Genetics, Cell Cycle, and Molecular Biology: Key Concepts and Processes

The early 1900s was pivotal for the science of genetics because of which of the following events?

- Thomas Hunt Morgan's identification of the first fruit-fly mutant

-All of the events mentioned here contributed. None of these events occurred in the 1900s.

-All of the events mentioned here contributed

-the rediscovery of Gregor Medel's scientific discoveries

-All of the events mentioned here contributed

Which of the following is not part of the eukaryotic cell cycle?

-S

-M

-G2

-S0

-G1

S0

In which part of the cell cycle is the DNA replicated?

S

Which statement is true of sperm?

Sperm may contain an X chromosome.

Imagine that you have discovered a new amphibian with sex chromosomes that you have named A and B. If the female is heterogametic and the male is homogametic, which of the following arrangements would be consistent with your findings?

female AB and male BB

The sex determination system where males develop from unfertilized eggs and females develop from fertilized eggs is best described as

haplodiploidy

Traits that exhibit an intermediate phenotype in a heterozygote, between a dominant and recessive phenotype, are said to be

incomplete dominance

What is the sexual phenotype of a Drosophila that has XXXY sex chromosomes and is diploid for its autosomes?

metafemale

What did Calvin Bridges attribute to his observation while studying the X-linked, recessive white-eye phenotype in fruitflies? Remember: he crossed a white-eyed female with a red-eyed male and unexpectedly observed that 5% of the males had red eyes and 5% of the females had white eyes.

nondisjunction

Which of the statements is not a difference between mitosis and meiosis?

Sister chromatids separate during mitosis but not during meiosis.

In bearded dragons, sex is determined by which characteristic?

both sex chromosomes and temperature

In dogs, black coat color (B) is dominant to brown coat color (b), and short coat length (L) is dominant to long coat length (l).

A black, long-haired dog (Bbl l) is crossed with a brown, short-haired dog (bbLl).

What percentage of the offspring will be black with long hair?

25

In Drosophila melanogaster, white eye color (w) is an X-linked recessive trait, while red eye color (w⁺) is dominant.

A red-eyed heterozygous female is crossed with a white-eyed male.

What percentage of the male offspring will have white eyes?

50

The spread of a complete metaphase chromosome set presented for diagnostic purposes is called a ______.

karyotype

Of all cases of primary Down syndrome, 92% are due to ______ of Chromosome 21

trisomy

______ is a type of polyploidy that arises from the hybridization between two different species.

alloploidy

Which statement about aneuploidy is true?

-One form of aneuploidy is a loss of both members of a homologous pair of chromosomes.

-The rarest aneuploidies in humans are those of the sex chromosomes.

-Aneuploidy is a change in number of chromosome sets

-Most autosomal aneuploids develop normally and have a normal life span

one form of aneuploidy is a loss of both members of a homologous pair of chromosomes.

Which statement about polyploidy is not true?

-Polyploidy results from failure to separate a whole set of chromosomes during cell division

-Polyploidy is possible only between the members of the same species.

-Polyploidy is a major mechanism by which new plant species have evolved.

-Polyploidy is found in many of the food crop plants we enjoy, such as bananas and strawberries.

Polyploidy is possible only between the members of the same species.

Which method of gene transfer in bacteria requires physical contact between donor and recipient cells?

conjugation

Mutant bacterial strains that lack one or more enzymes needed to make essential molecules are called:

auxotroph

what best describes an F' bacterial cell?

It contains an F plasmid that includes some bacterial genes.

What is the process called in which a virus has undergone major changes in its genome through the reassortment of genetic material from different strains of the virus?

antigenic shift

A phage cross is made with phage T2. One of the parents was h+r− and the other parent was h−r+.

What would be the two recombinant classes of progeny from this cross?

h+r+ and h−r−

When two genes show a high frequency of cotransduction, it can be assumed that:

The two genes are located close to each other.

Which of the types of bacterial cells would normally be able to undergo conjugation with an F+ cell?

F- cells

What characteristic is not necessary for a molecule that is the genetic material?

It must perform the action associated with the phenotype.

A key discovery leading to the structure of DNA was done by Chargaff. He found that

-the tetranucleotide hypothesis was false

-the amount of A equals the amount of T, and the amount of G equals the amount of C

What did Griffith discover with his experiments?

the transforming principle in bacteria

What does the term antiparallel mean?

-the 5' end of one strand is opposite the 3' end of the second strand.

