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MCM Test 2 > Principles of Genetic Inheritance > Flashcards

Principles of Genetic Inheritance Flashcards

1
Q

Gene

A

segments of DNA on a chromosome

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2
Q

What is a chromatid?

A

One of two identical copies of a chromosome

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3
Q

two chromatids are connected at the _____ to create a _______

A

Two chromatids are connected at the centromere to create a chromosome

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4
Q

Human somatic cells

A

diploid (2n)
23 pairs of chromosomes= 46 chromosomes
one from mom and one from dad

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5
Q

Gametes

A

haploid

23 chromosomes

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6
Q

Autosomes

A

chromosomes that are not sex chromosomes

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7
Q

What is the position of a metacentric centromere?

A

the q and p arms are both of equal lengeth

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8
Q

What is the position of a submetcentric centromere

A

P arm is smaller than q arm

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9
Q

What is the position of a acrocentric centromere

A

P arm is v small (almost cant see it), making the chromosome at the end. thus, little genetic info is there

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10
Q

homologous chromosomes

A

1 pair of chromosomes (1 from mom and 1 from dad)

Homologous chromosomes have variations of the same gene in the same location

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11
Q

Banding in a chromosome

A
  1. ARMS: p and q
  2. Arms are then divided into TWO REGIONS (1,2)
  3. Band
  4. Subband
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12
Q

Name the location of the band

17q11.2

A 
17th chromosome
Arm= q
Region= 1
Band=1
Subband=2
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13
Q

What are used to indicate bands?

A

Staining techniques

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14
Q

Karyotype

A

the entire set of a patients chromosomes

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15
Q

How are chromosomes in a karyotype presented?

A
  1. a single condensed chromosome

2. Duplicated chromosome

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16
Q

What is Lyonization

A

Lyonization is X-inactivation. Females inherit two X chromosomes. Thus, one of them is RANDOMLY condensed into a Barr body because too much gene expression is mad.

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17
Q

Can Barr bodies be passed down to offspring?

A

Yes, Barr bodies can be passed down to offspring.

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18
Q

Why do females not always inherit a genetic disorder that is present on one of their x chromosomes?

A

it can be on a barr body

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19
Q

p53 binds to

A

E6

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20
Q

E7 binds to _____

A

Rb and kick off EF2, to keep it dividing

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21
Q

lyonization can lead to ______

A

mociacism

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22
Q

What is mosaicism?

A

Mosaicism is a condition where the cells of a individual have different genotypes or karyotype. The proportion or normal cells to abnormal determines the severity of the disease

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23
Q

Example of mosaicism

A

person may have 46 chromosomes in 1 cell but 47 in another

Down syndrome–> there is a trisomy of chromosome 21 in a majority of cells

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24
Q

mosaicism in Klinefelters

A

Mosaicism is a condition where the cells of 1 person can have different genotypes

For example a person with Klinefelters will have some chromosomes with 46XY but a majority with 47XXY

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25
Q

mosaicism in Turners Syndrom

A

Mosaicism is a condition where the cells of 1 person can have a different genotype

For example, in Turner’s syndrome, 1 person can have some cells with 46XX and some have 45XO

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26
Q

2 ways cell division can occur

A

mitosis and meiosis

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27
Q

mitosis

A

Cell divides and forms 2 clones of itself

goes from diploid(2n)–> diploid(2n)

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28
Q

Meiosis

A

Cell divides and produces 4 haploid cells called gametes (sperm and egg) that are NOT clones of one another. they have half the amount of DNA.

2n–>n

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29
Q

Mitosis has 2 phases. What happens?

A
  1. Interphase–> DNA replication occurs to create 2 chromatins attached at a centromere.
  2. Cell division–> will produce 2 identical daughter cells
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30
Q

Mitosis produces what?

A

2 identical diploid cells

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31
Q

Meiosis produces

A

4 non-identical haploid (n) cells

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32
Q

2n means what

A

2 copies of each chromosome

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33
Q

In meiosis, is genetic material kept the same or reduced?

A

reduced.

We go from a diploid–> haploid

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34
Q

Meiosis consists of ___ round of DNA replication and ____ round(s) of division

A

1 round of DNA replication

2 rounds of division (1 to separate the homologs and 1 to separate sister chromatids)

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35
Q

how does meiosis produce 4 non-identical haploid cells?

A
  1. homologous recombination–> crossing over occurs between sister chromatids of homologs
  2. Random segregation of homologs
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36
Q

Euploidy

A

a cell with a normal amount of chromosomes (n in haploid and 2n in diploid)

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37
Q

Polyploidy

A

3n, 4n, 5n

When there are [complete sets of extra chromosomes]

3n= 3 copies of each chromsome

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38
Q

Aneuploidy

A

individuals chromosomes are missing or added

2n+1
2n-1

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39
Q

Having 45 chromosomes is aneuploidy/polyploidy

A

aneuploidy–> individual chromosomes are missing or added

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40
Q

2n+1 results in a

A

Trisomy

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41
Q

What is worse in aneuploidy: having an extra or having one missing?

