BIO 340 Final Exam - Spring 2024

Harris and Varsani Spring 2024 Semester

What type of bonds are formed between complementary DNA bases?

Hydrogen Bonds

Which of the following forms the backbone of a polynucleotide chain?

alternating sugar and phosphate groups

Guanine and adenine are purines found in DNA

true

What fraction of the nucleotides in a doubles-stranded DNA molecule are cytosine and thymine?

50%

What is one difference between DNA replication in bacteria versus eukaryotes?

Eukaryotic chromosomes have many origins of replication, while bacteria have only one origin of replication

What is the maximum rate between DNA replication in E. coli

1000 nucleotides

During DNA replication in E. coli, what is the role of DnaA?

DnaA bends DNA, hydrolyzing the hydrogen bonds in the 13-mer region of otic and creating an open complex

Which of the following statements about DNA replication is true?

Single-strand binding proteins stabilize the open conformation of the unwound DNA

Which of the following reagents is not required for the polymerase chain reaction?

Dideoxynucleotide triphosphate

Which of the following would you find in a Sanger sequencing reaction but not in a polymerase chain reaction?

ddNTPs

Which of the following statements about ddNTPs is true?

they have a hydrogen at the 3' carbon of the sugar

You wish to create a mutation in which you prevent access of RNA polymerase to the gene. Which region of a gene would you target?

promoter sequence

Which region(s) of a gene are not found within the mRNA transcript?

promoter region

Which of the following statements regarding Nucleotide Excision repair (NER) and Base Excision Repair (BER) is true?

both NER and BER involve the removal of one or more damaged bases by a nuclease

How large is an origin of replication of E. coli?

245 base pairs

Which of the following enzymatic activities is NOT involved in DNA replication

RNA- dependent DNA polymerase

Which activity of DNA polymerase is responsible for its ability to proofread newly synthesized DNA

3'>5' exonuclease which cleaves mismatched nucleotides

How many mutations would you expect to see in the human genome (6x10^9) if mismatches could not be repaired?

6x10^9/10^4= 600,000 mutations

What would the consequences be of having DNA polymerase with out 5' -> 3' exonuclease activity?

the RNA primer will stay

What is the correct order of enzyme action during DNA replication?

helices/topoisomerase activity, priming, DNA polymerization/proofreading, 5'-3' exonuclease activity/DNA polymerization, ligation

Why is telomerase important?

It is important for extension

You isolate a mutant of this gene that encodes the following protein:
N-Met-Gln-Cys-Lys-Ser-C
What mutation can give you this mutant protein

Deletion of a C

Which of the following statements are FALSE?

the Trp Operon is under positive control

Under which of the following conditions will E. coli make large amounts of B- galactosidase?

I+O+Z+, glucose absent, lactose present
I-OcZ+, glucose absent, lactose absent

Under what condition will E. coli make the least amount of B-galactosidase?

IsO+Z+, glucose absent, lactose present

For the lac operon gene regulation system, which of the following is false?

in the presence of low levels of glucose and lactose, even with mutation happening on the operator (operator cannot bind to repressor), there are still no transcription of lac genes

The expression of a gene can be increase by?

knocking out its repressor

In the Trp operon of E. coli, the Trytophan repressor protein, Trp R, will bind to the operator to prevent transcription only in the presence of tryptophan. What is tryptophan an example of?

Co-repressor

Which of the following is required for transcription

RNA polymerase

Which of the following nucleosomes modifications will lead to closed promoters

De-acetylation

All of the following codons/anticodons are associated with the amino acid Leucine. Which of the following anti-codon/codon pairs is an example of wobble paring

Anticodon: 5' UAA 3' paired with codon
5' UUA 3' or 5' UUG 3'

Why are mitochondria and plastid genomes highly reduced compared to their free living relatives (Ammar)

Gene loss and Endosymbiotic Gene Transfer

Where are most Mitochondrial genes encoded?

Nucleus

Which organelles are involved in the translation of membrane proteins?

Endoplasmic reticulum and Ribosome

How would you expect a mutation in the ori to affect a recombinant bacterial expression plasmid?

low plasmid copy number

Which of the following best represents the nucleic acid(s) to generate a transcriptional library?

mRNA and cDNA

Which of the following are reasons that crops have been genetically modified

increase nutritional content
herbicide resistance
caterpillar resistance

What trait was found in Bt that is now used in genetically modified crops?

endotoxins (cry genes)

Which statement is correct?

linked genes are always syntenic

What is the relative distance (in cM) of two unlinked genes.

50 cM

You are screening a population of 350 island sheep for coat color, and you count 100 black sheep and 250 white sheep. What is p, frequency of the "black" allele of the TYRP1 gene? Crossing true breeding black sheep with true breeding white sheep always results in 100% black sheep.

p= 0.1548

In the same population, if it is under Hardy-Weinberg equilibrium, howe many individuals do you expect to be heterozygous at TYRP1?

