The Molecular Basis of Inheritance

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4/24/13 The Molecular Basis of Inheritance & From Gene to Protein

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The Molecular Basis of Inheritance & From Gene to Protein

Due: 9:00am on Wednesday, April 24, 2013

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Activity: DNA and RNA Structure

Click here to complete this activity.

Then answer the quest ions.

Part A

In the accompanying image, a nucleotide is indicated by the letter _____.

ANSWER:

Correct

B is indicating a single nucleotide.

Part B

Which of these is a difference between a DNA and an RNA molecule?

ANSWER:

Biol 1002 - Spring 2013

The Molecular Basis of Inheritance &a... Resources

B

D

E

C

A

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Correct

(With some exceptions) DNA is a double-stranded molecule and RNA is a single-stranded molecule.

Part C

This is an image of a(n) _____.

ANSWER:

Correct

Nucleotides are composed of a pentose sugar, a nitrogenous base, and a phosphate group.

Part D

The letter A indicates a _____.

ANSWER:

DNA is a polymer composed of nucleotides, whereas RNA is a polymer composed of nucleic acids.

DNA contains five-carbon sugars, whereas RNA contains six -carbon sugars.

DNA contains uracil, whereas RNA contains thymine.

DNA is double-stranded, whereas RNA is single-stranded.

DNA contains nitrogenous bases, whereas RNA contains phosphate groups.

nucleic acid

amino acid

nucleotide

none of the above

thiol





Correct

Phosphate groups contain phosphorus..

Part E

A nitrogenous base is indicated by the letter _____.

ANSWER:

Correct

This is a nitrogenous base.

Part F

You can tell that this is an image of a DNA nucleotide and not an RNA nucleotide because you see a _____.

ANSWER:

phosphate group

nitrogenous base

sugar

none of the above

nucleotide

B

E

D

C

A




session.masteringbiology.com/myct/assignmentPrintView?assignmentID=1937216 4

Correct

DNA nucleotides are composed of deoxyribose sugars, whereas RNA nucleotides are composed of ribose sugars.

Part G

Which of these nitrogenous bases is found in DNA but not in RNA?

ANSWER:

Correct

DNA contains thymine; RNA does not.

Part H

Which of these is(are) pyrimidines?

ANSWER:

Correct

Pyrimidines are single-ring structures.

Part I

thymine nitrogenous base, not a uracil nitrogenous base

phosphate group, not a uracil

double-stranded molecule, not a single-stranded molecule

sugar with two, and not three, oxygen atoms

uracil nitrogenous base, not a thymine nitrogenous base

cytosine

uracil

adenine

guanine

thymine

B, C, and D A and B

B and C

C, D, and E

A, B, and C





In a nucleotide, the nitrogenous base is attached to the sugar's _____ carbon and the phosphate group is attached to the sugar's _____ carbon.

ANSWER:

Correct

The nitrogenous base is attached to the sugar's 1' carbon and the phosphate group is at tached to the sugar's 5' carbon.

Part J

Nucleic acids are assembled in the _____ direction.

ANSWER:

Correct

New nucleotides are added to the 3' end of a growing polynucleotide.

Part K

In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary st rand, and a guanine of one strand always pairs

with a(n) _____ of the complementary s trand.

ANSWER:

Correct

This is referred to as specific base pairing.

DNA Replication (1 of 2): DNA Structure and Replication Machinery (BioFlix tutorial)

DNA is composed of two strands that are bound together, resembling a rope ladder with rigid rungs. This DNA ladder is twisted, forming what is called the

double helix. The structure of the DNA double helix depends on the complementary pairing of bases between the two st rands.

Replication of DNA requires that the two strands of the helix separate, as shown in the image below. New daughter molecules are constructed by the

sequential addition of nucleotides and the formation of base pairs between the new strand and the parent (template) strand. The replication of the double

helix results in two daughter molecules, each composed of one parent strand and one new strand. The enzymes that accomplish the replication of DNA are

called DNA polymerases.

1' ... 2'

2' ... 1'

2' ... 3'

1' ... 5'

1' ... 3'

5' to 3'

2' to 3'

1' to 5'

4' to 5'

5' to 1'

guanine ... adenine

thymine ... cytosine

cytosine ... uracil

cytosine ... thymine

uracil ... cytosine











ANSWER:

Correct

In the example above, DNA pol III would add an adenine nucleotide to the 3' end of the primer, where the template strand has thymine as the next

available base. You can tell which end is the 3' end by the presence of a hydroxyl (-OH) group.

