BIL150- Week 8 Mastering Bio

The central paradigm of biochemistry holds that information flows from DNA to RNA to protein. The process of making protein from the mRNA is called translation. Translation is carried out by the ribosome, which binds to the mRNA and binds tRNA, which recognizes the codons on the mRNA and brings the appropriate amino acid with it. The ribosome forms the peptide bond between the new amino acid and the growing peptide chain.

1. Amino acids are attached to tRNA by enzymes called aminoacyl-tRNA synthetase. 2. The RNA that has an amino acid attached to it, and that binds to the codon on the mRNA, is called atRNA. 3. Terminationof translation happens when the ribosome hits a stop codon on the mRNA. 4. Initiationof translation always happens at the start codon of the mRNA. 5. The process, performed by the ribosome, of reading mRNA and synthesizing a protein is called translation.

When cells divide or multiply, the DNA must be copied, or replicated. All known organisms replicate their DNA by a method known as semi-conservative replication, in which each of the two strands of the parent DNA becomes part of the daughter DNA.

1. The new DNA strand that grows continuously in the 5' to 3' direction is called the leading strand. 2. During DNA replication, an open section of DNA, in which a DNA polymerase can replicate DNA, is called a replication fork. 3. After replication is complete, the new DNAs, called daughter DNA, are identical to each other. 4. The enzyme that can replicate DNA is called DNA polymerase. 5. Okazaki fragmentsare the short sections of DNA that are synthesized on the lagging strand of the replicating DNA.

Some bacteria may be able to respond to environmental stress by increasing the rate at which mutations occur during cell division. How might this be accomplished?

1. an increase in the number of mistakes in DNA replication 2. a decrease in repair enzymes activity

The table below shows four possible mRNA products of this gene. Use the labels to explain what mutation(s) may have resulted in each mRNA. Drag the correct label to each location in the table. Labels may be used once, more than once, or not at all.

1. mutation in a splicing signal sequence in intron 2 2.mutation in the gene's promoter sequence 3.mutation in splicing signal sequences in both intron 2 and intron 2 4.no mutation in any splicing signal sequence

How many amino acids are coded by a set of codons that share the same first two nucleotide bases?

18

Use the scheme to answer the question. The figure shows a simple metabolic pathway. According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?

2

A particular triplet of bases in the template strand of DNA is 5'-AAA-3'. The anticodon on the tRNA that binds the mRNA codon is ________.

3'-AAA-5'

An mRNA molecule with the sequence 5'-CCG-ACG-3'is being read by a ribosome. During translation which of the following tRNA anticodons will be the first to productively bind with this mRNA?

3'-GGC-5'

A particular triplet of bases in the template strand of DNA is 5'-AGT-3'. What would be the corresponding codon for the mRNA that is transcribed?

3'-UCA-5'

The sequence of nucleotides below is present at a DNA location where the chain opens to form a replication fork:3' C C T A G G C T G C A A T C C 5'An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence?

5' A C G U U A G G 3'

Referring to the figure, what bases will be added as DNA replication proceeds on the bottom strand?

5' A, G, A, C, G, A, C 3'

Which of the following structures is needed for the translation initiation complex to form in eukaryotes?

5' cap

Given a template strand of 3'-ATGCTTGGACA-5' and a partially-made complementary strand containing only 5'-TAC-3', what would be the sequence of the new strand of DNA (including the 5'-TAC-3') if the only additional nucleotides available to DNA polymerase were those containing the bases G, A, and C?

5'-TACGAACC-3'

Which codon on the mRNA strand codes for the amino acid carried by the aminoacyl-tRNA represented in the figure?

5'-UUC-3'

Identify a 5′→3′5′→3′ sequence of nucleotides in the DNADNA template strand for an mRNAmRNA coding for the polypeptide sequence Phe-Pro-Lys.

5′-CTTCGGGAA-3′

A sample of double-stranded DNA contains 42% cytosine. Approximately what percent of the nucleotides in this sample will be thymine?

8%

Which of the following combinations of base pairs will be found in a molecule of DNA?

