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MCM Final > Principles Of Genetic Inheritance > Flashcards

Principles Of Genetic Inheritance Flashcards

1
Q

Wildtype is also known as what

A

Normal

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2
Q

Lyonization is also known as what?

What does it create?

A

Known as x-inactivation, which occurs early in development

Condensation of one X creates a Barr body.

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3
Q

Mosaicism, what is it?

A

In women, when X heterozygous, some cells express the wildtype gene, some express the mutant gene.

These cells will exhibit different phenotypes

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4
Q

What event occurs in interphase?

A

Chromosome duplication

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5
Q

What is unique about stem cell mitosis?

A

It is asymmetrical, meaning that one stem cell and one daughter cell is produced.

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6
Q

Steps of mitosis

A 
Interphase
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
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7
Q

How many cells are produced in meiosis?

A

4 haploid gametes

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8
Q

Euploid

A

Cells with normal number of chromosomes

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9
Q

Polyploid

A

Complete extra set of chromosomes

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10
Q

Aneuploidy

A

Missing or additional chromosomes—monosomy or trisomy

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11
Q

What is translocation?

What are the two types?

A

Non homologous chromosomes exchange genetic material.

Reciprocal—between non homologous chromosomes

Robertsonian—long arm of two Afrocentric chromosomes are combined. SHORT ARM IS LOST

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12
Q

Turner syndrome

  1. Karyotype
  2. Physical effects
A
  1. 45, XO
2.
Female
Short
Ovarian hypofunction or failure
No puberty
Web neck
Low hair line
Normal intelligence
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13
Q

Klinefelter syndrome

  1. Karyotype
  2. Physical effects
A
  1. 47, XXY

2.

  • Varying degrees cognitive, social, behavioral, and learning difficulties
  • low T
  • small/undescended testes
  • tall
  • gynecomastia
  • infertility
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14
Q

Trisomies

  1. Name
  2. Karyotype
  3. Additional info
A
  1. Trisomy 21, (Down’s syndrome)
  2. 47, XX +21
  3. Most common/stable, increased risk with maternal age, can also occur due to translocation
  4. Trisomy 13, (patau syndrome)
  5. 47, XX+ 13
  6. Severe dev abnomralities, death within 1 week
  7. Trisomy 18 (Edwards syndrome)
  8. 47, XX+18
  9. Abnormal development, death within one year
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15
Q

What is genomic imprinting?

A

One allele is transcriptionally inactive depending on the parent it was received from.

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16
Q

~30 genes are paternally imprinted.

This means?

A

They are maternally expressed

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17
Q

~70 genes are maternally imprinted.

This means?

A

They are paternally expressed.

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18
Q

Explain genomic imprinting in terms of somatic vs germ cells

A

Somatic cells—imprinting remains throughout the lifespan of the individual.

Germ cells—imprinting resets at each generation

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19
Q

Prader-Willi syndrome

A

Deletion of region of chromosome 15 in the PATERNAL chromosome.

Prader-Willi kids will be short, obese, have small hands, and intellectual disabilities.

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20
Q

Angelman Syndrome

A

Deletion of a region of chromosome 15 on MATERNAL chromosome

Angelman kids will have severe intellectual disabilities, seizes, and ataxic gait.

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21
Q

What is uniparental disomy and how does it happen?

A

Two chromosomes are inherited from the same parent—this results in no gene product due to parent specific imprinting.

This is related to non-disjunction

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22
Q

What are the 3 Mendelian genetic mechanisms of disease?

A

Loss of function: dystrophin»Duchenne MD
Gain of function: oncogene»cancer
Protein alteration: beta-globulin»sickle cell anemia

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23
Q

Individuals with distinct geneotype can have one phenotype.

What is an example of this?

A

Cystic fibrosis
There are different classes of CF, meaning there are different gene mutations that result in the same disease (phenotype)

24
Q

Individuals with the same genotype can have multiple phenotypes.

What is this called and what is an example?

A

Known as pleiotropy

PKU is an example

25
Q

What is a proband?

A

First diagnosed person in a pedigree

26
Q

Describe autosomal dominant inheritance

What is an example?

A
  • Only 1 allele of gene needed for expression
  • unaffected individuals do not transmit
  • affected offspring have 1 affected parent
  • expected in every generation

Example: POSTAXIAL POLYDACTYLY

27
Q

Describe autosomal recessive inheritance

What is an example

A

-2 copies of the gene are needed to influence phenotype

Example: TYROSINE-NEGATIVE ABLINISM

28
Q

Describe x linked recessive

What is an example

A
  • Disease allele on X
  • When occurs in male, we say they are HEMIZYGOUS
  • females can be hetero- or homozygous

Example: DUCHENNE MUSCULAR DYSTROPHY

29
Q

Describe X linked dominant

What is an example

A

Very rare: no carriers

  • males with allele transmit the trait only to females %100 of the time
  • females with the disease transmit to male and female 50% of the time.

