Midterm 2 Flashcards
The term that describes the highly compacted regions of chromosomes observed during interphase is
heterochromatin
When Avery, MacLeod, and McCarty added RNase and protease to their DNA extracts, what happened?
The R strain was converted to the S strain.
Following semiconservative DNA replication, what are the compositions of the two double helices that are made?
Both double helices contain one original DNA strand and one new strand.
The location on the DNA where transcription begins is called
promotor
a collection of 64 codons that either specify amino acids or function to stop translation
“genetic code”
The two strands of a double-stranded DNA molecule are held together by
hydrogen bonds.
An organized unit of DNA sequences that enables a segment of DNA to be transcribed into RNA, and ultimately results in the formation of a functional product, is called a
gene
DNA replication begins at special sites on the parental DNA molecule known as
origin(s) of replication
A new DNA strand elongates only in the 5’ to 3’ direction because…
DNA polymerase can only add nucleotides to the free 3’ end.
The site where translation takes place is the
ribosome
Which of the enzymes synthesizes short segments of RNA?
DNA primase.
The regions within an mRNA that are removed during splicing are called
introns
Which of the following molecules is a regulatory transcription factor? Operon. Inducer. Promoter. Repressor.
repressor
Modification of DNA by the covalent attachment of methyl groups usually
silences gene expression.
Which of the following activities is not catalyzed by chromatin-remodeling complexes?
Change the positions of nucleosomes.
Evict histones from the DNA.
Degrade histone proteins.
Replace standard histones with variant histones.
Degrade histone proteins.
A protein that binds to the DNA and stimulates transcription is called
an activator.
How does having glucose in the environment inhibit transcription of the lac operon?
By reducing the levels of cAMP produced in the cell.
With regard to transcriptional regulation in eukaryotic cells, it has been shown that many genes are regulated by multiple factors. This phenomenon is referred to as
Combinatorial control.
in positive control of the lac operon, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. Which of the following environmental conditions causes an increase in CAP activity in stimulating transcription?
An increase in glucose.
A decrease in glucose and an increase in cAMP.
An increase in glucose and a decrease in cAMP.
A decrease in cAMP.
A decrease in glucose and an increase in cAMP.
Cell differentiation occurs because each cell
contains the same set of chromosomes, but their genes are regulated differently.
DNA segments that function to increase transcription levels in eukaryotes are called
enhancers.
How does active CAP induce expression of the genes of the lactose operon?
It terminates production of repressor molecules.
It degrades the substrate allolactose.
It stimulates splicing of the encoded genes.
It stimulates the binding of RNA polymerase to the promoter.
It stimulates the binding of RNA polymerase to the promoter.
The effect of allolactose is:
Conformational change in the lac repressor protein, inducing the lac operon.
Which of the following functions are characteristic of general transcription factors in eukaryotes?
They bind to other proteins or to the TATA box.
In bacteria, the regulation of gene expression most commonly occurs at the level of transcription. Gene regulation in bacteria can also occur at the level of
translation.
A unit of DNA that contains multiple structural genes and is under the control of a single promoter is called
operon
Which of the following conditions is most likely to cause the lactose operon to be transcribed?
There is more glucose in the cell than lactose.
There is glucose but no lactose in the cell.
The cAMP level is high and the lactose level is low.
The cyclic AMP and lactose levels are both high within the cell.
The cyclic AMP and lactose levels are both high within the cell.
A mutation prevents allolactose from binding to the lac repressor, but the repressor protein can still bind to the operator site. How would this affect the regulation of the lac operon?
The operon would be turned on both in presence and absence of lactose.
The operon would be turned off both in the presence and absence of lactose.
The operon would be turned on in the presence of lactose but turned off in the absence of lactose.
The operon would be turned off in the presence of lactose but turned on in the absence of lactose.
The operon would be turned on both in presence and absence of lactose.
For eukaryotic genes that can be transcribed, where are nucleosome-free regions (NFRs) found?
At both the beginning and end of genes.
Which of the following is an event of anaphase in mitosis?
The nuclear envelope breaks down.
Crossing over occurs.
Sister chromatids align longitudinally in the center of the cell.
Sister chromatids separate.
Sister chromatids separate.
A human cell containing 22 autosomes and a Y chromosome is
sperm
A student is looking at cells under the microscope. The cells are from an organism that has a diploid number of fourteen. For one particular slide, the cell has seven replicated chromosomes (7 pairs of sister chromatids) aligned at the metaphase plate of the cell. Which of the following statements accurately describes this particular cell?
The cell is in metaphase II of meiosis.
The process of mitotic cell division:
I. results in daughter cells with half the genetic material of the original cell.
II. is important for growth of an organism.
III. results in daughter cells genetically identical to the original cell. I and III only II only I only II and III only
II and III only
Which of the following is the correct order of the phases in mitosis?
