unit 3 quiz questions genetics

Homologous features can include:

-amino acid sequences in proteins -DNA sequences -body structures

Why are different genes expressed in different types of eukaryotic cells?

-different eukaryotic cell types express different transcription factors -different eukaryotic cells express different cell surface receptors

three mechanisms for control of transcription

-small molecule binding (hormone) -protein-protein (lucine zipper) -covalent modification (phosphorylation)

If an eukaryotic mRNA did not have its 5' cap, it would not be:

-spliced properly -translated properly -exported from the nucleus

Which is an example of horizontal gene transfer?

-transformation -conjugation -incorperation of free-living microbes into eukaryotic cells as chloroplasts

An organism with which of the following chromosome numbers would make aneuploid gametes?

3n = 18

what do eukaryotes have instead of shine-dalgarno sequence

5' cap (and poly A tail)

mRNAs are read

5' to 3'

The shine-dalgarno sequence is located in the

5' untranslated region of the mRNA

Which of the following mutations could result in production of a mutant protein that is a different length compared to the wild-type protein?

A mutation in a splice site of an intron

A response element is:

A sequence in DNA or RNA that can bind a protein as a consequence of the presence or absence of a specific small molecule

Inaccurate repair of DNA double strand breaks by non-homologous end joining can lead to

All of these answers are correct

A cell has a single copy of the Lac operon (no mutations) and a loss of function mutation in the lac I gene. The Lac operon will be expressed:

All the time, whether or not lactose is present

Mutations that create alleles that confer an antibiotic resistance phenotype in bacteria tend to also confer a competitive disadvantage when antibiotics are not present. This is because:

Antibiotic resistance alleles tend to subtly change normal cellular processes in ways that make the cells grow more slowly.

Paralogs are two versions of a gene that

Are both present in the same organism

Cis-acting regulatory elements:

Are typically binding sites for proteins

Mistakes during crossing over during meiosis can result in:

Both deleted and duplicated regions

Neutral mutations are mutations that:

Cannot be acted on by natural selection

Which of the following species would you expect to have the most introns per gene, on average?

Chimpanzees

The phenetic approach to constructing phylogenetic trees

Considers overall similarities only

Which type of chemical change to DNA can result in a thymine turning into a uracil?

Deamination

Which type of chemical change to DNA results in an abasic site?

Depurination

Removing the trp codons from region 1 (and not replacing them with anything) would make the cell behave as if:

It always had enough tryptophan, regardless of actual tryptophan levels in the cell

Lac I is not part of the Lac operon because

It has its own promoter that is different from the lac operon promoter

Replacing the trp codons from region 1 with stop codons would make the cell behave as if:

It never had enough tryptophan, regardless of actual tryptophan levels in the cell

A cell has a single wild-type copy of the Lac operon and a loss of function mutation in the gene for the Lac repressor protein. Which of the following could be supplied on a plasmid to restore normal function to the chromosomal Lac operon?

Lac I

The first tRNA binds in the:

P site, because IF1 blocks the A site and IF3 blocks the E site

Orthologs are versions of a gene that are

Present in related species that had a common ancestor

Which of the following is present in prokaryotes, but not eukaryotes?

Shine-Dalgarno sequences

The formation of the peptide bond is catalyzed by

The 23S rRNA

If the trpL gene is translated and tryptophan levels are HIGH,

The 3-4 stem-loop will form, and transcription will terminate

What is Lac Z?

The gene that codes for beta-galactosidase

Which of the following statements about the 3' poly-A tail on mature eukaryotic mRNAs is true?

The length of the tail determines how likely the mRNA is to be degraded (destroyed)

A mature (post-splicing) eukaryotic mRNA is placed in a test tube with the template strand of the gene that produced that mRNA. S1 nuclease is then added to the test tube. S1 nuclease destroys single stranded nucleic acids, but leaves double stranded nucleic acids alone. Which of the following will happen next?

The nuclease will destroy some of the DNA.

A prokaryotic mRNA is placed in a test tube with the template strand of the gene that produced that mRNA. S1 nuclease is then added to the test tube. S1 nuclease destroys single stranded nucleic acids, but leaves double stranded nucleic acids alone. Which of the following will happen next?

The nuclease will not destroy any of the nucleic acids in the tube.

RNA interference is a gene regulation mechanism that prevents:

Translation

Which of the following can the proofreading function of DNA polymerase not detect and correct?

Trinucleotide repeat expansion

Which of the following situations describes a monosomy?

