Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Genetics > L6, L7, L8, L9 Patterns of Inheritance > Flashcards

L6, L7, L8, L9 Patterns of Inheritance Flashcards

1
Q

define gene

A

sequence of DNA that codes for protein, includes the regulatory regions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is a regulatory region?

A

a segment of a nucleic acid molecule which is capable of increasing or decreasing the expression of specific genes within an organism.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

define locus

A

location of a gene on a chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

define allele

A

different version of a gene that occur on a locus - defines the amino acid or base sequences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

define polymorphism

A

multiple alleles of a gene in population - when an allele is found in > 10% of population and has a normal function - like different blood types

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

define homozygote

A

has same alleles at a locus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

define heterozygote

A

has different alleles at a locus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

define dominant

A

requires only one copy of the mutation to produce disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

define recessive

A

requires two copies of the mutation to produce disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what does recurrence risk mean?

A

the probability that the offspring of a couple will express the genetic disease.
for single gene disorders, it does not depend on the number of previously affected/unaffected offspring
DEPENDS ON THE MODE OF INHERTIANCE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is a pedigree

A

diagrammatic rep. of the family history

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is a proband

A

AFFECTED individual in the family who has gone to a physician for a consultation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is a consultand?

A

a NOT AFFECTED individual who has gone to a physician for consultation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

define consanguinity

A

people who share the same blood - the relationship of 2nd cousin or closer!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are autosomal disorders?

A

when the mutant gene is present on autosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is x linked disorders?

A

when the mutant gene is present on sex chromosomes (x chromosome)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

are there any Y-linked disorders?

A

no transmission from Y gene, but there are certain traits we should be aware of.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what are mitochondrial disorders?

A

when there is a mutation in a gene encoded by mitrochondrial DNA - NON-MENDELIAN

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

define autosomal cominant

A

when the presence of one copy of the mutant allele on one chromosome is sufficient to cause disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

in what state do autosomal dominant disorders manifest in

A

heterozygous state!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what are characteristics of autosomal dominant disorders?

A
  • affected child receives disease from affected parent
  • does not skip generations (vertical inheritance)
  • males and females are equally affected
  • male to male - father to son transmission is seen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

define vertical inheritace

A

when a disorder does not skip generations - common with autosomal dominant disorders

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what are examples of autosomal dominant disorders?

A
  • familial hypercholesterolemia - LDL receptor def.
  • huntingtons disease - triple repeat expansion
  • myotonic dystrophy - triple repeat expansion
  • Marfan syndrome
  • osteogenesis imperfecta
  • achondroplasia
  • neurofibromatosis type I
  • acute intermittent porphyria
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is myotonic dystrophy?

A
  • mutation in the DMPK gene
  • most pleiotropic phenotype of all unstable triple repeats disorders (affects multiple systems)
  • characterized by wasting of muscle, heart conduction defects, endocrine changes, myotonia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is achondroplasia?

A

mutation in FGFR3 - fibroblast growth factor receptor gene

  • FGFR3 codes for transmembrane receptor that is involved in differentiation of cartilage to bone
  • results in severe growth stunting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what is neurofibromatosis (NF1) aka von Recklinghausen disease

A

-mutation in neurofibriomin NF1 gene
-NF1 is cuased by different mutations in the NF1 gene — allelic heterogeneity = same gene is mutant but different type of mutation in different families - single point vs. nonsense
-NF gene usually codes for tumor suppressor protein
-pts have neurofirbomas - painless swellings in skin and CN
HAS VARIABLE EXPRESSION - can be less or more severe
Cafe-au lait spots
neuro fibromas
Lisch nodules in iris of eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is osteogenesis imperfecta

A

DOMINANT NEGATIVE MODEL

  • mutation in 1 allele of alpha 1 gene
  • association of the triple helical molecules with atleast one mutant alpha 1, results in the degradation of collagen - 25% of collagen is normal and 75% of collagen is degraded
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

why do autosomal dominant mutations manifest in the heterozygous state?

A
  1. Haplo-insufficiency
  2. dominant-negative mutations
  3. Gain-of-function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what is halo-insuffiency and what is an example?

