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AUDE 5310 > patterns of inheritance > Flashcards

patterns of inheritance Flashcards

1
Q

pedigree

A

chart/family tree that uses sets of symbols
-objective is to show the history of inherited traits through generations
-frequently rule out a certain mode of inheritance but not prove

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2
Q

how to show generations in a pedigree

A

marked vertically by roman numerals
-I being generation 1

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3
Q

how to show birth order on a pedigreee

A

marked horizontally by number 1, 2, 3 ….
-done individually with each generation
-typically oldest to youngest as you move to the right
-connected through horizontal lines above the symbols

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4
Q

how to show multiple siblings in one symbol

A

have that gender shape with the number there is present in the family

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5
Q

proband

A

who it is about, consultant
-marked by : an arrow on the bottom of the symbol pointing towards the shape

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6
Q

what must be included in a pedigree

A

proband, race/ethnicity, first name/initial of relatives, affected status for each individual, age of family members (or age of death), adoption status, pregnancy/abortion, consanguinity, marriage/divorce, mating, carrier status and is they are twins

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7
Q

how to show what the shading is of each individual

A

use a key with symbols to show what the shading means
-if multipole disorders are present, can use multiple shading/patterns

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8
Q

monozygotic twins

A

identical
-develops from a single fertilized egg and therefore must be the same gender
-splitting of zygote at any stage
-both implant separately
-more rare

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9
Q

dizygotic twins

A

fraternal
-develops from 2 eggs being fertilized by two different sperms
-they are no more similar than two siblings

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10
Q

carrier

A

you have the gene, but do not show the phenotype
-only occurs in recessive traits

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11
Q

locus (loci)

A

specific location of a gene or DNA sequence on a chromosome
-chromosome number, arm, region and band
-the numbers go outward from the centromere (meaning 1 is closest to the centromere and increases as you go outward)

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12
Q

homozygous

A

carrying identical alleles for one or more genes
-same allele, same gene

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13
Q

heterozygous

A

carrying two different alleles for one or more genes
-1 bad, 1 good

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14
Q

heterogeneity

A

variation within genes and phenotypes
-many genes can lead to the same phenotype
-for example HL/deafness has tons of genes that can result in it

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15
Q

ploidy

A

number

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16
Q

diploid cell

A

double number of chromosomes found in a mature germ cell
-somatic has 46 (23 pairs)

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17
Q

germ cells

A

egg and sperm cells
-haploid with half the number of chromosomes (23)

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18
Q

aneuploidy

A

abnormal number of chromosomes, can be extra or missing
-occurs at cell division and the cells do not separate equally between daughter cells
-leads to chromosomal abnormalities

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19
Q

knockout mouse

A

genetically engineered mouse with specific genes artificially deleted

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20
Q

cellular homeostasis

A

tendency of a cell or organisms to regulate its internal conditions, such as chemical composition of body fluids, to maintain health and functioning regardless of external conditions

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21
Q

phenocopy

A

environmentally caused trait that mimics a genetically determined traits
-it is not inherited but makes the conditions look as if they were
-ex. hair loss from chemotherapy can mimic the phenotype of alopecia

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22
Q

pleiotrophy

A

diverse effects of one gene or gene pair on several organ systems and functions resulting in multiple phenotypic effects in the body
-all syndromic due to affecting multiple organs
-example is marfan’s syndrome which is a genetic disorder of connective tissue (that develops into a lot of things within the body)

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23
Q

how do we classify genetic disorders

A

by chromosomal abnormalities, by single gene defect, by mitochondrial defect, by multifactorial/polygenic defect and by environmental influences

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24
Q

chromosomal abnormalities

A

will have effects on many parts of the body and most people with unbalanced chromosomes have pre- or post-natal onset growth deficiencies and intellectual disability (for example stunted growth)
-an individual with 2 anomalies is unlikely to have this with exception of sex chromosomes due to them being small

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25
Q

subcentric or submetacentric

A

p and q arms are unequal lengths

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26
Q

metacentric

A

two arms are roughly the same length

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27
Q

acrocentric

A

p arm is so short it is hard to observe
-in humans 13, 14, 15, 21, 22 and Y are this type naturally