92

You come back after the population has gone through one generation, and count 445 white sheep and 208 black sheep. What is the EXPECTED number of heterozygotes in the new generation, if this population is in hardy-weinberg equilibrium?

171

What is the OBSERVED number of heterozygotes in the new generation?

188

Using the same logic, you get the expected and observed number of homozygotes in the new generation, and run a x^2 test. You find your p-value is 0.8377. What can you say about this population?

This population is in Hardy-Weinberg equilibrium at the TYRP1 locus: the TYRP1 is not experiencing any force of evolution.

In which of these populations in Natural Selection more likely to occur?

A large population with high phenotypic variation

In eukaryotes, processing (capping, splicing) is taking place at the 5' end while the 3' end is still being synthesized. In prokaryotes, which is taking place while RNA is being synthesized?

Translation beginning at the 5' end while the 3' end is being synthesized

What would be the effect of a drug that altered the structure of allolactose so that it was unable to bind to the regulator protein?

The drug would prevent the individual from digesting lactose

All of the following are true of a single peptide EXCEPT:

Signal peptides determine when a protein is exposed

True about a single peptide

signal peptides determine where a protein should be transported
signal peptides can be combined
a signal peptide is removed after it serves its function
SRPs bind to the signal peptide

An adaptive allele A arises in a population such that AA individuals leave 10% more offspring AA+ individuals leaves 5% more offspring, and A+A+ individuals leave normal numbers of offspring. What is the probability of fixation of allele A?
(neutral = 1/2N)

.1

In bacterial plasmids, Ori is:

Where DNA replication starts

Which of the following is evidence for secondary symbiosis?

Nucleomorphs

An E. coli with the genotype, I+O-Z-/F'O+Z+ has low levels of lactose and low levels of glucose. What would you expect this to produce?

low expression of LacZ

The "sticky ends" generated by restriction enzymes allow:

pieces of DNA from different sources to hybridize

An increase in the inbreeding coefficient is likely to result in

reduced likelihood of heterozygotes being present in a population

Which of the following is not a cis regulatory element?

lacl

Several features of Gregor Mendel's experiments on plant breeding and patterns of inheritance distinguished his work from that of his contemporaries. Which of the following was a critical experimental innovation employed by Mendel that distinguished his experiments from those of his contemporaries?

Mendel performed controlled crosses with pure-breeding strains.

Many of Mendel's experiments involved crosses in which the sexes of the pure-breeding parents were switched. In each case he observed an F1 with the same phenotype. These pairs of experimental crosses are known as _______.

reciprocal crosses

Mendel's law of segregation predicts the following specific phenotypic ratios among the F1 and F2 progeny from crosses between two pure-breeding parents for a single trait (e.g., yellow vs. green peas).

F1 1:0 F2 3:1

Based on the law of segregation, what proportion of the F2 plants would be expected to produce F3 progeny phenotypes in a ratio of 3 dominant : 1 recessive?

1/2

Based on Mendel's law of independent assortment, what phenotypic ratios are expected among the F2 progeny from a dihybrid cross such as the one illustrated in figure above?

9:3:3:1

How many different combinations of alleles are possible among the gametes produced by an individual that is heterozygous for three separate genes?

Eight

In pedigree analysis, which of the following is a hallmark of an autosomal recessive disorder?

Individuals who have the disease are commonly born to normal (unaffected) parents.

The field of genetics has demonstrated that both molecular and transmission genetics characterize the same hereditary processes at different levels. For example, the wrinkled seed phenotype used by Mendel results from a defect in the gene that encodes which of the following products?

starch-branching enzyme

In the early 1900s, scientists noted that chromosome movements during cell division in reproductive cells mirrored the patterns of inheritance described by Mendel. These results and others confirmed that Mendel's hereditary units (genes) were located on chromosomes. The sum total of chromosomes in an organism constitute its __________, whereas the organism's observable traits constitute its __________.

genotype; phenotype

Which domain(s) of life include(s) multicellular organisms?

Eukarya

Watson and Crick derived their model of DNA structure not from their own laboratory research but rather through the analysis and interpretation of experimental data generated by others, such as Erwin Chargaff, Rosalind Franklin, and Maurice Wilkins. Which of the following provides evidence that DNA nucleotides are arranged as complementary base pairs?

Percentages of adenine and thymine are approximately equal to one another, and the percentages of cytosine and guanine are approximately equal to one another.

What type of bonds holds the two strands of DNA together through the formation of complementary base pairs?

Hydrogen bonds

Which of the following statements about DNA replication is NOT true?

A new DNA strand is synthesized with the same polarity (5′ and 3′ ends) as the template strand

What is a promoter?

