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MCM Exam II > Principles Of Genetic Inheritance > Flashcards

Principles Of Genetic Inheritance Flashcards

1
Q

Banding and nomenclature:

What does 17q11.2 mean

A 
17th chromosome
Q = longer arm
1 = closest band to the centromere
1 = band staining technique
.2 = specific portion of band 1
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2
Q

When is a karyotype made

A

During metaphase of the M phase

After replication

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3
Q

Lionizations (X-inactivation)

A

The inactivation of one of the X chromosomes in females; performed randomly

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4
Q

Mosaicism

A

A condition in which cells from a patient have different genotypes an karytopes

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5
Q

Mosaicism and Turner’s syndrome

A

Some cells will have 46XX (normal) and some will have 45XO

Around 30% of turner’s syndrome cases demonstrate mosaicism

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6
Q

Mosaicism and Down’s syndrome

A

Some cells are 46XX (normal) and some are 47XX+21

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7
Q

Mosaicism and Klinefelter Syndrome

A

Some cells are 46XY (normal) and some are 47XXY

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8
Q

How do stem cells divide

A

They undergo mitosis, but divide asymmetrically, resulting in one stem cell and one daughter cell

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9
Q

Homologous recombiantion (crossing over)

A

Produces new combinations of genes; part of the maternal chromosome switches with its counterpart in the paternal chromosome, resulting in a recombination of genes

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10
Q

Two ways in which meiosis creates genetic diversity

A
  1. Random segregation of homologs

2. Cross-over exchange (homologous recombination)

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11
Q

Euploid

A

Cells with normal number of chromosomes

- haploid gametes and diploid somatic cells

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12
Q

Polyploidy

A

Presence of a complete set of extra chromosomes in a cell

- often seen in plants

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13
Q

Aneuploid

A

Cells with a missing or additional individual chromosomes

- monosomy and trisomy

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14
Q

Symptoms of Turner Syndrome

A

45, XO karyotype
Female

  • short
  • ovarian hypofunction/premature ovarian failure
  • need hormone therapy for puberty
  • infertility
  • webbed neck (in 30% of cases)
  • low hairline on neck
  • cardiovascular defects
  • normal intelligence ***
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15
Q

Symptoms of Klinefelter syndrome

A

47XXY
Male

  • cognitive, social, behavioral, learning difficulties
  • primary hypogonadism (low T)
  • small/undescended testes
  • tall
  • infertility
  • gynecomastia (male breasts)

Patients can also not show symptoms

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16
Q

Reciprocal translocation

A

An exchange of material between nonhomologous chromosomes

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17
Q

Robertsonian translocation

A

When the long arms of two acrocentric chromosomes are combined and the short arm is lost (typically)

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18
Q

Patau Syndrome

A

47XX+13

Severe developmental abnormalities

Most perinatal death within 1 week

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19
Q

Edwards Syndrome

A

47XX+18

Abnormal development

Most perinatal death within 1 year

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20
Q

Genomic Imprinting

A

Essentially gene silencing through methylation of 5’ region of the gene

Causes chromatin condensation

At least 100 human genes are known to be imprinted
- clustered together

~ 30 genes that are paternally imprinted and maternally expressed

~ 70 genes that are maternally imprinted and paternally expressed

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21
Q

What happens to imprints during meiosis in germ cells

A

They are erased and new ones are set

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22
Q

Prader-Willi syndrome

A

Deletion of PWS region/AS gene on paternal chromosome 15

  • short
  • hypotonia (weak muscle tone)
  • small hands and feet
  • obesity
  • mild/moderate intellectual disability
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23
Q

Angelman Syndrome

A

Caused by a deletion in PWS region/AS gene on the maternal chromosome 15

  • severe intellectual disabilities
  • seizures
  • ataxic gait
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24
Q

Uniparental disomy

A

When two chromosomes are inherited from the same parent, instead of one being inherited from the father and one from the mother

Caused by nondisjunction in mother or father, which will cause 1/3 of gametes to have two chromosomes of one parent and none of the other

Can cause Prader Willi and Angelman

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25
Q

Law of segregation in Mendelian genetics

A

Allele pairs separate during gamete formation and randomly unite during fertilization

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26
Q

Law of independent assortment in Mendelian genetics

A

Individual hereditary factors assort independently during gamete formation

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27
Q

Does cystic fibrosis stem from multiple genotypes or multiple phenotypes

A

Distinct genotypes, single phenotype

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28
Q

Do patients with PKU have multiple genotypes or multiple phenotypes

A

Same genotype for all patients, multiple phenotypes (pleiotropy)

29
Q

Pleiotropy

A

When individuals have the same genotype but multiple possible phenotypes

30
Q

Proband (propositus)

A

First diagnosed person in a pedigree

31
Q

What kind of inheritance causes postaxial polydactyly

A

Autosomal dominant

32
Q

Albinism is caused by what kind of inheritance

A

Autosomal recessive

33
Q

Duchesse muscular dystrophy is caused by what kind of inheritance

A

X-linked recessive

34
Q

Hypophophatemia is caused by what kind of inheritance

  • also what is it
A

X-linked dominant

Low phosphorus in the blood due to defective reabsorption of phosphate in kidney

Deficient absorption of calcium in intensities casting softening of bone (rickets)

35
Q

Penetrance

A

The degree to which a gene manifests itself

36
Q

Retinoblastoma is caused by what kind of gene expression and gene inheritance

A

Reduced penetrance

Phenotype occurs in 90% of individuals inheriting gene defect, so 90% penetrance

Autosomal dominant inheritance

37
Q

Neurofibromatosis is caused by what kind of gene expression

A

Variable expressivity

Patients have pigmented areas the color of coffee with cream (cafe au lait spots)

