Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

UWorld - Biochemistry > Biochem - cellular + labs > Flashcards

Biochem - cellular + labs Flashcards

1
Q

Why is the genetic code considered degenerate?

A

Because more than 1 codon can code for a particular amino acid

(61 codons, 20 amino acids)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the Wobble Hypothesis?

A

Certain tRNA molecules can recognize multiple different codons coding for the same amino acid.

This is due to the first 2 positions on the mRNA codon require traditional (Watson-Crick) base pairing, whereas the third “wobble” nucleotide undergoes non-traditional pairing.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Which part of DNA replication is most different between the 2 daughter strands?

A

DNA Ligase

Since DNA synthesis can only occur in the 5’ –> 3’ direction”

1 strand is synthesized continuously (leading strand)

1 strand is synthesized discontinuously (lagging strand) in a direction away from the replication fork, resulting in the formation of Okazaki fragments which get joined together by DNA ligase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the function of the following in Prokaryotic DNA replication :

a. Helicase
b. Topoisomerase II (DNA Gyrase)
c. Single-Stranded DNA-Binding Protein
d. DNA Ligase

A

a. Unwinding of double helix
b. Removal of supercoils
c. Stabilization of unwound template strands
d. Joining of Okazaki fragments on lagging strand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the functions of DNA Polymerase III? (2)

A
  1. 5’ to 3’ DNA Synthesis
  2. 3’ to 5’ exonuclease (proofreading) activity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the functions of DNA Polymerase I? (3)

A
  1. 5’ to 3’ DNA synthesis
  2. 3’ to 5’ exonuclease (proofreading) ability
  3. Removes Primer

(5’ to 3’ exonuclease activity)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which amino acid is most abundant in collagen?

What is the conformation of collagen molecules?

A

Glycine

A triple helical conformation

(Glycine occupies every 3rd amino acid position)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Which letter corresponds to the amino acid binding site on the tRNA molecule?

A

A

The 3’ CCA Tail

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does a Northern Blot detect?

A

RNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does a Southern Blot detect?

A

DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does a Western Blot detect?

Example of a probe its used to detect?

A

Protein

Antibodies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does a Southwestern blot detect?

Example of a probe it can detect?

A

DNA-binding Protein

c-Jun and c-Fos

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Reverse Transcription Polymerase Chain Reaction (RT-PCR)

  1. What is it used for?
  2. How does it work?
A

1.

Detect and quantify levels of mRNA in a sample

2.

It uses reverse transcription to create a complimentary DNA template that is then amplified using standard PCR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Proteins phosphorylated with mannose residues in the Golgi are destined for which cellular location?

A

Lysosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Fluorence in situ Hybridization (FISH)

What is it used to identify?

A

Chromosomal translocation, duplications or deletions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Flow Cytometry

  1. What is it used to identidy?
  2. What pathology is it commonly used for diagnosis?
A

1.

Surface Markers (eg: CD10)

2.

Leukemias

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the function of a gap junction?

What protein is responsible for forming gap junctions?

A

Intercellular communication

Connexins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What proteins form tight junctions?

What is the function of a tight junction?

A

Claudins & Occludin

Cell Barrier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What protein forms a desmosome?

What protein forms a hemidesmosome?

A

Cadherins form desmosomes

Integrins form hemidesmosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the function of the CAAT & TATA boxes?

A

Promote Transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Ehlers-Danlos Syndrome

  1. What is the main issue?
  2. What are the main complications
  3. What step is impaired in this disease?
A
  1. Defective collagen synthesis which can cause:

- easy bruising

- hyperextendible skin

- hypermobile joints

  1. Berry + Aortic aneurysms, organ rupture

3.

N-terminal Peptide Removal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What enzyme removes the RNA primer?

A

DNA Polymerase I

(only one that has 5’ to 3’ exonuclease activity)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

I-cell disease

  1. How/Why does it occur?
  2. How does it present?
A
  1. Defect in N-acetylglucosamyl-1-phosphotransferase –>

failure of golgi to phosphorylate mannose on glycoproteins

(decreased mannose-6-phosphate) —>

proteins are secreted extracellularily rather than to lysosome

2.