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28
Q

telocentric

A

the centromere is located at the terminal end of the chromosomes
-not present within humans

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29
Q

holocentric

A

entire lengthe of the chromosome acts as the centromere
-found within worms and not within humans

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30
Q

mendelian or monogenic inheritance

A

inheritance of conditions is caused by mutation of a single gene
-has 2 laws (segregation and independent assortment)
-most causes are caused by a single gene and are classified by a mode of inheritance

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31
Q

1st law

A

law of segregation
-each parent passes a randomly selected gene copy or allele to the offspring
-the offspring will receive a pair of alleles of that gene for the trait by inheriting sets of homologous chromosomes from the parents

32
Q

2nd law

A

law of independent assortment
-separate genes for separate traits are passed from parents to offspring independently of one another
-biological selection of one gene has nothing to do with the selection of the other gene

33
Q

what are the single gene defects

A

autosomal dominant, autosomal recessive, x-linked dominant, x-linked recessive , y-linked

34
Q

autosomal dominant (AD)

A

you only need one bad gene to show the phenotype
-the bad gene “overpowers” the good gene to cause an abnormal phenotype
-mom or dad can pass it down
-affected people are heterozygous

35
Q

characteristics of AD

A

-vertical transmission (each generation will have it)
-unaffected individuals cannot transmit the disease
-males and females are affected equally
-variable expressivity and penetrance

36
Q

expressivity

A

the severity of the genetic condition for the affected individuals
-how it expressed

37
Q

penetrance

A

frequency of occurrence
-some can manifest later in life
-some could appear to have skipped a generation because they show no sign or symptoms

38
Q

what are the risks of the child within AD

A

50% per pregnancy since only one copy is needed
-can be DD, Dd or dd (anything with D will have it)

39
Q

autosomal recessive

A

two identical copies of the bad gene are needed to show the phenotype
-family members of the same generation are affected but not in other generations
-parents are carrier’s

40
Q

characteristics of AR

A

-two copies are needed
-will result in a homozygous offspring
-carrier parent is required
-horizontal family pattern
-either male or female can transmit the trait
-equal chance in both males and females

41
Q

what are the risks of the child within AR

A

50% chance a carrier, 25% they have it, 25% chance they do not have it per pregnancy
-can be RR (will have it), Rr (carrier), rr (has it)

42
Q

complementary mating

A

different genes but same phenotype
-when they mate offspring is not affected
-for example 2 deaf parents with different genes when mate will have an offspring that is not affected

43
Q

non-complementary mating

A

same gene and same phenotype
-parents are carriers and the offspring will be affected

44
Q

pseudo dominance

A

one recessive gene could result in the expression of the phenotype
-inheritance of a recessive trait mimics and autosomal dominant pattern

45
Q

x-linked recessive

A

females are carriers with no signs of the disease and males will show the phenotype when affected
-since men are hemizygous, they just need a gene error on the X to cause the disease (XY)
-women have two X genes so they are homozygous so need both bad genes

46
Q

characteristics of x-linked recessive

A

-no father to son transmission
-transmission from unaffected female carriers to males is a 50% chance (can give the good or bad)
-all daughters of a male with the trait will become carriers (since they have to pass down the X)
-trait may be transmitted through a series of carrier females (meaning multiple generations of carriers before a phenotype)

47
Q

what are the risks of the child within x-linked recessive

A

-50% unaffected and 50% carrier for females
-50% unaffected and 50% affected for males

48
Q

x-linked dominant

A

females with the abnormal gene on one X chromosome will manifest the disease condition regardless of what is on the other X chromosome
-all you need is 1 bad gene

49
Q

characteristics of x-linked dominant

A

-females if affected will show sings, if males are affected will show signs
-no father to son transmission

50
Q

what are the risks of the child within x-linked dominant

A

-both sons and daughters have a 50% chance of inheriting the condition from the mother
-the son will not be affected and the daughter has a 100% chance of being affected if inherited from the father

