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Semester 5 FSNM Exam 9 > Genetics 3 > Flashcards

Genetics 3 Flashcards

1
Q

Meiosis happens when

A

All the time

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2
Q

What is happening with meiosis

A

Somatic cell division where a cell divides and both of the daughter cells are genetically identical
Accomplished by separating the identical halves of the chromosomes

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3
Q

Mitosis - is what

A

Pulls apart the chromatids - makes two identical cells from one mother cell
No genetic info is lost

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4
Q

Meiosis separates what

A

the homologous chromosomes - so we have reduced the genetic information per cell

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5
Q

Meiosis - time period when the maternal and paternal copes are in close proximity

A

Synapsis
There can be homologous recombination and bits from maternal can be switched to the paternal and you get new combinations

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6
Q

What are the steps in meiosis 1

A 
Prohase/Metaphase
Synapsis
Crossover
Anaphase (disjunction)
Reduction division
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7
Q

After synapsis, what happens

A

Crossover - chance for error

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8
Q

After crossover, what happens

A

Anaphase disjunction - the chromosomes are separated and disjunction is when the spindle separates the homologous chromosomes and if this does not happen it is a non disjunction

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9
Q

After Anaphase/Disjunction - what happens

A

Reduction - reduced diploid and now we have haploid cells - equational division gives us 4 different haploid cells which is the major source of human variation

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10
Q

Chromosomal aberrations affect what

A

The expression of many genes
There are a lot of chromosomal aberrations but only some are compatible with life so we only see some out of the many that occur

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11
Q

Chromosomal aberrations can arise from

A

Unequal distribution of genetic material during meiosis I and II
Chromosome breaks that heal in an aberrant (incorrect) way

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12
Q

Chromosomal aberrations span more than just one system

A

You lose a bit of a chromosome and there are a lot of genes in there so this is why aberrations have a lot of different phenotypes

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13
Q

Chromosomal aberrations - How often do they occur

A

Frequently - in about 1 in 12 conceptions there is a detectable one

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14
Q

What is the most common cause of spontaneous aberrations

A

Chromosomal aberrations - 50%

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15
Q

Chromosomal aberrations - frequency at birth

A

1 in 150 live births have a detectable chromosomal aberration

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16
Q

Chromosomal aberrations - Deletion or duplication

A

Reduces gene dosage or increases it for a certain region

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17
Q

Chromosmal aberrations - Inversions

A

A bit breaks off and is being inserted back in opposite direction

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18
Q

Chromosomal aberrations - Insertion

A

Breaks off and is being inserted in center of another

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19
Q

Chromosomal aberrations - Translocation

A

Bits of chromosome of the end are breaking off and being exchanged with the end of another

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20
Q

Chromosomal aberrations - which can you usually live pretty well with

A

Insertions
Translocations
Inversions
No change in the amount of genetic material per cell - usually asymptomatic until next generation

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21
Q

Chromosomal aberrations - which are more serious

A

Deletion
Duplication
Genes that regulate development (haploinsufficiency) - Losing the second copy cannot be compensated for and have a third cannot either

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22
Q

Chromosome breaks - how do these happen

A

Common damage, both spontaneous and induced by environment

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23
Q

Chromosome breaks - how bad?

A

Are lethal to the cell if not repaired
Very important to repair even if repair is not done correctly though so can lead to translocation and possible abnormalities
Aberrant repair is rare but causes chromosomal abnormalities

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24
Q

Aberration - Deletion and Duplication - which is worse

A

Deletion of genetic material has more severe consequences than duplication

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25
Q

Aberration - deletion of a part of chromosome 5 results in

A

Cri du chat syndrome

Microcephaly, mental retardation, heart defect

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26
Q

Aberration - Translocations and Inversions

A

No genetic material lost, just rearranged (balanced alteration)

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27
Q

Aberration - Translocations and Inversions - symptoms

A

Mostly asymptomatic in the person who carries them but problems arise in the next generation when doing meiosis because you can get an imbalance

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28
Q

Aneuploidy - is what

A

We have extra or missing chromosomes

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29
Q

Aneuploidy - Arises from what

A

An error in meirosis (non disjunction)
One daughter cell receives both homologous chromosomes and the other receives none
Fertilization involving these gametes will lead to trisomy or monosomy

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30
Q

Aneuploidy - consequences

A

Very severe
Monosomy is lethal (except for X chrom)
Trisomy only observed in chrom 13, 18, 21 and the sex chromosomes

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31
Q

Trisomy 21 causes

A

Down syndrome and is the most commonly observed chromosomal aberration
NOT RARE

32
Q

Sex chromosome Aneuploidies

A 
Turner syndrome (45, X)
Klinefelter syndrome (47, XXY)
Klinefelter syndrome (48, XXXY)
33
Q

Sex chromosome Aneuploidies - Turner syndrome

A

1 in 3000 F births
Sterility, short stature and other physical characteristics are observed
No mental retardation

34
Q

Sex chromosome Aneuploidies - Klinefelter syndrome 47 XXY

A

1 in 1000 M births
NOT RARE
Sterility, development of breasts, high pitched voice

35
Q

Clinical cytogenetics - can detect what

A

chromosomal aberrations

36
Q

Clinical cytogenetics - indicated under what circumstances

A 
Problems of early growth/development
Stillbirth/neonatal death
Fertility problems
Pregnancy with advanced maternal age
Also sometimes CA, family hx
37
Q

