Molecular Structure of DNA and RNA Flashcards

Flashcards covering key vocabulary terms related to the molecular structure of DNA and RNA, derived from lecture notes.

Goal of Molecular Genetics

To use our knowledge of DNA structure to understand how DNA functions as a genetic material.

Disciplines Supporting Molecular Genetic Technology

Biochemistry, cell biology, and microbiology.

Four Criteria for Genetic Material

1. Information – contains info to construct an organism. 2. Transmission – must be passed from parents to offspring. 3. Replication – must be copied for cell division. 4. Variation – must account for phenotypic differences.

August Weismann and Carl Nägeli

Proposed that a chemical substance in cells transmits traits.

Chromosome Theory of Inheritance

The theory that chromosomes are carriers of genetic material.

Bacterium Studied by Frederick Griffith

Streptococcus pneumoniae (formerly pneumococci).

Types of S. pneumoniae used in Griffith’s Experiment

Type S (smooth, encapsulated) and Type R (rough, non-encapsulated).

Griffith’s Conclusion

A “transforming principle” from dead Type S converted Type R into Type S.

Transformation

Dead bacteria transferred genetic material to living bacteria.

Method to Identify Genetic Material

Biochemical purification of bacterial extracts.

Result of Mixing Type R with DNA Extract from Type S

Type R converted to Type S.

Conclusion of Avery, MacLeod, and McCarty Experiment

DNA is responsible for transformation.

Organism and Virus Used in Hershey and Chase Experiment

E. coli and T2 bacteriophage.

Parts of the T2 Phage

Head, sheath, tail fibers, base plate (composed of protein); DNA inside the head.

Radioactive Labels Used in Hershey and Chase Experiment

35S for proteins; 32P for DNA

Results of the Hershey and Chase Experiment

DNA entered bacterial cells

Discoverer of DNA

Friedrich Meischer in 1869 (called it “nuclein”).

Source of Acidity in Nucleic Acids

They release H+ and are negatively charged at neutral pH.

Four Levels of Nucleic Acid Complexity

1. Nucleotides 2. Linear strand 3. Double helix 4. 3D folding with proteins

Three components of a nucleotide

1. Phosphate group(s) 2. Pentose sugar 3. Nitrogenous base

Sugars Found in DNA and RNA

DNA: Deoxyribose, RNA: Ribose

Purines and Pyrimidines

Purines: Adenine (A), Guanine (G). Pyrimidines: Thymine (T), Cytosine (C), Uracil (U)

Examples of Nucleosides

ribose + adenine = adenosine, ribose + guanine = guanosine, ribose + cytosine = cytidine, ribose + uracil = uridine, deoxyribose + adenine = deoxyadenosine , deoxyribose + guanine = deoxyguanosine, deoxyribose + cytosine = deoxycytidine, deoxyribose + thymine = deoxythymidine

How a Nucleotide is Formed

By attaching one or more phosphate groups to a nucleoside via an ester bond.

Adenosine monophosphate (AMP)

ribose + adenine + 1 phosphate

Type of Bond Linking Nucleotides in a DNA or RNA Strand

Phosphodiester linkage

Backbone of DNA/RNA Strand

Sugar and phosphate groups

Reason the DNA/RNA Backbone is Negatively Charged

Because each phosphate group carries a negative charge.

Builders of Early Structural Models of DNA

Linus Pauling (built α helix models)

Discoverers of the DNA Double Helix Structure

Watson and Crick using model building and X-ray diffraction data

Rosalind Franklin’s Contributions

Helical structure, Double-stranded width, 10 base pairs per turn

Erwin Chargaff’s Discoveries

Amount of adenine ≈ thymine. Amount of guanine ≈ cytosine

Implication of Chargaff’s Rules

Adenine pairs with thymine, and guanine pairs with cytosine (Chargaff’s rule).

Key Features of Watson and Crick’s DNA Model

Two backbones outside with bases pointing inward, Hydrogen bonding between A-T and G-C, Antiparallel strands with 10 bp per turn

Recipients of the 1962 Nobel Prize

Watson, Crick, and Maurice Wilkins

What Happened to Rosalind Franklin

Her contributions were recognized posthumously; she died in 1958 and couldn’t share the Nobel Prize.

What Keeps the Width of the DNA Double Helix Constant

Pairing of purine with pyrimidine (A-T and G-C)

How Strands of DNA are Oriented

They are antiparallel

Predominant DNA Form in Living Cells

B-DNA (right-handed helix)

Z-DNA

An alternative left-handed conformation of DNA

Triplex DNA

A triple-helical DNA structure formed in vitro (synthetically)