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Term 2 > Genetics Pre-Midterm > Flashcards

Genetics Pre-Midterm Flashcards

1
Q

What is a phosphodiester bond?

A

Sugar-Phosphate

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2
Q

Why do we 5’ cap & 3’ poly-A tail mRNA?

A
  1. Protection from exonucleases/increase 1/2 life
  2. Necessary for nuclear export
  3. Cap binding complex necessary for translation
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3
Q

What are the 2 sites called before and after an intron?

A
  1. Donor site

2. Acceptor site

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4
Q

What holds everything together during splicing?

A

Spliceosome

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5
Q

Give an example of RNA editing

A

Apo-B-100 (liver) & Apo-B-48 (intestine)

* C –> U; a premature stop codon for the intestine isoform

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6
Q

What is a Lariat structure?

A

Circular structure that forms as 5’ donor site links to an invariant part of the intron

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7
Q

Humans only have 30,000 genes, but..

A

Alternative splicing can increase this in 60% of the genes

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8
Q

What are enhancers and activators and transcription factors?

A

All elements that regulate/stimulate transcription; can be upstream/downstream, in an intron, etc.

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9
Q

What is Chargoff’s rule?

A

A=T; G=C

Purines = Pyrimidines

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10
Q

How many H bonds are A-T vs. G-C

A

A-T: 2; G-C: 3

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11
Q

Who is bicyclic: purines or pyrmidines?

A

Purines

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12
Q

mRNA is linear or circular; single or double stranded?

A

Linear; single-stranded

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13
Q

A mutation in a donor site results in…

A

Longer gene

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14
Q

The regulatory sequences of genes regulate…

A

Rate of transcription

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15
Q

What does methylation do to DNA?

A

Inactivate / regulate the rate of transcription

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16
Q

How many genes do humans have?

A

25-30,000

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17
Q

What is the largest gene?

A

Dystrophin - 2.5Mb

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18
Q

Where on a chromosome are the genes located?

A

Between the telomere and the centromere

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19
Q

What are the 3 main divisions of DNA?

A

Nuclear, extragenic, mitochondrial

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20
Q

What are the 2 divisions of nuclear DNA?

A

Single gene, Multigene families (Classic, superfamilies)

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21
Q

What are the major divisions of multigene family genes?

A
  1. Classic - high degree of homology (HOX)

2. Supergene - low homology, similar fx (HLA, T cell receptor)

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22
Q

The 2 major categories of extragenic DNA:

A
  1. Tandem repeat (satellite, mini-telomeric, hypervariable-VNTR, micro-STR)
  2. Interspersed (short-Sines (30-40%) & Alu elements, long-Lines (20% & reverse transcriptase))
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23
Q

What part of DNA is used for fingerprinting & why?

A

STR (short tandem repeat)

STR & VNTR are polymorphic and inherited in a co-dominant fashion from mom/dad

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24
Q

Mitochondiral DNA is inherited…

A

Mother (cytoplasm of oocyte)

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25
Q

Differentiate between metacentric, submetacentric and acrocentric DNA.

A

Meta: P=Q – Chromo 1
Sub: P < Q – Chromo 4
Acro: P «< Q (satellite P) – Chromo 13,14,15,21,22

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26
Q

A karyotype is viewed during…

A

Metaphase

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27
Q

What is it called when both chromosomes of a pair are derived from the same parent?

A

Uniparental disomy

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28
Q

In what order are chromosomes arranged?

A

Largest to smallest (1-21)

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29
Q

What is asymmetric X inactivation?

A

When more than 50% of the cells of the maternal/paternal X is active

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30
Q

What is the barr body?

A

The inactivated X chromosome in females

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31
Q

When does lyonization take place?

A

After the development of female sexual organs

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32
Q

Who regulates Lyonization?

A

XIST (X inactivation center); which coats the inactivated X-chromosome

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33
Q

What is an epigenetic mechanism of DNA modification?

