PAST EXAM QUESTIONS Flashcards
Which of the following proteins keep parental DNA separated during DNA replication?
Single-strand binding proteins
Why can’t the lagging DNA strand be copied continuously like the leading strand?
because DNA polymerase can attach nucleotides in only one direction
What is the function of ligase during DNA replication?
joining Okazaki fragments
Which of the following is true of binary fission?
binary fission results in two daughter cells that are genetically identical to one another
During which phase of the cell cycle does DNA replication occur?
S
What is the term used to describe DNA wrapped around histone proteins?
nucleosome
During which phase of the cell cycle does the nuclear envelope reassemble?
telophase
You see a cell in a mitotic phase with its sister chromatids being pulled towards opposite poles; in which phase is this cell?
anaphase
Which of the following are expected to be identical to one another?
sister chromatids during mitosis
What structure forms first in a plant cell as it undergoes cytokinesis to separate it into two daughter cells?
cell plate
The sites of the physical exchange of DNA between chromatids are known as:
chiasmata
How are Meiosis I and Meiosis II different?
crossing over occurs during Meiosis I but not Meiosis II
Septum formation and cleavage furrow formation
differ because septa are produced by FtsZ protein and cleavage furrows are produced by actin and myosin microfilaments AND are necessary for cells to divide their cytoplasm
A telomere is
made up of repeated DNA sequences at the ends of chromosomes
Primase
synthesizes an RNA primer for DNA polymerase
During replication, DNA is unwound
by helicase at the replication fork
Which of the following is/are true about microtubules?
They are made of protein AND They may attach to kinetochores
The synaptonemal complex
is composed of protein AND forms between non-sister chromatids
Cells containing only one homologue of each chromosome would be produced by the end of:
meiosis I AND meiosis II
Crossing over
involves the reciprocal exchange of genetic material between the non-sister chromatids of homologous chromosomes
During which phase of the cell cycle do the poles of the cell move apart?
anaphase
Cell division in prokaryotes and eukaryotes both involve
segregation of genetic material
An activated cyclin dependent kinase
uh
A cell cycle checkpoint may occur
at the G1 to S transition at the G2 to mitosis transition at the metaphase to anaphase transition
Cells containing homologous pairs of chromosomes would be produced by which of the following processes?
mitosis
Sister chromatids are created during which process?
When DNA is replicated during the S phase
Which of the following is true regarding chromosomes during different forms of cell division?
None of the above are true
Which biological process would be directly affected if meiotic cell division was impaired?
Sexual reproduction
Which of the following are expected to be identical to one another?
Sister chromatids
What will happen to a cell that detects damage to DNA after the S phase of the cell cycle?
It won’t proceed through the G2/mitosis checkpoint until damage is fixed
In what phase of the cell cycle is DNA fully compacted and visible in a cell?
During mitosis
Males are more often affected by sex-linked traits than females because
Males are hemizygous for the X chromosome
The interaction between genes at different loci to determine coat color in Labradors is an example of?
epistasis
Which of the following is true about the F1 offspring from a P0 cross between true-breeding dominant and true-breeding recessive organisms?
They will all have the same phenotype
Transmission of signaling molecules through gap junctions is an example of
cell-to-cell contact signaling
What epigenetic modifications could make DNA more accessible to transcription factors?
Demethylation of cytosines followed by guanines AND Acetylation of histone tails
Hydrophilic ligands
bind to trans-membrane receptors
When histone tails are deacetylated
DNA binds more tightly with the histones because deacetylated lysines make the histones more positively charged
Zymogens are enzymes that are not active until they are
cleaved
Some genes are paternally imprinted and
those genes are only expressed on the maternal chromosome and mutants have enhanced growth.
In cystic fibrosis a mutation in the CTFR gene blocks the binding of the CFTR protein with its chaperones protein. What part of the CTFR protein structure will be disrupted?
Tertiary structure
A weak attractive force between two nonpolar amino acids due to small fleeting changes in atomic charge is known as
Van der Waals Interactions
A process or processes that allow one gene to code for multiple polypeptides is
alternative splicing
What is the highest level of protein structure a single polypeptide can achieve?
Tertiary
Transmembrane receptors can be
catalytic
After transcription, introns are removed by
the spliceosome
The 5’ methyl cap is added to mRNA
during transcription before addition of the Poly A tail.
In Alzheimer’s disease what happens to the Tau and beta-amyloid proteins in the brain?
They misfold which leads to the formation of plaques and tangles
Some key structural components of tRNAs are
a 3’ acceptor stem AND an anticodon loop
The genetic code is redundant which specifically means
there is more than one codon for some amino acids
SNP’s
are single base differences in DNA that vary among individuals
Wobble base pairing comes into play
during the elongation phase of translation
The following summarizes steps in the arginine biosynthetic pathway: Glutamate…ornithine…citruline…arginosuccinate…arginine. A Neurospora mutant could not grow on minimal media, or minimal media supplemented with ornithine alone, or citruline alone, or arginosuccinate alone but could grow if arginine alone were added to the media. Based on this information alone you could conclude that this mutant was
deficient in enzymes necessary to convert arginosuccinate to arginine
Beadle and Tatum’s results studying the arginine synthesis pathway using Neurospora mutants lead them to hypothesize
that one gene codes for one enzyme
Variable Nucleotide Tandem Repeats are an example of
short repeated DNA sequences that vary in length AND short repeated DNA sequences that vary in the number of repeats
G protein-coupled receptors
are transmembrane receptors that activate G proteins
The sequence of a transcribed mRNA is
complementary to the template strand of the gene with U’s substituted for T’s
Prokaryotes and eukaryotes differ because
prokaryotes couple transcription and translation and eukaryotes do not AND eukaryotes may have noncoding sequences removed from a pre-mRNA transcript and prokaryotes do not
Which of the following are true for tRNA?
