chapter 18, 19, 20 Flashcards
- Describe two main strategies cells use to control metabolism
- Regulate enzyme activity- product of pathway inhibits enzyme one
- Regulate gene expression- so enzymes are only produced when needed, product of pathway inhibits transcription of genes for enzymes of that pathway
- Using the trp operon as an example, explain the concept of an operon and the function of the operator, repressor and corepressor.
- Operon concept- an operon is a cluster of gens under control of a single promoter.
- Operator- a segment of DNA that acts as a on/off switch for transcription
- Repressor- a protein that binds to the operator blocking RNA polymerase inhibiting transcription.
- Corepressor- a small molecule that binds to the repressor, activating It. In the trp operon trptophan acts as the corepressor.
- Distinguish between structural and regulatory genes.
- Structural genes- encode proteins that perform structural or enzymatic fuctions in the cell
- Regulatory genes- the gene that makes a repressor is not in the operon and is usually turned on at a low rate.
- Describe how the lac operon functions and explain the role of the inducer, allolactose.
- The lac operon is a inducible operon that is usually off, but can be turned on when the substrate is present. Used method of regulation for a catabolic pathway.
- Inducer- the molecule that inactivates a repressor, so the genes turn on. Its often a substrate for the gene products in a catabolic pathway. Eg allolactose is the inducer for the lac operon
- Explain how repressible and inducible enzymes differ and how these differences reflect differences in the pathways they control.
- Repressible enzymes- typically involved in anabolic pathways eg- trp operon. Presence of the end product inhibits enzyme synthesis.
- Inducible enzyme- typically involved in catabolic pathways (eg lac operon) the presence of the substate induces enzyme synthesis
- Distinguish between positive and negative control and give examples of each from the lac operon.
- Negative control- involves repressors inhibiting transcription eg- lac operon with the lac repressor.
- Postive control- involves activators stimulating transcription eg- lac operon with cAMP-CRP complex.
- Using the Barr body as an example, describe the function of heterochromatin in interphase cells.
- Heterochromatin- tightly packed form of DNA, which transcriptionally inactive. The barr body is an example of heterochromatin, representing an inactivated X chromosome in female cells
- List and briefly describe the 6 levels of control of gene expression in eukaryotic cells
- Choromatin structure- modifiying histones and DNA methylation
- Transcriptional control- factors that promate or inhibit transcription
- Post-transcriptional control- RNA processing and editing
- Translational control- regulation of protein synthesis
- Post translational control- protein modification and degradation
- mRNA degradation- stability and lifespan of mRNA.
- Explain how histone acetylation, DNA methylation, and epigenetic inheritance influences chromatin structure.
- Histone acetylation- loosens chromatin structure, enhancing transcription
- DNA methylation- typically represses gene expression
- Epigenetic inheritance- heritable changes in gene expression not involing changes to the DNA sequence.
- Describe at what level gene expression is generally controlled.
mRNA processing- splicing can change the gene product, depending on needs of the cell.
- mRNA degradation- the rate of degradation may be changed.
- Protein processing- protein activation/inactivation may be controlled by phosphorylation protein transport can be regulated
- Describe the normal control mechanisms that limit cell growth and division, and how it relates to cancer.
- Normal mechanisms- include cell cycle checkpoints, growth factor signals and apoptosis. Cancer is the result of the breakdown of these mechanisms. Like uncontrolled cell growth and division.
Struturcal components of viruses
viruses consist of DNA or RNA enclosed in a capsid
Why are they obligatory parasites:
they cant reproduce or carry out metablosim outside a host cell. They rely on the host cell membranes and viral proteins.
Host range and virus recognition of host cells:
host range- the limited types of cells a virus can infect, determined by viral surface proteins and specifc host cell receptors.
Reproductive cycle-
attachment, entry, replication of viral genome, assembly of new virsues- exit…. Lytic cycle virus replicates rapidly, breaking the host cell….. lysogenic cycle viral DNA intergrates into host genome and replicates with host, potienally entering the lytic cycle later.
Describe the role of restriction enzymes to protect a host prokaryotic cell from a bacteriophage
restriction enzymes are part of the bacterial immune system that protects against bacteriophage infections by cleaving foreign DNA at specific recongniton sites while methylation protects the DNA from its own restriction enzymes.
List the differences between a bacteriophage and a typical animal virus.
bacteriophage-infects bacterial cells and have complex structure with a head, tail, and tail fibers. Goes under both lytic cycle and lysogenic cycle. It injects its genetic material into the bacterial cell. Uses tail fibers to recognized and bond. In cytoplasm.
animal virus- infects animal cells generally simpler structures, which can be helical. Can have either DNA or RNA. Typically undergoes attachment, entry, uncoating, replication, assembly, and release. Enters cell by fusion or endocytosis, uses glycoproteins to bind. Relicates in nucleus and cytoplasm.
What is retrovirus
A virus that uses reverse transcriptase to convert its RNA genome into DNA, which integrates into host genome.
Role of vaccines?
They stimulate the immune system to recognize and fight future infections. Antiviral drugs inhibit viral replication by targeting viral enzymes.
Describe the characteristics of prions.
are entirely made of proteins no nucleic acids. Make a lot of brain dieases and misfolded version of normal proteins
- Briefly explain how DNA sequencing is accomplished and read the DNA sequence from a Next-Gen flow-gram.
- DNA sequencing- it’s a process to determine the exact sequence of nucleotides in a DNA molecule. Techniques like sanger and next generation sequencing are used.
- Next gen flow gram- in NGS, a flow-gram represents the intensity of light signals emitted during the sequencing process, which correspond to the bases incorporated.
- Explain the process of DNA cloning using bacterial plasmids.
- Isolation of DNA- extract the DNA segment of interest
- Insertion into plasmid- insert the DNA fragment into a plasmid vector
- Transformation- introduce the recombinant plasmid into bacterial cells
- Selection- use antibiotic resistance markers to select transformed bacteria
- What is recombinant DNA?
- A form of DNA that is created by combining DNA sequences that wouldn’t normally occur together, using molecular cloning methods.
- Explain how restriction enzymes are used to isolate DNA fragments.
- Restriction enzymes they cut DNA at specific recognition sites, producing fragments with sticky or blunt ends, which can be used to isolate and manipulate DNA sequences