A DNA sequence that specifies the start site for transcription

The genetic code consists of a total of how many different codons?

64

Which of the following is NOT one of the four processes of evolution that lead to changes in the frequency of alleles in a population over time?

sexual reproduction

A recessive allele that results in a complete loss of gene function is known as which of the following types of mutation?

Amorphic

Consider a recessive mutation that results in a complete loss of gene function. If heterozygous individuals (mutant/wild-type) are phenotypically wild-type, then the wild-type allele would be described as being __________

haplosufficient

What types of mutants commonly result from regulatory mutations that increase the rate of transcription of a gene?

Hypermorphi

If two alleles of a gene (T1 & T2) are incompletely dominant, then selfing individuals that are heterozygous for these two alleles will produce what phenotypic ratios among the progeny?

1:2:1

The H antigen that directs the formation of ABO blood groups in humans depends on the activity of the final enzyme product of the H gene. Which of the following best describes the type of molecule on the surface of red blood cells that is responsible for the determination of ABO blood type?

glycolipid

In 1905, Lucien Cuenot observed that crosses between two yellow mice consistently produced progeny ratios of two yellow : one agouti (wild-type). What is the explanation for the observed 2:1 phenotype ratio?

The yellow allele is a recessive lethal.

What is the name given to the phenomenon in which some individuals with a particular genotype fail to display the corresponding phenotype?

Incomplete penetrance

What is meant by variable expressivity in genetics?

A single genotype produces a range of phenotypes that differ in the degree or magnitude of expression of the particular trait specified by the gene.

In complementary gene interactions, two genes work in tandem to produce a particular phenotype. Functional copies of both genes are required to produce the phenotype. What phenotypic ratios would be expected among the F2 progeny of a dihybrid cross involving dominant and recessive alleles for two such complementary genes?

9:7

In genetic complementation testing, crosses are performed between pure-breeding strains for recessive mutations that confer the same mutant phenotype. If the two mutations are in different genes, then what phenotypic ratios would be expected among the progeny?

All of the F1 progeny would be wild-type.

Who discovered the structure of DNA

Watson and Crick

Double-stranded DNA can be denatured into single-stranded DNA by heating, which breaking hydrogen bonds. What nucleotide content would describe a species that melts at a significantly higher temperature?

One in which there is a greater number of C-G base pairs, because there are three hydrogen bonds between C and G (compared to 2 hydrogen bonds between A and T)

DNA replication is

semi-coservative

Central Dogma of Molecular Biology

deals with the detailed residue-by-residue transfer of sequential information, it states that such info cannot be transferred from protein to either protein or nucleic acid

Which DNA template encodes the DNA sequence '5- GACCTC -3'

3'- CTGGAG-5'

Which DNA coding stand would be associated with the mRNA 3'- GCAUGC- 5'

3' GCATGC -5'

Which of the following are always encoded by the mitochondrial genome?

Mitochondrial rRNAs

Because of lenient rules for third-base wobble in translation, the minimum number of different tRNAs required in mammalian mitochondria is __________.

22

What name is given to the alteration of an RNA sequence after transcription?

RNA editing

What is the evidence that the ancient mitochondrial and chloroplast endosymbionts are related to the α-proteobacteria and cyanobacteria, respectively?

the sequence of the genes

Organisms have been created by nuclear transfer cloning, in which a diploid nucleus from a somatic cell of an adult animal is injected into an enucleated egg cell to create an embryo. Among the many species thus cloned, there has been a prevalence of mitochondrial defects. Which of the following is the most likely explanation?

The transferred nucleus may have mutations that alter mitochondrial function

Mitochondrial genome transcription, translation, and replication occur where?

in the mitochondrial matrix

You have a DNA sequence of 1600 bp. To characterize it, you decide to make a restriction map. Cutting with the first enzyme, you show by electrophoresis that the fragments produced are 400 and 1200 bp, respectively. After using the second enzyme, you recover 700-bp and 900-bp fragments. After treatment with both enzymes, fragments were 300, 400, and 900 bp. Which is the correct map?

-400-/300-/---900-----

In selecting recombinant bacteria, cells are chosen that are resistant to a specific antibiotic. How are the bacteria made resistant?

The antibiotic resistance gene is encoded in the vector.

Which of the following is a possible advantage for the environment of having farmers use plants that genetically produce Bt toxin?

Plants with genes for the toxin are eaten less often by insects, and therefore less insecticide is needed.

In using Agrobacterium tumefaciens to transfer genes into plants, what is transferred from bacterium to plant?

T-DNA

If a researcher is cloning a sequence by using pUC and uses the plasmid to transform bacteria, which are then plated on X-gal medium, would the recombinant plasmids be found in blue or white colonies or both?

white