(6) Principles of Genetic Inheritance Flashcards

1
Q

Define: Gene

A

Segments of DNA in a chromosome

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2
Q

Define: Chromatid

A

one of two identical copies of chromosome

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3
Q

Define: Centromere

A

Connects identical sister chromatids

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4
Q

Define: Telomere

A

Region at end of chromosome for stability

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5
Q

Human somatic cells are ________ cells

A

diploid

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6
Q

Homologous chromosomes refer to _________

A

pairs of chromosomes

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7
Q

Aa: what does the upper case and lower case letter represent?

A

A: wildtype

a: mutant

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8
Q

Describe AUTOSOMES

A
  • Chromosomes common in both genders

- One from each parent

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9
Q

Banding and nomenclature:

What does the small arm represent?

A

p

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10
Q

Banding and nomenclature:

What does the long arm represent?

A

q

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11
Q

Entire set of a pt. chromosmes represents their _____

A

karyotype

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12
Q

How many chromosomes in pt’s diploid cells

A

46

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13
Q

What is LYONIZATION?

A

X-activation

*The choice of which X chromosome to be inactivated is random

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14
Q

What is MOSAICISM?

A

Condition in which cells from a pt. have different genotypes & karyotypes

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15
Q

What are examples of conditions that result from mosaicism?

A
  • Downs syndrome
  • Klinefelter syndrome
  • Turner syndrome
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16
Q

What is Down’s syndrome caused by genetically?

A

Mosaicism:

46XX
47XX
Trisomy 21

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17
Q

What is Klinefelter syndrome caused by genetically?

A

Mosaicism:

46XY
47XXY

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18
Q

What is Turner syndrome caused by genetically?

A

Mosaicism:

46XX
45XO

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19
Q

Cell Cycle: Mitosis

What occurs during INTERPHASE?

A

Chromosome duplication

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20
Q

Cell Cycle: Mitosis

Unique about stem cells?

A

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

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21
Q

Meiosis:

Goal?

A

Reduce the total number of chromosomes by half, producing four gametes (haploid)

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22
Q

Meiosis consists of:

A
  • One round of DNA replication

- Two rounds of nuclear division

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23
Q

Meiotic errors:

Euploid=

A

Cells with a normal number of chromosomes

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24
Q

Meiotic errors:

Polyploidy=

A

presence of a complete set of EXTRA chromosomes in cells

*often seen in plants

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25
Q

Meiotic errors:

Aneuploidy=

A

Cells with a missing or additional individual chromsomes

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26
Q

TURNER SYNDROME:

What is the karyotype? Sx?

A

45, XO Karyotype

  • Short stature
  • Ovarian hypofunction
  • Many do not undergo puberty
  • Most infertile
  • 30% webbed neck
  • CV defects
  • Normal intelligence
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27
Q

KLINEFELTER SYNDROME:

Karyotype? Sx?

A

47, XXY

  • Some w/ limited/no sxs
  • Primary hypogonadism
  • Gynecomastia
  • Tall
  • Infertility
  • Variability in X numbers can increase symptoms
28
Q

Trisomy 13, 18, 21

Identify each disorder based on the trisomy:

A

13: PATAU SYNDROME
18: EDWARDS SYNDROME
21: DOWNS SYNDROME

29
Q

Genomic Imprinting:

What is it?

A

-Gene silencing via methylation of 5’ region of gene

30
Q

Genomic Imprinting:

Describe

A
  • Epigenetic imprints remain throughout the lifespan of the individual in SOMATIC cells
  • In germ cells, epigenetic imprints are reset at each generation
  • During meiosis, imprints are erased and new ones are set
31
Q

What are Prader-Willi/Angelman Syndromes defined by?

A

Deletion of a region of chromosome 15

32
Q

How to Prader-Willi/Angelman syndromes differ?

