Chapter 7: The Blueprint of Life, from DNA to Protein

Differences between DNA and RNA. (3)

- DNA is double-stranded, RNA is single-stranded. - DNA nucleotides contain deoxyribose whereas RNA nucleotides contain ribose. - There are multiple types of RNA with different functions whereas there is only one type of DNA.

Which of the statements about DNA and RNA are FALSE?

- RNA polymerase requires a primer. - Eukaryotic RNA is typically polycistronic.

Identify the steps in transcription. Not all labels are used.

1. RNA polymerase binds to promoter and melts short DNA stretch. 2. RNA is synthesized in the 5' to 3' direction as nucleotides are added. 3. At the terminator, RNA polymerase dissociates, releasing the new RNA.

Place the following events that occur in DNA replication in the correct order. - A different DNA polymerase removes the RNA primers and replaces them with DNA. - The leading strand is synthesized continuously while the lagging strand is synthesized in Okazaki fragments. - DNA polymerases build DNA by adding nucleotides onto the primers, extending them. - Primase synthesizes RNA primers. - Specific proteins bind the origin of replication and separate the two strands of DNA, forming two replication forks. - DNA ligase joins the Okazaki fragments.

1. Specific proteins bind the origin of replication and separate the two strands of DNA, forming two replication forks. 2. Primase synthesizes RNA primers. 3. DNA polymerases build DNA by adding nucleotides onto the primers, extending them. 4. The leading strand is synthesized continuously while the lagging strand is synthesized in Okazaki fragments. 5. A different DNA polymerase removes the RNA primers and replaces them with DNA. 6. DNA ligase joins the Okazaki fragments.

Arrange the following proteins in the correct order in which they participate in DNA replication. 1 = Primase 2 = Helicase 3 = DNA ligase 4 = DNA polymerase

2, 1, 4, 3

If the codon GGU is positioned in the A site of the ribosome, which of the following will occur

A tRNA with the anticodon CCA will deliver its amino acid to the site.

If an organism lost the ability to make primase, what would it be unable to do?

Add a short sequence of complementary RNA to the existing DNA strand.

Which of the following occur(s) in both prokaryotes as well as eukaryotes? - None of these - Translation - Transcription - DNA replication - All of these

All of these.

_____ are groups of three bases in mRNA that specify one amino acid in the amino acid chain

Codons

Which of the following shows the direction genetic information flows

DNA ---> RNA ---> protein

Which of the following statements regarding transcription and translation is TRUE?

Eukaryotes must splice out introns following transcription, while prokaryotes do not.

T or F: Eukaryotic mRNA usually specifies multiple proteins.

False. Eukaryotic mRNA usually specifies only a single protein.

T or F: The purpose of RNA synthesis is to provide a new copy of DNA as the original strand deteriorates over time.

False. No, DNA is a permanent copy of the genome that exists in the nucleus of eukaryotes or the nucleoid region of prokaryotes. RNA is a temporary copy that can be used to synthesize proteins from the original "blueprint" in the DNA.

T or F: Translation of eukaryotic mRNA can occur in the nucleus after exons are spliced together.

False. Translation occurs in the cytoplasm.

T or F: Translation occurs on ribosomes only in prokaryotes.

False. Translation occurs on ribosomes in both eukaryotes and prokaryotes.

A segment of DNA encoding a protein or an RNA molecule is a

Gene

After mRNA is made, what generally occurs

It is translated to protein.

What role does the sigma factor of RNA polymerase have in transcription?

It recognizes and binds to the promoter region of the template DNA.

On one of the strands of bacterial DNA, the new complementary strand is synthesized discontinuously in small pieces of DNA called ______.

Okazaki fragments

The initial transfer RNA occupies the _____ site on the ribosome

P site

The bond connecting amino acids is a ______ bond

Peptide

What three components make up RNA subunits?

Phosphate, nitrogenous base, ribose sugar.

What usually terminates the process of translation

Presence of a stop codon on mRNA

The processes of transcription and translation differ between prokaryotes and eukaryotes in the following way:

Prokaryotes transcribe and translate simultaneously.

Which of the following is not involved in the initiation of translation?

RNA polymerase. Recall that while RNA polymerase is needed to synthesize mRNA, this process is transcription. RNA polymerase has no role in translation.

Protein synthesis occurs on the ______.

Ribosomes

Which of these is base-paired correctly?

T-A

What happens when a hairpin loop forms in mRNA?

The RNA polymerase and the mRNA dissociate from the DNA.

What component of RNA is different from one person (or one bacterium) to the next?

The order of nitrogenous bases

A ______ is the physical expression of the genes present and can change depending upon what genes are turned "on"

The physical expression of the genes present is referred to as the phenotype.

Translation is needed because

The subunits of DNA and RNA are nucleotides while those of protein are amino acids

Why is translation needed?