The structure of DNA polymerase III is such that it can only add new nucleotides to the 3' end of a primer or growing DNA strand (as shown here).

This is because the phosphate group at the 5' end of the new strand and the 3' -OH group on the nucleoside triphosphate will not both fit in the

active site of the polymerase.

Part C - The replication bubble and antiparallel elongation

DNA replication always begins at an origin of replication. In bacteria, there is a s ingle origin of replication on the circular chromosome, as shown in the

The newly added nucleotide forms a bond with the hydroxyl (-OH) group on the 3' end of the primer.

The newly added nucleotide forms a bond with the phosphate group on the 3' end of the primer.

The newly added nucleotide forms a bond with the hydroxyl (-OH) group on the 5' end of the primer.

The newly added nucleotide forms a bond with the phosphate group on the 5' end of the primer.







Topoisomerase breaks a covalent bond between a deoxyribose sugar and a nitrogenous base in one parental strand.

Topoisomerase breaks a covalent bond in the backbone of one parental st rand.

Topoisomerase breaks covalent bonds in the backbones of both parental st rands.Topoisomerase breaks hydrogen bonds between the two parental s trands.

Single-strand binding proteins bind to the newly synthesized strand of DNA immediately after the DNA polymerase.

Single-strand binding proteins bind to double-stranded DNA, causing the two strands to separate into single strands.

Single-strand binding proteins bind to double-stranded DNA ahead of the replication fork, relieving the strain caused by helicase.

Single-strand binding proteins bind to parental DNA immediately after the helicase, preventing the two s ingle strands from joining and

re-forming a double helix.









Hint 2. In which direction do the leading and lagging strands elongate?

At a replication fork, the two parental DNA strands separate, and each strand is copied by a DNA polymerase III, synthesizing a new,

complementary st rand. The diagram below shows a replication fork with the two parental DNA strands labeled at their 3' and 5' ends. The newly

synthesized DNA strands are not shown, but the polymerase on each parental strand is shown (labeled 1 and 2).

Remembering that the new (daughter) DNA strands will run antiparallel to the parental strands, which of the following statements

correctly describes the direction in which the two strands will elongate?

ANSWER:

Hint 3. The role of RNA primers in DNA replicationDNA polymerase III cannot initiate the synthesis of a new daughter strand; it can only add nucleotides to the 3' end of an existing strand that is

paired with a parental (template, dark blue) strand. The enzyme primase creates a short RNA primer (red) that is complementary to the parental

strand. This primer serves as a starting point for DNA pol III, which adds nucleotides to the 3' end of the primer. Think about the number of

primers needed for a strand that is synthesized continuously versus a strand that is made in many smaller fragments.

ANSWER:

Both st rands elongate toward the replication fork.

Polymerase 1 elongates its strand away from the replication fork, but polymerase 2 elongates its strand toward the replication fork.

Both st rands elongate away from the replication fork.

Polymerase 1 elongates its strand toward the replication fork, but polymerase 2 elongates its strand away from the replication fork.







Rank the primers in the order they were produced. If two primers were produced at the same time, overlap them.

Hint 1. The role of RNA primers in DNA replication

DNA polymerase III cannot initiate the synthesis of a new daughter strand; it can only add nucleotides to an existing strand that is paired with a

parental (template, dark blue) strand. The enzyme primase c reates a short RNA primer (red) that is complementary to the parental strand. This

primer serves as a starting point for DNA pol III, which adds nucleotides to the 3' end of the primer.

Hint 2. Synthesis of the first primer on the lagging strand

As a replication bubble forms at an origin of replication, the primers for the leading strands are produced first. In the image below, you can see

that the first parts of the leading strands have already been synthesized by the time the first lagging strand primers are produced.

