Genetics Test 2

Let's assume that nucleosomes in the chromosomes of ring-tailed lemurs include 146 bp and 34 bp of linker DNA. If one of the lemur's chromosomes is 1.8 Mb in size, which of the following calculations provides an estimate of the number of nucleosomes that would be needed to organize this molecule? 1.8 Mb + 146 bp + 34 bp (146 bp +34 bp)/1.8 Mb 1.8 Mb/(146 bp + 34 bp) 1.8 Mb * (146 bp +34 bp)

1.8 Mb/(146 bp + 34 bp)

During gamete formation, what percentage of gametes arising from a single cell would be aneuploid if a nondisjunction event occurs during meiosis 1? 0% 25% 50% 100%

100%

Down syndrome is caused by the dosage effects of having an extra copy of chromosome______; in particular, the _______ region of the chromosome is responsible for many of the phenotypic outcomes that characterize the syndrome. 21, centromeric 18, DYRK 13, heterochromatic 21, DSCR

21, DSCR

How many pairs of chromosomes are found in a typical human somatic cell's karyotype? 23 22 46 44

23

Cynthia finally succeeded in capturing electron microscopic images of a newly-discovered protein complex in non-dividing cells derived from human liver tissue. She notices that the diameter of the protein complex is similar to the diameter of the cells' chromatin fibers in the nucleus. What is the diameter of Cynthia's protein complex? 10 nm 30 nm 300 nm 700 nm

30 nm

How does the development of a Drosophila embryo demonstrate the concept of combinatorial gene regulation in eukaryotes? A relatively small number of regulators combine in unique ways along the dorsal-ventral axis to establish and determine the identity of the various body segments A small number of regulatory molecules turn on sets of genes, organized into perons, that share common regulatory elements. In Drosophila, gene regulation requires the binding of regulatory molecules simultaneously to both promoters and terminators on genes A unique regulator is expressed in each of the thousands of cells in the embryo to turn on the genes necessary for determining each cell's fate.

A relatively small number of regulators combine in unique ways along the dorsal-ventral axis to establish and determine the identity of the various body segments

SHORT ANSWER: If a tRNA anticodon amino acid reads 5'-IAG-3', to which mRNA codon will it bind? What amino acid will the tRNA carry? Recall that inosine () is a deaminated version of will it bind? What guanine that forms third-base wobble pairs with U, C, or A.

CUU, CUA, CUC Leucine

Which of the following explains why the lac operon is regulated by catabolite repression, a positive control mechanism that is sensitive to the amount of glucose available to cell? Catabolite repression allows the cell to choose glucose over lactose when both are available. Catabolite repression allows the cell to stockpile the enzymes needed for lactose metabolism. Catabolite repression allows the cell to store sugars for use later. Catabolite repression inhibits synthesis of the lac repressor, lacl, until glucose is consumed

Catabolite repression allows the cell to choose glucose over lactose when both are available.

An enzyme that re-structures CpG islands in gene promoters when it forms 5-methylcytosine (5mC)

DNA methylase

Which of the following enzymes is capable of remodeling chromatin to achieve genomic imprinting, an epigenetic process that causes certain genes to be expressed in a "parent-of-origin-specific" manner (e.g., the allele inherited from the father is expressed, whereas the one inherited from the mother is silenced). A recent study showed that this enzyme also is responsible for sexual patterning in the brains of mammalian fetuses. DNA methylase dicer histone deacetylase RNA polymerase

DNA methylase

The figure below shows a lac repressor dimer bound to a DNA operator sequence. In which of the repressor domains indicated would you introduce a mutation to turn this repressor into a nonfunctional lacI- protein that can no longer bind to lacO? DNA-binding domain inducer-binding domain carboxy-terminal domain tetramerization domain

DNA-binding domain

The protein that is responsible for the translocation of the ribosome along the mRNA molecule during translation.

EF-G

A DNA sequence element that controls eukaryotic transcription initiation by binding to a regulatory protein called an activator

Enhancer

Which histone protein is not part of the core nucleosome structure? H4 H2A/B H3 H1

H1

A chromatin remodeling enzyme that adds acetyl groups to lysine residues on histones.