51
Q

how to differentiate x-linked recessive from x-linked dominant

A

look at the male offspring of the father
-the son should be unaffected because he will inherit the Y from his father BUT the daughter will show the disorder if affected with dominant

52
Q

y-linked

A

expressed only to male offspring because the father has to pass the Y to the son
-traits encoded on the y are passed directly from father to son
-there is no balancing of the mutant Y gene by X or another Y
-no transmission from daughter from father
-many Y traits are involved in abnormal male sexual development which results in decreased fertility

53
Q

multifactorial

A

traits result from the interplay of multiple environmental factors with multiple genes
-commonly associated with sporadic gene mutations
-example is oculo-auriculo-vertebral (OAV) spectrum disorder

54
Q

polygenic

A

traits or diseases caused by the impact of many different genes
-each gene has a small individual impact on the phenotype
-these traits are quantitative meaning the more genes involved, the more severe the manifestation will be
-example is cleft lip/palate

55
Q

mitochondrial inheritance

A

vertical pattern from mom, all generations will be affected
-during meiosis, the mitochondria are passed from the mother to the occyte (sperms do not contribute cytoplasm during fertilization which is where mitochondria is located)
-no children of fathers with the trait will inherit it
-ALL children of an affected mother will be affected

56
Q

genomic imprinting

A

process in which the phenotype differs depending upon which parent transmits a particular allele or chromosome
-phenotype will vary based on if it’s from mom or dad
-it is the same gene mutation but will result in a different phenotype
-example deletion of chromosome 15 will result in prader willi syndrome (paternal origin) and angelman syndrome (maternal)

57
Q

anticipation

A

due to allelic expansion, severity will get worse
-worsening of symptoms of a genetic disease from one generation to the next

58
Q

allelic expansion

A

the increase in gene size that occurs from the number of trinucleotide base sequences increasing

59
Q

what are examples of allelic expansion and anticipation

A

huntington’s disease (AD pattern)
-gene on tip of chromosome 4p
-normal has 6-37 but in an affected there is 35-121 copies

60
Q

why are men hemizygous? why are female homozygous?

A

men have XY, two different chromosomes
females have XX, two same chromosomes

61
Q

what chromosomes are most common with trisomy?

A

13, 18 and 21 within somatic cells

62
Q

what are the differences between autosomal dominant and autosomal recessive?

A

dominant : only need one bad gene to show the phenotype, if someone gets it they show it
recessive : need two identical to show the phenotype, includes carriers

63
Q

what are the differences between x-linked dominant and x-linked recessive

A

dominant : in females one will show the phenotype and in males one will show the phenotype, if inherited from the father from the daughter they will be affected
recessive : in females need two bad genes and in males only one will show the phenotype, if inherited from the father in a daughter they will be a carrier

64
Q

why are y-linked patterns rare?

A

the y chromosome is the smallest chromosome with a small amount of genes

65
Q

if you see carriers on a pedigree, what does this indicate right away?

A

it is a recessive type of inheritance

66
Q

what is an important characteristic about chromosomal abnormalities?

A

they affect multiple systems

67
Q

what are two common characteristics of chromosomal abnormalities?

A

growth defect and intellectual disability

68
Q

monosomic

A

only one copy of the chromosome is present
-missing one

69
Q

trisomic

A

extra copy of a chromosome
-added one

70
Q

nullisomic

A

no chromosome of that pair is present
-not survivable

71
Q

multifactorial vs. polygenic

A

multifactorial : multiple genes with the environment
polygenic : multiple genes interplaying together

72
Q

example of AD inheritance

A

waardenburg syndrome

73
Q

example of AR inheritance

A

sickle cell anemia

74
Q

example of x-linked recessive inheritance

A

colorblindness or hemophilia

75
Q

example of x-linked dominant inheritance

A

alport’s syndrome

76
Q

example of y-linked inheritance

A

webbed toes

77
Q

example of mitochondrial inheritance

A

leber’s hereditary optic neuropathy

AUDE 5310 (5 decks)

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