42
Q

Can males affected by an X-linked dominant disorder pass it on to their sons?

A

No

X-linked father can only pass X to daughters

43
Q

What percentage of female offspring of father with an X-linked dominant disorder will present with the condition?

A

100%

44
Q

Is pedigree analysis easy with X-linked dominant disorders, and how do the numbers of affected males and females differ?

A

Yes, fairly easy

Twice as many females as males in theory

45
Q

What type of disorder presents with a relatively high proportion of ocular anomalies?

A

X-linked recessive disorders

46
Q

If a father with an X-linked recessive trait has a daughter without the trait, what is true?

A

He is NOT the father

47
Q

What type of factors of human disease are important with expression of multifactorial/polygenic traits?

A

Environmental factors

48
Q

Does expression with multifactorial traits vary?

A

Yes

Continuous variation

49
Q

What is risk associated with in multifactorial traits?

A

Degree of relationship of family members

Number of affected family members

50
Q

What are 4 types of genetic syndromes?

A
  1. Down syndrome
  2. Marfan syndrome
  3. Turners syndrome
  4. Klinefelters syndrome
51
Q

What is another name for Down syndrome?

A

Trisomy 21

52
Q

What is the most common chromosomal disorder?

A

Down syndrome

53
Q

What gives a greater risk of a child being born with Down syndrome?

A

Increased age of the mother

54
Q

At what age are people with Down syndrome at greatly increased risk of Alzheimer’s and why?

A

40 years old

Collection of metabolites in the brain

55
Q

What are 6 ocular symptoms of Down syndrome?

A
  1. Oblique palpebral fissures
  2. Strabismus
  3. Refractive error
  4. Epicanthal folds
  5. Cataracts
  6. Blepharitis
56
Q

What is Marfan syndrome and what is it caused by?

A

A connective tissue disorder

Caused by a dominant allele

57
Q

What are 4 symptoms of Marfan syndrome

A
  1. Tall with long extremities
  2. Scoliosis
  3. Depressed sternum
  4. Mitral valve prolapse/ aortic deformities
58
Q

What are 5 ocular symptoms of Marfan syndrome?

A
  1. Lens subluxation (dislocation)
  2. Iris hypoplasia (poor iris development)
  3. Myopia
  4. Ptosis
  5. Strabismus
59
Q

What is Turners syndrome?

A

Complete or partial monosomy of X chromosome

Only occurs in females

60
Q

What are 4 symptoms of Turners syndrome?

A
  1. Short stature
  2. Low posterior hairline
  3. Webbing of neck
  4. No menstruation
61
Q

What are 5 ocular symptoms of Turners syndrome?

A
  1. Prominent epicanthal folds
  2. Ptosis
  3. Strabismus
  4. Blue sclera
  5. Cataracts
62
Q

What is Klinefelters syndrome?

A

Two or more X chromosomes and one Y

Only occurs in males

63
Q

How often does Klinefelters occur?

A

1 in 850 live male births