Example: HYPOPHOSPHATEMIA

30
Q

What is penetrance

A

The frequency a gene manifests itself.

31
Q

Retinoblastoma

A
  • Autosomal dominant

- occurs in 90% of individuals»90% penetrance

32
Q

Variable expressivity

Example

A

Describes the range of phenotypes that vary between individuals with a specific geneotype.

Example: Neurofibromatosis
Tumor like growths, have cafe-au-lait spots, spots different in number, shape, and size

33
Q

Locus heterogeneity

Example

A

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

Example: osteogenesis imperfecta

  • brittle bones
  • mutations in collagen genes
  • chromosome 7, 17
34
Q

Multiplication rule

A

Probability of a given outcome in multiple trials is the product of the probabilities of each trial outcome.

Ex: what the probability of producing 3 girls?

1/2 x 1/2 x 1/8 = 1/8

What is the probability or producing 3 boys?

1/2 x 1/2 x 1/8 = 1/8

35
Q

Addition rule

A

Probability of either one outcome or another is the sum of two probabilities

What is the probability of producing 3 girls or 3 boys?

1/8 + 1/8 = 1/4

36
Q

What is a gene frequency?

A

of alleles in question/# of alleles present total

The proportion of each allele in a population.

37
Q

What is a genotype frequency?

A

Proportion of each genotype in a population

of genotypes/ # of subjects

38
Q

What is the Hardy-Weinberg principle and what is the equation.

A

A relationship between the gene frequency and genotype frequency

p^2+2pq+q^2=1

39
Q

Consanguineous mating leads to what?

A

More likely to have offspring affected by rare autosomal recessive disorders

Mortality rates of offspring of first cousins are 9% higher than the general population

40
Q

How do we inherit mitochondrial DNA?

A

Maternally

41
Q

Why is the mutation rate for mitochondrial DNA higher? How much higher?

A

This is due to the lack of DNA repair mechanisms, as well as damage from free oxygen radicals released during OxPhos.

It is 10x higher!

42
Q

There is a ____ that must be met before some mitochondrial diseases present?

A

A threshold.

When the percentage of mutant mitochondria reaches a certain level, then symptoms may arise.

43
Q

Leber’s hereditary optic neuropathy (LHON)

A

Associated with mutation in mitochondrial DNA (mtDNA)

  • degeneration of retinal ganglion cells
  • acute or subacute loss of central vision
    • typically early teens/20s
44
Q

Mitochondrial encephalomyopathy, lactic acidosis, and stroke like episodes (MELAS)

A

Associated with mutations in mtDNA

  • affects many body systems, particularly brain, nervous, and muscle tissues.
  • stroke and dementia
  • lactic acidosis.
45
Q

Some traits are polygenic, what does this mean?

A

The variations in the trait are caused by the combined effects of multiple genes

46
Q

When is the term multifactorial used when referring to gene mutations?

A

When environmental factors cause the variation in the trait

47
Q

What type of traits usually follow a normal/bell shaped distribution in populations?

A

MULTIFACTORIAL, caused by environment and multiple genes.

48
Q

Pyloric stenosis

A

Multifactorial inheritance

Muscular hypertrophy between stomach and duodenum, leads to vomiting and obstruction.

  • five times more common in males, males need less risk genes to show the disease
  • children of women with pyloric stenosis are more likely to be born with the condition.
  • children of affected males, are less likely to be born with the condition
49
Q

The recurrence risk for multifactorial inheritance is ________ if more than one family member is affected

A

Higher

50
Q

What are three broad classes of cells in the human body?

A

Permanent, stable (quiescent), labile

51
Q

What cells remain in G0 and cannot be regenerated?

A

Permanent cells. These include the following:

Cardiac muscle cells, neurons, and red blood cells.

52
Q

what cells are able to exit the G0 phase and enter G1 when stimulated by growth factors?

A

Stable cells, including the following:

Hepatocytes, epithelial cells of the kidney tubules.

53
Q

What cells never enter G0 and are constantly dividing to replace the cell population?

A

Labile cells, including the following:

Gut epithelium, skin, hair follicles, and bone marrow.

54
Q

Somatic cells vs germ-line cells

A

Somatic—Diploid, contain 46 chromosomes.

Germ-line—Haploid, contain 23 chromosomes.

55
Q

What is a karyotyping?

A

Technique that allows the determination of the number, size, and gross structure of metaphase chromosome.

Used to identify genetic abnormalities.

56
Q

What is heteroplasmy?

A

Presence of more than one type of mitochondrial DNA within a cell or organism.

Symptoms usually don’t develop until adulthood, as these mutant mitochondrial alleles must undergo many cell decisions before the threshold is reached.

MCM Final (12 decks)

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