A + C = G + T

DNA strands are antiparallel. Which of the following statements defines "antiparallel"?

A 5' to 3' DNA strand is paired with the 3' to 5' DNA strand.

During the elongation phase of translation, which site in the ribosome represents the first location where a codon pairs with an anticodon?

A site

In analyzing the number of different bases in a DNADNA sample, which result would be consistent with the base-pairing rules?

A+G=C+T

The structure of all 20 amino acids are shown here. At each location of a patient mutation, the wild-type codon codes for the amino acid phenylalanine (Phe). From this figure, you can see that Phe has a nonpolar side chain and is hydrophobic. Compare the structure of Phe to the incorrect amino acid in each patient's insulin. Select the most appropriate conclusion about the impact of each mutation on the shape of the insulin protein.

All of the above

Which of the following processes will occur at the exposed 3' end of a tRNA molecule?

An amino acid will bind covalently. Submit

What is the %T in wheat DNA?

Approximately 28%

The amino acid location for each patient's nucleotide-pair substitution is provided in the table below the codon table. The wild-type amino acid at each location is also provided. Refer back to the table at the beginning of this exercise to find the mutated codon for each patient. This codon is from the cDNA coding (nontemplate) strand, so to convert it to mRNA, you just need to change T to U. Now use the codon table to identify the amino acid that will be made by the mutated codon in each patient's insulin sequence.

Cys, Ser, Leu

Hershey and Chase set out to determine which type of molecule is used for genetic inheritance. They completed a series of experiments where E. coli was infected by a T2 virus. Which molecular component of the T2 virus ended up inside the cell?

DNA

Which of the following characteristics allowed Hershey and Chase to determine whether the genetic material was made of DNA or protein?

DNA contains phosphorus, whereas protein does not. Submit

Radioactive thymine is added to media containing one actively dividing E. coli bacterium. Which of the following outcomes would be seen after a single cell division?

DNA in both daughter cells would be radioactive.

A student isolates, purifies, and combines in a test tube a variety of molecules needed for DNADNA replication. When she adds some DNADNA to the mixture, replication occurs, but each DNADNA molecule consists of a normal strand paired with numerous segments of DNADNA a few hundred nucleotides long. What has she probably left out of the mixture?

DNA ligase

In bacteria, which of the following proteins is responsible for removing nucleotides from the RNA primer that is used for initiation DNA synthesis?

DNA pol I

What catalyzes the formation of phosphodiester bonds between a DNA strand and a new nucleotide being added during DNA replication?

DNA polymerase

In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the 5' → 3' direction?

DNA polymerase III

What is the role of DNA polymerase during DNA synthesis?

DNA polymerase is the enzyme that catalyzes the addition of a nucleotide onto the 3' end of a growing DNA strand.

After DNA replication, the resulting daughter DNA double helix contains one strand of the original parental DNA and one new strand. What is the explanation for this phenomenon?

DNA replication is semiconservative.

What is the basis for the difference in how the leading and lagging strands of DNADNA molecules are synthesized?

DNADNA polymerase can join new nucleotides only to the 3′3′ end of a pre-existing strand, and the strands are antiparallel.

Which of the following is a reason that a new DNA strand elongates only in the 5' to 3' direction during DNA replication?

Dehydration reactions require a free -OH group.

Use Chargaff's rules to predict the missing values for E. coli, human, and ox DNA. Round your answers to the nearest whole number.

E. coli 25.5, 24.5 Human 19.8, 19.8 Ox 21, 21, 29

DNA replication is said to be semiconservative. Which of the following statements correctly explains what this means?

Each new double helix consists of one old and one new strand.

Which of the following statements describes the process of transformation in bacteria?

External DNA is taken into a cell, becoming part of the cell's genome

Nucleotides are added to a growing DNA strand as nucleoside triphosphates. What is the significance of this fact?

Hydrolysis of the two phosphate groups (P-Pi) and DNA polymerization are a coupled exergonic reaction.

What is the function of the release factor during translation in eukaryotes?

It binds to the stop codon in the A site in place of a tRNA.

Which of the following processes correctly describes alternative RNA splicing?

