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IMMS lectures > inheritance patterns > Flashcards

inheritance patterns Flashcards

1
Q

what are the 3 categories of genetic disorders

A

chromosome abnormalities
single gene disorders
multifactorial & polygenic disorders

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2
Q

give 3 examples of multi factorial and polygenic disorders

A

spina bifida
cleft lip
palate

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3
Q

define aneuploidy

A

the condition of having an abnormal number of chromosomes in a haploid set

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4
Q

define cytogenetics

A

the study of inheritance in relation to the structure and function of chromosomes.

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5
Q

what are the 6 common structural anomalies in clinical cytogenetics

A
  • translocations
  • inversions
  • deletions
  • duplications
  • ring chromosome
  • fragile site
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6
Q

what is chromosome 22q11 deletion syndrome

A

a disorder caused when a small part of chromosome 22 is missing

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7
Q

what are the clinical features of chromosome 22q11 deletion syndrome

A
  • characteristic facial features
  • congenital heart disease
  • palatal abnormalities
  • learning difficulties
  • psychiatric problems
  • immunodeficiency
  • hypocalcemia
  • renal abnormalities
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8
Q

what 3 laws did Mendel come up with

A
  • segregation
  • dominance
  • independent assortment
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9
Q

what does mendels law dominance mean

A

every gene has 2 alleles that code for a trait
in heterozygotes 1 allele is dominant meaning it will always show, one is recessive and is masked by the dominant one

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10
Q

what does mendels law segregation mean

A

allele pairs separate/segregate randomly from each other during meiosis - each cell has a single allele for each trait

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11
Q

what does mendels law independent assortment mean

A

traits are transmitted to offspring independently of one another

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12
Q

what does mendelian inheritance refer to

A

autosomal and sex linked
dominant and recessive

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13
Q

what does non-mendelian inheritance refer to (4)

A

imprinting
mitochondrial inheritance
multifactorial
mosaicism

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14
Q

define autosome

A

any chromosome, other than the sex chromosomes (X or Y), that occurs in pairs in diploid cells

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15
Q

define recessive

A

manifest only in homozygotes

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16
Q

define allele

A

one or more alternative forms of a gene at a given location (locus)

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17
Q

define homozygous

A

presence of identical alleles at a given locus
homozygotes are affected

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18
Q

define hetertozygotes

A

presence of 2 different alleles at a given locus
heterozygotes are unaffected and are usually referred to as carriers

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19
Q

define allelic heterogeneity

A

when different mutations within the same gene result in the same clinical condition
this means an individual with an autosomal recessive condition may be a compound heterozygote for 2 different mutations

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20
Q

what are 3 features of autosomal recessive inheritance

A
  • male and females affected in equal proportions
  • affected individuals only in a single population
  • parents can be related ie consanguineous
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21
Q

what is the most common autosomal recessive disease

A

cystic fibrosis

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22
Q

what does cystic fibrosis affect

A

mainly lungs and gut
but can also affect other systems

23
Q

whats the most common cystic fibrosis mutation

A

change in F508

24
Q

how many cystic fibrosis mutations are detected by standard carrier testing

A

top 29

25
Q

what kind of test is sweat testing

A

diagnostic

26
Q

define consanguinity

A

reproductive union between two relatives

27
Q

define autozygosity

A

homozygosity by descent ie inheritance of the same altered allele through two branches of the same family

28
Q

how do you show consanguinity on a pedigree diagram

A

double lines

29
Q

what is the risk of children having autosomal recessive disease if parents are carriers

A

1 in 4

30
Q

what is the risk of healthy siblings having autosomal recessive disease

A

2 in 3

31
Q

in what kind of families ar autosomal recessive diseases more common

A

consanguineous

32
Q

what are 4 features of autosomal dominant inheritance

A
  • male and females affected in equal proportions
  • affected individuals in multiple generations
  • transmission by individuals of both sexes, to both sexes
33
Q

what are autosomal dominant conditions

A

they are manifest in the heterozygous state so only one affected gene is needed

34
Q

define penetrance

A

the percentage of individuals with a specific genotype showing the expected phenotype

35
Q

define expressivity

A

refers to the range of phenotypes expressed by a specific genotype

36
Q

define recurrence risk

A

a statistic that estimates the probability that a condition present in one or more family members will recur in another relative in the same or future generations.hhhh

37
Q

define anticipation

A

The signs and symptoms of some genetic conditions tend to become more severe and appear at an earlier age as the disorder is passed from one generation to the next

this is usually due to expansion of unstable triplet repeat sequences

38
Q

define somatic mosaicism

A

genetic faults present in only some tissues in the body

39
Q

define gonadal (germline) mosaicism

A

genetic fault present in gonadal tissue

generally more common in X linked disorders

40
Q

define late onset

A

when a condition is not manifest at birth, esp in relation to other people with the condition.

eg hypertrophic cardiomyopathy

41
Q

define sex limited

A

a condition inherited in an autosomal domincant pattern that seems to affect one sex more than another

eg BRCA1/2

42
Q

define predictive testing

A

testing for a condition in a pre-symptomatic individual to predict their chance of developing condition

43
Q

what usually confirms autosomal dominant inheritance

A

male to male transmission

because a father passes on his Y chromosome to a son, male-to-male transmission cannot be seen with an X-linked trait

44
Q

what are 3 factors of X-linked inheritance

A
  • usually, only males affected
  • transmitted usually through unaffected females
    -no male-to-male transmission
  • an affected male cannot have affected sons, but all his daughters will be carriers
45
Q

define lyonization (X inactivation)

A

normally one of the two X chromosomes in every cell of a female individual is inactivated during embryonic development.

46
Q

what is genomic imprinting

A

an epigenetic (non genetic influence on gene expression) phenomenon that causes genes to be expressed in a parent of origin-specific matter

the process by which only one copy of a gene in an individual (either from their mother or their father) is expressed, while the other copy is suppressed.

47
Q

what causes PWS disease

A

missing genetic material in a group of paternal genes on chromosome number 15

48
Q

what causes angelman syndrome

A

loss of function of maternal UBE3A due to point mutation or deletion

so 2 paternal copies are inherited instead of 1 maternal and 1 paternal

49
Q

define homoplasmy

A

a eukaryotic cell whose copies of mitochondrial DNA are all identical (identically normal or have identical mutations)

50
Q

define heteroplasmy

A

the presence of more than one mtDNA type in an individual

identifies mutations which affect only a proportion of the molecules in a cell

level of heteroplasmy varies between cells in the same tissue or organ, from organ to organ within the same person and between individuals in the same family

51
Q

atdefine heteroplasmy

A

the presence of more than one mtDNA type in an individual

identifies mutations which affect only a proportion of the molecules in a cell

level of heteroplasmy varies between cells in the same tissue or organ, from organ to organ within the same person and between individuals in the same family

52
Q

what is mtDNA

A

DNA found in mitochondria instead of nucleus

all of it comes from our mothers - its not a mix of parents

usually identical to mothers mtDNA

53
Q

what is a mitochondrial genetic disease

A

a group of disorders caused by dysfunctional mitochondria

IMMS lectures (22 decks)

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