A

Imprinting: Methylation of CG islands close to the promoter; results in transcriptional repression

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34
Q

Differentiate between locus and allele

A

Allele: homologous chromosomes (homo/hetero)
Locus: location on a chromosome

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35
Q

Huntington’s disease is located …

A

Chromosome 4P

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36
Q

Which are the tumor suppressor genes (with respect to the cell cycle)?

A

p53 & Rb

* Between G1 & S

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37
Q

Who regulates the tumor suppressor genes?

A

Cyclins

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38
Q

What are the 3 major types of cells (with respect to the cell cycle)?

A
  1. Labile – multiply throughout life
  2. Stable – G0; can undergo division if stimulated
  3. Permeant – arrested in G0 (neuron, cardiac)
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39
Q

How does a cell in G0 get to S phase?

A

Through G1

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40
Q

Which stage of the cell cycle is most variable (time)?

A

G1

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41
Q

Cell spends maximum amount of time in Interphase or Mitosis?

A

Interphase

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42
Q

What is Turner Syndrome?

A

45, X (Non-disjunction)

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43
Q

What is Klinefelter Syndrome?

A

47, XXY

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44
Q

Differentiate between XYY & XXX (with respect to fertility)

A

XYY – fertile

XXX – infertile

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45
Q

Differentiate between the beginning of gametogenesis in males/females

A

Males: puberty
Females: embryonic life

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46
Q

Differentiate between number of mitoses in male sex cells vs. female

A

Male: 30-500; female 20-30

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47
Q

Males produce ___ gametes; females produce _____

A

4 spermatids; 1 ovum/3 polar bodies

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48
Q

Differentiate between nondisjuction in meiosis I vs. 2

A

I: XY, XY, no sex chromo * 2
II: XX, YY; no sex chromo * 2

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49
Q

How many chromosomes and chromatids at the beginning of mitosis?

A

46 chromosomes; 92 chromatids

50
Q

Where is the second check point in the cell cycle?

A

After G2

51
Q

What is the difference between cis & trans regulatory proteins?

A

Cis – same chromsome; trans – different chromosome

52
Q

Differentiate between (lac operon) with glucose, lactose, & glucose/lactose

A

Glucose: negative
Lactose: positive
Glucose+lactose: no cAMP (but also no repressor)

53
Q

In proks, what are the components of an operon?

A

promoter, operator (repressor), cAMP-binding

54
Q

What are the two different terms for the level of gene transcription in proks?

A

Constituitive (always on)

Regulated (on with certain conditions)

55
Q

How does the tryptophan operon function in proks?

A

In the absence of Trp, an inactive repressor is made & tryptophan is synthesized

56
Q

What suppresses/activates the operator in the lac operon?

A

Normally, suppressed; but when lactose is present, allolactose binds to and suppresses the suppressor

57
Q

Differentiate between the following mutations: non-functional repressor and a super-repressor in the lac operon.

A

Non-functional repressor: can’t bind to the operator (Lots of transcription!)
Super-repressor: repressor has mutation and is unable to bind to allocatose, so it won’t dissociate from the operator (NO transcription)

58
Q

Transcription factors have 3 domains (euks)

A
  1. DNA binding domain
  2. Dimerization domain
  3. Enhancer binding proteins
59
Q

What are the two different types of transcriptional modification in euks?

A
  1. Basal transcription

2. Enhancer transcription

60
Q

How do transcriptional repressors work in euks?

A

Competition, Quenching, Blocking

61
Q

What are hypoxia response elements?

A

HIF1-alpha, HIF1-beta;

Under normal conditions, HIF1-alpha is degraded by O2-dependent prolyl hydroxylase and FIH hydroxylase

In anoxia, the 2 proteins dimerize; angiogenesis, vasodilation, etc.

62
Q

What are hormone response elements?

A

Up/down regulate inflammation (glucocorticoids)

63
Q

What are MAX/MYC

A

MYC+MAX = gene activation
MAX alone = gene repression

MAX mutations – pheochromocytoma

64
Q

Describe the regulation of iron in the body.

A

Translational modification

Ferritin & Transferrin

65
Q

What are miRNA’s?