HAT/KAT

Jason isolated a temperature-sensitive yeast mutant that exhibits a 17-fold decrease in over all gene expression when grown at the non-permissive temperature. Further studies revealed that the cells accumulate acetyl-CoA in their nuclei. Based on these results, which of the following should Jason suspect is defective in his yeast mutant? PAP (polyadenylate polymerase) HAT/KAT RNA polymerase II SWI/SNF

HAT/KAT

Regulatory molecule (often a metabolite) that is capable of up-regulating gene expression

Inducer

In the lac operon in E. coli , a nonsense mutation in the _______ gene will result in a loss of β - galactosidase activity in the cell. lacZ lacI lacA lacY

LacZ

The failure of sister chromatids or homologous chromosomes to separate during cell division

Nondisjunction

At which level of eukaryotic gene regulation does the RISC complex participate? translation post-transcriptional post-translational transcription

Post-transcriptional

A posttranscriptional regulatory complex that includes the slicer and dicer proteins

RISC

A DNA binding regulatory protein that is capable of down-regulating gene expression

Repressor

An ATP dependent chromatin remodeling complex that slides, removes, or transfers histones bound to double-stranded DNA

SWI/SNF

Non-histone factors that make up the protein framework that gives a chromosome its overall shape during condensation

Scaffolding proteins

A consensus sequence found near the 5' end of bacterial mRNAs that is bound specifically by the 165S rRNA for initiating

Shine-Dalgarno sequence

You have isolated DNA for PCR and accidentally added topoisomerase instead of polymerase to your sample. What would you expect to see if you ran the topoisomerase-treated DNA on a gel? The DNA would show decreased supercoiling and have a lower electrophoretic mobility The DNA would show increased supercoiling and have a lower electrophoretic mobility The DNA would show decreased supercoil ing and have a higher electrophoretic mobility The DNA would show increased supercoiling and have a higher electrophoretic mobility.

The DNA would show decreased supercoiling and have a lower electrophoretic mobility

You have isolated bacterial plasmid DNA for PCR and accidentally added topoisomerase instead of polymerase to your sample. What would you expect to see if you ran the topoisomerase-treated DNA on a gel? Recall that plasmids are small, circular molecules. The DNA would show decreased supercoiling and have a higher electrophoretic mobility (it would run faster and end up near the bottom of the gel). The DNA would show decreased supercoiling and have a lower electrophoretic mobility (it would run slower and stay near the top of the gel). The DNA would show increased supercoiling and have a higher electrophoretic mobility (it would run faster and end up near the bottom of the gel). The DNA would show increased supercoiling and have a lower electrophoretic mobility (it would run slower and stay near the top of the gel).

The DNA would show decreased supercoiling and have a lower electrophoretic mobility (it would run slower and stay near the top of the gel).

A mutation causes a single guanine nucleotide to be deleted from the 17th codon in an mRNA's coding sequence. How will this affect the growing polypeptide chain during translation? The mutation won't effect translation because it occurs in the wobble position of a codon. Translation elongation will stop prematurely. The reading frame will be shifted, and the wrong amino acids will be added from this point on. There will be a single amino acid substitution in the polypeptide sequence.

The reading frame will be shifted, and the wrong amino acids will be added from this point on.

Which of the following statements regarding ploidy levels is CORRECT? The triploid chromosome number is the typical euploid condition for most animals. There seems to be no correlation between the euploid chromosome number and the complexity of animals. Animals tolerate polyploidy (more than two sets of chromosomes) much more often than do plants. The diploid number refers to the number of unique chromosomes in a single set for a given species

There seems to be no correlation between the euploid chromosome number and the complexity of animals.

How do the various types of RNA interference differ (e.g., miRNA, shRNA, sIRNA)? They differ in whether or not a functional RISC complex is formed. They differ in their inclusion / exclusion of slicer and dicer. They differ in the source of the interfering RNA molecules. They differ in that only one type leads to mRNA degradation.

They differ in the source of the interfering RNA molecules.

