Usmle Step 1 Dit: Biochemistry

Front 1

Histones are rich in what aminoacids?

Back 1

Lysine and arginine

Front 2

______charged DNA loops twice around _______charged histone octamer to form nucleosome bead.

Back 2

Negatively, positively

Front 3

What are the sources of carbon in purines?

Back 3

Glycine, tetrahydrofolate, c02

Front 4

What are the 5 things needed to make purines?

Back 4

Glycine, aspartate, glutamine, tetrahydrofolates, C02

Front 5

What are the 4 things needed to make pyramidines?

Back 5

Aspartate, c02, glutamine, ATP

Front 6

What enzyme helps convert glutamine + c02 into carbomyl phosphate?

Back 6

Carbomyl phosphate synthetase II

Front 7

What drug blocks carbomyl phosphate conversion into orotic acid?

Back 7

Leflunomide

Front 8

What sugar-phosphate complex is needed for pyrimidine and purine base production?

Back 8

Ribose 5-P

Front 9

What drug blocks ribonucleotide reductase?

Back 9

Hydroxyurea

Front 10

What drug blocks thymidylate synthase?

Back 10

5-FU

Front 11

What drug blocks dihydrofolate reductase?

Back 11

MTX, TMP

Front 12

What enzyme helps conversion from PRPP into IMP?

Back 12

Glutamine PRPP amidotransferase

Front 13

What drug blocks glutamine PRPP amidotransferase?

Back 13

6-MP

Front 14

What drug blocks GMP conversion by inhibiting IMP dehydrogenase?

Back 14

Mycophenolate

Front 15

Where is carbomoyl phosphate synthetase I and II located?

Back 15

I: Mitochondria

II: Cytosol

Front 16

In what pathyways do carbomoyl phosphate synthetase I and II work?

Back 16

I: urea cycle

II: Pyrimidine synthesis

Front 17

Where does carbomoyl phosphate synthetase I and II get its source of nitrogen?

Back 17

I: ammonia

II: glutamine

Front 18

Synthesis begins with making a temporary base and adding sugar and phosphate

Back 18

Pyrimidine synthesis

Front 19

Synthesis starts with sugar and phosphate and a base is added

Back 19

Purine synthesis

Front 20

Inability to convert orotic acid into UMP because of defect in UMP sunthase. Autosomal recessive.

Back 20

Orotic aciduria

Front 21

What is lesch nyhan syndrome?

Back 21

Results in excess uric acid production and de novo purine synthesis. Due to absent HGPRT (which converts hypoxanthine to IMP and guanine to GMP).

HGPRT (Hyperuricemia, gout, pissed off, retardation, dysTonia)

Front 22

What are the symptoms of lesch nyhan syndrome?

Back 22

Intellectual dissability, agression, self mutilation, hyperuricemia, gout, dystonia

Front 23

What is the treatment of lesch nyhan syndrome?

Back 23

Allopurinol, febuxostat

Front 24

What does eukaryote DNA polymerase alpha do?

Back 24

Makes own primer, builds okasaki fragments on lagging strand

Front 25

What does eukaryote DNA polymerase beta do?

Back 25

DNA repair

Front 26

What does eukaryote DNA polymerase gamma do?

Back 26

Replicates mitochondrial DNA

Front 27

What does eukaryote DNA polymerase delta do?

Back 27

Builds leading strand

Front 28

Y-shaped region along DNA template where leading and lagging strands are synthesized

Back 28

Replication fork

Front 29

Unwinds DNA template at replication fork

Back 29

Helicase

Front 30

Prevents strands from reannealing

Back 30

single-stranded binding proteins

Front 31

Creates a single or double stranded break in the helix to add or remove supercoils

Back 31

DNA topoisomerases

Front 32

Makes an RNA primer on which DNA polymerase III can initiate replication

Back 32

Primase

Front 33

Found in prokaryotes only, elongates leading strand by adding deoxynucleotides to the 3' end. Elongates lagging strand until it reaches primer preceding fragments.