-The strands run in opposite directions.

A left‑handed form of DNA is the

z DNA

A structure formed by a single-stranded DNA or RNA molecule that has complementary sequences is:

a hairpin

In Avery, MacLeod, and McCarty's experiments, under which condition would transformation *not* occur?

treatment with DNase

The major contribution of Franklin and Wilkins to the study of DNA was:

an X-ray diffraction pattern

The number of hydrogen bonds between complementary G−C pairs is:

3

In experiments involving tobacco mosaic virus, Fraenkel-Conrat and Singer demonstrated:

that in some cases, RNA can be the genetic material

Bacteria have acquired genes from other species of bacteria and sometimes from eukaryotic cells. The processes by which this occurs are known collectively as:

HGT

Which statement about retroviruses is NOT true?

-They replicate their DNA genomes in the cytoplasm of host animal cells.

-They produce the enzyme reverse transcriptase.

-They have three genes in common, and each gene can produce more than one type of protein

-They can make a DNA copy of their genome that integrates into the host cell genome.

-they may contain oncogenes.

They replicate their DNA genomes in the cytoplasm of host animal cells.

Which sequences are present in both the pre-mRNA and the mature mRNA? Select all that apply.

-5' UTR

-3' UTR

-exons

Which sequences are important to predict the protein sequence from the DNA sequence? Select all that apply.

-stop codon

-start codon

-intron splice site

t or f : RNA is a more stable molecule than DNA

false

Which class of RNA serves as the coding instruction read by the ribosome to produce a polypeptide chain?

mRNA

Which RNA type is found only in eukaryotes?

SnoRNA

The diagram represents a transcription unit comprised of three critical regions: the promoter, the coding region, and the terminator.

Which region would not be present in the final RNA transcript?

promotor

Frequently, important DNA regions with specific functions tend to contain short stretches of nucleotides that are conserved across different organisms (e.g., promoter sequence) and are recognized by specific proteins.

What are these conserved sequences called?

consensus sequences

How is the transcription start site determined in bacteria?

by the binding of RNA polymerase to the consensus sequences of the promoter

Most bacterial RNA polymerases are made up of five subunits that have distinct functions for transcription. Which of the subunits does not permanently associate with the enzyme core?

sigma

What is the most precise definition of a gene?

the entire DNA sequence that is required to transcribe and encode a single RNA molecule

the entire DNA sequence that is required to transcribe and encode a single RNA molecule

the ribosome binding site in bacterial RNA

What is not a characteristic of the 5' cap?

The 5' cap is a tag for mRNA degradation.

What is the outcome of RNA editing?

The protein translated from the edited mRNA has a sequence different from its gene.

Alternative splicing produces

mRNAs of different lengths from the same pre‑mRNA.

Transplicing

This process joins exons from different mRNA molecules, which creates an amino acid sequence that does not correspond to a single gene.

alternative splicing

This process produces different mRNA molecules from a single gene, which causes a single gene to produce different proteins

RNA-editing

This process adds nucleotides to the pre‑mRNA molecule after transcription, which results in an amino acid sequence that does not directly correspond to the original gene sequence.

What RNA sequences can potentially fold to form double‑stranded RNA via a hairpin loop?

5⁢′−.....AGUCC.......GGACU......-3⁢′

*the base pairs match when folded

Which statement is most consistent with the one gene, one enzyme hypothesis originally proposed by Beadle and Tatum?

Every gene encodes a separate enzyme.

Which of the statements about the genetic code are most accurate?

- The genetic code is generally non overlapping.

-An initiation codon sets the reading frame

What of these is the first step of translation elongation?

A charged tRNA binds to the A site.

What does the termination of translation require?

-GTP

-release factors

-stop codon on mRNA

Using the codon table, what conclusions can be drawn about the genetic code?

-Many amino acids are encoded by multiple codons.

-Three codons do not code for amino acids.

Which of the options are mechanisms of mRNA surveillance?

-nonsense mediated mRNA decay

-no go decay

-nonstop mRNA decay

what properties does bacterial cells have when it comes to replication?

-translation and transcription are coupled

-bacterial have shine dalgarno sequences

What statement about mutations is incorrect?

Germ-line and somatic mutations are both passed on to offspring.

What is a missense mutation?

a mutation that results in a different amino acid in a protei

What is a conditional mutation?

a mutation that affects the phenotype only under certain conditions

What is an example of a transversion mutation?

Adenine is replaced by thymine.

