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MCM-COM 2018 > Principles Of Genetic Inheritance > Flashcards

Principles Of Genetic Inheritance Flashcards

1
Q

What is the region at the end of a chromosome that is meant for stability

A

Telomere

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2
Q

Contrast Metacentric vs submetacentric vs acrocentric chromosomes

A

Metacentric- have a centromere in the center such that both arms are the same length

Submetecentric- has a centromere in the center such that one arm (p) is slightly shorter than the other (q)

Acrocentric- has a chromosome severely off set from the center such that there is one really short p arm and one really long q arm

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3
Q

_____ is a x-inactivation in which one X chromosome is in activated. It happens early in development and the inactivated X is called a Barr body

A

Lyonization

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4
Q

_____ is a condition in which cells from a patient have different genotypes and karyotypes because the different cells in the body have different arrangement or numbers of chromosomes

A

Mosaicism

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5
Q

Stem cells undergo mitosis, but divide asymmetrically, resulting in one _____ cell and one _______ cell

A

One stem cell, and one daughter cell

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6
Q

What is the big difference between mitosis and meiosis cell division

A

Mitosis results in 2 identical daughter cells that are diploid

Meiosis results in 4 non identical daughter cells that are haploid

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7
Q

What is responsible for producing new combination of genes in meiosis

A

Homologous recombination

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8
Q

Are homologous chromosomes identical

A

NO

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9
Q

_____ changes the sequence of alleles that are passed from generation to generation.

A

Mutations

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10
Q

T/F De novo mutations are solely hereditary

A

False

They can be hereditary or somatic

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11
Q

In meiosis there is one round of DNA replication and two rounds of nuclear division. The first separation is of _____ and the second separation is _______

A
  1. Homologs
  2. Sister chromatids

**Meiosis reduces the genetic material

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12
Q

What are two ways meiosis creates diversity

A
  1. Random segregation of homologs

2. Homologous recombination

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13
Q

Cells with a normal number of chromosomes (haploid gametes or diploid somatic cells) are called what

A

Euploid cells

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14
Q

_____ is the presence of a complete set of extra chromosomes in a cell (often seen in plants)

A

Polyploidy cells

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15
Q

____ are cells with missing or additional individual chromosomes (monosomy, trisomy)

A

Aneuploidy cells

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16
Q

45, XO karotype
-females with short stature, ovarian hypofunction, premature ovarian failure, infertile, CV defects, low hairline on neck, webbed neck, normal intelligence

A

Turners Syndrome

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17
Q

47, XXY karotype

  • limited symptoms
  • varying degree of cognitive/social/behavioral difficulties,
  • primary hypogondaism
  • small testes
  • gyneomastia (male breasts)
  • tall stature
  • infertile
  • can have a variable number of extra chromosomes
A

Klienfelter syndrome

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18
Q

47, XX +21

  • most common
  • increased risk of nondysjunction with maternal age
  • can also occur due to translocation 46, XX (14:21) (q10;10)+21
  • can be mosaic
A

Down Syndrome

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19
Q

47, XX +13
-severe developmental abnormalities
-most perinatal death within 1 week
(13% live births live to 10 y.o.)

A

Patau Syndrome

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20
Q

47, XX +18
-abnormal development
-most perinatal death within 1 year
(10% of live births survive to 10 y.o.)

A

Edwards Syndrome

21
Q

Explain Robertsonian Translocation

A

A robertsonian translocation is when two acrocentric chromosomes q arms combine to make “one”chromosome with the essential genes of two chromosomes. They can possibly pass on a robertsonian translocation and a normal chromosome and the child will result with an extra chromosome (trisomy)

22
Q

What are the acrocentric chromosomes

A

13, 14, 15, 21, 22

23
Q

What is genomic imprints

A

Imprinting is essentially gene silencing through methylation of the 5’ region of a gene or chromatin condensation

24
Q

When do epigenetic imprints reset for somatic and germ cells?

