Genetics Essentials: Exam 3 Flashcards
When a DNA molecule is described as replicating bidirectionally, that means that it has two:
An Okazaki fragment is a:
segment of DNA that is an intermediate in the synthesis of the lagging strand.
Which one of the following statements about enzymes that interact with DNA is true?
Exonucleases degrade DNA at a free end.
E. coli DNA polymerase III:
is the principal DNA polymerase in chromosomal DNA replication.
The proofreading function of DNA polymerase involves all of the following except:
reversal of the polymerization reaction.
The 5' → 3' exonuclease activity of E. coli DNA polymerase I is involved in:
removal of RNA primers by nick translation
Prokaryotic DNA polymerase III:
has a β subunit that acts as a circular clamp to improve the processivity of DNA synthesis.
At replication forks in E. coli:
RNA primers are synthesized by primase
Which of these enzymes is not directly involved in methyl-directed mismatch repair in E. coli?
The role of the Dam methylase is to:
modify the template strand for recognition by repair systems.
The functional unit of genetic information is called:
The process whereby RNA specifies a DNA sequence is known as:
Proteins interact predominantly within which portion of a double-stranded DNA helix?
AT-rich DNA will denature/melt
at a lower temperature than GC-rich DNA.
In Bacteria and most Archaea, the enzyme that introduces negative supercoils into DNA is known as
Ciprofloxacin, nalidixic acid, and novobiocin are effective antiobiotics because they inhibit the activity of
Most plasmids are
double-stranded DNA, though a few are not.
Housekeeping genes are present in
The precursor of each new nucleotide in a strand of DNA is a
DNA replication always proceeds from the ____ of the incoming nucelotide to the _____ of the previously added molecule
5' phosphate/ 3' hydroxyl
During DNA synthesis, the RNA primer is removed by a
Pol I exonuclease
The template for RNA polymerase is _____, and the RNA chain growth is _____ the chain growth of DNA.
DNA/ Identical to
Promoters are specific sequences of _____ that are recognized by ______.
DNA/ sigma factor
An example of nucleotide pairing is
A and T
Stop codons are also called ____ codons.
nonsense and termination
There are about ____ different tRNAs in bacterial cells and about _____ in mammalian cells
tRNA is released from the ribosome at the _____ site
Which statement is generally TRUE regarding protein synthesis?
the 23S rRNA plays a role in TRANSLOCATION; the 16S rRNA plays a role in INITIATION
Streptomycin inhibits _____ of protein synthesis, whereas tetracycline inhibits _____ of protein synthesis
In all cells, genes are composed of
Which of the following is an example of one codon?
Which of the following is NOT correct regarding DNA and RNA synthesis?
Both processes require an RNA primer to begin.
Termination of RNA synthesis is ultimately determined by
specific nucelotide sequences on the template strand.
GTP provides energy for
Transcription of chaperonins is greatly accelerated when a cell is stressed by
The flow of biological information begins with
Most of the genes that encode proteins are found in
Why was the discovery of the structure of DNA so important for understanding genetics?
Without knowledge of the structure of DNA, it was impossible to understand how genetic information was encoded or expressed.
If Avery, MacLeod, and McCarty had found that samples of heat-killed bacteria treated with rNase and DNase transformed bacteria, but that samples treated with protease did not, what conclusion would they have made?
protein is the genetic material
Could Hershey and Chase have used a radioactive isotope of carbon instead of 32p? Why or why not?
No: carbon is found in both protein and nucleic acid.
How do the sugars of rNA and DNA differ?
the sugar of rNA has a hydroxyl group that is not found in
sugar of DNA
the antiparallel nature of DNA refers to
the opposite direction of the two strands of nucleotides.
How does Z-DNA differ from B-DNA?
Z-DNA has a left-handed helix; B-DNA has a right-handed helix. The sugar–phosphate backboneof Z-DNA zigzags back and forth, whereas the sugar– phosphate backbone of B-DNA forms a smooth continuous ribbon
A DNA molecule 300 bp long has 20 complete rotations. this DNA molecule is
How does bacterial DNA differ from eukaryotic DNA?
Bacterial DNA is not complexed with histone proteins and is circular
Neutralizing their positive charges would have which effect on the histone proteins?
they would bind less tightly to the DNA
Which of the following is a characteristic of DNA sequences at the
telomeres? a. One strand consists of guanine and adenine or
nucleotides. b. they consist of repeated sequences. c. One strand protrudes beyond the other, creating some
single-stranded DNA at the end. d. All of the above
d. All of the above
how many bands of DNa would be expected in Meselson and Stahl’s experiment after two rounds of conservative replication?
Discontinuous replication is a result of which property of DNa
antiparallel nucleotide strand
Place the following components in the order in which they are first used in the course of replication: helicase, single-strand-binding protein, DNa gyrase, initiator proteins.
Initiator proteins, helicase, single-strand-binding protein, DNA gyrase
Primers are synthesized where on the lagging strand?