High plasma levels of lysosomal enzymes, coarse facial features, gingival hyperplasia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Signal Recognition Particle (SRP)

  1. What is its function?
  2. What occurs if it is dysfunctional?
A

1.

Traffics protein from the ribosomes to the RER

2.

Proteins accumulate in cytosol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What are the functions of the following vesicular trafficking proteins: 1. **_COPI_** 2. **_COPII_** 3. **_Clathrin_**
**_COPI_**: - Golgi --\> golgi - cis-golgi --\> ER (retrograde) **_COPII_**: ER --\> cis-golgi (anterograde) "**Two** (COP**II**) steps forward, **One** (COPI) step back" **_Clathrin_**: trans-golgi --\> lysosomes plasma membrane --\> endosomes
26
Disuse of a muscle due to being in a case can result in **atrophy**. How does this process occur?
**Cytoskleton** degredation via **_ubiquitin-proteosome pathway_**
27
What type of vitamin D do we get from: a. Sunlight b. Food/Plants
a. **Cholecalciferol** (D3) b. **Ergocalciferol** (D2)
28
In a patient who has **abnormal elastin** due to **defective cross-linking,** what amino acid would be most different in comparison to a normal persons elastin?
**_Lysine_** (responsible for cross-linking which gives elastin elastic propreties)
29
In a patient preganant with a child with **_Trisomy 21_** how would the following serum markers be altered: **1. Nuchal Translucency** **2. B-hCG** **3. PAPP-A (pregnancy associated plasma protein)** **4. Inhibin A**
**1. Increased nuchal translucency** **2. Increased B-hCG** **3. Decreased PAPP-A** **4. Increased Inhibin A**
30
In a patient preganant with a child with **_Trisomy 18 (Edwards Syndrome)_** how would the following serum markers be altered: **1. Nuchal Translucency** **2. B-hCG** **3. PAPP-A (pregnancy associated plasma protein)** **4. Inhibin A**
**1. Normal nuchal translucency** **2. decreased B-hCG** **3. Decreased PAPP-A** **4. normal/decreased Inhibin A**
31
In a patient preganant with a child with **_Trisomy 13 (Patau Syndrome)_** how would the following serum markers be altered: **1. Nuchal Translucency** **2. B-hCG** **3. PAPP-A (pregnancy associated plasma protein)** **4. Inhibin A**
**1. Normal nuchal translucency** **2. decreased B-hCG** **3. Decreased PAPP-A** **4. normal Inhibin A**
32
In patients with **breast/ovarian cancers** with the **BRCA1** mutation, what **DNA repair mechanism** is damaged?
**_Double Stranded Recombination Repair_** (A strand from the damaged dsDNA is repaired by using a complementary strand from an intact dsDNA)
33
What disease occurs as a result of a defect in **DNA mismatch repair?**
_Lynch Syndrome / Hereditary Nonpolyposis Colorectal Cancer_ (due to microsatelite instability)
34
What disease occurs as a result of having **damaged nucleotide exicison repair**?
**_Xeroderma Pigmentosum_** (inability to repair DNA pyrimidine dimers caused by UV exposure) Presents as: dry skin, extreme light sensitivity, increased risk for skin cancers
35
**_Mitochondrial Myopathies_** 1. How do they present? 2. Why do they occur? 3. How do they appear on muscle biopsy?
1.**_Myopathy_** (muscle damage) **_Lactic acidosis_** **_CNS issues (migraines, seizures)_** 2. Failure of oxidative phosphorylation 3. Ragged red fibers
36
**_C-reactive protein_** 1. What can it be used as a marker for? 2. Where is it synthesized?
1. **Inflammation** 2. **Liver** (like most proteins)
37
**_Nitrogen Balance_** 1. What is it? 2. What raises it? 3. What lowers it?
1. It is a measure of **nitrogen _input_ - nitrogen _output_** **2.** **Raised by food such meats, eggs, legumes** **3.** **Lowered by urine, feces, sweat**
38
What are the odds that a sibling has a **matching HLA type** to his sibling so he can be a transplant/bone marrow donor?