Prometaphase, prophase, metaphase, anaphase, telophase
Prophase, prometaphase, metaphase, anaphase, telophase
Anaphase, prometaphase, prophase, metaphase, telophase
Telophase, prometaphase, prophase, metaphase, anaphase
Prophase, prometaphase, metaphase, anaphase, telophase
Which of the following changes in chromosome structure does not affect the total amount of genetic material? Deletion. Duplication. Inversion. polyploidy
Inversion.
Which two types of proteins function to advance the eukaryotic cell through the phases of the cell cycle?
cyclins and cyclin-dependent kinases (cdks)
During the eukaryotic cell cycle, the cell alternates between
interphase and “M” phase
When homologous chromosomes crossover, what occurs?
Two non-sister chromatids of a bivalent break and re-join with their homologs.
The G2 checkpoint of the cell cycle ensures that
the DNA has been properly replicated.
After telophase I of meiosis, the chromosomal makeup of each daughter cell is __________.
haploid, and the chromosomes are each composed of two chromatids.
Crossing over most commonly occurs during
prophase in meiosis I.
Which of the following is a true statement about sexual vs. asexual reproduction?
Asexual reproduction produces only haploid offspring.
Offspring produced by sexual reproduction have twice as many chromosomes as their parents.
In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring.
In asexual reproduction, offspring are produced by fertilization without meiosis.
In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring.
A replicated chromosome in eukaryotes is composed of
two sister chromatids held together at the centromere.
a strand of DNA is formed by the
covalent linkage of nucleotides in a linear manner.
nucelotides contain
a phosphate group, a 5C sugar, and a nitrogen containing base.
Linked by covalent bonds between phosphorus and oxygen
phosphodiester linkage
What forms backbone of DNA or RNA
The phosphates and sugar molecules
Purine bases
Adenine and guanine, double ring structure, in both RNA and DNA.
Pyrimidine bases
thymine, uracil, and cytosine, have a single ring structure. (Cytosine in DNA and RNA. thymine in DNA, uracil in RNA)
Base sequences are
complementary
A/T (? H bonds) and G/C (? H bonds)
2, 3
Dna strands serve as a
template for the synthesis of daughter strands.
- DNA backbone of 2 strands farther apart
2. backbone of 2 strands closer together spiral around the double helix.
- Major groove
2. minor groove
Meselson and Stahl Mechanisms for DNA replications:
Semiconservative
Conservative
Dispersive
DNA replication produces DNA molecules with 1 parental strand and 1 newly made daughter strand.
Semiconservative
DNA replication produces 1 double helix with both parental strands and the other with 2 daughter strands
Conservative
DNA replication produces DNA strands in which segments of new DNA are interspersed with the parental DNA.
Dispersive
When is the DNA replication fork made
When DNA helicase unwinds the double helix structure of the DNA.
made continuously, continues to elongate.
Leading strand
made discontinuously, It is synthesized in fragments, the discontinuous replication results in several short segments
Lagging strand
First compacted by wrapping itself around a group of proteins
histones
When cells prepare to divide, chromosomes become more
condensed
2 noncoding RNA
transfer RNA
ribosomal RNA
where transcription begins
Promotor
site in DNA where it ends.
Terminator
sequences that function as sites for the binding of regulatory proteins that affect the rate of transcription.
Regulatory sequences
(needed to make polypeptides during translation)
transfer RNA
(forms part of ribosomes which is where translation occurs)
ribosomal RNA
produces an RNA copy of a gene from DNA.
Transcription
synthesizes a specific polypeptide.
Translation
The main reasons why genes are regulated:
conserves energy; protein encoded by genes will be produced only when needed.
Ensures that genes are expressed in appropriate cell types and in the correct stage of development.
epsilon and zeta globin genes on
Embryonic stage
alpha and gamma globin turned on
fetal stage
beta and alpha globin genes turned on
at birth
in bacteria, gene regulation occurs most commonly at level of
transcription
decreasing transcription rate, negative control
Repressor
increasing transcription rate, positive control
Activator
proteins that bind to regulatory sequences in DNA
regulatory transcription factors
regulatory transcription factors either…
increase or decrease the rate of transcripition
A. The promoter is used to transcribe 3 genes.
B. encodes B galactosidase (catalyzes the breakdown of glucose)
C. encodes lactose permease (transporter)
D. encodes galactoside transacetylase
E. The operator is a regulatory sequence in DNA
A. lacP B. lacZ C. lacY D. lacA E. lacO
provides a binding site for a repressor protein
lacO
regulatory DNA sequence that’s recognized by an activator protein.
CAP site