Turner syndrome

If one nondisjunction event occurs during meiosis II, how many of the resulting gametes will have an abnormal number of chromosomes? Assume that meiosis I proceeded normally.

Two

Trans-acting regulatory elements:

Typically are genes that code for diffusible regulatory proteins

E. coli is able to sense tryptophan levels in the cell by :

Whether or not the ribosome pauses at the trp codons in region 1 of trpL

Consider a copy of the Lac I gene with a missense mutation that produces a protein that can bind DNA, but cannot bind allolactose. What effect will this repressor protein have on the lac operon?

Will permanently shut down transcription whether or not lactose is present, UNLESS lac O is mutated.

Which of the following is most likely to affect binding of a regulatory transcription factor to chromatin?

a missense mutation in the amino-terminal tail of a histone

which of the following is most likely to affect the binding of a regulatory transcription factor to chromatin?

a missense mutation in the amino-terminal tail of histones

feedback inhibition

attach small molecules to tails of proteins/histones to shit on or off

mediator

bridge that can regulate phosphorylation of RNA pol 2 to C domain

If there is no glucose present:

cAMP levels are high, and the CAP activator is bound to the CAP site.

If glucose levels are high,

cAMP levels are low, and the CAP activator cannot stimulate expression of the lac operon.

covalent modification of histones

can move them and regulate DNA binding

antisense RNA

can prevent base translation by base paring to a complementary mRNA

splicing repressor

cause exon skipping

which of the following mechanisms of gene regulation is most "thrifty" in terms of cellular resources

changing levels of mRNA synthesis via hormone-induced activation of transcriptional factors

sources of deletions

chromosome crosses with itself double strand break from radiation

Lac O is a ______ regulatory element because it must be _______ a gene to control that gene

cis-acting ; next to

repressor proteins bind to silencer sequences and

decrease rate of transcription -prevents Tf2D from binding to core promoter)

Trisomy 21

down syndrome, extra chromosome 21

transcriptional factors that affect initiation

general transcription factors necessary for any transcription 1. TF2D first control point 5. phosphorylation of RNA pol2 is last thing to happen and control point

Consider a mutant CAP activator that cannot bind DNA. Under which condition will this mutation have a phenotype that differs from the wild-type phenotype?

high lactose, no glucose

gene duplication can be caused by mistakes when crossing over in

homologs and cause parlous

activator protein binds to enhancer sequences and

increases rate of transcription (makes TF2D easier to bind, interacts with mediator)

most translational regulation prevents what

initiation

The conversion of threonine to isoleucine is regulated by feedback inhibition. this means that if isoleucine levels are high,

isoleucine will bind to the first enzyme in the pathway and prevent it from binding threonine

how do riboswitches work

mRNA can bind to vitamin B1. will change shape and allow or prevent transcription

If a response element is located in the 3' UTR of an mRNA, protein binding to that response element most likely regulates:

mRNA stability

more complex species have __ introns

more and larger

Would a deletion of a single base pair in a promoter change the reading frame?

no

Would insertion of a single base pair in a Shine-Dalgarno sequence change the reading frame?

no

S1 nuclease

protein that destroys single stranded protein (introns) in experiments

transcription factor

proteins that influence the ability of RNA polymerase to transcribe a gene

Gene duplication can occur as a result of:

reciprocal translocations

riboswitch (mana molecule)

regulates transcription and translation, stability and splicing

riboswitch (mRNA molecule)

regulates transcription and translation. regulates stability and splicing

attenuation

regulation of transcription by formation of a terminator stem loop

what if you want to turn on multiple genes by one steroid receptor?

same DNA sequence infront of genes you want to turn on

low ttp(vitamin B) in riboswitch

shine-dalgarno antisequestor. stem loop forms and will hide shine dalgarno sequence and not transcribe

if different splice iso forms of a protein are made in different cell types, those cells probably express different

splicing enhancers/ repressors

signals from outside of the cell turn genes on and off

steroid receptors (Regulatory transcription factors)

which of the following is an example of a post translational modification that affects a proteins activity?

the C-terminal domain of RNA polymerase 2 is phosphorylated

An aminoacyl tRNA synthetase determines whether it has matched the correct tRNA and amino acid by using sequences in:

the anticodon and / or the variable regions, depending on the specific pairing involved

which of the following is an example of post-translational modification that affects a proteins activity?

the c-terminal domain of RNA polymerase 2 is phosphorylated

examples of attenuation

the trp operon and B. subtilit thi operon

If one nondisjunction event occurs in meiosis I, how many of the resulting gametes will have a normal number of chromosomes? Assume that meiosis II proceeds normally for all cells.

zero