1/4 (there is a 25% chance of 2 siblings inheriting the same haplotype)
39
What inhertiance pattern is seen in Sickle Cell disease?
Autosomal Recessive
40
**_Xeroderma Pigmentosum_** 1. What is defective these patients ? 2. What are effects?
1. **Defective Nucleotide Exicison Repair** Due to a deficiency in **UV-specific Endonuclease** **2.** Severe photosensitivity, hyperpigmentation is sun exposed areas, increased risk for skin cancers
41
**_Mosaicism_** 1. What is it? 2. What is the diffence between **Somatic and Gonadal/Germinline Mosaicism**?
1. Mosaicism is when there genetically different cells in the same individual. 2. **Somatic Mosaicism** is when the mutation occurs once the person is already born and presents with symptoms. Cannot be passed down to children. **Germline Mosaicism** is when the mutation occurs in the sperm/egg of an indiviudal. Mutation will pass to children
42
What codon signals initiation of protein synthesis? What codon signals termination of protein synthesis? (Stop codons)
Start: **_AUG_** STOP: **_UGA, UAG, UAG_** "U Go Away" "U Are Away" "U Are Gone"
43
What would be the **anticodon** for the following mRNA sequence? 5'---- **_UAG_** ----3'
5' ---- **CUA** ---- 3' Remember the **conon-anticodon binding** occurs in the **_opposide_** direction
44
**_Heterochromatin vs Euchromatin_** 1. Where is it located? 2. Is it transcriptonally active? 3. Is it heavily methylated?
1. **Heterochromatin**: periphery of nucleus **Euchromatin**: Dispersed throughout 2. **Heterochromatin**: no - doesnt make protein **Euchromatin**: yes "euchromatin is expresssed" 3. Only Heterochromatin is methylated and therefore inactive
45
_**Enhancers** and **Silencers**_ 1. What is their function? 2. Where are they located?
1. **_Enhancers_**: increase expression of a gene on a chromosome **_Silencers_**: Decrease expression of a gene on a chromosome 2. They can be located _upstream_**,** _downstream_ or _within_ the **_intron_**
46
What is the function of a **promotor site**?
It is **another site where RNA pol II** and other trancription factors can bind that is **upstream from the TATA box** They increase gene transcriptiom
47
Do tRNAs bind stop codons? How is protein synthesis terminated?
No tRNAs do not bind stop codons When the ribosome encounters a stop codon, **_releasing factor proteins_** bind to the ribosome and stimulate release of the formed polypeptide
48
**From childhood to puberty**, what meiosis stage is the **primary oocyte** arrested in? During **ovulation**, what meiosis stage is the **secondary oocyte** arrested in until fertilization?
Prophase of Meiosis I Metaphase of Meiosis II
49
**_Homeobox Genes_** 1. What do they code for? 2. What is their function?
1. **_Transcription factors_** 2. **Segmental orginization of the embryo** along the cranial-caudal axis
50
What is the best **test** to see if a gene is being transcribed/expressed?
**Northern Blot** to test for the presence of its **mRNA**
51
What is the function of **_Histone H1_** ?
It helps **condense DNA** into its heterochromatin form
52
What is **_Splicing_**?
It is a post-transcriptional modification process that **removes introns (non-coding DNA regions)** from the pre-cursor mRNA. This leaves only the **exons (DNA coding regions)** in the mRNA script to be translated.
53
What is **_alternative splicing_**? Can it have negative consequences?
Like regular splicing, the introns will be removed. However, **different combinations of exons** are selectively included and excluded from a mRNA transcript. This allows the DNA from a single gene to code for a diverse group of proteins Yes, it can be involved in disease processes such as cancer where it can allow cells to evade host defences
