Biology Practice Exam 3 – Flashcards

A synonymous mutation a. Changes the encoded protein but not the DNA b. Changes the DNA but not the encoded protein c. Is a nonsense mutation d. Causes a reading frameshift e. None of the above

Which of the following is required for the initiation of transcription? a. DNA ligase b. Promoter DNA c. Ribonucleoside triphosphates d. Terminator DNA e. DNA polymerase

Put the following four steps of eukaryotic gene expression in order, from beginning to end. (1) Pre-mRNA is processed to make mRNA (2) DNA is used as a template to make pre-mRNA (3) Ribosomes translate the mRNA message to make proteins (4) mRNA is transported to the cytoplasm a. 1; 4; 3; 2 b. 4; 3; 1; 2 c. 4; 1; 3; 2 d. 2; 1; 4; 3 e. 1; 2; 4; 3

At the origin of DNA replication, a. Helicase separates the strands of DNA b. Nucleases cut the DNA strands apart c. Primase adds dNTPs to synthesize Okazaki fragments d. Topoisomerase seals "nicks" in the sugar-phosphate backbone of DNA e. None of the answers are correct

The DNA double helix is of uniform width (or diameter) because a. Purines always pair with other purines b. Pyrimidines always pair with other pyrimidines c. Purines always pair with pyrimidines d. The number of hydrogen bonds is constant e. A and B are correct

A-T base pairs in a DNA double helix a. Are not accessible to DNA binding proteins b. Form three hydrogen bonds with each other c. Are of a different length than G-C base pairs d. Form two hydrogen bonds with each other e. Are more heat stable than G-C base pairs

The Meselson and Stahl experiment a. Demonstrated that the first round of DNA replication is dispersive b. Employed the use of radioactive isotopes 32P and 14C c. Demonstrated that DNA replication is semi-conservative d. Led to a Nobel Prize in 1967 e. A and C are correct

In DNA replication, what is a feature of lagging strand synthesis that is NOT involved in leading strand synthesis? a. DNA is replicated as short fragments b. RNA primers are required c. DNA polymerase is needed d. Primase is required e. All of the above

If guanine makes up 30% of the bases in a sample of double-stranded DNA, what percentage of the bases would be adenine? a. 10 b. 20 c. 30 d. 40 e. 60

A non-synonymous mutation a. Creates a stop codon b. Results in a shift in reading frame c. Results in a protein that is truncated from the N-terminal end d. Would not affect the activity of a protein e. Would change the primary structure of a protein

In eukaryotes, the first amino acid in a growing polypeptide chain is always _____ because the only codon for this amino acid is also the _____ codon. a. methionine; start b. tryptophan; stop c. alanine; start d. alanine; stop e. tryptophan; start

The DNA strand below is the template strand of a gene. Indicate the sequence of encoded mRNA. (3'-ACAGACTGC-5') a. 3'-ACAGACTGC-5' b. 5'-ACAGACUGC-3' c. 5'-UGUCUGACG-3' d. 3'-ACAGACUGC-5' e. 5'-CGTCAGACA-3'

The genetic code has _____ possible codons that code for _____ amino acids. a. 20, 64 b. 32, 60 c. 16, 64 d. 16, 32 e. 64, 20

An insertion of 2 nucleotides into the coding region of a gene may a. Add 1 amino acid to the resulting protein b. Add 2 amino acids to the resulting protein c. Cause a frameshift mutation d. Cause a synonymous mutation e. B or D could be true depending on the sequence of the nucleotides

Redundancy (aka degeneracy) of the genetic code means that a. Changes at the 3rd position of a codon will not always change the encoded amino acid b. Non-synonymous changes at the 3rd codon position will not always change the encoded amino acid c. A single codon can code for multiple amino acids d. Several amino acids can be encoded by the start codon e. Improper base pairing between the codon and ribosome will not change the encoded amino acid

Which of the following statements about tRNAs is true? a. Specific enzymes bind amino acids to their corresponding tRNAs b. tRNAs interact with mRNA c. tRNAs interact with ribosomes d. tRNAs have anticodon sequences that are complementary to codons on mRNA e. All of the above

Termination of translation involves a. Placement of a tRNA with a termination amino acid in the A site of the ribosome b. Placement of a tRNA with a termination amino acid in the P site of the ribosome c. Placement of a protein release (or termination) factor in the A site of the ribosome d. Addition of a poly-A tail e. None of the above

If an amino acid properly bound to its tRNA is chemically changed (e.g. changing cysteine to alanine), what would happen during translation? a. The ribosome would recognize the amino acid carried by the tRNA, regardless of its anticodon b. The tRNA would be treated as a stop signal c. The ribosome would recognize the anticodon of the rRNA regardless of the amino acid it carries d. Both cysteine and alanine would be added to the polypeptide chain e. None of the above

The role of tautomerism in causing mutations relates to the fact that the process ultimately affects the... a. Deoxyribose sugar b. Ability of DNA to replicate at all c. Number of chromosomes d. Hydrogen bonding affinities of the base e. Phosphate group

Why did the original "one-gene, one-enzyme" hypothesis have to be modified? a. Wobble allows more than one gene to code for an enzyme b. Not all proteins are coded by genes c. Some enzymes are made up of more than one polypeptide d. All genes code for multiple enzymes e. Not all enzymes are coded for by genes

Which feature(s) of mRNA in eukaryotes is created after transcription is complete? a. Introns b. Exons c. Ribosome binding site d. 5' cap, poly-A tail e. The start codon

If the mRNA codon for leucine is 5'-UUG-3', the corresponding tRNA anticodon would be a. 5'-UUG-3' b. 3'-UUG-5' c. 5'-TTC-3' d. 5'-AAC-3' e. 3'-AAC-5'

Alternative exon splicing a. Results in multiple tRNAs recognizing a codon b. Means that an organism can make a greater number of proteins than it has genes c. Causes alternative pairing between the large and small ribosomal subunits d. Results in redundancy similar to the genetic code e. Splices together different introns to form the mature mRNA

Antibiotics a. Kill retroviruses as well as bacteria b. Kill fungi, viruses and bacteria c. Target molecular process specific to bacteria d. Only affect eukaryotic cells e. B and C are correct

By allowing only cells that possess mutations conferring resistance to survive and multiply, antibiotics a. Induce new resistance mutations to occur b. Cause the spread of resistance due to genetic drift c. Allow proliferation only of cells that already possess resistance mutations d. Cause spread of resistance due to natural selection e. C and D are correct

Gene expression can be regulated a. At initiation of transcription b. During mRNA processing c. Via mRNA degradation d. Via post-translational modification of polypeptides e. All of the above

During the phage lytic cycle, a. Host RNA polymerase transcribes phage genes b. Host ribosomes translate phage proteins c. Transcription of many host genes occurs d. The phage integrates into the host chromosome e. A and B are correct

The lac repressor is an allosteric molecule because a. It catalyzes the synthesis of lactose b. It lowers the transcription rate c. It inhibits the synthesis of lactose d. It catalyzes mutations on the operon e. It interacts with another molecule to change the shape of the repressor's active site

The expression of the three lac structural genes is _____ when lactose is absent from the cell's environment and is _____ when lactose is available because lactose binds to the _____ and inactivates it a. low; high; lac repressor b. high; low; lac inducer c. low; high; lac promoter d. high; low; lac operator e. low; high; lac operator

Enhancer sequences a. Are DNA regulatory elements b. Bind transcription factors c. Are features of eukaryotic gene regulation d. Bind RNA polymerase e. All but D are correct

Nucleosomes a. Are inactivated chromosomes b. Are densely packed in expressed gene regions c. Are regions of methylated DNA d. Are visible only during mitosis and meiosis e. Are cores of histone proteins with DNA wrapped around them

Which of the following statements is true of an enhancer? a. Enhancers are downstream of the promoter b. Enhancers are usually specific for many genes c. Enhancers may be thousands of nucleotides from the gene they are associated with d. One gene cannot have more than one enhancer e. None of the answers are correct

Coupled (i.e. simultaneous) transcription and translation of the same mRNA a. Is facilitated by the nuclear membrane b. Occurs in the golgi apparatus c. Is regulated by DNA methylation d. Is only found in prokaryotes e. None of the above

Plasmids commonly used for cloning DNA a. Contain genes for antibiotic resistance and blue color production b. Induce the lysogenic phage cycle c. Do not contain restriction endonuclease recognition sites d. Must be linear to transform bacteria e. A and B are correct

The influenza pandemic of 1918 a. Killed more people in one year than any disease in recorded history b. Was due to an H1N1 strain of the virus c. Originated through a new combination of hemagglutinin and neuraminidase genes d. Contained some genes from the swine form of the virus e. All of the above

Cocktails of antiretroviral drugs are commonly prescribed to treat HIV because a. The virus may recombine with genes from the swine form of the virus b. New forms of the virus are frequently introduced into the population through the bushmeat trade c. The virus attacks red blood cells d. The virus may be rapidly spread through sneezing, from doorknobs, etc. e. The virus rapidly evolves resistance to single drugs

Positive gene regulation means that transcription _____ when a regulatory protein is bound (e.g. to the operator), and negative gene regulation means that transcription _____ when a regulatory protein is bound (e.g. to the operator). a. will occur, will not occur b. will not occur, will occur c. is facultative, is constitutive d. is repressed, is induced e. None of the above

How many different gametes can an individual with the genotype RrSs produce? a. 1 b. 2 c. 4 d. 8 e. 16

In this cross, RrSs x RrSs, how many different phenotypes would be expected in the offspring? a. 1 b. 2 c. 4 d. 9 e. 16

X-linked traits a. Most often appear in males b. Most often appear in females c. Are passed from father to son d. Appear in female carriers e. Only occur in European royal families