A
  • loss of function mutations in which half normal levels of the gene product results in disorder
  • familial hypercholesterolemia - LDL receptors
  • rarely there is an enzyme deficiency
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what is dominant-negative mutations and what is an example?

A

a mutant gene product interferes with the function of the normal gene product

  • osteogenesis imperfecta
  • marfan syndrome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what is gain of function and what are examples?

A

result from increased levels of gene expression or the development of a new function of the gene product

  • huntingtons disease
  • achondroplasia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what is the homozygous state of autosomal dominant disorders?

A

much more severe or lethal like of OI

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what state are autosomal recessive disorders expressed in?

A

homozygous state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

who are carriers of the mutant gene in autosomal recessive disorders

A

both parents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

in autosomal recessive disorders, carriers are what?

A

phenotypically normal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

autosomal recessive disorders are usually seen in only one___

A

generation - horizontal inheritance = siblings are more commonly affected - males and females affected equally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

is it possible to trace mutant allele transmission through the family without genetic testing

A

no! - why- because carriers are phenotypically normal!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

most enzyme deficiencies are what mode of transmission?

A

autosomal recessive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

what are common autosomal recessive disorders?

A 
cystic fibrosis
MSUD
homocystinuria *
Sickle cell anemia
Phenylketouria
Tay-Sach's disease (Hexosaminidase A def.)
Congenital deafness
Hemochromatosis *
Galactosemia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

what do loss of function mutations (molecular basis for autosomal recessive disorders) result in?

A
  • reduced activity (hypomorph)

- complete loss of gene product (null allele or amorph) = enzyme deficiencies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What is the mutations seen in Hemochromatosis?

A

C282 Y mutation of the HFE gene = most common

H63D and S65C are other mutations of the HFE gene

= ALLELIC HETEROGENEITY - same gene, different mutations possible to produce the same phenotypical manifestations!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

when is the age of onset for hemochromatosis?

A

delayed age of onset

43
Q

define pseudo-autosomal dominant

A

autosomal recessive condition present in individuals in 2 or more generations of a family - it looks like its following a dominant inheritance pattern = like sickle cell anemia in African Americans

an affected parent may have affected child - might see vertical transmission
high carrier frequency in pop
high consanguinity

44
Q

what are the common explanations of pseudo-autosomal dominant disorders?

A
  • high carrier frequency in population
  • birth of an affected child to an affected individual
  • genetically related (consanguineous) reproductive partner
45
Q

what factors can increase the incidence of an autosomal recessive trait in a population (leading to pseudo-autosomal dominant)?

A
  1. consanguinity
  2. heterozygote advantage
  3. genetic isolation - geo, religion, culture
  4. assortative mating - people who are deaf marry other deaf people?
46
Q

what is the pseudoautosomal region of a sex chromosome?

A

region of chromosomes that match - it is necessary to line up chromosomes correctly during meiosis

males are hemizygous

47
Q

what are characteristics of X-linked recessive disorders?

A
  • males require 1 copy of mutation (hemizygous) to be affected
  • more common in males
  • skipped generations
  • affected father makes daughters carriers and then those girl transmit the mutation to their sons
  • male to male transmission not seen
48
Q

who are obligate carriers of mutant genes in x-linked recessive disorders?

A

the mothers of affected sons

the daughters of affected males

49
Q

what are common x-linked recessive disorders?

A 
duchenne MD
Becker MD
Glucose 6 phosphate dehydrogenase def.
Hemophilia A and B
Lesch-Nyhan syndrome
Red-Green blindness
Rett syndrome
50
Q

what is muscular dystrophy

A

Duchenne and Becker - both have mutations on dystrophin gene

Duchenne - males die young, don’t really reproduce - “low reproductive fitness”
Becker - DO reproduce and can transmit mutation to sons

51
Q

what does a G6PD deficiency result in?

A

hemolytic anemia on ingestion of drugs like priaquine, sulfa drugs

52
Q

what is hemophilia A and B and what does it result in?

A

def. of clotting factor VIII because of mutation

bleeding tendencies

53
Q

what does Lesch-Nyhan syndrome result in?

A

HGPRT def. is problem = causes hyperuricemia and self mutilation

54
Q

manifesting heterozygote in females with bleeding tendency is most commonly due to?