Back 33

DNA polymerase III

Front 34

Prokaryotic only. Degrades RNA primer; replaces it with DNA.

Back 34

DNA polymerase I

Front 35

Joins okazaki fragments in prokaryotes

Back 35

DNA ligase

Front 36

What is a primosome?

Back 36

Helicase + primase

Front 37

Mutation that occurs due to nucleotide substitution that codes for same amino acid, and often a base changes in 3rd position of codon

Back 37

Silent mutation

Front 38

Nucletide subsitution resulting in changed amino acid

Back 38

Missense

Front 39

Nucleotide subsitution resulting in early stop codon

Back 39

nonsence

Front 40

Deletion or insertion of a number of nucleotides, resulting in misreading of all nucleotides downstream, resulting in a truncated, nonfunctional protein

Back 40

Framshift

Front 41

What is a classic example of a missense mutation?

Back 41

Sickle cell disease

Front 42

What is a classic example of frameshift mutation?

Back 42

Duchenne muscular dystrophy

Front 43

DNA repair mechanism that is damaged in xeroderma pigmentosum

Back 43

Nucleotide excision repair

Front 44

DNA repair mechanism that is defective in hereditary nonpolyposis colorectal cancer

Back 44

Mismatch repair

Front 45

DNA repair mechanism that is defective in ataxia telangiectasia

Back 45

Nonhomolous end joining

Front 46

DNA repair where;

1. Endonucleases remove damaged bases

2. DNA polymerase fill gap

3. Ligase reseals gap

Back 46

Nucleotide excision repair

Front 47

DNA repair where;

1. Glycosylase removes altered base

2. Endonucleases cut and remove sugar

3. Polymerase-B fills gap

4. Ligase seals gap

Back 47

Base excision repair

Front 48

DNA repair where new strand is recognized, mismatched nucleotides are removed and gap is filled

Back 48

Mismatch repair

Front 49

DNA repair where 2 ends of DNA fragments are joined to repair double stranded breaks

Back 49

Nonhomologous end joining

Front 50

Bloom syndrome

Back 50

Helicase mutation where there are problems with DNA replication and repair.

- Hypersensitivity to sunlight

- Increased risk of leukemia/linfoma

- Facial abnormalities, infertility

Front 51

Where does aminoacyl-tRNA synthetase work?

Back 51

3' end of tRNA

Front 52

What antibiotics affect 50S subunit?

Back 52

Chloramphenicol, linezolid, macrolides, clindamycin, lincomycin, streptogramins

Front 53

What antibiotics affect 30S subunit?

Back 53

Tetracyclines, aminoglycosides

Front 54

Which antibiotics block initiation of protein synthesis?

Back 54

Aminoglycosides: before initiation

Linezolid

Tetracyclines: during initiation

Front 55

What initiates initiation of protein synthesis?

Back 55

GTP hydrolysis

Front 56

Antibiotics that block elongation of protein synthesis?

Back 56

All the ones that block 50S except linezolid

Chloramphenicol, clindamycin, lincomycin, macrolides (azitTHROmycin, clarithromycin, erythromycin), streptogramins (quinupristin, dalfopristin)

Front 57

Antibiotic that binds to 23S subunit on 50S and inhibits peptidyltransferase

Back 57

Chloramphenicol

Front 58

What are the stop codons?

Back 58

UGA, UAA, UAG

Front 59

Posttranslational modifications that include removal of N- or C-terminal propeptides from zymogen to generate mature protein

Back 59

Trimming

Front 60

Posttranslational modifications that include phosphorylation, glycosylation, hydroxilation

Back 60

Covalent alterations

Front 61

Inheritance that is often due to defects in structural genes, both female and males affected.