A

*Difference occurs based on if deletion is on paternal or maternal chromosome

33
Q

Describe the sx of Prader-Willie syndrome

A
  • Short stature
  • Hypotonia
  • Small hands/feet
  • Obesity
  • Mild to moderate intellectual disability
34
Q

Describe the sx of Angelman syndrome

A
  • SEVERE intellectual disability
  • Seizures
  • Ataxic gait
35
Q

What is Uniparental Disomy?

A

When two chromosomes are inherited from the same parent; they will have parent-specific imprinting

36
Q

Mendelian Genetics:

What demonstrated law of segregation in pea plants?

A

Tall or Dwarf

37
Q

Mendelian Genetics:

What demonstrated law of independent assortment?

A

Wrinkled/tall vs wrinkled/dwarf

38
Q

Examples of genetic mechanisms of disease:

Loss of function =

Gain of function =

Protein alteration =

A

Dystrophin (Duchenne MD)

Oncogene (Cancer)

Beta-globin (Sickle cell anemia)

39
Q

Define:

Genotype

A

Individuals genetic makeup

40
Q

Define:

Phenotype

A

What is actually observed

41
Q

Individuals with distinct genotypes can have a ___________

A

Single phenotype

*ex: Cystic fibrosis

42
Q

What is PLEIOTROPHY?

A

Same genotype can have multiple phenotypes

43
Q

Example of Autosomal Dominant Inheritance:

A

Postaxial polydactyly

44
Q

How are AUTOSOMAL DOMINANT pedigrees identified?

A
  • Affected offspring have one affected parent
  • Unaffected individuals do not transmit trait
  • Both males and females can transmit trait to both males and females
  • Trait is expected in every generation at 50%
45
Q

AUTOSOMAL recessive inheritance

A

2 copies of gene is needed

*example: tyrosinase negative albinism

46
Q

How to identify a autosomal recessive pedigree?

A
  • Affected individuals have normal parents

- Occurrence is more likely among individuals who share genes (cousin mating)

47
Q

Example of X-linked recessive

A

Duchenne muscular dystrophy

48
Q

Example of X-linked dominant

A

*super rareeeee

Hypophosphatemia

49
Q

The frequency of a gene manifests itself as _______

A

penetrance

50
Q

Example of reduced penetrance?

A

Retinoblastoma

51
Q

What is VARIABLE EXPRESSIVITY?

A

There is a range of phenotypes that vary b/w individuals with a specific genotype

52
Q

Example of Variable Expressivity?

A

Neurofibromatosis

53
Q

Example of Locus Heterogeneity?

A

Osteogenesis Imperfecta

54
Q

Probability:

What is the multiplication rule?

A

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

*What is the probability of producing three girls? 1/2 x1/2 x1/2 =1/8

55
Q

Probability:

What is the addition rule?

A

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

*What is the probability of producing either three boys or three girls? 1/8 + 1/8 = 1/4

56
Q

Mitochondrial Inheritance

A

INHERITED FROM MOM

57
Q

Traits in which variations are thought to be caused by the combined effects of multiple genes are called _______

A

polygenic

58
Q

When environmental factors cause variation in the trait, the term _________ is used

A

Multifactorial

59
Q

What is an example of multifactorial inheritance?

A

Height

60
Q

Prader-Willi syndrome:

sx?

A

Short stature, hypotonia, small hands/feet, obesity, mild to moderate intellectual disability

61
Q

Angelman syndrome:

sx?

A

Severe intellectual disability, seizures, ataxic gait

62
Q

How many genes can be imprinted by the father?

A

30

63
Q

How many genes can be imprinted by the mother?

A

70

64
Q

Mitochondrial Disorders

What are the two?

A

Lebers (LHON)

MELAS

65
Q

Mitochondrial Disorders

What is LHON?

A

Leber’s hereditary optic neuropathy

loss of vision

66
Q

Mitochondrial Disorders

MELAS?

A

Encephalopmyopathy, lactic acidosis, stroke-like episodes

67
Q

What is an example of Multifactorial Inheritance?

A

Pyloric Stenosis

Muscular hypertrophy b/w stomach and duodenum