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Med Gen Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

How can a frameshift result in no protein production?

A

Change in reading frame
likely induction of premature termination codon
Induction of Nonsense Mediated Decay Pathway

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2
Q

List the stages of the cell cycle?

A

G0, G1, S, G2, M

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3
Q

What occurs at G0 in the cell cycle?

A

Quiescent phase- metabolically active but not dividing

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4
Q

What occurs at the G1 phase of the cell cycle?

A

cells are metabolically active and growing

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5
Q

Wha occurs at the S phase of the cell cycle?

A

Synthesis of organelles for mitosis to occur

DNA synthesis and replication

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6
Q

What occurs at the G2 phase of the cell cycle?

A

Protein synthesis
Growth
Prepare to divide

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7
Q

What occurs at the M phase of the cell cycle?

A

Mitosis occurs

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8
Q

What are snRNP’s?

A

small nuclear ribonucleoproteins

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9
Q

What is the function of U2AF?

A

U2 Auxiliary Factor
binds to polypyramidine tract
Required for binding of U2 to branch site

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10
Q

What is the function U1?

A

Binds to 5’ donor site

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11
Q

What is hnRNP?

A

Heterogeneous Ribonucleoprotein particles

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12
Q

What does hnRNP bind?

A

Intron splicing silencer elements
Exon splicing silencer elements
(ISS’s and ESS’s)

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13
Q

What effect do hnRNP’s have on splicing?

A

Inhibit Splicing

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14
Q

What are SR proteins?

A

Serine Argenine Rich Proteins

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15
Q

What do SR proteins bind?

A

Intron Splicing Enhancer elements
Exon Splicing Enhancer elements
(ISE’s and ESE’s)

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16
Q

What is a presymptomatic test?

A

Before a patient is showing signs predicting what will happen in the future

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17
Q

What is a diagnostic test?

A

Patient showing symptoms of a particular disease

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18
Q

What age is a presymptomatic test usually done?

A

18 years old minimum

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19
Q

Why would a presymptomatic test be done on someone under 18?

A

If test could directly benefit by allowing medical/surgical intervention

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20
Q

What are the key differences between apoptosis and necrosis?

A

Apoptosis:

  • Programmed
  • normal cellular process
  • No inflammatory response
  • Activated by cellular factors (p53)

Necrosis

  • Unprogrammed
  • Associated with disease
  • Associated with inflammatory response
  • Activated by external factors (viruses)
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21
Q

Why is a consangenuieous relationship more likely to result in offspring with genetic abnormalities?

A

Every individual has rare deleterious, recessive mutations

when parents related, it increases chance of both parents carrying the same mutation

Increased risk in offspring inheriting a mutation on both chromosomes

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22
Q

Define intron

A

region of transcript that is not fully processed RNA as it

excised during splicing

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23
Q

Define exon

A

region of transcript that is fully included in processed mRNA

Generates transcripts that are coding and translated into proteins OR are non-coding transcripts that aren’t translated

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24
Q

Define promoter

A

A cis-acting regulatory DNA element that binds upstream of a transcription unit and binds to RNA polymerase

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25
Q

Define 3’ UTR

A

The untranslated region between a stop codon and the poly A tail

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26
Q

Define coding region

A

Entire exonic sequence that is translated, not the 5’UTR or 3’ UTR

27
Q

What is Anticipation?

A

Disease severity increases with each generation

28
Q

Define 5’ UTR?

A

region between the transcription and translation start site

29
Q

Define start codon

A

3 base pairs that result in the initiation of ribosomal translation

30
Q

Define intergenic region

A

Regions of the genome that do not encode for protein-encoding genes

31
Q

What is mtDNA?

A

mitochondrial DNA

32
Q

Describe Transcription (3)

A

RNA polymerase
makes pre-mRNA
from template DNA strand

33
Q

Describe splicing (3)

A

Splicesomal proteins bind to pre-mRNA template
Intron removed in the form of a lariat
2 exons ligated to form a mature mRNA

34
Q

Define epigenetics:

A

Reversible regulation of gene expression through changes in DNA methylation and chromatin structure, independent of DNA sequence

35
Q

What are 2 examples of epigenetic modifications?

