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Patho 2023 > LaCount Lec 2 > Flashcards

LaCount Lec 2 Flashcards

1
Q

what is meant by karyotype analysis and how it can be used to diagnose genetic diseases.

A

a. Tells if chromosomes are:
1. Missing
2. Duplicated
3. Broken
4. Have deletions, insertions, or inversions
b. Report:
1. Total # of chromosomes
2. Sex chromosome
3. Description of abnormality
4. Ex: 47, XY, +21 (male with trisomy 21)

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2
Q

describe the most common genetic changes that cause down syndrome and turner syndrome.

A

a. Down syndrome
– Trisomy 21 type: 47, XX, +21
– Translocation type: 46, XX, der(14;21)(q10;q10), +21
– Mosaic type: 46, XX/47, XX, +21
b. Turner syndrome
– Monosomy X

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3
Q

what are Cytogenetic disorders

A
  1. Chromosomal abnormalities are frequent
    –> Approx 1/200 newborn infants
  2. Changes in chromosome number or structure
    –> Autosomes or sex chromosomes affected
  3. Disorders characterized by a change in autosome number are more severe than single gene disorders
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4
Q

what is translocation

A

Transfer part of one chromosome to another

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5
Q

what is an isochromosome

A

Centromere divides horizontally rather than vertically, resulting in 2 short arms and 2 long arms

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6
Q

what is a deletion

A

loss of portion of chromosome

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7
Q

what is an inversion

A

When there are 2 interstitial breaks in a chromosome, segment reunites but is flipped

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8
Q

what is a ring chromosome

A
  1. Variant of deletion.
  2. After loss of segments from each end of the chromosome, arms unite to form a ring
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9
Q

what are examples of recessive disorders

A

cystic fibrosis, loss of function, effects of mutations on drug discovery

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10
Q

describe cystic fibrosis

A
  1. Most common lethal genetic disease that affects caucasian population (1/3200)
  2. Caused by loss of function mutations in cystic fibrosis transmembrane conductance regulator (CFTR)
  3. Many differ mutations
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11
Q

what is loss of function in terms of recessive

A
  1. Unmutated copy of gene is unable to make up for loss of expression or activity from mutant gene
    –> No dosage compensation
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12
Q

what is mutations effects on terms of recessive and drug discovery

A

a. CFTR variants have differ effects of CFTR
1. People with variants that have partial activity fare better than those with complete loss of function
2. Variants establish a dose response relationship
3. People with CFTR alleles with 10-20% have mild CF
–> Ivacaftor
——- Increase function of CFTR protein
——- Works only with specific genotype
——- Improves clinical symptoms

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13
Q

what is triple repeat disease

A
  1. Some genes contain repeats of 3 nucleotides
  2. Longer repeats are associated with disruption of gene function
  3. 40 diseases associated with triplet repeats
    –> All are associated with neurodegeneration
  4. CAH repeats encode poly-glutamine (polyQ disorders)
  5. Mostly dominant
    –> Friedreich ataxia - only triplet disorder that is recessive
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14
Q

what are examples of triple repeat

A

familial retardation and fragile X

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15
Q

what is fragile X syndrome

A

Elongated face
Protruding ears
Low muscle tone

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16
Q

what is familial dysfunction

A

FRM1 gene on X chromosome repeat (>45x)

17
Q

what is mitochondrial mutations

A

Have separate genome
Are inherited only from mother
Present in multiple copies/cells

18
Q

what is mitochondrial mutations caused by ?

A
  1. mutations in mitochondrial genes are rare
  2. Mutations in mitochondrial genes are transmitted to progeny by daughters, but not sons
19
Q

what Is affected from mitochondrial mutations

A
  1. Affected organs that depend most on oxidative phosphorylation
    –> Skeletal muscle, heart, brain
20
Q

wha tare imprinting defects

A
  1. Parent of origin transmission
  2. Some regions of DNA are turned off in copy received from mother or father
  3. Imprinting occurs in ovum or sperm and stably transmitted to all somatic cells derived from zygote
  4. If region turned off in maternal copy it is mutated in paternal copy, genes in that region will not be expressed
21
Q

what are examples of imprinting defects

A

prader- will and angel man and complex inheritance patterns

22
Q

what are prader will and angel man similarities

A
  1. Phenotypes are partially overlapping, but distinct
  2. Similar region of chromosome 15 deleted in both
23
Q

what is prader willi

A
  1. Deletion inherited from father
  2. Mental retardation, short stature, hypotonia, obesity, small hands and feet, hypogonadism
24
Q

what is angel man syndrome

A

1.Deletion inherited from mother
2. Mental retardation, ataxic gait, seizures, inappropriate laughter

25
Q

what are examples of autosomal dominant

A

complete loss of function, partial loss of function, and gain of function

26
Q

what are some mutations of autosomal dominance

A
  1. Familial hypercholesterolemia (FH)
  2. Mutations in the LDL receptor (LDL-R)
27
Q

what is complete loss of function in terms of dominance?

A
  1. Some variants act as dominant negatives
  2. Mutated proteins interferes with the function of unmutated version
  3. More severe
  4. Not able to make up for loss of expression or activity from mutant gene
  5. Osteogenesis imperfecta
28
Q

describe osteogenesis imperfecta

A
  1. Caused by defects in production of collagen
    –> Structure, support, strength
  2. Collagen trimer
    –> 2 subunits of alpha 1
    –> 1 subunit of alpha 2
29
Q

describe gain of function in autosomal dominance

A

Some PCSK9 mutations have gain of function and LDL-R levels are regulated by PCSK9

30
Q

describe LDL-R levels are regulated by PCSK9

A
  1. Binds LDL-R on cell surface
  2. Internalized with LDL-R
    3.Directs LDL-R to lysosome
  3. LDL-R completely degraded
  4. Reduces the number of LDL receptors on cell surface
31
Q

describe how some PCSK9 mutations have gain of function

A
  1. Increase affinity for LDL-R
  2. Enhance sorting of LDL-R to lysosome

Patho 2023 (37 decks)

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