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INHERITANCE PATTERNS > ALL THE THINGS > Flashcards

ALL THE THINGS Flashcards

1
Q

What is a phenotype?

A

observable characteristic of a person

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2
Q

What is a genotype?

A

genetic information of an organism. The DNA SEQUENCE

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3
Q

What are genes and what do they encode?

A

unit of hereditary information

functional product - protein or RNA

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4
Q

What is an allele?

A

variant form of a gene

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5
Q

What genotype parents did Mendel cross for his F1 generation?

A

Purebred (TT x tt)

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6
Q

What was the result of Mendel’s F1 cross?

A

All heterozygous offspring (Tt)

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7
Q

What genotypes did Mendel cross for his F2 cross?

A

Tt x Tt

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8
Q

What were the genotypic and phenotypic ratios that Mendel saw after his F2 cross?

A

1 TT : 2 Tt : 1 tt (Geno)

3 (TT, Tt Tt) : 1 (tt) (Pheno)

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9
Q

What are Mendel’s Laws?

A

Dominance (Uniformity)

Segregation

Independent Assortment

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10
Q

What is the law of Dominance?

A

crossing two homozygotes with different alleles yields identical F1 offsping - All Heterozygotes

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11
Q

What is the law of Segregation?

A

Each individual carries two genes for a characteristic but only on is passed on to the next generation at each mating

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12
Q

What is the law of Independent Assortment?

A

Members of different gene pairs segregate to offspring independently of each other

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13
Q

The human genome is made up what two types of DNA?

A

nuclear and mitochondrial DNA

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14
Q

What is the shape of mitochondrial DNA?

A

circular

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15
Q

Are there multiple copies of the mitochondrial DNA per mitochondrion?

A

Yes - > 1000 copies per cell

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16
Q

How many genes present in the mitochondrial genome?

A

37 genes

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17
Q

What are the mitochondrial genes involved in?

A

ETC and Oxidative phosphorylation

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18
Q

Are there histones in the Mitochondrial genome?

A

NO!

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19
Q

How is mitochondrial DNA inherited?

A

Maternally

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20
Q

In a pedigree, who is the Proband?

A

The member through whom a family with a genetic disorder is first brought to attention

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21
Q

Is the Proband usually a patient?

A

Yes, but could be any family member

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22
Q

Who is the Consultand?

A

an unaffected individual seeking counseling - can also be the proband

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23
Q

Examples of first degree relationships

A

parent, sib, child

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24
Q

% of genes common in first degree relationships

A

50%

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25
Q

Examples of second degree family relationships

A

aunt, uncle, niece, nephew, etc.

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26
Q

% of genes common in second degree relationships

A

25%

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27
Q

Example of third degree family relationships

A

first cousins

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28
Q

% genes common in third degree family relationships

A

12.5%

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29
Q

Case 1 of Huntington Disease Characteristics

A

pt was forgetful, depresed, restless. Had choreiform movements and family history of presentation.

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30
Q

What % chance does one affected parent have to transmit the phenotype to each offspring in AD inheritance?

A

50%

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31
Q

Are successive generations affected in AD inheritance?

A

Yes, no skipping of generations

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32
Q

What transmission pattern is observed in AD inheritance?

A

Vertical transmission

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33
Q

Are males and females affected equally in AD inheritance?

A

Yes

34
Q

Is there Male to Male transmission in AD inheritance?

A

Yes!

35
Q

Where would a spontaneous mutation occur in a family presenting AD inheritance out of nowhere in a pedigree?

A

In the meiosis of one of the parents

36
Q

Since AD diseases are selected against, what is the obvious explanation for a pedigree with an out of the blue occurrence of an AD disorder?

A

Spontaneous Mutation

37
Q

Is it likely that siblings in a case of spontaneous mutation for AD inheritance will be affected?

A

Possible, but unlikely

38
Q

What are the common AD inheritance disorders?

A 
Huntington Disease
Marfan Syndrome
Achondroplasia
Osteogenesis Imperfecta
Neurofibromatosis
ADPKD
39
Q

What can create the appearance of skipped generations in AD inheritance pedigrees?

A

Incomplete penetrance

40
Q

What is penetrance?

A

Probability thatindividuals with a specific genotype will manifest the corresponding phenotype.

41
Q

What kind of measure is Penetrance?

A

All or none and severity is not considered

42
Q

What is incomplete penetrance?