It has a 3’ acceptor stem AND It may be charged with the assistance of aminoacyl-tRNA synthetase
Which of the following are components of the ribosomes?
rRNA and ribosomal proteins
Correct positioning of RNA on a ribosome as part of initiation is aided by
the 5’ methyl cap of mRNA in eukaryotes
Which of the following is a correct statement about elongation during protein synthesis?
The ribosome is translocated along the mRNA, so an uncharged tRNA occupies the E site.
Stop codons
do not code for an amino acid AND are recognized by release factors
Which of the following are involved in blocking translation of an RNA?
micro RNAs
In the levels of protein structure, motifs represent
secondary structure
Which of the following suppresses transcription of genes?
The methylation of DNA at cytosines followed by guanines AND The deacetylation of histones
What is true about second messenger molecules?
They are short-lived intracellular signaling molecules The activation of G protein couple receptors can lead to their formation Their removal or degradation can terminate the cellular response
What are the roles of HATs and HDACs?
The acetylation and deacetylation of histones
What event initiates development?
fertilization
What factor has the strongest influence on the cleavage pattern of an embryo?
amount of yolk
Cells move inward from the surface of the blastula in a carefully-orchestrated migration called
gastrulation
What is the period of rapid cell division in which the embryo does not increase in overall size?
cleavage
Very early in development, each cell is capable of becoming any cell type. This is referred to as
totipotency
Which protein or proteins determine the anterior/posterior axis of the fruit fly embryo and are expressed from mRNAs that came from the mother?
The bicoid and nanos proteins.
Programmed cell death is a process called
apoptosis
A cell’s developmental fate can be determined by contact with neighboring cells in a process called
induction
Gastrulation results in the formation of which germ layer(s)?
ectoderm, mesoderm, and endoderm
Genes which regulate the development of anatomical structures in various organisms are called
homeotic genes
In vertebrates, the ______ nervous system is composed of the brain and the spinal cord
central
What are the branched extensions of a neuron that receive signals called?
dendrites
What is the elongated extension of a neuron that nerve impulses travel along?
axon
A rapid inward diffusion of Na+ that produces a dramatic change in the membrane potential of a neuron is called what?
depolarization
The membrane of a resting neuron is most permeable to which of the following ions?
Cl-, Ca2+, Na+, K+
When neurons are not producing electrical signals, there is still a voltage difference across their membranes. What is this voltage called?
Resting potential
What is the process in which action potentials jump from node of Ranvier to node of Ranvier?
saltatory conduction
Which figure correctly illustrates the mechanism of action of the sodium-potassium pump?
C
What diffuses across the synaptic cleft from the presynaptic membrane to the postsynaptic membrane to transmit a nerve impulse?
Neurotransmitter
Place the following events that occur at the neuromuscular junction in the correct order. I-Depolarization of the muscle cell membrane. II-Generation of an action potential in the neuron. III-Stimulation of Ca2+ entry into the end of the axon. IV-Release of acetylcholine into the synaptic cleft.
II, III, IV, I
Sodium ions are single atoms. Why can’t they simply diffuse through the cell membrane’s lipid bilayer?
Since they are charged, ions can’t cross the hydrophobic center of the membrane without a channel or pump.
Botulinum toxin, or “botox”, has become popular for cosmetic surgery. The toxin prevents the release of neurotransmitters from a signaling neuron. How would this toxin most likely affect signaling at the neuromuscular junction?
Since neurotransmitters are not released, the muscles are not activated to contract and remain relaxed
Which of the following types of muscles are striated?
skeletal and cardiac
Action potentials conducted along the transverse tubules of the muscle stimulate
the release of calcium ions from the sarcoplasmic reticulum
Sarcomeres are anchored on each end by the
Z line
The thick filaments in sarcomeres are composed of
myosin
When animals die, the lack of ATP causes muscles to stiffen in rigor mortis because
actin and myosin cannot separate without ATP.
Which statement about the structures shown in this figure is true?
Structure 2 blocks myosin-binding sites
Fast-twitch skeletal muscle fibers are characterized by
the rapid development of high tension and rapid fatigue.
Slow-twitch skeletal muscle fibers
are well supplied with mitochondria
The skeletal muscles in the legs of competitive cross-country skiers and long-distance runners are likely to have
more slow-twitch than fast twitch fibers
Which line represents the glycolytic system for muscle energy generation?
B
Which line represents the oxidative system for muscle energy generation?
C
Which line represents the system for muscle energy generation that uses preformed ATP and ATP regeneration using creatine phosphate?
A
