Chapter 7 DNA structure and Gene Function

place the following events in order from occurring first to occurring last in the production of albumin, a milk protein

1. the albumin gene is transcribed 2. RNA moves into the cytoplasm 3. amino acids are assembled into a protein

two strands of DNA within the double helix are said to be complementary to each other because ___ on one strand always pairs with thymine on the opposite strand, and cytosine on one strand always pairs with ___ on the opposite strand

A (adenine) ; G (guanine)

shortly after transcription in eukaryotic cells, a string of 100-200 adenines is added to the 3' end of the mRNA molecule, producing what i known as a poly ___ tail, and a short sequence of nucleotides called the 5' ___ is added to the 5' end of the mRNA molecule

A; cap

during transcription, RNA nucleotide bases bind with the exposed complementary bases on the template strand of ___

DNA

the information that each cell needs to produce proteins is stored in a molecule called

DNA

select all the statements about nucleotides that are accurate

DNA always contains the same sugar in its nucleotides; they are composed of a sugar, a nitrogen-containing group, and one or more phosphorus-containing groups

the modern definition of gene is any stretch of DNA that is transcribed to

RNA or protein

in transcription, a(n) ___ molecule is produced from the information that is encoded in a(n) ___ molecule

RNA; DNA

gene

a sequence of nucleotides that codes for a specific protein of RNA molecule

frameshift

adds or deletes nucletotides in any number other than a multiple of three

protein processing and degradation is a method of regulating gene expression that occurs

after translation

a variant of a gene is referred to as a(n)

allele

mutations are important to evolutionary change because they create new ___, which are alternate versions of genes

alleles

what gene regulation mechanism allows for the production of different proteins from the same mRNA

alternative splicing of exons

what represents chargaff's discovery about the amounts of the nitrogenous bases A, G, C and T in the DNA molecule

amount of A = amount of T; amount of G = amount of C

what 3-base site of a tRNA molecule is complementary to an mRNA codon

anticodon

although the two chains of the DNA double helix are parallel to each other, they are oriented in opposite directions. this head-to-tail configuration is referred to as a(n) ___ arrangement

antiparallel

nucleotide

building block of nucleic acids

what type of illness is characterised by unregulated cell division and can be caused by defective transcription factors?

cancer

epigenetic is the study of changes in gene expression due to

chemical modifications of histones of DNA bases

select all of the following that are mutagens

chemicals in tobacco, harmful chemicals, radioactive fallout, ultraviolet radiation

what is a discrete package of DNA and its associated proteins?

chromosome

messenger RNA contains ___, which are triplets of bases that act as "code-words" corresponding to the ___ acid monomers that make up a polypeptide

codons; amino

as RNA is synthesised in transcription, it can curl into a three-dimensional shape that is dictated by ___ within the molecule

complementary base pairing

during the elongation phase of translation, a ___ bond is formed between the incoming ___ acid and the growing polypeptide chain, and empty tRNAs are released from the ribosome to be reused

covalent; amino

plant breeders can induce mutations to

create new varieties of crop species

a mutation that causes a single codon to be removed such that a protein lacks one amino acid is a ___ mutation

deletion

within the DNA double helix, the so-called backbone is composed of ___ sugars alternating with phosphate groups

deoxyribose

the term 3' and 5' refer to numbered carbon atoms within the ___ of DNA, and at one end of the DNA double helix, there is a free ___ on one backbone and a free ___ on the other backbone

deoxyribose sugar; 3' carbon; 5' carbon

chromosome

discrete package of DNA roiled around proteins

DNA has a ___ helical structure that consisting of there intertwining strands of ___

double; nucleotides

transcription, translation, nucleotide synthesis, and modifying mRNA are all processes that require

energy

in eukaryotes, transcription factors can bind at near or distant regulatory DNA sequences called

enhancers

modifications to DNA, such as methylation, that do not change the nucleotide sequence but do affect gene expression are called ___ modifications

epigenetic

___ are portions of mRNA that get spliced together to form a mature mRNA prior to translation

exons

in a(n) ___ repeat mutation, the number of copies of a three-or four- nucleotide sequence increases over several generations

expanding

t/f: since the nineteenth century, scientists have known that DNA is the molecule of heredity

false

whereas ___ wipes away most epigenetic markers on the genome, ___ does not; therefore, identical twins may accumulate epigenetic differences throughout life

fertilisation; cell division

after translation is complete, the newly synthesised polypeptide must ___, as determined by some regions of the amino acid chain

folds into its functional shape

using synthetic mRNA molecules in test tubes with all the translation machinery, researchers in the 1960s deciphered the ___, which determines what amino acid is specified by each three-nucleotide ___

genetic code; mRNA codon

all of the genetic material that is within a cell is called its

genome

a(n) ___ mutation is one that occurs in the cells that give rise to sperm or egg

germline

a(n) ___ mutation occurs in cells that give ride to sperm and egg cells, whereas a(n) ___ mutation occurs in non-sex cells

germline; somatic

in an average mRNA molecule that has just been transcribed, the amount of genetic material devoted to introns is ___ the amount devoted to exons

greater than

select all of the following that are present in a bacterial operon

group of genes, promoter, operator

select all of the following that are functions of the 5' cap and 3' poly A tail added to mRNA after transcription in eukaryotes

help ribosomes attach to 5' end of mRNA ; protect RNA from degradation

within the DNA double helix, the nitrogenous bases in base pairs joined by ___ bonds, which are collectively strong but can also be pulled apart if the cell needs access to the DNA

hydrogen

select all of the following that are true about prokaryotic versus eukaryotic gene expression

in eukaryotes the nuclear membrane separates transcription from translation; in eukaryotes mRNA is altered before it leaves the nucleus

what is one major difference between eukaryotes and prokaryotes with respect to translation

in prokaryotes, translation can take place even before transcription is complete

DNA molecule

includes many genes

geneticists can study development and gene function by

inducing mutations in model organisms

what process describes the removal of spacer portions of mRNA to produce mRNA consisting of regions to be translated

intron removal and splicing together of exons

a(n) ___ is a portion of RNA that averages about 1000 nucleotides long and that is removed before translation

introns

transcription of the three genes in the Iac operon occurs when

lactose is present in the environment and binds to the repressor

the Iac operon in E. coli bacteria includes three genes that produce

lactose-degrading proteins

each ribosome has one ___ subunit and one ___ subunit that join at the initiation of protein synthesis

large; small

select all of the correct statements regarding the results of Frederick Griffith's 1928 experiment involving Streptococcus pneumoniae

live S strains caused pneumonia in mice; heat-killed S strains mixed with live R strains caused pneumonia in mice

to determine which codons correspond to which amino acids, scientists synthesised ___ and put them in a test tube containing the ingredients for translation. they they analysed the resulting ___

mRNA molecules; proteins

in transcription, the genetic information is DNA is copied into a(n) ___ molecule, and in translation, the "message" in an mRNA molecule is translated into a(n) ___ sequence

mRNA; amino acid

if a substitution mutation changes a codon such that it specifies a different amino acid, it is called a ___ mutation

missense

some eukaryotic organelles, such as ___ and ____, contains their two genomes in addition to the cells nuclear DNA

mitochondria; chloroplasts

a transposable element is a short DNA sequence that can cause mutations because it

moves and inserts randomly within the genome

a(n) ___ is any external agent, such as x-rays or chemicals, that induces mutations

mutagen

a(n) ___ is a change in a cells DNA sequence

mutation

silent

mutation that encodes the same protein as the original gene version

missense

mutation that results in the change of a codon for one amino acid into a codon for another amino acid

nonsense

mutation that results in the creation of a "stop" codon

homeotic genes control the formation of body parts in many animals, and ___ in homeotic genes have led to limb modifications that profoundly influenced animal evolution

mutations

select all of the following that are true regarding mutations

mutations can be the causes of diseases, some mutations have little to no effect on protein folding, mutations are alterations in DNA sequences

in the DNA double helix resembles a ladder, the interior "rungs" of the DNA ladder consist of

nitrogenous bases joined by hydrogen bonds

a substitution mutation that changes an amino acid into a "stop" codon is called a(n) ___ mutation and shortens that protein product

nonsense

in the synthesis of RNA from DNA, the enzyme RNA polymerase adds ___ to the ___ end of the growing RNA molecule

nucleotide; 3 prime (3')

a major difference between eukaryotic and prokaryotic chromosomes is that in eukaryotes, multiple, linear chromosomes ar housed within an organelle called the ___, and each chromosome consists of DNA associated with proteins

nucleus

in eukaryotic cells, transcription occurs in the ___, whereas translation occurs in the ___

nucleus; cytoplasm

in bacterial operons, a DNA sequence that exists between the promoter and the protein coding region is called the ___ and is where a repressor protein can bind

operator

during the hershey-chase experiment, radioactive ___ was used to label the DNA, and radioactive ___ was used to label the protein

phosphorus; sulfur

what RNA modification in eukaryotes decrease the chance that the mRNA will be degraded before translation

poly A tail

RNA ___ is the enzyme that builds the RNA chain during transcription

polymerase

select all of the following that are true of a nonsense mutation

polypeptide synthesis terminates prematurely, results in a shortened protein product, could be caused by a codon change from UGG to UGA

some proteins are composed of multiple ___ that join together after translation

polypeptides

what mechanism of regulating gene expression acts after RNA processing but before translation

preventing mRNA exit from the nucleus

select all of the following that are ways to control gene expression after translation

preventing the protein from reaching its correct destination; blocking addition of a necessary sugar to a newly synthesised protein; degrading the protein

splicing of different axons together from the same mRNA molecules can result in

production of different proteins

a change in the amino acid sequence of a protein can cause the protein to be nonfunctional because ___ is affected by the amino acid sequence

protein folding

having multiple ribosomes bound to an mRNA is one way a cell increases the rate of

protein synthesis

during translation, a(n) ___ is produced from the information that is encoded in a(n) ___

protein; RNA molecule

proteins combine with ___ to form a ribosome

rRNA

select three types of RNA

rRNA, mRNA, tRNA

bacterial cells and skin cells are more likely to accumulate mutations than other types of cells because they

replicate their DNA and divide frequently

the sugar in RNA nucleotides is called ___, whereas the sugar in DNA nucleotides is called ___

ribose; deoxyribose

a complex of rRNA and proteins called a(n) ___ is the physical location of protein synthesis

ribosome

select all of the following that are utilised in the process of translation

ribosome, tRNA, mRNA, amino acids

select all of the following that are genes

sequence of DNA nucleotides that codes for a specific RNA molecule, sequence of DNA nucleotides that codes for a specific proetin

a mutation that causes an mRNA nucleotide to change from GGC to GGA is a ___ mutation

silent

select all of the following that are true about RNA

single stranded but can form loops, can act as an enzyme, contains the bases A,U,G, and C, contains the sugar ribose

___ mutations do not pass from generation to generation because they occur in non-sex cells

somatic

select all of the following agents or processes that can cause mutations

some forms of radiation, errors in DNA replication, chemical mutagens

a(n) ___ mutation is caused by the replacement of one nucleotide with another

substitution

___ is a type of RNA that serves as a "connector" between the mRNA codon and a particular amino acid

tRNA

a specific sequence on the DNA called a(n) ___ sequence signals the end of a gene during transcription

terminator

if an mRNA was blocked from exiting the nucleus, what would happen to expression of the gene from which the RNA transcript was made?

the gene would be silenced

select all of the following that are true about the termination stage of translation

the large and small ribosomal subunits separate, a release factor protein prompts the release of the last tRNA from the ribosome, the polypeptide is released

select all the reasons why the polypeptide product of translation may be nonfunctional

the polypeptide misfolds or clumps, the DNA sequence is altered due to mutation, the amino acid sequence of the protein is altered

at the beginning of transcription, RNA polymerase binds to

the promoter

what would result if a mutation caused the addition of the three-base codon GUG?

the protein product would contain one extra amino acid

select all of the following that are true about E. coli bacteria in an environment lacking lactose

the repressor binds to the operator of the Iac operon, the three genes of the Iac operon are not transcribed

select all of the following that are true about the genetic code

the same genetic code is used by nearly all species, AUG encodes methionine and "start", there are three codons that act as "stop" codons

wilkins and franklin performed X-ray diffraction that revealed details about

the three-dimensional shape of the DNA molecule

select all of the following that are true about codons

they are composed of three mRNA bases, they correspond to one amino acid

in a frameshift mutation, nucleotides are added or deleted in any number other than a multiple of

three

in the 1950s, the biochemist Erwin Chargaff found that in DNA, the amount of the nucleotide base adenine always equals the amount of the nucleotide base ___, and the amount of the nucleotides base cytosine always equals the amount of the nucleotide base ___

thymine; guanine

select all the reasons a cell regulates gene expression

to have a specialised function, to respond to changing conditions

eukaryotic cells can compact their DNA or add methyl groups to make their DNA unavailable for

transcription

a signal molecule binding to a target cell can turn on eukaryotic gene transcription by activating a

transcription factor

in eukaryotes, what regulatory proteins are required for RNA polymerase to bind to the promoter and initiate transcription

transcription factors

in the "central dogma: describing the flow of genetic information from DNA to protein, DNA is copied to RNA in a process called ___, and the information in RNA is used to direct the synthesis of a protein in a process called ___

transcription; translation

in eukaryotes, mRNA degradation regulates gene expression by preventing

translation

t/f: although mutations often cause changes that are harmful, they are also the source of genetic variation for evolution

true

t/f: during the early part of the twentieth century, some biologists believed that proteins were more likely than DNA to be the molecule of heredity

true

select all of the following that are true about the frequency of mutations that arise during DNA replication

varies among organisms and among genes; average about 1 in 100,000 bases for most genes; generally higher in bacteria

select all the ways that cells can make DNA less available for transcription

wind DNA more tightly, tag DNA with methyl groups