A

skewed x-inactivation (asymmaetic x inactivation)

if the skewed x inactivation occurs in liver - carrier may have factor VIII activity level below normal

symptoms are more mild in females compared to males

55
Q

define skewed x inactivation?

A

the number of cells that contain the active mutant X are large compared to the cells that contain the active normal X

56
Q

what is Rett Syndrome?

A

x linked disorder = lethal in males

affects females more often than males
because males usually die in utero or soon after birth
the mom does not have the manifestations of the disease - due to skewed x inactivation or due to a germline mutation in the female

57
Q

what are characteristics of X-linked dominant disorders?

A
  • does not skip generations
  • more females are affected than males
  • no male to male transmission***
  • affected male transmits to ALL daughters, no sons
58
Q

what are the two X-linked dominant diseases?

A
  • vitamin D resistant Rickets (Hypophosphatemic rickets)

- incontinentia pigmenti

59
Q

what is incontinentia pigmenti?

A
  • males in utero with disorder typically die in utero
  • females are less severely affected
  • expression is variabe
  • manifests as rashes and blisters in early life
  • later - patches of hyper pigmentation “marble cake appearance” of skin
  • mental retardation in some
  • retinal detachment in some
60
Q

What are the genes on the Y chromosome in males involved in?

A

spermatogenesis - mutation = sterility = not passed on usually, but if it is = disease is only passed to sons because they have Y, not girls

61
Q

what are examples of Y-linked inheritance?

A
  • various mutations in the SRY genes
  • H-Y histocompatibility antigen
  • hairy ears
62
Q

what is full penetrance

A

if all the people carrying the mutation express the manifestations of the disease

63
Q

huntingtons disease has a ______ penetrace but a ____ age of onset

A

high

delayed

64
Q

how do you calculate recurrent risk based on penetrance?

A

penetrance of autosomal dominant disease x recurrent risk for every new child born to couple
/ 100

80% x 50% / 100 = 40% risk for next offspring when penetrance is 80%

65
Q

define variable expression?

A

with individuals who inherit a mutant allele, there are some individuals who are severely affected and some who are mildly affected

66
Q

what are diseases that show variable expression?

A

hemachromatosis - more severe in males (autosomal recessive)

xeroderm pigmentosum (autosomal recessive) - more severe in individuals exposed more frequently to UV radiation

osteogenesis imperfecta (autosomal dominant)

neurofibromatosis type I (autosomal dominant) - high penetrance

67
Q

what does pleiotrophy mean?

A

disease causing mutation affects multiple organ systems

68
Q

what are examples of pleiotropic diseases?

A

marfan syndrome - skeletal, joints, ocular, CV system etc.

Osteogenesis imperfecta - bone, sclera

69
Q

what is locus heterogeneity?

A

mutations at different loci that cause the same disease phenotype

70
Q

what are examples of diseases with locus heterogeneity?

A

osteogenesis imperfecta - defect in collagen, mutations of chromosome 17 or 7

sensorineural hearing impairment

retinitis pigmentosa

charcot marie tooth disease

breast cancer

71
Q

define allelic heterogeneity

A

different mutations at the same locus cause the disease

72
Q

what are diseases that display allelic heterogeneity?

A

neurofibromatosis 1
hemochromatosis
Cystic fibrosis

73
Q

what are the characteristics of a new mutation?

A
  • transmitted from unaffected parent to affect offspring
  • maybe see an increase in age of father
  • no family history of disease
74
Q

what are examples of new mutation diseases?

A

neurofibromatosis
achondroplasia
Duchenne muscular dystrophy

osteogenesis imperfects
marfan syndrome
some x-linked recessive disorders
- couples risk of recurrence is low

75
Q

define Germline moasicism

A

presence of 2 affected children with no family history - the mutation is present in a proportion of germline cels

76
Q

define new mutation

A

single affected child with no family history

77
Q

what are delayed age of onset diseases?

A

huntingtons disease
hemochromatosis
familial breast cancer

78
Q

what are characteristics of mitochondrial inheritance?

A

mitochondria are inherited from mother
ALL offspring of an affected mother are affected - both male and female children
only females transmit the disease
affected father cannot transmit to children

79
Q

what is responsible for the variable severeity of mitochondrial disorders?

