Molecular Genetics Rapid Review for AP Biology

For a more thorough review of the terminologies below, refer to these concepts:

• Structure, Replication, and Transcription of DNA for AP Biology
• Structure, Process, and Translation of RNA for AP Biology
• Gene Expression and Genetics for AP Biology

Briefly review the following terms:

DNA: contains A and G (purines), C and T (pyrimidines), arranged in a double helix of two strands held together by hydrogen bonds (A with T, and C with G).

RNA: contains A and G (purines), C and U (pyrimidines), single stranded. There are three types: mRNA (blueprints for proteins), tRNA (bring a. acids to ribosomes), and rRNA (make up ribosomes).

DNA replication: occurs during S-phase, semiconservative, built in 5' to 3' direction. Helicase unzips the double strand, DNA polymerase comes in and adds on the nucleotides. Proofreading enzymes minimize errors of process.

Frameshift mutation: deletion or addition of nucleotides (not a multiple of 3); shifts reading frame.

Missense mutation: substitution of wrong nucleotide into DNA (e.g., sickle cell anemia); still produces a protein.

Nonsense mutation: substitution of wrong nucleotide into DNA that produces an early stop codon.

Transcription: process by which mRNA is synthesized on a DNA template.

RNA processing: introns (noncoding) are spliced out, exons (coding) glued together: 3' poly-A tail, 5' G cap.

Translation: process by which the mRNA specified sequence of amino acids is lined up on a ribosome for protein synthesis.

Codon: triplet of nucleotides that codes for a particular amino acid: start codon = AUG; stop codon = UGA, UAA, UAG. (For specifics on translation, please flip to text for a good description.)

Promoter: base sequence that signals start site for transcription.

Repressor: protein that prevents the binding of RNA polymerase to promoter site.

Inducer: molecule that binds to and inactivates a repressor.

Operator: short sequence near the promoter that assists in transcription by interacting with transcription factors.

Operon: on/off switch for transcription. Allows for production of genes only when needed. Remember the lac operon—lactose is the inducer, when present, transcription on; when absent, it is off.

Viruses: Parasitic infectious agent unable to survive outside the host; can contain DNA or RNA, or have a viral envelope (protective coat).

• Lytic cycle: one in which the virus is actively reproducing and kills the host cell.
• Lysogenic cycle: one in which the virus lies dormant within the DNA of the host cell.

Retrovirus: RNA virus that carries with it reverse transcriptase (HIV).

Prion: virus that converts host brain proteins into misshapen proteins (mad cow disease).

Viroids: tiny plant viruses.

Phage: virus that infects bacteria.

Bacteria: prokaryotic cells; consist of one double-stranded circular DNA molecule; reproduce by binary fission (e.g., plasmid—extra circle of DNA present in bacteria that replicate independently of main chromosome).

Genetic Recombination

Transformation: uptake of foreign DNA from the surrounding environment (smooth vs rough pneumococcus).

Transduction: movement of genes from one cell to another by phages, which are incorporated by crossover.

• Generalized: lytic cycle accidently places host DNA into a phage, which is brought to another cell.
• Specialized: virus leaving lysogenic cycle brings host DNA with it into phage.

Conjugation: transfer of DNA between two bacterial cells connected by sex pili.

Genetic Engineering

Restriction enzymes: enzymes that cut DNA at particular sequences, creating sticky ends.

Vector: mover of DNA from one source to another (plasmids are good vectors).

Cloning: somewhat slow process by which a desired sequence of DNA is copied numerous times.

Gel electrophoresis: technique used to separate DNA according to size (small = faster). DNA moves from: – to +.

Polymerase chain reaction (PCR): produces large quantities of sequence in short amount of time.