The reason for this lag is that about 1500 nucleotides (the average length of a bacterial lagging strand segment) of parental DNA must be

exposed at the replication fork before lagging strand synthesis can begin. This makes room for the first lagging strand segment between the

first primer and the origin of replication. DNA polymerase III produces the first lagging strand segments (not shown) by adding nucleotides to the

3' ends of the lagging s trand primers.





binds to the 3' end of an RNA primer

replaces the RNA nucleotides of primers with DNA nucleotides

leaves a gap in the sugar-phosphate backbone after replacing the last RNA nucleotide of a primer

joins the sugar-phosphate backbone between a new DNA fragment and the previous fragment







DNA is transcribed to messenger RNA (mRNA), and the mRNA is translated to proteins on the ribosomes. A sequence of three nucleotides on an mRNA

molecule is called a codon. As you can see in the table, most codons specify a particular amino acid to be added to the growing protein chain. In addition,

one codon (shown in blue) codes for the amino acid methionine and functions as a “start” signal. Three codons (shown in red) do not code for amino acids,

but instead function as “stop” signals.

Part A - Understanding the genetic code

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.

Drag each item to the appropriate bin.

Hint 1. How to interpret the table of codons

The table of codons shows the start codon in blue and the three stop codons in red. All other codons (shown in black) appear in the middle of

the amino acid sequences that make up proteins.

To read the table, locate the first letter in the codon on the left side of the table, then locate the second letter along the top, and the third letter

down the right side of the table. Follow those letters across and down to identify the amino acid associated with that three-letter codon.

Hint 2. What is the start codon?

Identify the start codon.

ANSWER:

Hint 3. What are the stop codons?

Enter the three stop codons, separated by commas.

ANSWER:

ANSWER:

AUG

UAG, UGA, UAA







Hint 4. Can you decode GCA?

Which amino acid does the codon code for?

Express your answer using the three-letter abbreviation of the amino acid.

ANSWER:

ANSWER:

Correct

An amino acid sequence is determined by strings of three-letter codons on the mRNA, each of which codes for a specific amino acid or a stop

signal. The mRNA is translated in a 5’ → 3’ direction.

Part C - The role of DNA in determining amino acid sequences

Before a molecule of mRNA can be translated into a protein on the ribosome, the mRNA must first be t ranscribed from a sequence of DNA.

What amino acid sequence does the following DNA nucleotide sequence specify?

Express the sequence of amino acids using the three-letter abbreviations, separated by hyphens (e.g., Met-Ser-His-Lys-Gly).

Hint 1. How to approach the problem

Follow these steps to convert a DNA sequence into an amino acid sequence.

1. First, transcribe the DNA sequence to determine the mRNA sequence. Be sure to remember the following:

The mRNA strand is complementary to the DNA strand.

Uracil (U) takes the place of thymine (T) in RNA to pair with A on the DNA.

The RNA is assembled in an antiparallel direction to the template s trand of DNA. A 3’→ 5’ direction in DNA is

transcribed in a 5’ → 3’ direction in RNA.

2. Next, subdivide the mRNA sequence into the individual three-letter codons in the 5’ to 3’ direction.

Ala

Met-Ala-Arg-Lys





3. Then, refer to the table of codons to identify the three-letter abbreviation for the amino acid that corresponds to each codon.

Hint 2. An example problem

This chart shows how to decode an example DNA sequence. Remember to first determine the mRNA sequence that is complementary to the

DNA template strand’s sequence. Be sure to write the mRNA sequence in a 5’ to 3’ direction, and to use U to pair with A.

Example DNA sequence (template strand)

Complementary DNA sequence

mRNA sequence

Codon sequence

Amino acid sequence (three-letter abbreviation) Met Leu Ser Arg His

Hint 3. What mRNA sequence is transcribed from the DNA sequence?

What mRNA nucleotide sequence would be transcribed from the DNA sequence in this problem?

ANSWER:

ANSWER:

Correct

Before mRNA can be translated into an amino acid sequence, the mRNA must first be synthesized from DNA through transcription. Base pairing

in mRNA synthesis follows slightly different rules than in DNA synthesis: uracil (U) replaces thymine (T) in pairing with adenine (A). The codonsspecified by the mRNA are then translated into a string of amino acids.

Activity: Overview of Protein Synthesis



Part A

Click on the diagram to start the animation. What name is given to the process in which a strand of DNA is used as a template for the manufacture of

a strand of pre-mRNA?

Met-Ser-Cys-His








ANSWER:

Correct

Transcription is the process by which a DNA template is used for the manufacture of several different types of RNA.

Part B

Click on the diagram to start the animation. What name is given to the process in which the information encoded in a strand of mRNA is used to

construct a protein?

ANSWER:

Correct

Translation is the process by which information encoded in RNA is used to manufacture a polypeptide.

Part C

Click on the diagram to start the animation. What name is given to the process in which pre-mRNA is edited into mRNA?

