Ch 18: Genetics of Viruses and Bacteria
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24 terms
Terms | Definitions |
|---|---|
 Capsid | The protein shell that encloses a viral genome. |
| Conjugation | a process of DNA exchange between bacteria |
| Inducer | A specific small molecule that inactivates the repressor in an operon. |
| Lysogenic cycle | A phage replication cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage and does not kill the host. |
| Lytic cycle | A type of viral (phage) replication cycle resulting in the release of new phages by lysis (and death) of the host cell. |
| Operator | In prokaryotic DNA, a sequence of nucleotides near the start of an operon to which an active repressor can attach. The binding of the repressor prevents RNA polymerase from attaching to the promoter and transcribing the genes of the operon. |
| Operon | A unit of genetic function common in bacteria and phages, consisting of coordinately regulated clusters of genes with related functions. |
| Prion | An infectious form of protein that may increase in number by converting related proteins to more prions. |
| Prophage | A phage genome that has been inserted into a specific site on the bacterial chromosome. |
| Provirus | Viral DNA that inserts into a host genome. |
| R plasmid | A bacterial plasmid carrying genes that confer resistance to certain antibiotics. |
| Regulatory gene | A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes. |
| Repressor | A protein that suppresses the transcription of a gene. |
| Retrovirus | An RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome |
| Reverse transcriptase | An enzyme encoded by some certain viruses (retroviruses) that uses RNA as a template for DNA synthesis. |
| Temperate phage | A phage that is capable of reproducing by either the lytic or lysogenic cycle. |
| Viral envelope | A membrane that cloaks the capsid that in turn encloses a viral genome. |
| Virulent phage | A phage that reproduces only by a lytic cycle. |
| Transduction | occurs when new DNA is introduced into the genome of a bacteria by a virus |
| Transformation | occurs when bacteria absorb DNA form their surroundings and incorporate it into their genome |
| Controls the breakdown of lactose - when the operator region is occupied by the repressor, RNA polymerase is unable to transcribe several structural genes that code for enzymes that control the uptake and subsequent breakdown of lactose - When lactose is available, it combines with the repressor to make it inactive - When the represor is inactivated, RNA polymerase is able to transcirbe the genes that code for th enzymes that break down lactose - lactose is required to induce (turn on the enzyme) so it's an inducible enzyme | How does the lac operon work? |
| Controls the synthesis of the amino acid trypotophan - a regulatory gene produced an inactive repressor that doesn't bind to the operator - RNA polymerase transcribes the structural genes to produce enzymes that synthesize trpotophane - when tryptophan is available from the surrounding environment, tryptophan reacts with the inactive repressor to make it active - since it stops produced enzymes only in the presence of an active repressor, they are called repressible enzymes | How does the trp operon work? |
| Nucleosome packing | influences where a section of DNA will be transcribed. Methylated DNA makes transcirption difficult while acetylation uncoils the DNA to make transcription of DNA easier |
| DNA fingerprinting | RFLPs in every person is different |
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