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Semester 5 FSNM Exam 9 > Genetics 3 > Flashcards

Genetics 3 Flashcards

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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
Aberration - deletion of a part of chromosome 5 results in
Cri du chat syndrome | Microcephaly, mental retardation, heart defect
26
Aberration - Translocations and Inversions
No genetic material lost, just rearranged (balanced alteration)
27
Aberration - Translocations and Inversions - symptoms
Mostly asymptomatic in the person who carries them but problems arise in the next generation when doing meiosis because you can get an imbalance
28
Aneuploidy - is what
We have extra or missing chromosomes
29
Aneuploidy - Arises from what
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
30
Aneuploidy - consequences
Very severe Monosomy is lethal (except for X chrom) Trisomy only observed in chrom 13, 18, 21 and the sex chromosomes
31
Trisomy 21 causes
Down syndrome and is the most commonly observed chromosomal aberration NOT RARE
32
Sex chromosome Aneuploidies
``` Turner syndrome (45, X) Klinefelter syndrome (47, XXY) Klinefelter syndrome (48, XXXY) ```
33
Sex chromosome Aneuploidies - Turner syndrome
1 in 3000 F births Sterility, short stature and other physical characteristics are observed No mental retardation
34
Sex chromosome Aneuploidies - Klinefelter syndrome 47 XXY
1 in 1000 M births NOT RARE Sterility, development of breasts, high pitched voice
35
Clinical cytogenetics - can detect what
chromosomal aberrations
36
Clinical cytogenetics - indicated under what circumstances
``` Problems of early growth/development Stillbirth/neonatal death Fertility problems Pregnancy with advanced maternal age Also sometimes CA, family hx ```
37
Inheritance of a chromosomal defect -
Usually dominant, new mutations Multiple abnormalities in affected children - often with developmental delay Spontaneous abortions/multiple miscarriages Infertility
38
Pedigree of a chromosomal defect - how can a person pass on a chromosomal aberration without being sick
Balanced alteration will perform a normal life but they will run into issues when they reproduce
39
Karyotype of a cancer cell line
3 or 4 or more copies of a certain chromosome because these do not stop dividing even if a genome goes wrong
40
Epigenetics is the study of
Heritable changes that do not involve changes in DNA sequence
41
Epigenetics - how do they work
Changes silence or activate chromosomal regions by DNA methylation/demethylation OR Histone acetylation/deacetylation
42
Epigenetics influences
Tee expression without changing the genomic sequence
43
Epigenetics - DNA methylation - methylation of DNA occurs where
On cytosine residues in CpG repeats
44
Epigenetics - DNA methylation - CpG repeats are found in
CpG islands - non methylated | Repetitive DNA - methylated
45
Epigenetics - DNA methylation - about 70% of the CpGs are
methylated (silenced)
46
Epigenetics - Histone acetylation - Acetylation of histones occurs wher
on the tail region
47
Epigenetics - Histone acetylation - acetylation of the histone changes what
the charge of the histone Acetyl group = neg charge Histones = need to be pos charged
48
Epigenetics - Histone acetylation - acetylation of histones does what
decreased the affinity to DNA so it makes it stick less well to the DNA And you are facilitating transcription of that region
49
Epigenetics - Histone acetylation - Deacetylated histones bind
more tightly to DNA
50
Epigenetics - Histone acetylation - Histone deacetylation
silences chromosomal regions | Increases their binding affinity and silences transcription
51
Epigenetics - Histone acetylation - In addition to acetylation, there are other histone modifications - what are they
Methylation Phosphorylation Ubiquitination These modifications might constitute a "histone" code imposed on the DNA
52
Imprinting - what is it
Imprinting silences chromosomal regions by DNA methylation and histone deacetylation
53
Imprinting - reversible or stable?
Can be reversed but in general is stable through somatic cell division
54
Imprinting occurs -
During gemetogenesis to mark the paternal origin of chromosome During development to permanently change the gene expression pattern of a cell line
55
Imprinting - is also the mechanism by which
X chromosome inactivation occurs
56
X chromosome inactivation - mediated by
Transcripts of the XIST gene
57
X chromosome inactivation - DNA is ____ and histones ____
DNA is methylated | Histones deacetylated
58
Imprinting related diseases - imprinting does what
silences a maternal or parental allele
59
If imprinting is incorrect, what happens
Gene dosage problems may arise where you have too much or too little genes in a cell
60
Imprinting occurs when
during development
61
Imprinting - explains what
Parent of origin effect of some mutations | Detrimental effects of uniparental disomy
62
What are two examples of parent of origin effects and issues with imprinting
Prader willi syndrome Angelman Syndrome Beckwith Wiedemann Syndrome
63
Prader Willi Syndrome - Caused by
Deletion on paternal copy of Ch 15 or maternal uniparental disomy
64
Prader Willi Syndrome - Rare or Common
Rare
65
Prader Willi Syndrome - s/s
Excessive food seeking bx Hypogonadism Mental retardation Small hands, feet, facial features, hypotonia,
66
Angelman syndrome - caused by
Deletion on maternal copy of Ch 15 or paternal uniparental disomy
67
Angelman Syndrome - rare or common
Rare
68
Angelman syndrome - characterized by what
Unusual facial features (large mandible, open mouth) Excessive laughter Seizures, mvmnt and gait disorder Severe mental retardation, absence of speech
69
Beckwith Wiedemann Syndrome - can be caused by what
Parternal uniparental disomy
70
Beckwith Wiedemann Syndrome - rare or common
Rare
71
Beckwith Wiedemann Syndrome - Characterized by
Micocephaly, macroglossia, umbilical hernia Overabundance of growth factor 2 - multiple organ problems Susceptible to CA
72
DNA silencing and CA
DNA silencing is important for preventing continuous cell division (CA)
73
DNA silencing and CA - Global hypomethylation
of DNA outside of CpG islands is found in most cancers
74
DNA silencing and CA - hypomethylation of DNA causes
Genetic instability: - elevated activity of mobile genetic elements - chromosomal abnormalities
75
DNA silencing and CA - hypomethylation of DNA causes genetic instability which causes
Cancer | Cancer causes genomic instability too
76
DNA silencing and CA - Hypermethylation of CpG islands in promoter
can shut down tumow suppressor geners | Effect of silencing equals effect of null mutation
77
DNA silencing and CA - Hypermethylation - rare or common
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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