A

having a deleted one.

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42
Q

How do we end up in errors in DNA chromosome counting?

A

Non-disjunction–> the failure of homologous chromosomes to divide appropriately or sister chromatids to divide appropriately

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43
Q

When does the risk of non-disjunction increase?

A

after 35.

It rapidly accelerates after 40.

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44
Q

69 chromosomes: aneuploidy or polyploidy?

A

polyploidy because it is a multiple of 23 (3n)

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45
Q

What is translocation?

A

when non-homologous chromosomes exchange genetic information

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46
Q

Recipricol translocation

A

when non-homologous chromosomes exchange genetic information

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47
Q

Robertsonian translocation

A

when the long arms of two acrocentric chromosomes combine and the short arm is lost

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48
Q

Turner syndrome karyotype

A

45XO

People with turner syndrome are missing an X chromosome. Thus, can only be females.

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49
Q

Turner syndrom sx

A

Females have normal intelligence, but developmental delays.

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50
Q

Klinefelters

A

47XXY

Males have 1 extra X chromosome, resulting in 47 chromosomes. As the number of X’s increase, the more severe.

51
Q

Klinefelters sx

A

Often times limited symptoms. But they could have varying degrees of [cognitive, social, behavorial and learning difficulties]

Main sx: hypogonadism (low T), small or undescended testes,
gynocomastia–> enlarged breasts
Tall

52
Q

Do trisomy 13, 18 and 21 occur on sex chromosomes?

A

No. they are AUTOSOMAL trisomies and do not occur on sex chromosomes.

53
Q

Down syndome

A

Trisomy 21
[47XX +21]

  • There are 3 copies of chromosome 21.
  • Most common trisomy
  • As mother gets older, there is an increased risk
54
Q

Patau syndrome

A

Trisomy 13
[47XX +13]

Patau syndrome results in severe developmental abnormalities and most die within 1 week (13% survive up to 10 yo)

55
Q

Edwards syndrome

A

Trisomy 18
[47XX +18]

Abnormal development and most die within 1 week

56
Q

Genomic imprinting is independent/dependent to mendelian inheritance

A

independent

57
Q

Usually, when you inherit a gene, both copies are ____

A

on

58
Q

In gene imprinting, instead of both copies being turned on, then?

A

in genomic imprinting, instead of both inherited being turned on, one is turned off through silencing

which one that is turned off is pre-determined which parent you inherited it from

59
Q

how does gene silencing occr

A
  1. methylation of 5’ end

2. chromatin condensation

60
Q

____ human genes are imprinted

A

100

61
Q

___ genes are paternally imprinted, maternally expressed

A

30 are maternally expressed

62
Q

____ genes are maternally imprinted, paternally expressed

A

70 are paternally expressed

63
Q

In a _____ cell, imprints remain throughout life span

A

somatic

64
Q

In ____ cells, imprints are reset at each generation.

A

Germ cells.

During meiosis, they’re erased and new ones are sets

65
Q

Depending on which parent you get the gene from, it determines the phenotype you express when one of the genes is methylated.

A

a

66
Q

Say you have a deletion on chromosome 15. If the deletion is on the paternal chromosome–>

If the deletion is on the maternal chromsome–>

If you inherited it from your mom–>

A

Deletion is on the paternal chromosome–> Prader Willie

Deletion is on the maternal chrosome–> Angelman

67
Q

The phenotype of Angelman and Prader Willie depend on what?

A

If the chromosomal deletion is on the paternal or maternal chromosome 15

68
Q

Prader Willie

A

short, fat, mild to moderate intellectual disability

dark vader

69
Q

Angelman syndrome

A

severe intellectual disability

70
Q

Uniparental disomy

A

occurs when 2 copies of a chromosome come from 1 parent; instead of 1 from mom and 1 from dad

71
Q

Law of segregation

A

gametes receive 1 copy of a gene

72
Q

law of independent assortment

A

genes are inherited independently of one another

73
Q

Monogenic inheritance

A

when a trait is determined by the expression of a single gene or allele

74
Q

Can people with different genotypes have 1 phenotype?

A

Yes

Ex. Cystic fibrosis

75
Q

Can people with the same genotype have different phenotypes?

A

Yes

Ex. PKU

76
Q

Pleiotropy

A

1 genotype–> different phenotypes

Ex. PKU

77
Q

proband

A

red arrow that indicates the first dx person in the pediagree

78
Q

In autosomal traits, males and females are ____ affected

A

in autosomal traits, males and females are equally affected.

thus, they can pass it on to a M or F

79
Q

Autosomal dominant trait

A
  • Only 1 allele is needed to express
  • thus, one of your parents must have the trait
  • unaffected offspring do not pass down the trait
80
Q

In autosomal dominant, if you have kids with someone who is unaffected, what is the reccurent risk

A

50%

81
Q

Autosomal recessive

A
  • need 2 alleles
  • affected individuals tend to have normal parents; skips generations
  • thus, clusters around siblings
  • higher in those who share genes (consanguinity-first cousin mating)
82
Q

X-linked traits are more common in

A

men, because they only need one copy

83
Q

X-linked dominant
Common?
father affected?
mother affected?