A

Gene silencing; Drosha–long pre-miRNA’s processed to mature miRNA’s

DICER processes them to ssRNA & forms RISC (RNA induced silencing complex)

  • Regulation gene expression by BP’ing to 3’UTR
66
Q

What is siRNA?

A

Short, interfering RNA; can silence genes

67
Q

How is Fragile X related to miRNA/siRNA?

A

Misprocessing, low levels of FMRP gene; RISC complex

68
Q

What are the features of autosomal dominant disorder?

A
  • Vertical – doesn’t skip generations
  • Equal M/F
  • Father –> Son
69
Q

Define recurrence risk

A

Probablity that offspring will have the disorder

70
Q

What are the characteristics of autosomal recessive?

A
  • Horizontal inheritance; skips generations

* M/F equal distribution

71
Q

What are the major autosomal dominant disorders & characteristics?

A 
Huntington's Disease
Myotonic dystrophy (DMPK gene)
Familial hypercholesterolemia
Margan
Achondroplasia (FGF3); cartilage-->bone
OI (alpha-1)
Neurofibromatosis (NF1)
Acute intermittent prophyria
72
Q

What disorders are triplet repeat disorders?

A

Huntington

Myotonic dystrophy

73
Q

What are two examples of dominant negative mutations?

A

Mutant gene interferes with normal gene function (Marfan, OI)

74
Q

What is an example of a haplo-insufficiency disorder?

A

Familial hypercholesterolemia; half normal levels of the gene (LDL receptors) defected

75
Q

What are two examples of gain-of-function mutations?

A

Huntington/Achondroplasia; increased level of gene expression; ne functional gene producyt

76
Q

What is the classical variable expressivity autosomal dominant mutation?

A

Neurofibromatosis I

77
Q

Define incomplete penetrance

A

An autosomal dominant mutation skips a generation

  • Pt has genotype, but not phenotype (Huntingtons)
  • Can calculate the penetrance risk
78
Q

Define variable expression

A

Spectrum of the disorder (different phenotypic manifestations)
I.E. Hemochromatosis, Xeroderma pigmentosum, OI, NF

79
Q

Define Pleiotropy

A

Affects multiple organ systems (Marfans)

80
Q

Define locus heterogeneity

A

Same phenotype, different location of the mutation, i.e. NF, BRACA1/2

81
Q

Define allelic heterogeneity

A

Different mutations at the same loucs (and same phenotype, i.e. CF

82
Q

Define new mutation

A

Father (increased paternal age) has germ-line mutation due to decreased recognition of DNA errors, i.e. Achondroplasia, Apert, Marfans

83
Q

Differentiate between the 2 causes of Prader-Willi & Angelman.

A

Microdeletion

Uniparental disomy

84
Q

Describe the genetic differences between Prader-Willi & Angelman

A

Prader-Willi: deletion of paternal SNRPN

Angelman: deletion of maternal UBE3A

85
Q

Describe the 4 triplet repeat disorders

A

Promoter: Fragile X (CGG)
Intron: Fredrich Ataxia (GAA)
Exon: Huntington (CAG)
3’ UTR: Myotonic Dystrophy (CTG)

86
Q

There is a high/low chance of recombination for genes far apart from one another.

A

High; genes CLOSE to each other are considered LINKED

87
Q

ASO probes can be used for…

A

CF, hemochromatosis

88
Q

What are the limitations of PCR

A
  • Won’t ID Heterozygous/Homozygous

- Won’t ID carriers

89
Q

What are the limits of karyotype analysis?

A

Unable to detect microdeletions

90
Q

What is CGH used for?

A

Tumor biology

91
Q

Describe the following terms: silent, missense, nonsense, transversion, transition

A 
Silent: no change in AA code
Missense: change in protein
Nonsense: stop codon
Transition: purine for purine, etc.
Transversion: purine for pyr, etc.
92
Q

PCR won’t detect…

A

heterozygotes

93
Q

What is the poly T tract in CF?

A

Associated with alternative splicing / mRNA is less stable

94
Q

What are the 4 major types of OI?