Patients also developed tumor-like growths called neurofibromas

38
Q

Variable expressivity

A

When there is a range of phenotypes that vary between individuals with a specific genotype

  • Neurofibromatosis
39
Q

Locus heterogeneity

A

A single disorder, trait, or pattern of traits caused by mutations in genes at different chromosomal loci

Ex: osteogenesis imperfecta
- can be caused by mutation at chromosome 7 or 17

40
Q

Osteogenesis imperfecta is caused by what genetic defect

A

Locus heterogeneity

Can be caused by mutations in collagen genes at two different loci (chromosome 7 or chromosome 17)

Mutations at 7 or 17 will both cause the disease

41
Q

How to calculate the probability of ~either~ one outcome or another

A

Addition rule

Sum of the two probabilities

42
Q

How to calculate the probability of ~both~ outcomes occurring

A

Multiplication rule

Multiply the probabilities together

43
Q

How to calculate genotype frequency

A

of that genotype/ total # of genotypes in that study

44
Q

How to calculate allele frequency

A

of individual alleles/ total # of alleles in the study

Total # of alleles in the study is the # of people x2 (2 alleles per person)

45
Q

Cystic fibrosis is caused by what kind of inheritance

A

Autosomal recessive

46
Q

Autosomal dominant inheritance characteristics

A
  • only one parent is affected
  • vertical transmission of disease phenotype
  • no skipped generations
  • equal male and females affected
  • father —> son transmission
  • recurrent risk: 50%
47
Q

Autosomal recessive inheritance characteristics

A
  • parents are normal
  • clustering of disease phenotype among siblings
  • disease not usually seen among parents or other ancestors
  • equal number of males and females affected
  • consanguinity ~may~ be present
  • recurrent rate: 25%
48
Q

consanguineous mating

A

Incestuous mating; second cousin or closer

More likely to produce offspring affected by rare autosomal recessive disorders

Each person carries 1-5 recessive mutations lethal to offspring if matched with another copy of the mutation

49
Q

Mitochondrial DNA (mtDNA)

A
  • several copies of 16,569 double stranded circular mtDNA per mitochondria
  • encodes rRNA, tRNA, and 13 polypeptides
  • transcription takes place in mitochondria, not nucleus
  • no introns

***inherited exclusively through maternal line

50
Q

Why is the mutation rate higher in mitochondrial DNA

A

Relative lack of DNA repair mechanisms

Damage from free oxygen radicals released during oxidative phosphorylation

51
Q

Mitochondrial inheritance

A

All children get mitochondrial DNA from their mother; if the mother has a disease associated with mtDNA, every child will have it

Men will have the mtDNA but do not pass it to their offspring if their wife is normal

52
Q

Leber’s hereditary optic neuropathy (LHON)

A

Mitochondrial disorder

Degeneration of retinal ganglion cells

Acute or subacute loss of central vision
- typically in early teens or 20s

53
Q

Mitochondrial encephalopmyopathy, lactic acidosis, and stroke-like episodes (MELAS)

A

Mitochondrial disorder

Affects many body systems, particularly brain and nervous system, and muscles

Stroke and dementia

Lactic acidosis

54
Q

Polygenic traits

A

Traits caused by combined effects of multiple genes

55
Q

Multifactorial traits

A

When environmental factors cause variation in traits

56
Q

Pyloric stenosis

  • what kind of inheritance causes it
  • men vs women
A

Multifactorial inheritance

5x more common in males than females

Why? Males need less risk genes to show disease

Women transmit the disease more than men, however

57
Q

Multifactorial inheritance

A

Caused by the simultaneous influence of multiple genetic and environmental factors

58
Q

Metacentric chromosome

A

Centromere is at the mid region, short and long arms are more equal

59
Q

Submetacentric chromosome

A

The centromere is off from the center of chromosome, but both haves matter

60
Q

Acrocentric chromosome

A

Centromere is very pushed off to one side and there is very little info on the short side of the chromosome

61
Q

What happens to epicenetic imprints in somatic cells

A

They remain through the lifespan of the individual

62
Q

Punnet Square and pedigree for autosomal dominant inheritance

A

Aa x aa; 50% of offspring expected to have disease

One parent is affected; females can give disease to males and males can give the disease to females; trait expected in 50% offspring

63
Q

Punnet square and pedigree for autosomal recessive inheritance

A

Need two copies of the gene to influence phenotype

Aa x Aa
(Carrier female with carrier male)

Both parents are normal; recurrent with heterozygous parents is 25%; affects males and females equally

64
Q

Which inheritance is more common with consanguinity (first cousins mating)

A

Autosomal recessive inheritance

65
Q

How X-linked recessive inheritance is passed on to daughters and sons

A

Affected males will pass the disease on to 100% of their daughters

Affected females will pass the disease on to 50% of their daughters and 50% of their sons

66
Q

How is X-linked dominant passed down to sons and daughters

A

Affected males will pass disease on to 100% of daughters

Affected females will pass disease to 50% of daughters and 50% of sons

67
Q

Mitochondrial inheritance pedigree

A

DNA is passed through the mother

The original mother will be affected, all of her children will be affected, and all of her grandchildren of her affected daughters will be affected

68
Q

Threshold of liability

A

The threshold that must be crossed before the disease is expressed; concept used in multifactorial diseases that are either present or absent

Below the threshold, the person appears normal

Above the threshold, the person is affected by the disease

MCM Exam II (14 decks)

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