ANSWER:

RNA processing

gene expression

polypeptide formation

transcription

translation

RNA processing

gene expression

polypeptide formationtranscription

translation










Correct

RNA processing edits the RNA transcript that has been assembled along a DNA template.

Part D

Polypeptides are assembled from _____.

ANSWER:

Correct

Proteins are composed of amino acid monomers.

Part E

RNA processing converts the RNA transcript into _____.

ANSWER:

Correct

The editing of the RNA transcript produces mRNA.

Activity: RNA Synthesis

Click here to view this animation.

RNA processing

gene expression

polypeptide formation

transcription

translation

hexoses

glycerol

nucleotides

proteins

amino acids

a protein

DNA

a eukaryotic cellmRNA

a polypeptide








Part A

What is the process called that converts the genetic information stored in DNA to an RNA copy?

Hint 1.

Most of these terms describe part of the gene expression process. One describes the process of making two identical copies of DNA from one

parental DNA molecule.

ANSWER:

Correct

DNA is transcribed to give an RNA copy.

Part B

DNA does not store the information to synthesize which of the following?

Hint 1.

DNA contains the code to make specific types of products, including copies of itself.

ANSWER:

Correct

Synthesis of organelles is not directly coded in the DNA.

Part C

Transcription begins at a promoter. What is a promoter?

Hint 1.

A promoter is an essential part of a gene.

ANSWER:

Correct

This is the site where the RNA polymerase must bind to initiate transcription.

Transcription

Replication

Translation

Translocation

Organelles

DNA

Proteins

Messenger RNA

A site found on the RNA polymerase

A site in DNA that recruits the RNA Polymerase

A site where many different proteins will bind

A nontranscribed sequence on the DNA

Part of the RNA molecule itself





Part D

Which of the following statements best desc ribes the promoter of a protein-coding gene?

Hint 1.

Transcription of a gene is initiated by it s promoter.

ANSWER:

Correct

The promoter is t he regulatory region of a protein-coding gene at which RNA polymerase must bind to initiate t ranscription—it is not transcribed

into the RNA.

Part E

What determines which base is to be added to an RNA strand during transcription?

Hint 1.

Consider the purpose of the template.

ANSWER:

Correct

Transcription involves the formation of an RNA strand that is complementary to the DNA template st rand.

Part F

Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?

Hint 1.

The relationship between the RNA strand and the DNA template s trand is s imilar to that of the two strands of a DNA double helix.

ANSWER:

Correct

Because the template strand determines the nucleotides to be added to the RNA strand, using the same complementarity rules of the DNA, they

will be complementary to each other.

The promoter is a nontranscribed region of a gene.

The promoter is a site found on RNA polymerase.

The promoter is part of the RNA molecule itself.

The promoter is a site at which only RNA polymerase will bind.

The order of the chemical groups in the backbone of the RNA molecule

The previous base

Base pairing between the DNA template st rand and the RNA nucleotides

Base pairing between the two DNA strands

Complementary

Identical

Permanently base-paired

Covalently bound





Part G

What happens to RNA polymerase II after it has completed t ranscription of a gene?

Hint 1.

In eukaryotes, RNA polymerase II can transcribe any protein-coding gene, depending on the presence of regulatory proteins.

ANSWER:

Correct

The enzyme is free to transcribe other genes in the cell.

Activity: Transcription



Part A

In the diagram below, the gray unit represents _____.

ANSWER:

Correct

RNA polymerase untwists a portion of the DNA double helix.

Part B

In the diagram below, the green unit represents _____.

It joins with another RNA polymerase to carry out transcription.It is free to bind to another promoter and begin transcription.

It begins transcribing the next gene on the chromosome.

It is degraded.

RNA

DNA

transcription factors

RNA polymerase

the promoter







ANSWER:

Correct

The promoter is t he region of DNA at which the process of transcription begins.

Part C

In the diagram below, the two blue strands represent _____.

Hint 1.

RNA is not a double helix.

ANSWER:

Correct

DNA is a double helix.

Part D

Which of these correctly illustrates the pairing of DNA and RNA nucleotides?

ANSWER:

RNA

DNA


RNA polymerase

the promoter

RNA

DNA


RNA polymerase

the promoter





Correct

In RNA, uracil takes the place of thymine.

Part E

The direction of synthesis of an RNA transcript is _____.