A

Some individuals with a genotype do not manifest the corresponding phenotype.

43
Q

What is variable expressivity?

A

variation in phenotype amongst individuals carrying the same genotype. Variations observed in symptoms and severity

44
Q

Case 2 Cystic Fibrosis characteristics

A

confirmed with sweat test. lung disease, lung infections, malabsorption, salty sweat, male infertility, meconium ileum

45
Q

If both parents are carriers, what % chance do they have of having an affected child under AR inheritance?

A

25%

46
Q

What kind of pattern is observed in AR inheritance pedigrees?

A

Horizontal pattern. disorder occurs in one generation typically.

47
Q

Can siblings be affected in AR inheritance?

A

Yes.

48
Q

Is there vertical transmission in AR inheritance?

A

Possible, but rare.

49
Q

Are males and female affected in AR inheritance?

A

Yes

50
Q

Is there male to male transmission in AR inheritance?

A

Yes.

51
Q

In AR mating, do both parent have to carriers?

A

YES!

52
Q

Examples of AR inheritance diseases

A

Metabolic disorders (Enzyme issues) - Alkaptoneuria, PKU, etc.

Cystic Fibrosis
Thalassemias
Sickle Cell Disease

53
Q

Case 3 Characteristics

A

Parents were first cousins and had a child who was normal but had profound bilateral hearing loss

54
Q

What are consanguineous matings?

A

matings between individuals who are 5th degree (or closer) relatives. Second cousins or closer.

55
Q

In consanguineous matings, the closer the degree of relationship, the more —

A

likely an AR phenotype will be expressed

56
Q

What is Pseudodominance?

A

recessive trait mimics dominant pattern. Multiple generations affected

57
Q

What is Complementation?

A

mating between individuals with the same phenotype results in offspring without the phenotype.

Phenotype due to mutations in different genes results in heterozygous offspring

58
Q

2/3 Rule

A

traits inherited in an AR manner, an unaffected sibling of an affected individual has a 2/3 risk of being a carrier

59
Q

Case 4 Characteristics

A

son of normal parents. delayed motor milestones. Uses Gower’s maneuver to rise. Maternal history of DMD

60
Q

Are females affected in XR inheritance?

A

Few (if any). Males affected in multiple generations

61
Q

Is there male to male transmission in XR inheritance?

A

NO!

62
Q

If a mother is a carrier for XR disease —

A

50% of her daughters are carriers

50% of her sons are affected

63
Q

If a father is affected with a XR disease —

A

0% of his sons are affected

100% of his daughters are carriers

64
Q

Who are obligate carriers?

A

individuals who must be carriers based on logical pedigree analysis

65
Q

If you see an isolated case of XR disease it may be due to —

A

Spontaneous mutation. Not safe to assume mother is a carrier

66
Q

Examples of XR disorders

A

DMD

Hemophilia

Red-green color blindness

67
Q

Is there male to male transmission in XD inheritance?

A

NO!

68
Q

Which sex is affected twice as much in XD inheritance?

A

Females

69
Q

Affected mothers with XD disorder will have —

A

50% daughters that are affected

50% sons that are affected

70
Q

Affected fathers with XD disorder will have —

A

None of his sons affected

100% of daughters are affected

71
Q

Example of XD disorders

A

Rett Syndrome

Fragile X Syndrome

72
Q

Case 6 Characteristics

A

blurred vision and loss of color distinction. Parents are healthy but maternal uncle and aunt are blind or have impaired vision. suspect LHON

73
Q

In mito inheritance, how are the disorders inherited by offspring?

A

Maternally

74
Q

Children of affected mito disorder males are —

A

never affected

75
Q

Children of affected mito disorder females are —

A

always affected (except with reduced penetrance)

76
Q

Describe a person expressing a mosaic

A

individual who’s body contains two or more genetically distinct cell lines

77
Q

Where do situations of mosaicism occur?

A

due to mutations occurring post - fertilization. The sooner the mutation occurs post fertilization, the more cells will be affected

78
Q

What are the two types of mosaicism?

A

Somatic and Germline

79
Q

Describe Germline mosaicism

A

mutation exists in the germline. Can be passed to offspring

80
Q

Describe somatic mosaicism

A

Mutation does not occur in the germline but may occur in other tissues. Can’t be passe to offspring

INHERITANCE PATTERNS (1 decks)

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