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MCM-1 > Test 2 > Flashcards

Test 2 Flashcards

1
Q

What is a somatic cell?

A

cell with two copies of chromosome. Not gametes

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2
Q

What is an autosome?

A

chromosome that is not a sex chr.

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3
Q

What is an allosome?

A

sex chr. (X/Y)

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4
Q

What is a homologous chr?

A

consists of 2 chr in a diploid, where 1 is maternal and 1 is paternal

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5
Q

What is allelic heterogeneity?

A

alleles of different origin

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6
Q

What is locus heterogeneity?

A

locus that consist of different origin.

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7
Q

What is a polymorphism?

A

A natural DNA variation that accumulate within an allele.

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8
Q

What is hemizygous?

A

only 1 copy of chr is present in a diploid. Diploid loses 1 copy of chr.

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9
Q

What is pleiotropism?

A

effect where 1 gene mutation can lead to 2+ phenotypic genetic mutations.

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10
Q

What is an example of pleitropism?

A

occulodentodigital dysplasia

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11
Q

How do you describe incomplete dominance?

A

both allele types are expressed leading to phenotypic expression of both the dominant and recessive expression

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12
Q

What is codominance?

A

this occurs when both the dominant and recessive alleles are expressed.

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13
Q

what does a box represent on a pedigree?

A

box=male

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14
Q

what does a circle signify on the pedigree?

A

circle = woman

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15
Q

An autosommal dominant gene will express how?

A
  1. equal m/f affect

2. carried through all generations

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16
Q

What is common of autosommal recessive gene expression?

A
  1. equal m/f affected

2. tendency to skip generations

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17
Q

What is common of X-linked recessive?

A
  1. X-linked= no m-m transfer
  2. F–>M causes affected M always
  3. tendency to skip generation
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18
Q

What is common of X-linked dominant?

A
  1. M–>M not seen
  2. present in all generation
  3. all women are affected
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19
Q

An affected male produces a son with no genotypic defect, but all 4 daughters contain the defect, what is most likely the inheritance pattern? assume mother is unaffected.

A

X-linked dominant.

- X-linked recessive would occur if not ALL the daughters were affected.

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20
Q

What is haploinsufficiency?

A
  1. a giploid loses 1 gene, and the phenotype is based on only remaining gene. Can be seen with unaffected parents, but the defect is inherited down the pedigree.
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21
Q

What is penetrance?

A

the frequency to which an allele is expressed in a phenotype.

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22
Q

An individual is told they are at a 75% chance of developing cancer due to a mutation of RB gene. What is the pentetrance of that gene?

A

penetrance is 75%. If 100 people had a mutated RB gene then 75 would be at risk for cancer development.

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23
Q

What is incomplete penetrance?

A

This occurs when individuals carry the allele that normally causes disease but have no presentation of the disease and appear fine.

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24
Q

How does X-inactivation occur?

A
  1. somatic cells are methylated forming heterochromatin, which begins at blastocyst formation.
  2. leads to formation of barr bodies
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25
Q

What is random X-inactivation?

A

equal probability of either paternal or maternal allele silencing

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26
Q

What is fixed X-inactivation?

A

this occurs when an allele is silenced and that same allele remains silenced throughout downstream generations.

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27
Q

What is incomplete X-inactivation?

A
  • some regions of the chromosome are not completely inactivated and this leads to presentation similar to X-linked recessive.
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28
Q

What are the main consequences of enzyme deficiency?

A
  1. substrate accumulation (could be toxic to cells)
  2. reduced product formed(multiple effects)
  3. inability to regulate toxins or inability to control zymogens
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29
Q

What is a germline mutation?

A

this mutation could become present in every cell of the offspring, as the mutation affects the gamete producing genes.

30
Q

What are the most likely outcomes of a germline mutation?

A
  1. reduced fertility

2. high mortality

31
Q

What is unique about trinucleotide repeat mutations?

A
  1. the symptoms of the mutations will continue to be seen more and more early in life as the mutation progresses to further generations.
32
Q

A trinucleotide repeat mutation, adding CGG is commonly referred to as____?

A

fragile X syndrome

33
Q

What leads to Fragile X syndrome?

A

trinucleotide repeat mutation of CGG

34
Q

A trinucleotide repeat mutation, adding CTG leads to what disease?

A

Myotonic dystrophy

35
Q

Myotonic dystrophy is a result of what?

A

CTG trinucleotide repeat mutation

36
Q

A trinucleotide repeat mutation of CAG leads to what disease?

A

Huntington’s disease

37
Q

Huntington’s disease is characterised by what DNA sequencing?

A

trinucleotide repeat of CAG

38
Q

What process occurs that produces trinucleotide repeat mutations?

