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Biochem > Test 2 > Flashcards

Test 2 Flashcards

1
Q

How many chromosome pairs do humans have

A

We each have 23 pairs of chromosomes

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2
Q

What type of bonds between histones and dna

A

Hydrophobic interactions and salt linkages

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3
Q

What prevalant amino acids are in histones and what charge do they give the protein?

A

Lys and arg make up 20% of histones AA’s and this gives it a + charge which is attracted to the slight negative charge of dna

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4
Q

What is a nucleosome

A

Basic unit of dna packaging where there is DNA and 8 histones all combined

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5
Q

What is chromatin

A

Protein + nuclear dna

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6
Q

Euchromatin is?

A

Lightly packed chromatin, usually in the areas of genes where there is often active transcription. (92% of our genes are euchromatin)

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7
Q

Heterochromatin is?

A

Very condensed chromatin. Basically genetically inactive. It is highly concentrated at centromeres and telomeres.

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8
Q

What is the position effect in regards to heterochromatin?

A

Activity of a gene depends on its position on a chromosome where heterochromatin is usually near telomeres and centromeres.

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9
Q

Percent of dna in exons

A

1.5%

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10
Q

99% of all introns begin with what and end with what?

A

Begin - GT
End - AG
GET EGG

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11
Q

What is histone deacetylase and histone acetyltransferase ?

A

HDAC pulls off acetyl groups from histones and acetyltransferase puts them on histone.

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12
Q

Why does it matter if the histone is acetylated or not?

A

Being acetylated causes the Dna to be less tightly wound around the histones. This means that the dna on the histone area will be transcribed.

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13
Q

Silent mutation

A

No change in AA coded for

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14
Q

Missense mutation

A

Change in AA but no change in protein function

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15
Q

Nonsense mutation

A

Changes it to a premature stop codon

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16
Q

Frameshift mutation

A

One or more nucleotide are deleted or inserted that causes the codons to be read out of frame.

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17
Q

What causes sickle cell anemia genetically speaking

A

Missense mutation in 6th codon in hbb - substitutes valine (hydrophobic) to Glu (neg charged and Hydrophilic ) messes up RBCs By forming rigid rod like proteins

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18
Q

What 2 ways does sickle cell anemia decrease o2 carrying of cells

A

Poor o2 capacity and clog capilaries

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19
Q

Duchenne muscular distrophy

A

Large in frame and out of frame deletions to the dystrophin gene.
Oof - deletion leads to little to no expression of the gene - severe form of disease - causes muscles to waste away
If- deletion gives milder form of disease

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20
Q

Structure of mRNA

A

5’ 7-methylguanosine cap.
Poly A tail
Untranslated region before and after the coding region.

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21
Q

What is tRNA structure

A

Cloverleaf shape
2 unmatched nucleotides are vital for function
The anticodon loop which binds codons
And the 3’ CCA region that binds the corresponded AA to the codon

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22
Q

What is an aminoacyl tRNA

A

Complex of AA with tRNA
AA needs to be activated by aminoacyl tRNA synthetases
Each AA has its own synthetase - these serve as second genetic code

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23
Q

Human ribosomes are what size?

A

60s and 40s

80 S total

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24
Q

3 sites on ribosomes

A

APE
Acceptor site
Peptidyll
Exit

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25
Q

Creutzfeldt-jakob disease

A

Misfolding of prion proteins - transmissible ; prions can cause other proteins to misfold
Belongs to transmisible spongiform encephalopathies

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26
Q

Huntingtons disease

A

Mutation in huntingtons gene results in expansion of CAG triplet repeats
Results in polygln repeats
Selective death of cells in basal ganglia cause symptoms

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27
Q

Parkinsons disease

A

Agregation of alpha-synuclein which deposit lewy bodies in dopaminergic neurons in substantia nigra
Symptoms from reduuction in dopamine availability
AS mutations cause familial parkinsons
Brain aging is the common denominator for non familial

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28
Q

Alzheimers disease

A

APP amyloid precursor protein breaks down to form Amyloid beta peptide. Misfolding of ABeta forms plaques in brain
Hyperphosphorylationof tau - neurofibrilary tangles
APP and Tau mutations cause familial versions
Brain aging is common denominator of sporadic form

29
Q

Proteins such as histones are typically acetylated on what residue and with what?

A

On lysine residues with acetyl coa used at the acetylator

30
Q

Protein disulfide isomerases do what

A

Help formation and reorganization of disulfide bonds between cysteine residues in the ER lumen,

31
Q

What type of kinase are used in phosphorylation regulation

A

Thr/ser and tyr kinase forms an ester bond between phosphate and OH of aa

32
Q

O links in O-glycosidic proteins use the hydroxyl groups of what residues ?