At the beginning of every Okazaki fragment
Which bacterial enzyme removes the primers
DNA polymerase I
Bind to origin and separate strands of DNa to initiate replication
Unwinds DNa at replication fork
attach to single-stranded DNa and prevent secondary structures from forming
Moves ahead of the replication fork, making and resealing breaks in the double-stranded helical DNa to release the torque that builds up as a result of unwinding at the replication fork
Synthesizes a short rNa primer to provide a 3'-Oh group for the attachment of DNa nucleotides
DNa polymerase III
elongates a new nucleotide strand from the 3'-Oh group provided by the primer
DNa polymerase I
removes rNa primers and replaces them with DNa
joins Okazaki fragments by sealing breaks in the sugar– phosphate backbone of newly synthesized DNa
What are some differences from prokaryotes in the genome structure of eukaryotic cells that affect how replication takes place?
The size of eukaryotic genomes, the linear structure of eukaryotic chromosomes, and the association of DNA with histone proteins
What would be the result if an organism’s telomerase were mutated and nonfunctional?
Chromosomes would shorten each generation.
Why is recombination important?
Recombination is important for generating genetic variation.
Stem Loop structures are a critical part of
Rho- dependent termination and rho-independent termination
The main purpose of recombination is
To align truly homologous chromosomes
The function of gyrase is
To relieve torsional stress from unwinding DNA
The molar ratio of Histone H1 to H2 in the core is
If a splice site were mutated so that splicing did not take place, what would the effect be on the mrNA?
It would be longer than normal.
What evidence indicated that eukaryotic genes are not colinear with their proteins?
When DNA was hybridized to the mRNA transcribed from it, regions of DNA that did not correspond to RNA looped out
What is the function of the sigma factor?
The sigma factor controls the binding of RNA polymerase to the promoter.
What is the difference between the template strand and the nontemplate strand?
The template strand is the DNA strand that is transcribed into an RNA molecule, whereas the nontemplate strand is not transcribed.
Which class of rNA is correctly paired with its function?
transfer rNA (trNA): attaches to an amino acid
In a polyribosome, the polypeptides associated with which ribosomes will be the longest?
those at the 3' end of mrNA
In elongation, the creation of peptide bonds between amino acids is catalyzed by
In elongation, the creation of peptide bonds between amino acids is catalyzed by
The Shine–Dalgarno sequence
Amino acids bind to which part of the trNA
through wobble, a single __________ can pair with more than one _____________.
A codon is
three nucleotides that encode an amino acid
What determines the secondary and tertiary structures of a protein?
The amino acid sequence(primarystructure) of the protein
Which one of the following statements is not true for all E. coli DNA polymerases?
They possess 5'to 3' exonuclease activity.
Which statement is true regarding negative supercoiled DNA ?
Negative supercoiled DNA is under-rotated and allows for easier strand separation during replication and transcription
What would Avery, Macleod, and McCarty have concluded if their results had been that only RNAse treatment of the heat-killed bacteria prevented transformation of genetic virulence?
RNA is the genetic material
Okazaki fragments are found associated with
After the first round of replication, Meselson and Stahl saw only one DNA band of density intermediate to DNA containing only 15N or 14N. After this observation, which hypothesis for DNA replication could be eliminated ?
DNA synthesis in eukaryotes is?
According to Chargaff’s rules, if a genome is 30% adenine, then what percentage of the genome should be guanine?
How many base pairs per turn on DNA
What is the function of DNA Polymerase I in E.coli
Removes and replaces primers
What is the function of DNA Polymerase III in E.coli
What is the function of DNA Polymerase II, IV, and V in E.coli
DNA repair for all, ttranslesion DNA synthesis for V, II Halts synthesis, IV just repairs
Binds to origin and separates strand of DNA to initiate replication
Unwinds DNA at replication fork
Attach to single-stranded DNA and prevent reannealing
Moves ahead of the replication fork, making and resealing breaks in the double-helical DNA to release torque that builds up as a result of unwinding at the replication fork
Synthesizes short RNA primers to provide a 3-OH group for attachment of DNA nucleotides.
Elongates a new nucleotide strand from the 3-0H group provided by the primer
DNA polymerase III
Removes RNA primers and replaces them with DNA
DNA Polymerase I
Joins Okazaki fragments by sealing nicks in the sugarophoshate backbone of newly synthesized DNA
After crossing over results in recombination and non-recombination products take place after what?
How does Holiday junction predict crossover of recombinant DNA?
Ir depends if it was cut horizontal or vertical
Correct order of the Central Dogma
information from DNA--- transcription to RNA translated to protein
Transcribed in both eukaryotic and prokaryotic cells.
Messenger RNA (mRNA), Ribosomal RNA (rRNA), Transfer RNA (trna)
Transcribed in only eukaryotic celss
Pre-messenger RNA (pre-mRNA), Small nuclear RNA (snRNA), Small nucleolar RNA (snoRNA), MicoRNA(miRNA), small interfering RNA (siRNA)
Structural and functional components of the ribosome
Carries genetic code for proteins
helps incorporate amino acids into polypeptide chain
Processing of pre-mRNA
processing and assembly of rRNA
Inhibits the translation of mRNA
Triggers the degradation of other RNA Molecules
In translated RNA what sequence is only found in prokaryotes
In translated RNA what sequence is only found in eurakryotes
in excision of transcripts 5 prime is
the branch point
in excision of transcripts 3 prime is
The consensus sequence
u1 in a spliceosome
Purines are what base nucleotides
A and G
pyridines are what base nucleotides
T and C
In mRNA 5' to 3' goes from what chemical group to the other.
Amino to Carboxyl
Basic order of charged TRNA
First Aminoacyl second Peptidyl and E exit.