A
  1. replicate DNA strand detaches and loops form at CG rich regions
  2. the looped region is then re-synthesized
  3. the CG rich loop then unloops and rebinds to DNA strand leading to multiple repeats.
39
Q

What is unique of mitochondrial genes?

A
  1. majority code for mRNA/tRNA formation

2. 13 are for respiratory chain.

40
Q

How would mitochondrial mutations be expressed on a pedigree?

A
  1. all offspring from an affected mother would be affected.
41
Q

Trisomy are a very common example of what type of mutation?

A
  1. aneuploidy is the result

but mosaicism

42
Q

What is mosaicism?

A
  1. presence of 2 different genotypes in a person developed from one zygote.
  2. can be somatic (trisomy 21) or gonadal
43
Q

What is a chimera?

A

person who contains different cell types that were produced in separate zygotes.
- seen in twins where one zygote engulfs the other.

44
Q

How does a ring chromosome form?

A
  1. the ends of chromosome are deleted and the “new ends” link up to form a ring, that can’t be replicated/
45
Q

What is a common disease seen with ring chromosomes?

A

epilepsy

46
Q

What is paracentric inversion?

A
  1. the gene sequences on a chromosome invert but do not cross the kinetocore
47
Q

What is pericentric inversion?

A

the gene sequences of a chromosome invert by flipping over the kinetocore.

48
Q

What is the best explanation of balanced chromosome translocation?

A
  1. equal portions of material are exchanged among the p and q arms
49
Q

What is unbalanced translocation?

A

uneven material exchange among the p and q arms

50
Q

What is the Robertsonian translocation?

A
  1. material between 2 normal chr is switched.
  2. produces one Xlong chr, and 1 Xshort chr.
  3. the Xshort is lost–> producing person with 45 chromosomes.
51
Q

What are common chromosomes that undergo robertsonian translocations?

A

13, 14, 15, 21, 22

52
Q

What is uniparental disomy?

A

occurs when either Mother/Father donate both chromosome copies to offspring.

53
Q

What are the two methods that can cause disomy?

A
  1. heterodisomy: the pair is inherited from one parent.

2. isodisomy: 1 chromosome is inherited form 1 parent, and Meiosis II error replicates the chromosome.

54
Q

What is the significance of uniparental disomy?

A
  1. leads to genomic imprinting.

2. isodisomy more commonly leads to expression of recessive genes.

55
Q

What is a linkage disequilibrium?

A

a single nucleotide polymorphism that is inherited due to its close proximity to a diseased gene

56
Q

What are restriction fragment length polymorphisms?

A
  1. regions on DNA that endonuclease cleave at. produce variety of DNA strand lengths.
57
Q

How can restriction fragment length polymorphisms be helpful?

A
  1. compare a normal person to diseased person and look for differences. altered chain lengths correspond to altered # of RFLP.
58
Q

What analysis methdos are used to analyze the different lengths of the RFLP?

A

Southern blot= DNA
Northern blot=RNA
western blot= protein

59
Q

What is a microsatellite repeat?

A
  1. polymorphism repeat unique to individuals. often called short tandem repeats.
  2. used for forensic testing.
  3. (2-6) bp long
60
Q

What is a minisatellite repeat?

A

also short tandem repeat used for forensic analysis.

2. 70bp long

61
Q

What are common variable number tandem repeats?

A
  1. microsatellites

2. minisatellites.

62
Q

What are copy number variatiants?

A
  1. these consist of varying lengths of repeating nucleotide sequences.
  2. lengths vary among individuals
  3. commonly seen as trinucleotide repeat sequences–> disease
63
Q

What is the difference between linked and unlinked genes?

A
  1. linked: close proximity generally inherited together and do not undergo recombination
  2. unlinked: generally large separation and likely to undergo recombination before inheritance together.
64
Q

What does the hardy weinberg rule state?

A

that alleles will remain the same in a large population with natural selection, random mating, and no mutation or genetic drift occurring.

65
Q

What is the founder effect?

A

occurs when small group of individuals leave a large group, establish their own group and have an INCREASE expression of recessive genotypes.

66
Q

What is natural selection?

A

The increased allelic frequency seen in animals that survive various environmental challenges.

67
Q

What type of disease is more common in natural selection events?

A

dominant types

68
Q

What is genetic drift?

A

a change in the population’s allele frequency resulting from a random variation in the distribution of alleles from one generation to the next

69
Q

What type of populations are affected teh most with genetic drift? The least?

A
  1. most: small population

2. least: large population.

70
Q

What type of laboratory testing can be used to locate SNP?

A
  1. allele-specific oligonucleotide probe.
    - nucleotide sequence base pairs with complementary strands that produces a hybridized DNA strand based on the SNP you are looking for.
  2. The probe complements the strand you want to identify.

MCM-1 (8 decks)

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