Inheritance of a chromosomal defect -

A

Usually dominant, new mutations
Multiple abnormalities in affected children - often with developmental delay
Spontaneous abortions/multiple miscarriages
Infertility

38
Q

Pedigree of a chromosomal defect - how can a person pass on a chromosomal aberration without being sick

A

Balanced alteration will perform a normal life but they will run into issues when they reproduce

39
Q

Karyotype of a cancer cell line

A

3 or 4 or more copies of a certain chromosome because these do not stop dividing even if a genome goes wrong

40
Q

Epigenetics is the study of

A

Heritable changes that do not involve changes in DNA sequence

41
Q

Epigenetics - how do they work

A

Changes silence or activate chromosomal regions by DNA methylation/demethylation OR Histone acetylation/deacetylation

42
Q

Epigenetics influences

A

Tee expression without changing the genomic sequence

43
Q

Epigenetics - DNA methylation - methylation of DNA occurs where

A

On cytosine residues in CpG repeats

44
Q

Epigenetics - DNA methylation - CpG repeats are found in

A

CpG islands - non methylated

Repetitive DNA - methylated

45
Q

Epigenetics - DNA methylation - about 70% of the CpGs are

A

methylated (silenced)

46
Q

Epigenetics - Histone acetylation - Acetylation of histones occurs wher

A

on the tail region

47
Q

Epigenetics - Histone acetylation - acetylation of the histone changes what

A

the charge of the histone
Acetyl group = neg charge
Histones = need to be pos charged

48
Q

Epigenetics - Histone acetylation - acetylation of histones does what

A

decreased the affinity to DNA
so it makes it stick less well to the DNA
And you are facilitating transcription of that region

49
Q

Epigenetics - Histone acetylation - Deacetylated histones bind

A

more tightly to DNA

50
Q

Epigenetics - Histone acetylation - Histone deacetylation

A

silences chromosomal regions

Increases their binding affinity and silences transcription

51
Q

Epigenetics - Histone acetylation - In addition to acetylation, there are other histone modifications - what are they

A

Methylation
Phosphorylation
Ubiquitination
These modifications might constitute a “histone” code imposed on the DNA

52
Q

Imprinting - what is it

A

Imprinting silences chromosomal regions by DNA methylation and histone deacetylation

53
Q

Imprinting - reversible or stable?

A

Can be reversed but in general is stable through somatic cell division

54
Q

Imprinting occurs -

A

During gemetogenesis to mark the paternal origin of chromosome
During development to permanently change the gene expression pattern of a cell line

55
Q

Imprinting - is also the mechanism by which

A

X chromosome inactivation occurs

56
Q

X chromosome inactivation - mediated by

A

Transcripts of the XIST gene

57
Q

X chromosome inactivation - DNA is ____ and histones ____

A

DNA is methylated

Histones deacetylated

58
Q

Imprinting related diseases - imprinting does what

A

silences a maternal or parental allele

59
Q

If imprinting is incorrect, what happens

A

Gene dosage problems may arise where you have too much or too little genes in a cell

60
Q

Imprinting occurs when

A

during development

61
Q

Imprinting - explains what

A

Parent of origin effect of some mutations

Detrimental effects of uniparental disomy

62
Q

What are two examples of parent of origin effects and issues with imprinting

A

Prader willi syndrome
Angelman Syndrome
Beckwith Wiedemann Syndrome

63
Q

Prader Willi Syndrome - Caused by

A

Deletion on paternal copy of Ch 15 or maternal uniparental disomy

64
Q

Prader Willi Syndrome - Rare or Common

A

Rare

65
Q

Prader Willi Syndrome - s/s

A

Excessive food seeking bx
Hypogonadism
Mental retardation
Small hands, feet, facial features, hypotonia,

66
Q

Angelman syndrome - caused by

A

Deletion on maternal copy of Ch 15 or paternal uniparental disomy

67
Q

Angelman Syndrome - rare or common

A

Rare

68
Q

Angelman syndrome - characterized by what

A

Unusual facial features (large mandible, open mouth)
Excessive laughter
Seizures, mvmnt and gait disorder
Severe mental retardation, absence of speech

69
Q

Beckwith Wiedemann Syndrome - can be caused by what

A

Parternal uniparental disomy

70
Q

Beckwith Wiedemann Syndrome - rare or common

A

Rare

71
Q

Beckwith Wiedemann Syndrome - Characterized by

A

Micocephaly, macroglossia, umbilical hernia
Overabundance of growth factor 2 - multiple organ problems
Susceptible to CA

72
Q

DNA silencing and CA

A

DNA silencing is important for preventing continuous cell division (CA)

73
Q

DNA silencing and CA - Global hypomethylation

A

of DNA outside of CpG islands is found in most cancers

74
Q

DNA silencing and CA - hypomethylation of DNA causes

A

Genetic instability:

  • elevated activity of mobile genetic elements
  • chromosomal abnormalities
75
Q

DNA silencing and CA - hypomethylation of DNA causes genetic instability which causes

A

Cancer

Cancer causes genomic instability too

76
Q

DNA silencing and CA - Hypermethylation of CpG islands in promoter

A

can shut down tumow suppressor geners

Effect of silencing equals effect of null mutation

77
Q

DNA silencing and CA - Hypermethylation - rare or common

A

Probably rather common 10-15% of non familial breast CA due to hypermethylation of BRCA1 (not mutation)

Semester 5 FSNM Exam 9 (4 decks)

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