Molecular Biology: Central Dogma, DNA Structure, and Genetic Techniques W1

What is the Central Dogma of molecular biology?

The Central Dogma describes the general flow of genetic information within a cell: DNA is transcribed into RNA, and RNA is translated into protein.

Why are RNA viruses considered an exception to the Central Dogma?

RNA viruses are exceptions because they can replicate their RNA genome directly or use reverse transcriptase to synthesize DNA from an RNA template, bypassing the standard DNA-to-RNA flow.

What is the role of telomerase as an exception to the Central Dogma?

Telomerase is an exception because it acts as a reverse transcriptase, using its own RNA template to synthesize DNA, thereby extending the telomeres of chromosomes.

What are the primary structural differences between DNA and RNA nucleotides?

DNA nucleotides contain deoxyribose (lacking a 2' OH group) and the base thymine, while RNA nucleotides contain ribose (with a 2' OH group) and the base uracil.

What are the components of a standard DNA/RNA nucleotide?

A nucleotide consists of a 5-carbon sugar (pentose), a nitrogenous base attached to the 1' carbon, and a phosphate group attached to the 5' carbon.

What is the melting temperature (Tm) of DNA?

The Tm is the temperature at which 50% of the double-stranded DNA molecules in a solution have denatured into single strands.

How does G-C content affect the melting temperature (Tm) of DNA?

Higher G-C content increases the Tm because G-C base pairs are held together by three hydrogen bonds, whereas A-T base pairs are held by only two.

What forces stabilize the DNA double helix?

The DNA double helix is stabilized by hydrogen bonding between complementary base pairs and base stacking interactions between adjacent bases.

What is the purpose of nucleic acid hybridization?

Nucleic acid hybridization is used to detect the presence of specific DNA or RNA sequences by allowing a labeled probe to bind to its complementary target sequence.

What are the two primary requirements for genetic information according to the Watson/Crick model?

Genetic information must contain the instructions to dictate the cell's components and must be easily duplicated to be passed on during cell division.

What was the significance of the Hershey-Chase experiment?

The experiment used radioactive labeling of proteins (sulfur) and DNA (phosphorus) in bacteriophages to demonstrate that DNA, not protein, is the hereditary material injected into host cells.

What is a gene?

A gene is a specific sequence of DNA that encodes a functional product, typically a polypeptide or an RNA molecule.

What is an auxotroph?

An auxotroph is a mutant organism that is unable to synthesize a specific compound required for its growth and therefore must be supplied with that compound in its environment.

What is a selection marker in molecular biology?

A selection marker is a gene introduced into a cell that confers a specific phenotype, such as antibiotic resistance or the ability to synthesize a nutrient, allowing researchers to identify cells that have taken up the gene.

What are the components of a gene?

A gene typically includes a promoter, the protein-coding sequence (which may be interrupted by introns), and a 3' untranslated region (UTR).

What is a genome?

A genome is the entire set of genetic material (DNA or RNA) that constitutes an organism, including both coding and non-coding sequences.

What is the function of a spectrophotometer in DNA analysis?

A spectrophotometer measures the absorbance of light by DNA, which is used to monitor DNA denaturation as the strands separate and absorbance increases.

What does it mean for DNA strands to be anti-parallel?

Anti-parallel means the two strands of the DNA double helix run in opposite directions, with one strand oriented 5' to 3' and the other 3' to 5'.

What is the role of the phosphodiester backbone in DNA?

The sugar-phosphate backbone forms the structural exterior of the DNA helix, providing stability and protecting the nitrogenous bases inside.

What is transformation in the context of Griffith's experiment?

Transformation is the process by which a cell takes up foreign genetic material from its environment, resulting in a change in the cell's genotype or phenotype.

How does extreme pH affect DNA stability?

Extreme pH levels can disrupt the hydrogen bonds between base pairs, leading to the denaturation of the DNA double helix.

What is the 'one gene, one polypeptide' hypothesis?

Proposed by Beadle and Tatum, this hypothesis states that each gene is responsible for the synthesis of a single specific polypeptide chain.

What is the purpose of a ViroChip?

A ViroChip is a type of microarray used to rapidly identify viruses in a sample by hybridizing viral genetic material to a chip containing probes for known viral sequences.

Why is DNA considered the preferred molecule for genetic information over RNA?

DNA is more stable than RNA because it lacks the 2' hydroxyl group, which makes RNA more susceptible to hydrolysis, and it uses thymine instead of uracil, which is more resistant to mutation.

What is the result of treating heat-killed virulent bacteria with nuclease in a transformation experiment?

Treating the sample with nuclease destroys the DNA, preventing transformation; therefore, the bacteria remain non-virulent and the mouse lives.

What is the significance of the NeoR gene as a selection marker?

NeoR confers resistance to the antibiotic neomycin, allowing researchers to select for cells that have successfully incorporated the plasmid containing the marker.