A relatively small genetic element that includes genes for structural proteins and replication enzymes necessary for hijacking a host cell and its machinery

Viral genome

The inducer of the lac operon is _____, whereas the effector (corepressor ) of the trp operon is _______. tryptophan, allolactose lactose arabinose galactose, tryptophan allolactose, tryptophan

allolactose, tryptophan

A post-transcriptional regulatory mechanism that allows more than one protein to be produced from a single gene.

alternative splicing

An atypical chromosome number, usually caused by a gain or loss of one or more chromosomes relative to the normal number

aneuploid

Tautomeric shifts in the nitrogenous bases of certain nucleotides_____. lead to the formation of standard Watson-Crick base pairs change the hydrogen bonding capabilities of the bases introduce frameshift mutations after multiple rounds of DNA replication

change the hydrogen bonding capabilities of the bases

A DNA molecule plus associated proteins, including both histone and nonhistone elements.

chromatin

Which of the following mechanisms for eukaryotic gene regulation occurs relative to central dogma at a point that differs from the point at which the other three occur? RNA interference chromatin remodeling alternative polyadenylation alternative splicing

chromatin remodeling

Which of the following is a gene regulatory mechanism utilized by both prokaryotic and eukaryotic cells? chromatin remodeling clustering of genes within operons combinatorial gene regulation cis-acting DNA regulatory sequences

cis-acting DNA regulatory sequences

A bridging molecule that binds to activators and transcription factors to control transcription initiation in eukaryotes

coactivator

A figure similar to the one below was published recently by researchers working at the National Center for Biotechnology Information and the European Bioinformatics Institute (Balaji et al. 2006 J Mol Biol 360:213-227). The figure illustrates the numerous ways in which a relatively small number of regulatory proteins interact to regulate the transcription of many genes. Which of the following phrases best describes this overall approach to eukaryotic gene regulation? coincident transcription/translation catabolite repression combinatorial gene regulation chromatin remodeling

combinatorial gene regulation

Frameshift mutations typically result in a polypeptide that ________. consists of a jumbled mess of amino acids, most of which are different from the intended amino acids has the same primary structure as the wild-type polypeptide is truncated by a premature stop codon that occurs at the site of the frameshift is fully functional, just like the wild-type polypeptide

consists of a jumbled mess of amino acids, most of which are different from the intended amino acids

Hydrolyzing the glycosidic bond between an adenine nitrogenous base and its deoxyribose sugar is an example of _______. depurination alkylation deamination hydroxylation

depurination

Which of the following lists eukaryotic gene regulatory elements in a manner that is consistent with their molecular interaction/ binding capabilities? It may help to picture a DNA element is indicated double-stranded DNA molecule on the bottom of a stack of interacting regulators. The DNA element is indicated first in each list for consistency. promoter-transcription factor-repressor enhancer-corepressor-repressor TATA box-mediator-transcription factor enhancer-activator-coactivator

enhancer-activator-coactivator

The first amino acid of most bacterial polypeptides.

f-Met

What technique would you use to detect a target sequence in an intact chromosome using a labeled molecular probe? fluorescence in situ hybridization PCR karyotyping Southern blotting

florescence in situ hybridization

Attenuation in trp gene regulation is accomplished by ______. blocking transcription initiation at the trp operon's promoter forming secondary mRNA structures in the leader region of the transcript repressing the trp operon's operator reducing the cell's permeability to the effector molecule, tryptophan

forming secondary mRNA structures in the leader region of the transcript

TFIID and TFIIH are examples of ______ that bind to gene _____. general transcription factors, promoter general transcription factors, enhancers activators, enhancers repressors, TATA boxes

general transcription factors, promoters

Based on your knowledge of the regulation of the trp operon in bacterial cells the following most likely functions as the effector molecule that would activate a repressor to turn off the transcription of a hypothetical "usually-on" histidine operon? Recall that histidine is an amino acid found in polypeptides. histidine tryptophan lactose glucose

histidine

In eukaryotes, genes that code for functionally-related proteins typically are not clustered together into operon-like assemblies on the chromosomes. Which of the following DNA elements provides an example of how eukaryotic cells change the expression of a large number of genes together in response to environmental stimulus? hormone response element (HRE) TATA box intron-exon junction polyadenylation sequence

hormone response element (HRE)