ANSWER:

Correct

Nucleotides are added to the 3' end of RNA.

Chapter 17 Question 8

Part A

Which of the following provides some evidence that RNA probably evolved before DNA?

ANSWER:

Correct

Activity: RNA Processing

GTTACG

CAATCG

GTTACG

CAAUGC

GTTACG

GTTACG

GTTACG

ACCGTA

GTTACG

UAACAU

1' —> 5'

5' —> 3'

1' —> 3'

3' —> 5'

2' —> 4'

RNA polymerase makes a single-stranded molecule.

RNA polymerase uses DNA as a template.RNA polymerase does not require localized unwinding of the DNA.

DNA polymerase has proofreading function.

DNA polymerase uses primer, usually made of RNA.







Part A

During RNA processing a(n) _____ is added to the 5' end of the RNA.

ANSWER:

Correct

The 5' cap consists of a modified guanine nucleotide.

Part B

During RNA processing a(n) _____ is added to the 3' end of the RNA.

ANSWER:

Correct

A poly-A tail is added to the 3' end of the RNA.

Part C

Spliceosomes are composed of _____.

ANSWER:

Correct

These are the component of spliceosomes.

3' untranslated region

a long string of adenine nucleotides


coding segment

modified guanine nucleotide


a long string of adenine nucleotides


coding segment

modified guanine nucleotide

snRNPs and other proteins

polymerases and ligases

introns and exons

the RNA transcript and protein

snRNPs and snurps







Part D

The RNA segments joined to one another by spliceosomes are _____.

ANSWER:

Correct

Exons are expressed regions.

Part E

Translation occurs in the _____.

ANSWER:

Correct

Ribosomes, the sites of translation, are found in the cytoplasm.


Part A

Which of the following is the first event to take place in translation in eukaryotes?

ANSWER:

Correct


Part A

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?

ANSWER:

caps

exons

snRNPs

tails

introns

cytoplasm

lysosome

nucleus

mitochondrion

nucleoplasm

binding of the larger ribosomal subunit to smaller ribosomal subunits

covalent bonding between the first two amino acids

base pairing of activated methionine-tRNA to AUG of the messenger RNA

the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA

elongation of the polypeptide





Correct


Part A

The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following is true?

ANSWER:

Correct


Part A

The following question refers to this table of codons.

All organisms have experienced convergent evolution.

A gene from an organism can theoretically be expressed by any other organism.

DNA was the first genetic material.

The same codons in different organisms translate into the different amino acids.

Different organisms have different numbers of different types of amino acids.

If a single mRNA molecule is found to translate to more than one polypeptide when there are two or more AUG sites.

If several codons are found to translate to the same amino acid, such as serine.

If one stop codon, such as UGA, is found to have a different effect on translation than another stop codon, such as UAA.

If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only).

If prokaryotic organisms are able to translate a eukaryotic mRNA and produce the same polypeptide.




A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the following sequences in the coding s trand of the DNA could code for this

peptide?

ANSWER:

Correct

Chapter 17 Pre-Test Question 4

Part A

What is the function of RNA polymerase?

Hint 1.

Compare RNA polymerase to DNA polymerase.

ANSWER:

Correct

RNA polymerase has several functions in transcription, inc luding unwinding the DNA double helix and adding RNA nucleotides.


Part A

Which of the following is a function of a poly-A signal sequence?

ANSWER:

Correct

5' ACT-TAC-CAT-AAA-CAT-TAC-UGA

5' GGG-AAA-TTT-AAA-CCC-ACT-GGG

3' AUG-AAA-GGG-TTT-CCC-AAA-GGG

5' TTT-CCC-AAA-GGG-TTT-CCC

3' UUU-CCC-AAA-GGG-UUU-CCC

It relies on other enzymes to unwind the double helix.

It proceeds slowly along the DNA strand, requiring about a minute to add two nucleotides to the growing mRNA molecule.

It unwinds the double helix and adds nucleotides to a growing strand of RNA.

It adds nucleotides to the 5' end of the growing mRNA molecule.

All of the above.

It is a sequence that codes for the hydrolysis of the RNA polymerase.

It codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage ~10–35 nucleotides away.

It adds the poly-A tail to the 3' end of the mRNA.

It allows the 3' end of the mRNA to attach to the ribosome.

It adds a 7-methylguanosine cap to the 3' end of the mRNA.

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The Molecular Basis of Inheritance