A

Ser and thr

33
Q

N links in N glycosidic linkage uses the OH from what residue
And have what 2 types

A

Asparganine
Mannose rich and complex type
Precursor sugar is transfered from phospho dolichol

34
Q

Chaperone

A

protect protein and help fold in proper tertiary structure

35
Q

Chaperonin

A

Barrel shaped compartment that admits unfolded protein and catalyzes its folding in an atp dependant manenr.

36
Q

Lysosomal digestive proteins are called

A

Acid hydrolases

37
Q

I-cell disease

A

Mannose 6 phosphate tagging is defective of acid hydrolases in lysosome

38
Q

ER targeting signal peptide

A

15-60 aa’s at the N terminus
1-2 basic AA’s
An extremely hydrophobic 10-15 residues on the c terminus of the basic residues

39
Q

Signal recognition particle

A

Binds to the ribosome -mrna- peptide complex and tethers it to the ER membrane and halts translation temporarily - enzymes on the luminal side cleave the signal to release the protein from srp

40
Q

Tryptophan domain - signal sequence for what

A

Secratory proteins

41
Q

N terminus apolar region -signal sequence

A

For membrane proteins

42
Q

Mannose 6 phosphate - signal sequence

A

For lysosomal proteins

43
Q

signal sequence for ER lumen proteins

A

K - lysine d - Aspartic acid E - glutamic acid L - leucine

For ER lumen proteins.

44
Q

Nuclear import signals

A

Nuclear pores - small proteins

Nuclear localization signals - for large proteins Four contiguous basic residues (arg lys )

45
Q

Mitochondrial protein import

A

Transporter outer membrane
Transporter inner membrane
Unfolded proteins are protected by chaperones in particular heat shock proteins 70

46
Q

Where do proteins go if they have no translocation signals?

A

Cytoplasm

47
Q

Mitochondria signal sequence

A

N terminal hydrophobic alpha helix

48
Q

Puromycin

A

Causes premature chain termination in pro/euk by resembling 3’ end of aminoacetylated tRNA - enters the A site and adds to the growing peptide leading to premature release of the peptide through unknown mechanism

49
Q

Cycloheximide

A

Euk elongation inhibitor - inhibits peptidyl transferase

50
Q

Diphtheria toxin

A

Eukaryote elongation inhibitor - inactivates GTP bound eEF-2 interfering with ribosomal translocation

51
Q

Shiga toxin and Ricin

A

Binds to lrg 60 SU (euk) blocking entry of aminoacyl tRNA to ribosomal complex (eukaryotic elongation inhibitor)

52
Q

Tetracycline

A

Binds small 30 SU (prok ) blocking entry of tRNA to ribosomal complex

53
Q

chloramphenicol

A

Inhibits peptidyl transferase - prokaryotic elongation inhibitor

54
Q

Clindamycin and erythromycin

A

Prok elongation inhibitor - binds to 50 s SU blocking translocation of the ribosome ( erythromycin is commonly used to treat pertussis)

55
Q

Streptomycin

A

Binds to 30 S subunit interferes with binding of fmet-tRNA interferes with 30s associations with the 50S subunit - elongation inhibition in prok

56
Q

What is a polysome

A

Cluster of ribosomes simultaneously translating a single RNA molecule

57
Q

What are the stop codons

A

UAA, UAG, and UGA

58
Q

What do release factors do

A

Bind to the A site of ribosomes and cleave the ester bond between the c terminus of aa and the tRNA - GTP hydrolysis then dissociates the ribosomal complex

59
Q

Base excision repair

A

Fixes single base mismatches and nondistorting alterations through DNA glycolases, AP endonuclease , AP lyase and DNA polymerase beta, and DNA ligase

60
Q

Prader Willi syndrome

A

Deletion on chromosome 15 on the paternal chromosome this is because you have genetic imprinting on the maternal genes and so you have deficiencies without the paternal gene

61
Q

Angelman syndrome

A

Due to chromosome 15 deletion on maternal chromosome

Imprinting on paternal chromosome leads to genetic deficiencies.

62
Q

Turner syndrome

A

45, XO karyotype
Female
Short
Webbed neck

63
Q

Klinefelter syndrome

A 
47 XXY 
Males 
Learning issues
Can be mosaic 
Variability in xxxxxy vs xxy can change intensity
64
Q

Trisomy 13 18 and 21

A

21 is downsyndrome
13 is patau
18 is edward syndrome

65
Q

Uniparental disomy

A

2 chromosomes are both inherited from same parent will lead to only male or only female imprinting

66
Q

Locus heterogeneity

A

1 disorder caused by mutations that are different

67
Q

Consanguinity

A

These are matings between 1st cousins that increase risk for shared recessive mutations

68
Q

Lebers hereditary optic neuropathy

A

Acute or subacute loss of central vision due to degeneration of retinal cells - this is a mitochondrial disease

69
Q

Mitochondrial encephalomyopathy lactic acidosis and stroke like episodes

A

Effects high energy use systems - mitochondrial pass genetiucs

Biochem (3 decks)

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