It can allow the production of proteins of different sizes and functions from a single mRNA.

Which answer best describes the role of telomerase in replicating the ends of linear chromosomes?

It catalyzes the lengthening of telomeres, compensating for the

Which of the following statements best describes the significance of the TATA box in the promoters of eukaryotes?

It is the recognition site for the binding of a specific transcription factor.

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

It joins Okazaki fragments together.

During translation, nucleotide base triplets (codons) in mRNA are read in sequence in the 5' → 3' direction along the mRNA. Amino acids are specified by the string of codons. What amino acid sequence does the following mRNA nucleotide sequence specify? 5′−AUGGCAAGAAAA−3′5′−AUGGCAAGAAAA−3′ Express the sequence of amino acids using the three-letter abbreviations, separated by hyphens (e.g., Met-Ser-Thr-Lys-Gly).

Met-Ala-Arg-Lys

What amino acid sequence does the following DNA nucleotide sequence specify? 3′−TACAGAACGGTA−5′

Met-Ser-Cys-His

What amino acid sequence will be generated based on the following mRNA codon sequence? 5'-AUG-UCU-UCG-UUA-UCC-UUG-3'

Met-Ser-Ser-Leu-Ser-Leu

A summary of your results is shown in the table. Now classify each patient's nucleotide-pair substitution mutation. Is the mutation a silent, missense, or nonsense mutation? Drag the mutation types to fill in the table. Labels may be used once, more than once, or not at all.

Missense, missense, missense

In E. coli, a mutation in a gene called dnaB prevents the helicase from binding at the origin of replication. Which of the following events would you expect to occur as a result of this mutation?

No replication fork will be formed.

Which of the following is true of RNARNA processing?

Nucleotides are added at both ends of the RNARNA.

Which answer correctly compares prokaryotic and eukaryotic codons?

Organisms utilize codons that are nearly universal among all organisms.

Which of the following statements accurately describes differences between DNA replication in prokaryotes and DNA replication in eukaryotes?

Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

If a bacteria contained a mutant aminoacyl-tRNA synthetase that attaches a lysine instead of the normal phenylalanine to tRNAs with the anticodon AAA which of the following would occur?

Proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.

Which of the following processes occurs as part of transcription?

RNA is synthesized

In eukaryotes, there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a protein?

RNA polymerase II

Which of the following is a reason that the low error rate of DNA replication is important to evolution?

Rare errors are the source of variation.

Addition of a nucleotide onto a DNA strand is an endergonic reaction. What provides the energy to drive the reaction?

Release of pyrophosphate from the incoming nucleotide, and then hydrolysis of the pyrophosphate to inorganic phosphate

What materials does DNA polymerase require in order to synthesize a complete strand of DNA?

Single-stranded DNA template All four deoxyribonucleotides triphosphates (containing A, C, T, or G) 3'-OH end of the new DNA strand

Which of the following statements correctly describes the difference between the leading and the lagging strands of DNA in DNA replication?

The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

Which of the following is most likely to occur if a researcher removes the 5' cap and poly-A tail of an mRNA and inserts the mRNA molecule into a eukaryotic cell?

The molecule will be degraded by enzymes.

Which of the following statements correctly describes the difference between ATP used in metabolism and the nucleotides used as a building block during DNA synthesis?

The nucleotides have the sugar deoxyribose; ATP has the sugar ribose.

Which of the following best explains the observation that in bacteria, there are 61 mRNA codons that specify an amino acid, but only 45 tRNAs?

The rules for base pairing between the third base of a codon and tRNA are flexible.

Indicate at which step of the replication-transcription-translation process each type of RNA first plays a role. During which step of the replication-transcription-translation process does each type of RNA first play a role? Drag each item to the appropriate bin. (Not every bin has to be filled.)

Transcription/RNA processing mRNA Translation rRNA tRNA

Which of the following statements is true about protein synthesis in prokaryotes?

Translation can begin while transcription is still in progress.

Does the distribution of bases in sea urchin DNA and salmon DNA follow Chargaff's rules?