Back 61

Autosomal dominant

Front 62

Inheritance where 25% of offspring from 2 carrier parents are affected. Often due to enzyme deficiency, usually seen only in 1 generation

Back 62

Autosomal recessive

Front 63

Sons of heterozygous mothers have a 50% chance of being affected. No male-to-male transmission

Back 63

X-linked recessive

Front 64

Transmitted through both parents, Mothers transmit to 50% of daughters and sons; fathers transmit to all daughters but no sons

Back 64

X-linked dominant

Front 65

Transmitted only through mother. All offspring of affected demales may show signs of the disease

Back 65

Mitochondrial inheritance

Front 66

When both alleles contribute to the phenotype of the heterozygote, it is called...

Back 66

Codominance

Front 67

When one gene contributes to multiple phenotypic effects, it is called...

Back 67

Pleiotropy

Front 68

When there is presence of genetically distinct cell lines in the same individual, it is called....

Back 68

Mosaicism

Front 69

When there is mutation at different loci that can produce a similar phenotype, it is called...

Back 69

Locus heterogenity

Front 70

When at some loci, only one allele is active, the other is inactive (but the active one is deleted->disease)

Back 70

Imprinting

Front 71

Both prader willi syndrome and angelman syndrome are due to ________

Back 71

Imprinting. Mutation or deletion on chromosome 15

Front 72

Paternal gene is deleted/mutated.

Back 72

Prader willi sx

POP

Prader, Overeating/obesity, Paternal deletion

Other sx: hypogonadism, hypotonia, short stature, intelectual disability

Front 73

Maternal gene is deleted/mutated

Back 73

AngelMan syndrome

MAMA

Maternal gene, Angelman, Mood(happy), Ataxia

Other sx: seizures, severe intellectual disability

Front 74

Molecular biology laboratory procedure used to amplify a desired fragment of DNA. Useful as a diagnostic tool.

Back 74

Polymerase chain reaction (PCR)

Front 75

What occurs during denaturation step in PCR?

Back 75

dna is denatured by heating to generate 2 separate strands.

Front 76

What occurs during annealing step in PCR?

Back 76

During cooling, excess premade DNA primers anneal to a specific sequence on each strand to be amplified.

Front 77

What occurs during elongation step in PCR?

Back 77

Heat-stable DNA polymerase replicates the DNA sequence following each primer

Front 78

Blotting procedure with DNA sample and DNA probe

Back 78

Southern blot

Front 79

Blotting procedure with RNA sample and DNA probe

Back 79

Northern blot

Front 80

Blotting procedure with protein sample and Ab probe

Back 80

Western blot

Front 81

Blotting procedure with DNA-binding protein sample and oligonucleotide probes

Back 81

Southwestern blot

Front 82

Used to detect the presence of either a specific antigen or a specific antibody in a patients blood sample

Back 82

ELISA (indirect or direct, respectively)

Front 83

Enzyme-linked immunosorbent assay that uses a test antigen to a specific antibody

Back 83

Indirect ELISA

Front 84

Enzyme-linked immunosorbent assay that uses a test antibody to see if a specific antigen is present in the patients blood

Back 84

Direct ELISA

Front 85

Fluorescent DNA or RNA probe bindds to specific gene site of interest on chromosomes

Back 85

FISH

Front 86

What steps are taken in cloning recombinant DNA molecules?

Back 86

1. Isolate eukaryotic mRNA

2. Reverse transcriptase to produce cDNA

3. Insert cDNA fragments into bacterial plasmids

4. Transform recombinant plasmid into bacteria

5. Surviving bacteria on antibiotic medium produce cDNA

Front 87

Random insertion of gene into mouse genome

Back 87

Constituive insertion

Front 88

Targeted insertion or deletion of gene through homologous recombination with mouse gene

Back 88

Conditional insertion

Front 89

Removing a gene, taking it out

Back 89

Knock out

Front 90

Inserting a gene

Back 90

Knock in

Front 91

A process in which metaphase chromosomes are stained ordered, and numbered according to morphology, size, arm-length ratio and banding pattern.

Back 91

Karyotyping

Front 92

What is karyotyping typically used to diagnose?

Back 92

Chromosomal imbalances such as autosomal trisomies, sex chromosome disorders