54
**_Telomerase_** 1. What is its function? 2. Which type of cell most commonly has them?
1. Telomerase is a reverse transcriptase that **lengthens telomeres** by adding TTAGGG repeasts to its 3' end **to prevent cell death** **2.** **Stem cells (ex. epidermal basal cells)**
55
**_Lesch-Nyhan Syndrome_** 1. What enzyme is defected? 2. What does it result in? 3. How does it present?
1. **Hypoxanthine-Guanine Phosphoribosyltransferase (_HGPRT_)** 2. Defective purine salvage/rescur ---\> **increased uric acid** **3. "HGPRT"** **_H_**yperuricemia, **_G_**out, **_P_**issed off (agression, self-harm), **_R_**etardation, **_D_**ystonia
56
**_HbA, HbS, HbC_** 1. What amino acid differences are seen between them? 2. What type of mutation results in HbS and HbC 3. How would they differ on electrophoresis?
1. **_HbA_** - normal **_HbS_ - glutamate replaced with valine** **_HbC_ - glutamate replaced with lysine** (ly**C**ine) 2. Both are **Missense** mutations 3. **HbA \> HbS \> HbC**
57
**_snRNPs_** (small nuclear ribonucleoproteins) 1. What is their function? 2. In what disease can they be affected?
1. They are an important component of the **spliceosome** and are required for **splicing** **2. _Lupus**_ due to its _**anti-smith antibodies_ which are directed _against snRNPs_**
58
If there is a build-up of many very long chained or branced fatty acids, which organelle is most likely not functioning?
**_Peroxisome_** Function: oxidation of very long and brached chain fatty acids
59
A mutation involving the enzyme **Phosphoribosyl Pyrophosphate (PRPP) sythetase gene** is most likely to result in what?
**_Gout_** Due to increased production and degredation of purines
60
**_Propionic Acidemia_** 1. What will be elevated? 2. What enzyme is deficient? 3. Which amino acids can cause it?
1. **Propionyl Co-A** 2. Propionyl Co-A Carboxylase 3. **Valine, isoleucine, methionine, threonine** odd-chain fatty acids
61
**_Methylmalonic Acidemia_** 1. What will be elevated? 2. What enzyme is deficient? 3. Which amino acids can cause it?
1. **Methylmalonyl Co-A** 2. Methylmalonyl Co-A Carboxylase 3. **Valine, isoleucine, methionine, threonine** odd-chain fatty acids
62
What is the base sequence at the 3'end of a tRNA?
CCA tail
63
What is the most important function of the **Smooth Endoplasmic Reticulum (SER)**?
**Steroidgenesis** (it is involved in the processing and synthesis of hydrophobic compounds)
64
Which enzyme is responsible for causing bruises to appear greenish?
Heme Oxigenase | (converts heme to bilverdin)
65
What substance is responsible for regulating **both** fatty acid synthesis and breakdown (beta-oxidation)?
**_Malonyl-CoA_** (it is the rate limiting step in FA synthesis) (it can also inhibit B-oxidation)
66
**_Tetrahydrobiopeterin_** 1. What is its abbreviation? 2. What products require it for formation?
1. **_BH4_** 2. **Tyrosine, Dopamine, Serotonin**
67
_Protein kinase B (**Akt**)_ 1. What signalling pathway does it activate? 2. What does it?
1. **_mTOR pathway_** 2. It **translocates to nucleus** and induces genes involved in **cell-survival, anti-apoptosis and angiogenesis**
68
What process causes **vitamin C** deficiency to result in **_scurvy_**? Where does this process normally take place?
Vitamin C is needed for **hydroxylation of proline and lysine** in collagen This takes place in Rough Endoplasmic Reticulum (**_RER_**)
69
Which amino acid is most likely to become essential in a patient with homocystinuria? Why?
**_Cysteine_** Since its most commonly due to Cystathione Synthase deficinecy which results in the inability to convert homocysteine to cysteine

UWorld - Biochemistry (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions