Exam 2 BIOL 221

What is an operon?

A set of bacterial genes that is transcribed into a single mRNA

Which of the following methods is NOT used by cells to regulate the amount of protein in the cell? A. DNA polymerase is recruited differently at the promoter B. Genes can be transcribed into mRNA at different rates C. Proteins can be tagged with ubiquitin, marking them for degradation D. Different numbers of ribosomes can bind to a single mRNA molecule

A. DNA polymerase is recruited differently at the promoter

Which of the following statements about RNA splicing is FALSE?: A. Every exon must be removed from the primary transcript on every mRNA molecules in all cell types B. Splicing, capping, and polyadenylation are processing events that occur between transcription and mature mRNA formation C. Conventional introns are not found in bacterial genes D. If splicing does not take place correctly, the RNA may not leave the nucleus

A. Every exon must be removed from the primary transcript on every mRNA molecules in all cell types

Which of the following statements is not typically true of laboratory plasmid? A. It can exist in linear form, replacing bacterial chromosomes B. It has a selectable property, such as an antibiotic resistant gene C. It has an origin of replication D. It has cleavage sites for restriction enzymes

A. It can exist in linear form, replacing bacterial chromosomes

Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus A. The ribosome binds to the mRNA B. RNA polymerase dissociates C. The mRNA is polyadenylated at its 3' end D. 7-methyl-G cap is added to the 5' end of the mRNA

A. The ribosome binds to the mRNA

Which of the following statements is NOT true about the differences between liver cells and kidney cells in the same organism? A. They contain different genes B. They express different genes C. They contain different proteins D. They contain the entire set of instructions needed to form the whole organisms

A. They contain different genes

Using the procedure of polymerase chain reaction, after 30 rounds of replication and beginning with one template molecule of double-stranded DNA, how many copies of target sequence would you expect?

About 1 billion

In the bacterial cell, the tryptophan operon encodes the genes needed to synthesize tryptophan. When the concentration of tryptophan inside the cell is high, tryptophan

Activates tryptophan repressor which shuts down the tryptophan operon

In our human ancestors, the enzyme lactase, which allows us to digest the milk sugar lactose, was produced only during infancy. Today, many adults can digest lactose, while others cannot. Which group was born with a point mutation in the regulatory DNA of their lactase genes?

Adults who can digest lactose

Researchers assayed the activity of enzyme F in three different types of tissue from the same mouse by determining the amount of enzyme product produced per milligram of tissue per unit. As shown in the graph below, results indicate more product generation in the liver compared to the kidney and muscle samples A. Differences in the transcription of the gene encoding the enzyme among the tissue types B. Differences in the translation of the mRNA encoding the protein among hte tissue types C. Differences in the post-translational modification of the enzyme among the tissue types D. All of these are good explanations

All of these are good explanations

Bacterial mRNAs

Are transcribed and translated simultaneously

Which of the following pairs of codons might you expect to be read by the same tRNA as a result of wobble? A. 5'-GAU-3' and 5'-GAT-3' B. 5'-CAC-3' and 5'-CAU-3' C. 5'-CUU-3' and 5'-UUU-3' D. 5'-AUU-3' and 5'-AGU-3'

B. 5'-CAC-3' and 5'-CAU-3'

What is not true about codons in mRNA molecules A. Some codons do not code for amino acids B. Some codons code for more than one amino acid C. Codons in mRNAs bind to complementary anticodons in tRNAs D. In some cases, several different codons code for the same amino acid

B. Some codons code for more than one amino acid

Which of the following is not a mechanism of genetic variation?: A. Gene duplication and divergence B. Mutation within the regulatory DNA of a gene C. Misreading of an mRNA by a ribosome D. Exon shuffling; Mutation within the coding sequence of a gene

C. Misreading of an mRNA by a ribosome

Which of the following statements about PCR is FALSE? A. PCR uses a DNA polymerase from a hot springs prokaryote B. PCR is particularly powerful because after each cycle of replication there is an exponential increase in the amount of DNA available C. PCR uses two primers that are the complement of one another D. For PCR, every round of replication is preceded by the denaturation of the double-stranded DNA molecules

C. PCR uses two primers that are the complement of one another

Genes in eukaryotic cells often have intron sequences coded for within the DNA. These sequences are ultimately not translated into proteins. Why?

Intron sequences are removed from RNA molecules in the nucleus

RNA in cells differs from DNA in that

It is single-stranded and can fold up into a variety of structures

What feature of DNA polymerase causes the end replication problem solved by telomerase

Its requirement for an RNA primer to begin polymerization

Transcription is similar to DNA replication in that

Nucleotide polymerization occurs only in the 5'-to-3' direction

What effect on cancer does telomerase have?

Telomerase is upregulated allowing cells to divide out of control

Which point mutation would likely cause the most harm to a cell

The insertion of one nucleotide at the beginning of a coding region

Several organisms have a homologous protein (inherited from a common ancestor) that is highly similar at the amino acid level. You are comparing the genes that code for these proteins in the different organisms when you note that one of the codon nucleotide positions shows more nucleotide variation than other nucleotide positions. In which codon nucleotide position do you expect to see the most variability among species?

The third nucleotide position

Although all of the steps involved in expressing a gene can be regulated, the most important point of control for the majority of the genes is:

Transcription initiation

Which form of control directly influences which mRNAs are selected by ribosomes for the synthesis of proteins?

Translational control

During agarose gel electrophoresis, DNA fragments

Travel through a matrix containing a microscopic network of pores

True or false? A restriction enzyme would cut chromosomal DNA into a greater number pieces if it had a 4 bp recognition site rather then 6 bp recognition site

True

True or false? An ORF stands an open reading frame, and indicates you may have a protein-encoding gene if it is roughly 100 or more codons long

True

True or false? An enhancer region on genomic DNA is often thousands of base pairs away from a gene but can still activate its transcription

True

True or false? One reason the number of human genes turned out to be much less than expected is because scientists that a single gene can be spliced differently to result in many different forms of a protein

True

True or false? The Bicoid mRNA in a Drosophila embryo is made by the mother rather than the zygote

True

Theoretically, a vast number of different proteins can be assembled from 20 different amino acids. How many polypeptide chains are possible that are 5 amino acids

20^5

What is a polyribosome?

A cluster of ribosomes translating the same mRNA, but positioned at different sites along the mRNA

What does a genomic DNA library consist of?

A collection of plasmid plus cloned DNA fragments in bacteria

Which of the following types of genes would be most likely to accumulate change to its sequence

A gene that has recently been duplicated in the genome

Approximately how many genes are in the human genome?

20,000

Which of the following libraries would be expected to be essentially the same? A. cDNA and genomic libraries made from mouse kidney cells B. cDNA libraries made from mouse liver and kidney cells C. cDNA and genomic libraries made from mouse liver cells D. Genomic libraries made from mouse liver and kidney cells

D. Genomic libraries made from mouse liver and kidney cells

Which of the following is NOT true about noncoding DNA sequences? A. They are virtually the same in humans and mice B. Changes in these sequences are often involved in the formation of new species C. They contain regulatory elements that ultimately dictate each organism's development D. Their sequences have been shaped by evolution

D. Their sequences have been shaped by evolution

Which of the following enzymes allows scientists to join together two DNA fragments

DNA ligase

True or false? A gradient of the Bicoid forms of Drosophila embryo, ultimately making the Bicoid protein produce different cell types

False

True or false? In general, an error made when DNA polymerase synthesized a strand of DNA is potentially less harmful than an error made when RNA polymerase synthesized that strand of RNA

False

True or false? One DNA fingerprinting technique for paternity testing relies on the fact that different individuals have different numbers of repeats in STR (Short Term Repeat) regions in their genome

False

True or false? The aminoacyl tRNA synthetases are small enzymes, and therefore can only bind the 3' end of the tRNA where the amino acid is bound

False

True or false? The human genome is roughly 3.2 million base pairs

False

In eukaryotes, what must assemble at a promoter before RNA polymerase can transcribe a gene?

General transcription factors