The figure below shows a lac repressor dimer bound to a DNA operator sequence. In which of the repressor domains indicated would you introduce a mutation to turn this repressor into a nonfunctional lacS protein that can bind to, but cant be removed from, the operator lacO? DNA-binding domain inducer-binding domain carboxy-terminal domain tetramerization domain

inducer-binding domain

A method for displaying an organism's chromosomes by grouping them into homologous pairs

karyotype

In the lac operon in E. coli , a nonsense mutation in the _______ gene will result in a loss of permease activity in the cell. lacZ lacI lacA lacY

lacY

High-level expression (transcription) occurs in regions of chromatin that are located ______. within the telomeres within histone-bound core DNA large distance away from the MARS near the MARS

large distance away from the MARS

The ribosomal subunit with which the peptidyl transferase activity is associated.

large subunit

What is the role of tRNA in translation? lt serves as an adaptor molecule that establishes a physical association between an mRNA codon and its corresponding amino acid. It catalyzes peptidyl transferase activity for peptide bond formation. It stabilizes the interactions between the small and large subunits of a ribosome. It acts as a molecular chaperone to help newly-synthesízed polypeptides fold properly

lt serves as an adaptor molecule that establishes a physical association between an mRNA codon and its corresponding amino acid.

Which type of chromosome has a p arm that is roughly the same length as its q arm? acrocentric telocentric metacentric submetacentric

metacentric

A transition mutation changes a codon from TGG to CGG. Which of the following outcomes is most likely to result from this base-pair substitution? missense mutation silent (synonymous) mutation nonsense mutation frameshift mutation

missense mutation

Luria and Delbruck's fluctuation test demonstrated that ______. mutation is not an important component of evolution it takes roughly the same amount of time for new traits to emerge in separate populations when they're exposed to the same environmental challenge organisms acquire new traits adaptively by interacting with their surroundings new traits emerge randomly via mutation, regardless of an individual's environment

new traits emerge randomly via mutation, regardless of an individual's environment

Where are bacterial chromosomes located within a bacterial cell? mitochondria nucleus nucleoid (cytosol) outer surface of the plasma membrane

nucleoid (cytosol)

A DNA sequence region that is recognized and bound by a repressor protein like Lacl.

operator

A series of functionally-related bacterial genes that are regulated and transcribed as a single unit.

operon

Considering the three operons we studied in lecture, which of the following mechanisms for gene regulation in prokaryotes is unique to the arabinose operon? attenuation via mRNA secondary structures catabolite repression via CAP-CAMP binary control via repressor/operator interactions operon silencing via the bridging together of multiple cis-acting regulators

operon silencing via the bridging together of multiple cis-acting regulators

Mutations that occur in non-coding regions of DNA, like promoters and introns collectively are called _______ mutations. spontaneous frameshift silent regulatory

regulatory mutations

A short, single-stranded nucleic acid that targets RNA molecules for degradation

siRNA

A cylindrical filament of coiled nucleosomes that is roughly 30 nm in diameter

solenoid

Which of the following mutagens or mutagenic processes is responsible for amplifying a trinucleotide repeat during DNA replication? Fragile X syndrome is a genetic condition caused by this type of mutation. intercalating agents alternative splicing strand slippage oxidizing agents

strand slippage

Which type of chromosome has no p arms? telocentric acrocentric submetacentric metacentric

telocentric

Hypersensitive sites on double-stranded DNA are ______. always methylated transcriptionally-active regions susceptible to digestion by DNase I

transcriptionally-active regions susceptible to digestion by DNase I

A biological mutagen capable of moving from one location to another within a genome.

transposon

Which of the following partial diploid strains of E. coli will be capable of synthesizing the amino acid tryptophan when grown under conditions of tryptophan starvation? [HINT: In the trp operon, trpR codes for the aporepressor, trpO is an operator sequence, trpL is the leader sequence, and trpA-E code for structural enzymes.]

trpR+ trpO+ trpL- trpE- trpD+ trpC+ trpB- trpA+ —------------------ trpR+ trpO+ trpL- trpE+ trpD- trpC- trpB+ trpA-

Which of the following is a form of non-ionizing radiation that can cross-link pyrimidine bases into dimeric structures? x-rays gamma rays 5-bromodeoxyuracil ultraviolet light

ultraviolet light