A

heteroplasmy

unequal distribution of mutant and non-mutant mitochondrial DNA

80
Q

what does the severity of the mitochondrial disorder depend on (heteroplasmy)?

A

the number of mitochondria that have the mutant gene

81
Q

what are examples of mitochondrial diseases?

A

MELA (mitochondrial encephalopathy, lactic acidosis and stroke like symtoms

leber hereditary optic neuropathy

MERRF (myoclonic epilepsy with ragged red muscle fibers)

82
Q

what are other diseases that lead to non-Mendelian inheritance patterns?

A 
Digenic disorders
- retinitis pigmentosa
Imprinting
-Prader Willi syndrome
- Angelman syndrome
Triplet repeat disorders
-Huntingtons disease
Myotonic dystrophy
-Fragile X syndrome (x-linked)
83
Q

what is a digenic disorder?

A

mutations in 2 genes (A,B) are necessary to produce the disorder

84
Q

what is retinitis pigmentosa

A

disease of progressive visual impairment

result of a mutation in 2 independent genes - ROM1 and Peripherin

85
Q

explain impriting (parent of origin effects)

A

some genes, maternal loci (UBE3A) are active and for other genes paternal loci (SNRPN) are active

in normal, there are 2 SNRPN and 2 UBE3A - there is a methylation of 1 of each so you are left with 1 UBE3A and 1 SNRPN

86
Q

what is Prader Willi syndrome?

A

absence of paternal SNRPN - micro deletion of 15q11-13

UBE3A is active

87
Q

how is Prader willi syndrome detected?

A

FISH using specific probes against the region

88
Q

what are the symptoms of Prader Willi syndrome?

A

obese
mental and developmental delay
underdeveloped genetalia
hypotonia in infancy, failure to thrive

89
Q

what is uniparental disomy- Prader willi syndrome?

A

condition when a child has two copies of the maternal chromosome 15 - no SNRPN, 2 copies of UBE3A

trisomy 15 is not capatable with life - 1 of the chromosome are thrown out to preserve the zygote

90
Q

how is uniparental disomy- Prader willi syndrome detected?

A

methylation analysis -
restiction enzyme does not cleave methylated DNA
restriction enzyme does cleave methylated DNA

91
Q

what can be used to differentiate the cause of Prader Willi syndrome (due to microdeletion of paternal ch15 or due to uniparental disomy of materal ch15)?

A

polymorphic marker analysis - different color and letters for mom and dad to see what kid has

92
Q

what is Angelman syndrome?

A

deletion of maternal 15q11-13 - no UBE3A gene, 2 copies of SNRPN = uniparental disomy of paternal chromosome 15

93
Q

what are the symptoms of Angelman syndrome?

A 
happy puppet syndrome
happy disposition, laugh inappropriately 
severe mental retardation
seizures
puppet like posture of limbs
94
Q

what are the 4 classes of triplet repeat?

A

fragile x syndrome
Friedrich ataxia
Huntingtons disease
Myotonic dystrophy

95
Q

what sequences and location is Fragile x syndorme?

A 
CGG
promoter region (5' end of the FMR1 gene)
96
Q

what sequences and location is Friedrich ataxia?

A

GAA

intron - results in abnormal mRNA processing

97
Q

what sequences and location is Huntingtons disease?

A

CAG
coding region of the gene = polyglutamine expansion in the protein

CAG - codes for glutamine

98
Q

what sequences and location is Myotonic dystrophy?

A

CTG

3’ end (3’ UTR) of the gene

99
Q

what is responsible for the instability of repeats and then repeat size influence disease severity?

A

anticipation! - characteristic for triplet repeats!

mutations probably in oogenesis or spermatogenesis

100
Q

the ____ the number of repeats, the _____ the age of onset and then more _____ the disorder

A

greater
earlier
severe

101
Q

in huntingtons disease, the disorder is more severe is transmitted from the ______

A

father

102
Q

what are symptoms of fragile x syndrome?

A 
mentral retardation
learning difficulties
prominent ears
elongated face
macro orchidism - big balls

shows anticipation in succesive generations

103
Q

how is fragile x syndrome diagnosed?

A

southern blot analysis

cytogenic test

Genetics (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions