Chapter 4 Smart Book

A polypeptide is made of 31 amino acids. What is the minimum number of DNA nucleotides needed to code for this number of amino acids?

93 base pairs

Roughly what percentage of human DNA is noncoding DNA?

98%

Which of the following statements about codons are true?

A codon is a three-base sequence of mRNA. The genetic code is expressed as a sequence of codons.

There are three steps in translation: initiation, elongation, and termination. What is elongated in the second stage?

A polypeptide

Which of the following best describes a histone?

A protein component of chromatin that helps to organize and package DNA

Which of these demonstrate accurate base pairing according to the law of complementary base pairing?

A-T

Which codon is a start codon?

AUG

During translation, transfer RNA (tRNA) binds which molecule in the cytosol and delivers it to the ribosome?

Amino acid

Which of the following statements are true regarding introns?

An intron is a portion of mRNA that must be removed before translation. An intron is a portion of mRNA that does not code for protein.

Which of the following refers to a 3-base sequence found in tRNA?

Anticodon

Which term refers to a sequence of three DNA nucleotides that codes for one amino acid?

Base triplet

Which term refers to the filamentous material composed of DNA and associated proteins that is found in the nucleus of a cell?

Chromatin

In the nucleus of a typical human cell, there are 46 DNA filaments. Which term refers to one of these structures?

Chromosome

A three-base sequence of mRNA is called a(n)

Codon

Which statement best summarizes the role of DNA in protein synthesis?

DNA contains the genetic code that determines the amino acid sequences of proteins.

Which of the following statements are true regarding the DNA structure?

Each sidepiece is a sugar-phosphate backbone composed of phosphate groups alternating with the sugar deoxyribose. The nitrogenous bases face the inside and hold the two backbones together with hydrogen bonds. The basic three-dimensional structure of DNA is the double helix.

Amino acids are brought to the ribosome by tRNA and are joined together to form a polypeptide chain during which step of translation?

Elongation

Translation occurs in three steps. Choose the names of these steps from the list below.

Elongation Termination Initiation

Which molecules are responsible for modifying new proteins in the cistern of ER?

Enzymes

Following transcription, only some portions of the mRNA code for the final protein. The sections of mRNA that contain necessary code are called ________________, whereas the mRNA sections that do not code for the final protein are called ____________ .

Exons, introns

True or false: Proteins that must be packaged into a lysosome or secreted from the cell are synthesized in free ribosomes. True false question.

False

True or false: The coding portion of DNA contains genes that constitute about 98% of the DNA.

False

Which of the following terms refers to a segment of DNA that codes for the production of a molecule of RNA?

Gene

This figure illustrates a process by which the expression of a gene can be turned on (or off) according to the functions of cells or physiological needs. For example, casein is only produced when a mother is lactating. Name this process.

Gene regulation

Regulatory proteins turn these on and off in accordance with changing needs for the proteins they encode.

Genes

When a woman gives birth the hormone prolactin stimulates her mammary glands to produce casein, a protein that her body has never synthesized before. This demonstrates which of the following?

Genes can be turned on or off.

Since there are no genes coding for carbohydrates, nucleic acids, or lipids, how do cells produce them?

Genes encode enzymes that synthesize these products.

Which term refers to all the DNA, both coding and non coding, in one complete set of 23 chromosomes?

Genome

When synthesized proteins are to be exported out of the cells, they are packaged into secretory vesicles that originate in what organelle?

Golgi complex

Alternative splicing helps explain which of the following?

How one gene can produce more than one protein

Where does the making of mRNA from DNA take place?

In the nucleus

The first tRNA to bind to a ribosome at the start of translation is known as what?

Initiator tRNA

Place these events in the order they occur during protein processing and secretion.

- protein formed by ribosomes on RER.- protein packaged into transport vesicles, which bud from ER- transport vesicles unload protein into Golgi complex- golgi complex modifies protein structure- secretory vesicles release protein by exocytosis.

Describe chaperones.

-they aid a newly synthesized protein in folding to its proper shape -they help prevent improper associations between different proteins -they are also known as stress proteins or heat shock proteins

You were able to radioactively tag an amino acid that is used to make insulin, a hormone that will be exported out of the cell. Put the following locations in order to trace the pathway of the tagged amino acid

1. Rough ER 2. Transport vesicle 3. Golgi complex 4. Golgi vesicle 5. Extracellular fluid

What is the role of mRNA in protein synthesis?

It carries the genetic code from the nucleus to the cytoplasm.

Which of the following is true about the centromere?

It is where sister chromatids are joined together.

Which of the following are characteristics of ribonucleic acid (RNA)?

It leaves the nucleus and can be found in the cytoplasm. It contains nitrogenous bases A, U, C, G. It plays an important role in the production of proteins.

How does newly synthesized mRNA pass from within the membrane-bound nucleus into the cytosol?

It passes through nuclear pores.

Which of the following statements are true concerning the first tRNA to bind to a ribosome at the the start of translation?

Its anticodon is complementary to the codon AUG (the start codon). It is called the initiator tRNA.

DNA ligase

Joins the newly synthesized segments of DNA

Which of the following are involved in the initiation step of translation?

Methionine mRNA Initiator tRNA Ribosomal subunits

The basic unit of a nucleic acid is shown in this picture. It is called a _____________ and it has three components: a phosphate group, a sugar (like deoxyribose), and a nitrogenous base (like adenine).

Nucleotide

What are the monomeric subunits that comprise a molecule of DNA called?

Nucleotides

Where does translation take place?

On a ribosome

DNA helicase

Opens the DNA helix exposing the nitrogenous bases

Which of the following are components of nucleotides?

Phosphate groups Nitrogenous bases Sugars (ribose or deoxyribose)

A cluster of several ribosomes (illustrated in the figure labeled A) reading one mRNA during translation is called a

Polyribosome

One mRNA can have several ribosomes attached to it at one time during translation of mRNA. Which term refers to this cluster of ribosomes?

Polyribosome

The nuclear envelope is perforated with openings called nuclear __________ that regulate the movement of molecules through the envelope.

Pores

Changes to the structure of a new protein (i.e removal of some amino acids, folding of the protein, adding carbohydrates, etc.) are collectively known as what?

Posttranslational modification

Which molecule contains introns and exons?

Pre-mRNA

How are DNA and RNA different?

RNA is much smaller. DNA, by contrast, averages more than 100 million base pairs long. RNA consists of only one nucleotide chain whereas DNA is a double helix. RNA contains a sugar called ribose whereas DNA contains a sugar called deoxyribose.

Which enzyme is responsible for transcribing DNA?

RNA polymerase

DNA polymerase

Reads nitrogenous bases and matches them with complementary free nucleotides

The process by which a cell makes a copy of its DNA, creating two new strands is referred to as which of the following?

Replication

rRNA is short for ______ RNA.

Ribosomal

______ are the cell structures that process coded genetic messages and assemble amino acids into proteins.

Ribosomes

Golgi vesicles containing proteins to be released from the cell will become which type of vesicle?

Secretory

When a cell is preparing to divide, it makes an exact copy of all its nuclear DNA. Each chromosome then consists of two parallel filaments called what?

Sister chromatids

When the ribosome reaches a stop codon, its A site binds a protein called a release factor instead of a tRNA. The release factor causes the finished protein to break away from the ribosome. Which step of translation does this describe?

Termination

Which step of translation requires a stop codon?

Termination

Which of the following are true statements about the genetic code?

The genetic code relates mRNA codons to protein structure. The genetic code allows 20 amino acid to be coded by only 4 different nucleotides. The genetic code is expressed as three-nucleotide long sequences called codons.

How many hydrogen bonds do guanine and cytosine form with each other?

Three

In a molecule of DNA, which two nitrogenous bases form two hydrogen bonds with each other? Select two answers from the list below.

Thymine Adenine

Which of the following can be considered the essential function of RNA?

To use the instructions coded in DNA to synthesize proteins

The enzyme RNA polymerase participates in which of the following processes?

Transcription

Indicate the events that occur during translation.

Transfer RNA (tRNA) anticodon binds to complementary mRNA codon. Ribosome binds messenger RNA (mRNA). A new amino acid is linked to the growing peptide chain. Transfer RNA (tRNA) delivers an amino acid to the ribosome.

Which term refers to the conversion of nucleotide sequences into amino acid sequences?

Translation

Which term refers to the step of protein synthesis in which mRNA is "read" to make protein?

Translation

True or false: It is possible to predict the sequence of one strand of DNA if we know the sequence of the complementary strand.

True

True or false: There are no genes for glycogen, fat, steroids, phospholipids, and many other compounds, yet their synthesis is under indirect genetic control.

True

How many hydrogen bonds do adenine and thymine form with each other?

Two

At one end of each tRNA there is a sequence of three nucleotides known as the __________ This sequence is complementary to the bases on mRNA.

anticodon

Sister chromatids are joined together at a pinched spot called the

centromere

The protein that guides newly synthesized proteins in folding into their proper shape and helps to prevent improper associations between different proteins is a ___________

chaperones

In the nucleus, DNA is complexed with proteins to form a fine filamentous material called

chromatin

In the nucleus, DNA is complexed with proteins to form a fine filamentous material called _________

chromatin

In the nucleus of a dividing cell, the chromatin condenses so that each _____________ , now made of two sister chromatids, can be seen with a light microscope.

chromosome

Where is RNA usually found?

cytoplasm

Transcription is the process of copying genetic instructions from a molecule of __________ to mRNA.

dna

If a protein is going to be used in the cytosol, it is likely to be made by ______. However, if it is going to be secreted from the cell, it is made by ______.

free ribosomes, polyribosomes on the RER

A(n) _______ is an information-containing segment of DNA that codes for the production of a molecule of RNA, and that in most cases codes for one or more proteins.

gene

All the coding and non coding DNA found in the haploid number of chromosomes from one organism is known as the

genome

Which term refers to the protein "spools" that help organize DNA into nucleosomes?

histones

Which molecule binds to the small ribosomal subunit during the initiation step of translation?

mRNA

Which molecule carries the genetic code from the nucleus to the cytoplasm?

mRNA

mRNA is short for ______ RNA.

messenger

Where does transcription take place?

nucleus

Histones are ______.

proteins

The process by which a cell makes a copy of its DNA so it can give complete and identical copies of all of its genes to each daughter cell is DNA

replication

When a protein must be exported outside the cell, it is synthesized in ribosomes bound to the ______ (indicated by a "A"). Then it is modified and packaged into a ______ (indicated by "B").

rough endoplasmic reticulum, transport vesicle

When a cell is preparing to divide, it makes an exact copy of all its nuclear DNA. Each chromosome then consists of two parallel filaments called __________ chromatids.

sister

A centromere holds _______ together.

sister chromatids

During translation, three nucleotide sequences (UAG, UGA or UAA) terminate the process and are therefore called _________ codons

stop

Anticodons are found on which type of molecule?

tRNA

In DNA, the base adenine pairs with the base

thymine

________ occurs in three steps called initiation, elongation, and termination.

translation

A base__________ is a consecutive sequence of three DNA nucleotides that codes for one amino acid.

triplet

True or false: Different codons can code for the same amino acid.

true