A

Somatic cell epigenetics last a lifetime

Germ cells are reset during meiosis, when imprints are erased and new ones are set

25
Q

What two diseases are a result of genomic imprinting (silencing of one parental chromosome)

A

Prayer-willi
And
Angelmans syndrome

26
Q

What are diseases caused by nondisjunction

A 
Klienfelter 
Down syndrome
Patau syndrome
Edwards syndrome 
Turner syndrome
27
Q

Deletion of a region on chromosome 15 of the parental chromosome causes ____

A

Prader-Willi syndrome

-causes short stature, hypotonia, small hands/feet, obesity, mild - moderate intellectual disability

28
Q

Deletion of region of chromosome 15 of the maternal chromosome causes ______

A

Angelmans Syndrome

-severe intellectual disability, seizures, ataxic gait

29
Q

What is related to both non-disjunction and genomic imprinting? Two chromosomes are inherited from the same parent and they have parent-specific imprinting meaning only two chromosomes are expressed but they are both from the same parent

A

Uniparental disomy

Can cause both Prader Willi and angelmans because only one parent is expressing chromosome 15

30
Q

Law of segregation vs law of independent assortment

A

Segregation says you can either be tall or short (1 dominant gene for that trait)

IA- says you can be tall and wrinkly or tall and non wrinkly (different genes for different phenotypes are independently assorted )

31
Q

What is an example of someone with a distinct genotype on exhibiting one single phenotype

A

Cystic fibrosis

32
Q

What is an example of individuals with the same genotype having multiple different phenotypes (pleiotropy)

A

PKU

33
Q

What is pleiotropy

A

When one gene influences two or more seemingly unrelated phenotypic traits

34
Q

What is the first diagnosed person in a pedigree called

A

Proband (propositus):

Denoted by an arrow in a pedigree

35
Q

Percent chance of autosomal dominant and recessive, and x linked recessive and x linked dominant appearing in a generation?

A

Dominant- 50% - postaxial polydactlyl
Recessive- 25% -albinism

X-linked recessive - duchenne muscular dystrophy

X linked -dominant (non carriers) - hypophosphatemia [causes rickets]

36
Q

What is consanguinity

A

First cousin mating

37
Q

The frequency a gene manifests itself is _____

A

Penetrance

38
Q

If someone with a mutation and do not develop the features of the disorder then the diseases is said to have ____

A

Reduced penetrance

-ex: retinoblastoma (autosomal dominant with 90% P)

39
Q

___ is the range of phenotypes that can vary between individuals with a specific genotype

A

Variable expressivity

Ex: neurofibromatosis
-neurofibromas cause spots that range in size and color and number

40
Q

A single disorder, trait, or pattern of traits caused by mutation in genes at different chromosomal loci/genes.

Same phenotype from mutation on two different genes

A

Locus heterogeneity

-ex:
Osteogenesis imperfecta
*brittle bones and mutations in collagen genes (c 7 and 17)

41
Q

When would you use the multiplication rule or addition rule of probability

A

Multiplication:
-probability of a given outcome in multiple trials
Ex: probability of having 3 girls
1/2 x 1/2 x 1/2 = 1/8

Addition:
-probability of either one or another outcome
Ex: probability of having 3 girls or three boys ?
1/8 + 1/8 = 2/8 = 1/4

42
Q

You can used Hardy Weinberg principle when you are given the incidence of a disease and you want to find population frequency or allele frequency

A

P + q = 1

43
Q

what has its own circular DNA

  • contains no introns
  • inherited solely by mother
  • mutation rate is 10x that of nDNA bc lack of DNA repair mechanisms and damage from free radicals released during OxPhos
A

Mitochondrial DNA (mtDNA)

  • encodes rRNA and tRNA and 13 polypeptides used in OxPhos
  • transcription takes place in the mitochondria independent of the nucleus
44
Q

Mitochondrial inheritance

A

*passed through the mother

**IF mother is mutated/infected then every child gets infected/mutated mitochondria

*but the degree of mutation is different for each infected individual therefore some may lead to mitochondrial disease and some may not (this is because mitochondria are distributed unequally)

45
Q

Traits in which variations are thought to be caused by combined effect s of multiple genes

A

Polygenic

46
Q

When environmental factors cause variation in the trait the term _______ is used

A

Multifactorial

47
Q

Multifactorial inheritance follows what pattern?

If they do not follow the normal pattern then there is an underlying _____

A

Follow a bell shaped distribution in populations

-underlying liability distribution. Some may have a threshold of liability where the disease is either present or absent.

***A result of polygenic traits. (Simultaneous influence of multiple genetic and environment factors)

48
Q

What type of inheritance is exhibited by muscular hypertrophy?

A

Multifactorial inheritance

*men need less risk genes vs females

(The least affected sex has a higher risk threshold and transmits the condition more often to the more affected sex)

49
Q

Explain the Recurrence Risks of multifactorial inheritance

**varies more greatly than single-gene diseases bc it is population based

A
  • the recurrence risk is higher if more than one family member is affected
  • if the expression is severe in the proband, the reccurence risk is higher
  • the recurrence risk if higher if the proband is the less affected sex
  • the recurrence risk for the disease usually decreases rapidly in more remotely related relatives

MCM-COM 2018 (14 decks)

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