Updated: 9/15/2016

Molecular Biology Basics

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Questions
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Evidence
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Videos
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Nuclear structures
  • Chromosomes
    • 46 in humans (23 pairs)
      • 22 pairs of autosomes, 1 pair of sex chromosomes
    • contains DNA and RNA
  • Deoxyribonucleic acid (DNA)
    • Thymine, adenine, guanine, and cytosine
      • adenine linked to thymine (A-T)
      • guanine linked to cytosine (G-C)
    • double stranded
    • strands linked together by phosphate groups
    • 2' hydrogen group
    • regulates cell division
    • mRNA is produced from DNA
      • an exon is portion of gene that codes for mRNA
      • exon is expressed
  • Gene
    • segment of DNA that contains the information needed to synthesize a protein
    • determines the unique biologic qualities of a cell
    • exon
      • coding information 
    • intron
      • does not code for mRNA
  • Ribonucleic acid (RNA)   
    • usually single stranded but can be double stranded
      • double stranded RNA found in some viruses
      • certain interactions between single stranded RNA in human cells can form double stranded RNA
    • has ribose sugar
    • Uracil, adenine, guanine, and cytosine (no thymine)
    • less stable than DNA
    • 2' hydroxyl group
    • can be located in either the nucleus or cytoplasm
    • messenger RNA (mRNA)
      • translates DNA information into protein
    • ribosomal RNA (rRNA)
      • major part of ribosome, which helps synthesize a protein
    • transfer RNA (tRNA)
      • transfers amino acids to mRNA
Genetic Terms
  • Nucleotides
    • thymine, adenine, guanine, and cytosine
  • Codon
    • sequence of three nucleotides
    • each codon correlates to one of the 20 amino acids
    • linking of the amino acids create a protein
  • Gene promotor
    • regulatory portion of DNA that controls initiation of transcription
  • Gene enhancers
    • site on DNA that transcription factors bind to
    • regulate transcription
  • Transcription 
    • DNA => mRNA
  • Translation 
    • mRNA => protein
  • Haploid
    • Haploid is the amount of DNA in a human egg or sperm cell (half the amount of DNA in a normal cell)
Cell Cycle
  • Phases 
    • G0
      • represents a "stable" phase
      • cells are diploid (2N) in the G0 and G1 phases
    • G1
      • initial growth phase
      • cells are diploid (2N) in the G0 and G1 phases
    • S
      • DNA replication/synthesis phase 
      • cells become tetraploid (4N) at the end of S and for the entire G2 phases
    • G2
      • gap phase
      • cells become tetraploid (4N) at the end of S and for the entire G2 phases
    • M
      • mitosis phase
Apoptosis
  • Defined as programmed cell death
  • Requires a series of intracellular signaling events
  • Different from cell lysis - where a cell releases its contents into the surrounding area
  • One hallmark of cancer is the cell's loss of apoptosis 
Research techniques
  • Agarose gel electrophoresis
    • separates DNA based on size
    • DNA is negatively charged
    • gel exposed to electric field
    • smaller pieces moves through gel faster
  • Southern blotting
    • restriction enzymes cut up DNA
    • separate on agarose gel
    • identifies DNA sequence
  • Northern blotting
    • restriction enzymes cut up RNA
    • separate on agarose gel
    • identifies RNA sequence
  • Western blotting
    • SDS-PAGE gel
    • identifies protein
  • DNA ligation
    • combining different DNA fragments not found together naturally to create recombinant DNA
  • Plasmid vector
    • an extrachromosomal element, often circular, that can replicate and be transferred independently of the host chromosome 
    • one example of the function of a plasmid is antibiotic resistance
    • can be introduced into bacteria in the process of transformation
  • Polymerase chain reaction (PCR)
    • DNA => DNA
    • a molecular biology tool used to generate many copies of a DNA sequence 
    • uses "primers" specific to a segment of DNA
    • requires temperature-mediated enzyme DNA polymerase
  • Reverse transcription polymerase chain reaction (RT-PCR) 
    • RNA => DNA
    • variant of polymerase chain reaction (PCR) used in molecular biology to generate many copies of a DNA sequence from fragments of RNA
    • RNA strand is first reverse transcribed into its DNA complement
    • amplification of the resulting DNA proceeds using polymerase chain reaction
 

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(OBQ04.195) Tumor necrosis factor receptor 1 is involved in which of the following cellular events? Review Topic

QID: 1300
1

Replication

4%

(37/916)

2

Agenesis

2%

(14/916)

3

Apoptosis

92%

(840/916)

4

Senescence

2%

(16/916)

5

Ectopy

1%

(5/916)

ML 2

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

(OBQ04.199) Which of the following statements best describes a plasmid? Review Topic

QID: 1304
1

An extrachromosomal, circular piece of DNA that replicates independently of host DNA

88%

(402/457)

2

An extrachromosomal, linear piece of RNA which replicates independently of host DNA

8%

(35/457)

3

A protein which promotes transcription of DNA to RNA

4%

(16/457)

4

A gene which leads to cancerous cell transformation

0%

(2/457)

5

A gene which suppresses cancerous cell transformation

0%

(1/457)

ML 2

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

(OBQ05.122) All of the following statements regarding RNA are true EXCEPT? Review Topic

QID: 1008
1

RNA uses thymine while DNA uses uracil

66%

(300/453)

2

RNA may be either single or double-stranded

12%

(56/453)

3

RNA has a hydroxyl group at the 2' position in the ribose

8%

(35/453)

4

DNA has a hydrogen group at the 2' position in the deoxyribose

6%

(28/453)

5

RNA helix is of A-Form

7%

(32/453)

ML 3

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PREFERRED RESPONSE 1

(OBQ07.178) DNA replication occurs during which phase of the cell cycle? Review Topic

QID: 839
1

M

16%

(173/1097)

2

S

59%

(652/1097)

3

R

11%

(119/1097)

4

G1

10%

(105/1097)

5

G2

4%

(41/1097)

ML 4

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

(OBQ07.157) What is the post-amplification product of reverse transcription polymerase chain reaction (RT-PCR)? Review Topic

QID: 818
1

RNA

34%

(531/1552)

2

DNA

58%

(905/1552)

3

Protein

6%

(94/1552)

4

Mitochondria

0%

(6/1552)

5

Immunoglobulins

1%

(12/1552)

ML 3

Select Answer to see Preferred Response

PREFERRED RESPONSE 2
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