test 4
list three ways pre-mRNA is modified prior to translation.
-a 5' cap is added -poly A' tails -RNA splicing
put the following events of elongation in prokaryotic translation in chronological order. 1. binding of mRNA with small ribosomal subunit 2. recognition of initiation codon 3. complementary base pairing between initiator codon and anticodon of initiator tRNA 4. base pairing of the mRNA codon following the initiator codon with its complementary tRNA 5. attachment of the large subunit
1,2,3,5,4
list and define the three sites on the ribosome that can be occupied by tRNA
A-site: where tRNA enters the amino acid P-site: peptide E-site: exit site; temerol
in the process of transcription, ____.
RNA is synthesized
in eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a global protein?
RNA polymerase II
in eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a protein?
RNA polymerase II
the DNA of telomeres has been highly conserved throughout the evolution of eukaryotes. This most likely reflects ___.
a critical function of telomeres
which of the following types of mutation would convert a proto-oncogene into an oncogene?
a mutation that greatly increases the amount of the proto-oncogene protein
which of the following supports the argument that viruses are nonliving?
at some level they rely on the machinery within a cell to replicate their genome, transcribe mRNA and translate protein.
the trp repressor blocks transcription of the top operon when the repressor ____.
binds to tryptophan
alternative RNA splicing ____.
can allow the production of proteins of different sizes and functions from a single mRNA
the fact that plants can be cloned from somatic cells demonstrates that____.
differentiated cells retain all the genes of the zygote
what is the difference between euchromatin and heterochromatin? Which one would be more likely to contain genes that are transcriptionally active?
euchromatin- active regions for gene transcription and the genes are loosely wound heterochromatin- the tips and centromeres on the chromatin; tightly wound euchromatin
muscle cells differ from nerve cells mainly because they
express different genes
in colorectal cancer, several genes must be mutated for a cell to develop into a cancer cell. which of the following kinds of genes would you expect to be mutated?
genes involved in control of the cell cycle
which of the following can be effective in preventing the onset of viral infection in humans?
getting vaccinated
a signal peptide ___.
helps target a protein to the ER
what is the role of SRP protein during translation? list one reason this step would be critical for a receptor protein.
it delivers membrane proteins and secretory proteins to the translocation channel in the plasma membrane. it's important for single peptide bonding
emerging viruses arise by
mutation of existing viruses, the spread of existing viruses to new host species, and the spread of existing viruses more widely within their host species
at the beginning of this century, there was a general announcement regarding the sequencing of he human genome and the genomes of many other multicellular eukaryotes. many people were surprised that the number of protein-coding sequences was much smaller than they had expected. Which of the following types of DNA make up the rest of the human genome?
non-protein-coding DNA that is transcribed into several kinds of small TNAs with biological function
what type of molecule is a prion? name one prion associated disease
protein ex. mad cow disease
why do RNA viruses appear to have higher rates of mutation?
replication of their genomes by RNA polymerase doesn't involve proofreading
the lactose operon is likely to be transcribed when ____.
the cyclic AMP and lactose levels are both high within the cell
what is a telomere
the ends of linear chromosomes
HIV is inactivated in the lab after a few minutes of sitting at room temp, but the flu virus is still active after sitting for several hours. What are the practical consequences of these findings?
the flu virus can be transmitted more easily from person to person than HIV
the host range of a virus is determined by
the glycoprotein spikes on its surface and the receptors on the host cell
imagine that you've isolated a yeast mutant that contains histones resistant to acetylation. What phenotype do you predict for this mutant?
the mutant will show low levels of gene expression
viruses use the host cell's machinery to make copies of themselves. However, some human viruses require a type of replication that humans do not normally have. For example, humans normally do not have the ability to convert RNA into DNA. How can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires?
the viral genome codes for specialized enzymes not found in the host cells
Which of the following processes do normal proto-oncogenes typically exhibit?
they stimulate normal cell growth and division.
briefly define the terms oncogene and tumor suppressor. why are they important
tumor suppressor- breaks cell divisions so they don't continue to grow oncogene- a gene that in certain circumstances can transform a cell into a tumor cell they are important because they limit cancer cells from spreading
which of the following represents a difference between viruses and viroids?
viruses have capsids composed of protein, whereas viroids have no capsids