A

RARE DISORDERS!!!
If father is affected–> will pass down to all daughters but not sons

If mother is affected–> will pass down to 50% of daughters and 50% sons.

84
Q

Are there carriers in X-linked dominant?

A

No. It is a dominant trait so you either have it or you dont

85
Q

Ex of X-linked dominant dx

A
  1. Hypophosphotemia–> low phosphorus in blood because kidney cannot reabsorb phosphate.
    difficult to reabsorb Ca2+, leading to softening of the bone –> RICKETS!
    Vitamin D metabolism is abnormal
86
Q

Penetrance

A

Frequency that a gene is expressed

87
Q

Rb has a penetrance of 90%. What does this mean?

A

90% of people who have this gene will show the phenotype

88
Q

Variable expressivity

A

A person with gene can show variable expressions of the phenotype.

89
Q

Locus heterogenuity

A

Mutations at different sites can cause the same disorder

90
Q

Ex. of locus heterogeneity

A

Osteogenensis imperfecta can be caused by a mutation at chromosome 17 or 7

91
Q

What rule is used when you want to figure out the probability of an outcome of successive trials?

A

multiplication rule

92
Q

Ex. of multiplication rule

A

What is the probability of having 3 boys?

93
Q

What is the rule that you use when you want to figure out the probability of one outcome OR another?

A

addition rule

94
Q

Genotype frequency

A

the frequency of genotypes in a population

95
Q

Gene frequency is also called

A

allele frequency

96
Q

What is gene frequency

A

the frequency of each allele in a population

Frequency of
M and m

97
Q

HW equation tells us the relationship between

A
  1. gene frequency

2. genotype frequency

98
Q

HW eqn

A

p+q=1

p2+2pq+q2=1

99
Q

Cystic fibrosis is a ______________ ___________ disoder

A

autosomal recessive

you can only get it if you have [aa]

100
Q

Cosanguineous (1st cousin matings) are more likely to produce kids with _______________ disorders

A

autosomal recessive

101
Q

the mortality rate amongst children from 1st cousin mating is _____ higher

A

9%

102
Q

Each person has ______ recessive mutations that are lethal to offspring

A

1-5

103
Q

mT DNA

A

double stranded
circular
no introns
inherited directly from mother

104
Q

in mT DNA, an infected mom will pass down the disorder to ______.

What about an infected dad?

A

mom–> all her kids

infected dad–> none

105
Q

in mTDNA, mutations are ____ higher than in regular DNA. Why

A

10x higher

mT DNA does not have repair mechanisms and can be damaged by free radicals

106
Q

Mitochondrial disorders

A
  1. LHON- lebers hereditary optic neuropathy

2. MELAS–> mitochondrial encephalopathy, lactic acidosis and stroke like episodes

107
Q

LHON

A

lebers heriditary optic neuropathy

mitochondrial disorder

108
Q

MELAS

A

mitochondrial encephalopathy, lactic acidosis and stroke like episodes

mitochondrial disorder

109
Q

polygenic traits

A

polygenic traits are those that are determined by multiple genes.

Interaction of mulitple genes result in 1 trait

110
Q

multifactorial inheritance

A

multifactorial inheritance is determined by the additive effects of many genes at different loci and also the invironment

shows familial tendency

111
Q

does multifactorial inheritance show familial tendency

A

yes?

112
Q

mulitfactorial inheritance follows what kind of curve?

A

bell shaped

113
Q

before a multifactorial inherited gene can be expressed, what must happen?

A

the person must pass the threshold of liability. the threshold of liability are all of the factors that can influence the dz.

114
Q

below threshold

A

person is normal

115
Q

above threshold

A

person is not norla.

116
Q

If a dz is more common in males, would the males have a higher or lower threshold?

A

lower. they are more predisposed, thus, need less risk for the gene to be displayed

117
Q

the least/most affected sex will have a higher risk threshold

A

least

118
Q

the least affected sex will transmit the dz more often to …

A

a person of higher risk

119
Q

is the recurrent risk stable?

A

no, it changes from popoulation to population because gene frequencies and enironment changes

120
Q

recurrence is higher/lower when:

more than one member of family is affected

A

higher

121
Q

recurrence is higher/lower when:

expression is more severe

A

higher

122
Q

recurrence is higher/lower when:

the proband is of the less commonly affected sex

A

higher

123
Q

reccurent risk increases/decreases in remotely related relatives

A

decrreases

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