Yes, because the %A approximately equals the %T and the %G approximately equals the %C in both species.

Calculate the average percentage for each base in your completed table. Do Chargaff's equivalence rules still hold true when you consider those six species together?

Yes, the average for A approximately equals the average for T, and the average for G approximately equals the average for C.

A hydroxyl is present at the 3' end of the growing DNA strand. What is at the 5' end?

a phosphate group

Frederick Griffith heat-killed a culture of pathogenic bacteria. He split the sample and injected half of it into mice. The mice lived. He then mixed the other half with a living, nonpathogenic bacteria strain and injected the mixture into mice. The mice died. These results best support which of the following conclusions.

a substance had been transferred from pathogenic to nonpathogenic bacteria Submit

Rosalind Franklin's X-ray crystallography data suggested DNA is double stranded and has a uniform diameter. These observations can be used to rule out base pairing between two of the same nucleotide because ________.

an A-A pair is wider than a C-C pair Submit

A phosphorescent red strain of bacteria is heat-killed and mixed with a living, colorless strain. Further observations of the mixture show that some of the living cells are now red. Which of the following observations would provide the best evidence that red color is a heritable trait?

as the living cells divide the number of red cells increases

The elongation of the leading strand during DNA synthesis

depends on the action of DNADNA polymerase.

Frederick Griffith heat-killed a culture of pathogenic bacteria. He split the sample and injected half of it into mice. The mice lived. He then mixed the other half of the sample with a living, nonpathogenic bacteria strain and injected the mixture into mice. The mice died. Which of the following describes a treatment that would help clarify interpretation of these data?

examining tissue from the dead mice (injected with mixed sample) for the presence of pathogenic bacteria

What is the function of helicase in DNA replication?

it untwists the double helix and separates the two DNA strands

According to the central dogma, which of the following intermediate molecules correctly completes the flow chart describing the flow of information in a cell blank? DNA - ________ - Proteins

mRNA

Which of the following molecular structures contains codons?

mRNA

E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?

one low-density and one intermediate-density band Submit

In the Hershey and Chase experiment that helped confirm DNA, not protein, was the hereditary material, what was the key finding?

radioactively-labeled phosphorus was present inside the infected bacteria

What is the function of the enzyme topoisomerase in DNA replication?

relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix

Which of the following characteristics of DNA allows it to carry a vast amount of hereditary information?

sequence of bases

In his work with pneumonia-causing bacteria and mice, Griffith found that

some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.

Use the table to sort the following ten codons into one of the three bins, according to whether they code for a start codon, an in-sequence amino acid, or a stop codon.

start/methionine AUG, stop codon UAA UGA UAG amino acid UGC ACU AUC AAA CAC GCA

Knowing that the genetic code is almost universal, a scientist uses molecular biological methods to insert the human β-globin gene (shown in the figure below) into bacterial cells, hoping the cells will express it and synthesize functional β-globin protein. Instead, the protein produced is nonfunctional and is found to contain many fewer amino acids than does ββ-globin made by a eukaryotic cell. Why?

stop codon, introns, translation, introns, RNA splicing, RNA splicing, incorrect, introns

Sort each description by the type of RNA it describes.

tRNA contains an anticodon has amino acids covalently attached mRNA specifies the amino acid sequence for a protein contains exons rRNA is a component of ribosomes is the most abundant form of RNA

Which evolutionary explanation accounts for this pattern? Match the terms in the left column to the appropriate blanks in the sentences on the right. Not all terms will be used.

tRNAs, wobble, tRNA anticodons, mRNA codons

In DNA polymerization, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and which of the following atoms or molecules of the last nucleotide in the polymer?

the 3' OH

What are telomeres?

the ends of linear chromosomes

Which answer correctly compares the primary transcript in a prokaryotic cell with the functional mRNA?

the primary transcript is the same size as the mRNA

Griffith's experiments with S. pneumoniae were significant because they showed that traits could be transferred from one organism to another. What else did he find that was significant?

the transferred traits were heritable

In bacteria, what is the function of DNA polymerase III?

to add nucleotides to the 3' end of a growing DNA strand