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Name the four nitrogenous bases in DNA.
Adenine, cytosine, guanine, thymine.
Name the purines and pyrimidines.
The purines are adenine and guanine.
The pyrimidines are cytosine, thymine and uracil.
What is the base-pairing in DNA? How many bonds hold the bases together?
Adenine and thymine (A=T) 2 hydrogen bonds.
Cytosine and guanine (G=C) 3 hydrogen bonds.
Name the three difference between RNA and DNA.
- RNA uses ribose instead deoxyribose.
- RNA replaces thymine with uracil.
- RNA is usually single-stranded.
(T/F) DNA synthesis proceeds in the 3' to 5' direction.
False, DNA synthesis proceeds in the 5' to 3' direction.
What are the four types of RNA, and what are their functions?
Messenger RNA (mRNA) - contains the codons for peptide chain synthesis.
Transfer RNA (tRNA) - transports amino acids to the ribosome during protein synthesis.
Ribosomal RNA (rRNA) - structural component of ribosomes.
Heterogeneous nuclear RNA (hnRNA) - precursor of mRNA.
What is transcription?
Transcription is the process whereby mRNA is synthesized from a DNA template.
What is translation?
Translation is the process whereby proteins are synthesized from a mRNA template.
What is an exon? An intron?
An exon is a coding sequence on a gene.
An intron is a non-coding sequence on a gene.
What is a codon?
A codon is a 3-base sequence on mRNA that codes for a specific amino acid.
What is an anticodon?
An anticodon is a 3-base sequence on tRNA that is complementary to a mRNA codon.
What are the three stages of polypeptide synthesis?
The three stages of polypeptide synthesis are initiation, elongation, and termination.
What are the three types of base pair mutations that can occur during protein synthesis?
Types of base-pair mutations are substitutions, insertions, and deletions.
(T/F) A frameshift mutation usually leads to a non-functioning protein.
What types of nucleic acid can be found in a virus?
A virus can contain DNA or RNA.
What is a retrovirus?
A retrovirus is an RNA virus that codes for the enzyme reverse transcriptase, which uses the RNA as a template for DNA synthesis.
What is a prophage (provirus)?
A prophage is a virus that has integrated its DNA into the host cell's DNA.
What is a bacteriophage?
A bacteriophage is a virus that attacks only bacteria.
Describe the lytic and lysogenic cycles.
Bacteriophage infection results in either a lytic or a lysogenic cycle.
A lytic cycle results in the production of new progeny that cause the cell to burst (lyse).
A lysogenic cycle results in incorporation of the viral DNA into the bacterial DNA where it remains inactive. A lyosogenic cycle may progress to a lytic cycle.
What are the three mechanisms by which bacteria can increase genetic variability?
Transformation - incorporation of foreign chromosome fragments.
Conjugation - transfer of genetic material between two bacteria.
Transduction - virus carries DNA between two bacteria.
What is an operon?
An operon is a gene that regulates (bacterial) transcription.
What is a repressible system?
A repressible system is in a constant state of transcription unless a corepressor is present to inhibit transcription.
What is an inducible system?
An inducible system requires the presence of an inducer for transcription to occur.