A

Histone modifications

Methylation at CpG sites

36
Q

Define the Nonsense Mediated pathway (5 points)

A

-Exon Junction Complex deposited at sites where splicing has occurred
-UPF1,2,3 bind to EJC
-Translation release factors associate with the ribosome at the site of premature termination
- Release factors interact with UPF1
mRNA is decapped, deadenylated and degraded

37
Q

What does RNA polymerase I produce?

A

rRNA

38
Q

What does RNA polymerase II produce?

A

mRNA

39
Q

What does RNA polymerase III produce?

A

tRNA and snRNA

40
Q

What are the 5 key trnascription Factors?

A 
TFIID
TFIIB
TFIIF
TFIIE
TFIIH
41
Q

What premature ageing syndrome can be caused by mutations in TFII complex genes (TFIIH)?

A

Cockayne’s Syndrome?

42
Q

What triggers the change of the initiation complex to the elongation complex in transcription?

A

Gross structural changes in RNA polymerase II

43
Q

What are the 3 components of RNA Processing?

A
  • 5’ Capping
  • Splicing
  • Polyadenylation
44
Q

What is the 5’ cap?

A

Modified G residue with unusual 5’ to 5’ bond

45
Q

What is the function of the 5’ cap?

A

prevention of 5’ exonuclease degredation

identified as normal 3’ mRNA by degredation machinary

46
Q

How is the 5’ cap used to regulate nuclear export?

A

Cap binding complex is recognised by nuclear pore for export

47
Q

What are the 4 steps of the mRNA splicing reaction?

A
  • Adenine residue in intron attacks 5’ splice site
  • The cut 5’ end of intron, binds to Adenine, creating a loop
  • Released 3’OH end of exon, reacts with start of the next exon sequence, joining the 2
  • Intron released as a ‘lariat’ and then degraded
48
Q

What effect do SR proteins have on splicing?

A

Enhance Splicing

(by binding to Intron/exon Splicing Enhancer Elements

49
Q

What is the role of CPSF in polyadenylation/?

A
  • Cleavage + Polyadenylation Specificity factor

- Identifies Poly A signal

50
Q

What is the role of CFI+CFII?

A
  • Cleavage Factors

- Cut mRNA to allow addition of PolyA tail

51
Q

What is the role of CstF?

A
  • Cleavage stimulation Factor

- promotes cleavage by CFI+CFII

52
Q

What is the role of PAP?

A
  • Polyadenylate Polymerase

- Adds PolyA

53
Q

What is the role of PABI+PABII?

A
  • PolyA bindin proteins

- regulate mRNA stability

54
Q

How are RNA’s directed to specific locations?

A

by sequences in the 3’ UTR of transcript

55
Q

What 2 subunits make up the 80S ribosome?

A

40S and 60S

56
Q

What are the 3 stages in translation?

A
  1. Initiation
  2. Elongation
  3. Termination
57
Q

What is involved in translation initiation?

A

Initiation factors, poly A binding protein, and the association of the ribosomal proteins

58
Q

what is involved in Translation elongation?

A
  • delivery of aa’s in correct sequence by tRNA’s
  • peptide bonds form between adjacent aa’s
  • polypeptide chain
59
Q

What occurs during translation termination?

A
  • Termination codon encountered
  • Binds release factors (eRF1)
  • Final polypeptide bond is hydrolysed
  • polypeptide released
60
Q

What proteins determine RNA turnover?

A
  • RNA Binding Proteins (RBP’s)
61
Q

What is the role of RBP’s?

A

bind specific sequences in transcripts that regulate RNA stability

62
Q

What is the role of AU rich elements (ARE’s) in RNA degredation?

A

bind to RBP’s to elicit degredation

63
Q

What do C-rich elements bind to, to stabilise mRNA’s?

A

AlphaCP Proteins

Medical Genetics (2 decks)

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