What changes does UV light produce in DNA molecules?

pyrimidine dimers

What is the Ames test?

a test to screen for mutagenic chemicals

Which is not a characteristic of transposable elements?

only found in plants

How does transposition cause mutations?

Transposable elements can insert themselves into other genes and disrupt their function.

What generally causes thymine dimers to form in a strand of DNA, and why are thymine dimers a problem?

Ultraviolet light can cause thymine dimers, potentially creating a mutation that could lead to cancer.

An insertion sequence contains a large deletion in its transposase gene. Under what circumstances would this insertion sequence be able to transpose?

There is another transposable element of the same type present in the cell, and it expresses a functional transposase enzyme.

somatic mutations occur in:

Nonreproductive cells

Frameshift mutations result from:

insertions or deletions not in multiples of three

Expanding trinucleotide repeats cause disease by:

increasing the number of copies of a nucleotide sequence

intercalating agents such as acridine orange

Insert between bases and cause insertions/deletions

A suppressor mutation:

Suppresses the effect of another mutation

An intragenic suppressor mutation

Occurs within the same gene as the original mutation

What is a mutation?

A heritable change in genetic information

Base analogs are mutagenic because of which characteristic?

They are similar in structure to normal bases.

A transversion mutation is

Purine ↔ pyrimidine

Which of the examples listed is not a DNA repair mechanism?

insertion sequence repair

Do mismatch‑repair enzymes in E. coli differentiate between the old and new strands of DNA?

methylation of the adenine in the GATC sequence of the old strand

How does direct DNA repair restore damaged DNA to its original sequence?

It removes functional groups or bonds from the altered nucleotide to restore the original structure

Eyes in Drosophila melanogaster result from an X‑linked recessive mutation. Occasionally, white‑eyed mutants give rise to offspring that possess white eyes with small red spots. The number, distribution, and size of the red spots are variable.Explain how a transposable element, or transposon, could be responsible for this spotting phenomenon.

Excision of a transposable element out of the eye color locus during eye development produces a patch of cells that produce red pigment.

AZT is a drug used to treat acquired immunodeficiency syndrome (AIDS). AZT blocks reverse transcriptase, an enzyme used by HIV, the causative agent of AIDS. Which types of transposable elements would be affected by AZT, and what would be the most likely effect? Select all that apply.

-Transposable elements that use an RNA intermediate for transposition would be affected, as the RNA intermediate would not be able to be converted into DNA

-All types of retrotransposons would be blocked at the reverse transcription step

DNA technology is a set of molecular methods used to isolate, manipulate, and study DNA.What does recombinant mean, in this case?

that the DNA used is often derived from two or more sources and combined

Endonucleases

can be used to create pieces of DNA with cohesive ends.

Separating a complex mixture of DNA fragments according to size, identifying a specific fragment of interest

can be accomplished by using a probe complementary to only part of the sequence.

All of the following are required for genome editing with the CRISPR-Cas9 system except which one

All of the following are required for genome editing with the CRISPR-Cas9 system except which one

Select all items that are used as cloning vectors

-artificial chromosomes

-cosmids

-plasmids

PCR requires all of the steps except

transforming cells so that, in the pool of cells, all genes are represented.

Which of the following are not a DNA sequencing technique? Select all that apply.

-Mullis chain‑terminating sequencing.

-DNA fingerprinting.

Analysis of mutants (natural or induced) to determine gene function is known as

forward genetics

Which of the following is not used in reverse genetics to determine gene function?

reverse transcription

Which of the following is NOT a biotechnology application that uses recombinant DNA or gene editing techniques?

artificial selection for larger fruit size in crops.

Which of the following are advantages of CRISPR-Cas systems over restriction enzymes and engineered nucleases for DNA editing?

-Single guide RNAs (sgRNAs) can introduce new DNA sequences into the cells of living animals.

-Relatively long recognized nucleotide sequences produce unique cuts in DNA.

-Relatively long recognized nucleotide sequences produce unique cuts in DNA.

which of the following are ways bacterial defense systems have been adapted for use as tools in molecular genetic analysis?

-CRISPR‑Cas systems occur naturally in bacteria as a form of protection against viruses.

-Restriction enzymes occur naturally in bacteria as a form of protection against viruses.

Which of the following will result in DNA without a mismatch?

Replicated error

Which of the following is a key advantage of next-generation sequencing over traditional Sanger sequencing?

t sequences millions of DNA fragments in parallel