exam 4 prep
The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?
A gene from an organism can theoretically be expressed by any other organism.
22) Allolactose, an isomer of lactose, is formed in small amounts from lactose. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following occurs when the lactose enters the cell?
Allolactose binds to the repressor protein
DNA template strand 5' ____________________________ 3' DNA complementary strand 3' ____________________________ 5' 13) Given the locally unwound double strand above, in which direction does the RNA polymerase move?
B) 3' → 5' along the template strand
16) Which of the following is not true of RNA processing?
Exons are cut out before mRNA leaves the nucleus
23) Two potential devices that eukaryotic cells use to regulate transcription are
DNA methylation and histone modification.
19) In prophase I of meiosis in female Drosophila, studies have shown that there is phosphorylation of an amino acid in the tails of histones of gametes. A mutation in flies that interferes with this process results in sterility. Which of the following is the most likely hypothesis?
Histone tail phosphorylation prohibits chromosome condensation.
Why do histones bind tightly to DNA?
Histones are positively charged, and DNA is negatively charged
Describe the eukaryotic chromosome?
It consists of a single linear molecule of double-stranded DNA plus proteins.
6) During splicing, which molecular component of the spliceosome catalyzes the excision reaction?
RNA
4) Which of the following statements best describes the termination of transcription in prokaryotes?
RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.
28) Which of the following statements describes proto-oncogenes?
They can code for proteins associated with cell growth.
27) The first cloned cat, called Carbon Copy, was a calico, but she looked significantly different from her female parent. Why?
X inactivation in the embryo is random and produces different patterns.
12) Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?
a deletion of two nucleotides
26) Which of the following problems with animal cloning might result in premature death of the clones?
abnormal gene regulation due to variant methylation
14) In eukaryotes, general transcription factors
bind to other proteins or to a sequence element within the promoter called the TATA box.
20) The role of a metabolite that controls a repressible operon is to
bind to the repressor protein and activate it.
9) Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the
bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.
7) Alternative RNA splicing
can allow the production of proteins of different sizes from a single mRNA
5) A transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that
many noncoding stretches of nucleotides are present in mRNA.
15) When DNA is compacted by histones into 10-nm and 30-nm fibers, the DNA is unable to interact with proteins required for gene expression. Therefore, to allow for these proteins to act, the chromatin must constantly alter its structure. Which processes contribute to this dynamic activity?
methylation and phosphorylation of histone tails
10) A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that
proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.
29) The cancer-causing forms of the Ras protein are involved in which of the following processes?
relaying a signal from a growth factor receptor
25) The product of the bicoid gene in Drosophila provides essential information about
the anterior-posterior axis.
21) The lactose operon is likely to be transcribed when
the cyclic AMP and lactose levels are both high within the cell.
24) What is considered to be the first evidence of differentiation in the cells of an embryo?
the occurrence of mRNAs for the production of tissue-specific proteins
11) Which of the following is the first event to take place in translation in eukaryotes?
the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA
30) What is proteomics?
the study of the full protein set encoded by a genome
8) In the structural organization of many eukaryotic genes, individual exons may be related to which of the following?
the various domains of the polypeptide product