A
  1. Classic, blue sclera
  2. Lethal, fetal
  3. Progressive onset
  4. No blue sclera
95
Q

Describe MM, MZ, SZ, ZZ mutations in A1AT deficiency.

A

Less –> Most severe

96
Q

Dominant negative mutation

A

A dysfunctional protein is incorporated into a multisubunit protein (Sickle Cell)

97
Q

Gain of function mutation

A

Huntington

98
Q

Haploinsufficiency

A

Familial hypercholesterolemia

99
Q

Heteroplasmy

A

Mitochondiral inheritence

100
Q

Anticipation

A

Triplet repeat disorders (increasing severity with newer generations

101
Q

Overexpression of SHH

A

Hypertelorism

102
Q

Differentiate between CGH and microarray cDNA

A

CGH: copy number variants
Microarray: gene expression
* Can both be used for tumors

103
Q

Children with increased number of cervical ribs have a higher frequency of __________ due to ____________.

A

Cancer; loss of HOX gene

104
Q

An example of a gain of function mutation is…

A

Achondroplasia; causes a decrease in chondrocyte differentiation and the formation of osteoblasts

105
Q

46 XY - Swyer (Pure Gonadal Dysgenesis)

A

Loss of function of the SRY gene

  • Female genatalia, clitoromegaly, bilateral gonads
  • Increased risk of germline tumors; gonads removed
106
Q

46 XX - Male Syndrome – de la Chappelle syndrome

A

Caused by a translocation of the SRY gene

* Typical boys and men; hypospadias, no Mullerian duct; infertile

107
Q

AZF (azoospermia factor) mutation

A

Infertile men

108
Q

FGF3 mutations (Most –> least severe)

A

Most severe  least severe

* Thanatophoric dysplsia (lethal) – Saddan dysplasia – ACH – hypochondroplasia

109
Q

Achondroplasia

A

AD; FGF3 mutation (FGFR normally inhibits chondrocyte growth)
G-C transversion at 1138: glycine  arginine
* Sperm with the mutation actually have selective advantage
* A gain of function mutation

110
Q

SHH-PTCH Gli Pathway Disorders

A

Holoprosencephaly: SHH or Six3 gene; single incisor; cyclopia
SLOS: 7-dehydrocholestrol reductase (in the SHH pathway); retardation
Gorlin (Nevoid basal cell carcinoma): PTCH – early basal cell ca
Pallister Hall: Brain tumor, polydactly
Rubenstein-Taybi: CREBP gene; broad thumbs, small stature

111
Q

Rubenstein-Taybi

A

CREBP gene; broad thumbs, small stature (SHH)

112
Q

Pallister Hall

A

Brain tumor, polydactly (SHH)

113
Q

Gorlin (Nevoid basal cell carcinoma)

A

PTCH – early basal cell ca (SHH)

114
Q

SLOS

A

7-dehydrocholestrol reductase (in the SHH pathway); retardation (SHH)

115
Q

Holoprosencephaly

A

SHH or Six3 gene; single incisor; cyclopia

116
Q

Define the 4 categories of single developmental anomolies.

A

Malformation: primary genetic problem (congenital heart defect)
Disruption: Short arms secondary to a decreased vascular supply (phocomelia)
Deformation: Club foot (due to low amniotic fluid)
Dysplasia: Monogenic; problems with tissue organization (FGF)

117
Q

Define the 3 categories of multiple developmental anomolies.

A

Sequences: cascade effects
Syndromes: groups of anomolies
Associations: traits

118
Q

Phocomelia

A

Disruption: Short arms secondary to a decreased vascular supply

119
Q

Sonic Hedgehog protein

A

Tissue patterning, ventral floor plate, hair, tooth, lung, pancreas; limb patterning

120
Q

On what chromosome is SHH?

A

Long arm 7

121
Q

What are the HOX genes?

A

Anterior/Posterior axis; segmentation; gradient is important

* Kids with an extra cervical rib –> higher risk of cancer

Term 2 (8 decks)

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