Chapter 11
True/False:
A signal can have different effects in cells with different proteins and pathways
True
True/False: Nonsense mutations have no effect on the amino acid produced by a codon because of redundancy in the genetic code
False, Silent Mutations
__________ control elements are located close to the promoter. __________ control elements may be far away from a gene or even located in an intron.
A _______ is an infectious particle consisting of genes packaged in a protein coat
Virus
__________ signaling is signaling over short distances. __________ signaling is signaling over long distances.
Paracrine, Endocrine
____________ are the sites of translation.
Ribosomes
Cell ____________ is the process by which cells become specialized in structure and function. The physical processes that give an organism its shape constitute is morphogenesis
differentiation, morphogenesis
________ are infectious proteins that appear to cause degenerative brain diseases in animals. ________ are infectious RNA molecules that lack a protein component
Prions, Viroids
What is a second messenger?
–These are small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion
–Second messengers participate in pathways initiated by G P C R s and R T K s
–Cyclic A M P and calcium ions are common second messengers
In a ribosomes, the ______ site holds the tRNA that carries the next amino acid to be added to the chain
A
What is DNA methylation?
The addition of methyl groups to certain bases in DNA, condensing the chromatin and reducing transcription
Why are viruses not cells?
Lack cytoplasm, ribosomes (no independent protein synthesis), no metabolic pathways, independent genome replication machinery, no ATP production.
Name the four aspects of signal regulation.
–Amplification of the signal (and thus the response)
–Specificity of the response
–Overall efficiency of response, enhanced by scaffolding proteins
–Termination of the signal
Name and explain the two stages of gene expression.
•Transcription is the synthesis of RNA using information in DNA
–Transcription produces messenger RNA (mRNA)
•Translation is the synthesis of a polypeptide, using information in the mRNA
Tumor suppressing proteins normally... (3 things)
–repair damaged DNA
–control cell adhesion
–act in cell-signaling pathways that inhibit the
cell cycle
Name and explain the two altnerative reproduction mechanisms that phages do.
The lytic cycle is a phage replicative cycle that culminates in the death of the host cell.The lytic cycle produces new phages and lyses (breaks open) the host’s cell wall, releasing the progeny viruses
The lysogenic cycle replicates the phage genome without destroying the host.The viral DNA molecule is incorporated into the host cell’s chromosome
Name and explain the three steps in cell signaling
Reception = the target cell detects a signaling molecule that binds to a receptor protein on the cell surface
Transduction= the binding of the signaling molecule alters the receptor and initiates a signal transduction pathway; transduction often occurs in a series of steps
Response= the transduced signal triggers a specific response in the target cell
Name and explain the three stages of transcription
Invitation – occurs when the enzyme RNA polymerase binds to a region of a gene called the promoter. This signals the DNA to unwind so the enzyme can ''read'' the bases in one of the DNA strands.
Elongation – the stage when the RNA strand gets longer, thanks to the addition of new nucleotides. During elongation, RNA polymerase "walks" along one strand of DNA, known as the template strand, in the 3' to 5' direction
Termination - occurs when RNA polymerase crosses a stop (termination) sequence in the gene. The mRNA strand is complete, and it detaches from DNA
Name and explain the two operons.
BONUS: Name what binds to each protein to begin the process
•A repressible operon is one that is usually on; binding of a repressor to the operator shuts off transcription
–The trp operon is a repressible operon
•An inducible operon is one that is usually off; a molecule called an inducer inactivates the repressor and turns on transcription
–The lac operon is an inducible operon and contains genes that code for enzymes used in the hydrolysis and metabolism of lactose
*Tryptophan, Allolactose
Name and explain the two kinds of immunity.
Active immunity:
- Develops when our own bodies produce antibodies against that pathogen
- Occurs naturally; not received from an outside source
- Happens when we are exposed to a certain pathogen
- Can also acquire it through vaccination, which introduces antigens to the body in a harmless form
Passive immunity:
- Develops when antibodies that were not made by our own bodies are received
- A human fetus acquires antibodies from exchanges between its blood and its mother’s blood.
- A nursing baby receives passive immunity to a broad range of pathogens passed in breastmilk.
- Mother’s milk is rich in antibodies because the mother’s immune system has encountered many antigens and made many antibodies in her lifetime.
- Passive immunity produces no memory cells.
- Wears off as the received antibodies degrade, usually within a few weeks or months