The subunits of nucleic acids are nucleotides, while those of proteins are amino acids

Which nucleotide is not found in RNA?

Thymine

What does the word "transcribe" mean?

To make a copy.

Place the steps of translation in order.

Total of 7 steps. Translation steps in sequence are initiation, elongation, and termination.

T or F: Replication, transcription and translation take place in the bacterial cytoplasm

True. Bacteria lack a nucleus; therefore, all three processes take place in the cytoplasm.

T or F: If you know the sequence of nucleotides in mRNA, you can deduce the DNA sequence it was transcribed from

True. Due to the complementary nature of bases, if you know the mRNA sequence, you can deduce the DNA sequence.

T or F: Unlike DNA, RNA is usually single-stranded.

True. Generally, RNA is a single strand of ribonucleotides, whereas DNA is generally double-stranded.

T or F: Prokaryotes lack membrane-enclosed organelles.

True. In contrast to eukaryotes, prokaryotes lack membrane-enclosed organelles, such as a nucleus, mitochondria, and endoplasmic reticulum.

T or F: Only eukaryotic mRNA is processed before translation.

True. Introns are removed from eukaryotic mRNA, and exons are spliced together before translation. Prokaryotic mRNA is translated as it is being synthesized.

T or F: The encoded protein of the DNA sequence 3' TAC CGC TTA CAT GAG 5' (assume it is the minus strand) has the amino acid sequence met-ala-asn-val-leu. Use the genetic code.

True. Remember that you first have to transcribe the DNA sequence to mRNA before decoding it to protein.

T or F: The sequence of DNA bases ultimately determines the sequence of amino acids in a polypeptide.

True. The sequence of DNA bases is the "blueprint" for the assembly of amino acids in a polypeptide. Remember that genetic information flows from DNA to RNA to protein.

T or F: In prokaryotes, the mRNA transcript encounters ribosomal subunits immediately as it leaves the DNA.

True. Translation can begin before transcription is complete in prokaryotes.

If one strand of DNA contains the bases ACAGT, what would be the complementary bases on the mRNA strand?

UGUCA

An open reading frame or a possible protein-encoding region of prokaryotic DNA is

a region of DNA that begins with a start codon (ATG) and ends with a stop codon.

In the absence of lactose,

a repressor protein binds to the operator

In the absence of lactose, the lac repressor is

active and can bind to the operator

The two strands of the DNA molecule are ______

antiparallel

Repressible operons (such as the arg operon)

are usually in the "on" mode.

Introns are removed and exons are spliced together

before translation

DNA polymerase

can only add nucleotides in a certain direction

One bacterial chromosome replicates to become two chromosomes with

each made of one strand of DNA from the original chromosome and one newly synthesized strand.

Binding of an activator to an activator binding site on DNA

enhances the ability of RNA polymerase to bind to the promoter site.

One advantage of having genetic control mechanisms is

enzymes are only produced when they are needed.

The lac operon is expressed when

glucose is low and lactose is present.

Early in the process of DNA replication, the enzyme ______ separates the two strands.

helicase

The two strands of DNA are joined to each other or held together by

hydrogen bonding

Synthesis of mRNA is

in the 5' to 3' direction with new nucleotides being added to the 3' end of the mRNA molecule.

Eukaryotic mRNA contains non-coding regions called ______.

introns

When a repressor binds to the operator site on DNA,

it blocks RNA polymerase binding and mRNA synthesis.

When a bacterium is grown on glucose only

it must synthesize all the amino acids it needs.

In an inducible operon, when a substrate or inducer is present

it reacts with the repressor and inactivates it.

Use the genetic code below to translate the mRNA sequence 5' AUGCACUCAAGAGCAGUA 3'

methionine - histidine - serine - arginine - alanine - valine

RNA is a chain of ______.

nucleotides

A(n) ______ is a cluster of genes that perform related functions, found in ______.

operon, prokaryotes

Coordinated sets of genes that are regulated as a single unit are referred to as ______.

operons

The specific point on the DNA molecule where replication begins is the

origin of replication

The three basic parts of a DNA nucleotide are

phosphate, deoxyribose sugar, nitrogenous base

Translation of mRNA into protein begins before transcription is complete in ______.

prokaryotes only

Transcription begins when RNA polymerase binds to the

promoter on DNA.

DNA polymerase

requires a template for the synthesis of DNA

In some degradative pathways, in the absence of an inducer (such as arabinose),

the activator protein can't bind to DNA, and RNA polymerase can't bind to the promoter site.

When an amino acid such as arginine binds to a repressor,

the repressor binds to the operator site

Two different mechanisms for copying the DNA strands are used because

the strands are oriented in opposite directions.

The process of transcription is similar to

the synthesis of the leading strand during DNA replication.

A mechanism that blocks transcription

will block the production of mRNA