Biology Chapter 17

Front 1

Gene Expression

Back 1

the process by which information encoded in DNA directs the synthesis of proteins and RNAs

Front 2

One Gene-One Enzyme Hypothesis

Back 2

the idea that each gene only codes for a particular enzyme

Front 3

Going from DNA to protein requires ______ stage(s).

Back 3

Going from DNA to protein requires two stages.

Front 4

Transcription

Back 4

synthesis of RNA using a DNA template

Front 5

Messenger RNA (mRNA)

Back 5

a type of RNA synthesized with a DNA template that specifies the primary structure of a protein

Front 6

Translation

Back 6

synthesis of a polypeptide using genetic information encoded in an mRNA molecule

Front 7

Ribosomes

Back 7

a complex of rRNA and proteins that functions as a site of protein synthesis in the cytoplasm; consists of a large and small subunit

Front 8

Transcription occurs in the ____________ and translation occurs in the _______________.

Back 8

Transcription occurs in the nucleus and translation occurs in the cytoplasm.

Front 9

Primary Transcript

Back 9

an initial RNA transcript from any gene

Front 10

pre-mRNA

Back 10

a primary transcript of an RNA molecule destined to code for a protein

Front 11

In eukaryotic cells, DNA is transcribed into ________________, which then becomes ____________ after _______________.

Back 11

In eukaryotic cells, DNA is transcribed into pre-mRNA, which then becomes mRNA after RNA processing.

Front 12

The genetic instructions for a polypeptide chain are written in DNA based on a _________ code.

Back 12

The genetic instructions for a polypeptide chain are written in DNA based on a triplet code.

Front 13

For each gene, only the _____________ strand is transcribed.

Back 13

For each gene, only the template strand is transcribed.

Front 14

Codon

Back 14

three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal

Front 15

Codons are typically written in the (3'→5'/5'→3') direction.

Back 15

Codons are typically written in the 5'→3' direction.

Front 16

There are __________ amino acids that DNA can code for.

Back 16

There are twenty amino acids that DNA can code for.

Front 17

A nontemplate strand, or ____________ strand, has the same sequence as the _______ (except for having a T wherever there is a(n) ____).

Back 17

A nontemplate strand, or coding strand, has the same sequency as the mRNA (except for having a T whever there is a U).

Front 18

Three codons in mRNA code to (start/end) translation.

Back 18

Three codons in mRNA code to end translation.

Front 19

The start codon, ______, also codes for an amino acid called _____ for short. This amino acid may be removed by ___________ after the full polypeptide chain has been created.

Back 19

The start codon, AUG, also codes for an amino acid called Met for short. This amino acid may be removed by enzymes after the full polypeptide chain has been created.

Front 20

Reading Frame

Back 20

on an mRNA, the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis

Front 21

The genetic code is __________, which means that each codon translates to (one/two/many) amino acid(s). This can allow an organism to _________ genes from another species.

Back 21

The genetic code is universal, which means that each codon translates to one amino acid. This can allow an organism to express genes from another species.

Front 22

RNA Polymerase

Back 22

an enzyme that links ribonucleotides into a growing RNA chain during transcription based on complementary binding to nucleotides on a DNA template strand

Front 23

RNA polymerases can only assemble a polynucleotide in the (5'→3'/3'→5') direction.

Back 23

RNA polymerases can only assemble a polynucleotide in the 5'→3' direction.

Front 24

Promoter

Back 24

a specific nucleotide sequency int he DNA of a gene that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place

Front 25

Terminator

Back 25

in bacteria, a sequence of nucleotides in DNA that marks the end of a gene and signals RNA polymerase to release the new RNA and detach

Front 26

Molecular biologists refer to the direction of transcription as (upstream/downstream).

Back 26

Molecular biologists refer to the direction of transcription as downstream.

Front 27

Transcription Unit

Back 27

the stretch of DNA downstream from the promoter that is transcribed into an RNA molecule

Front 28

While bacteria have one type of RNA polymerase, eukaryotes have at least _______.

Back 28

While bacteria have one type of RNA polymerase, eukaryotes have at least three.

Front 29

The RNA polymerase that is used for pre-mRNA synthesis in eukaryotes is called __________________.

Back 29

The RNA polymerase that is used for pre-mRNA synthesis in eukaryotes is called RNA polymerase II.

Front 30

Describe the stages of transcription.

Back 30

1. Initiation - RNA polymerase binds to promoter and begins to unwind the DNA strands; RNA polymerase initiates RNA synthesis at start point on template strand

2. Elongation - RNA polymerase moves downstream, unwinding the DNA andelongating the RNA transcript 5'→3'. The DNA rewinds after the polymerase passes.

3. Termination - RNA polymerase releases the RNA transcript and detaches from the DNA

Front 31

Transcription factors

Back 31

collection of proteins in eukaryotes that mediate the binding of RNA polymerase and the initiation of transcription

Front 32

Transcription Initiation Complex

Back 32

complex of transcription factors (proteins) and RNA polymerase II bound to the promoter

Front 33

TATA box

Back 33

a DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex

Front 34

The template strand runs in a (3'→5'/5'→3') direction.

Back 34

The template strand runs in a 3'→5' direction.

Front 35

During RNA processing, a(n) ____________ made of _________ nucleotides is added to the 5' end of the RNA molecule and a(n) __________ made of __________ nucleotides is added to the 3' end. In addition, portions of the RNA molecule, called _______, may be removed and the remaining parts, called _______, are spliced together.

Back 35

During RNA processing, a 5' cap made of modified guanine nucleotides is added to the 5' end of the RNA molecule and a poly-A tail made of adenine nucleotides is added to the 3' end. In addition, portions of the RNA molecule, called introns, may be removed and the remaining parts, called exons, are spliced together.

Front 36

What functions do the 5' cap and poly-A tail serve?

Back 36

1. Facilitate exportation from nucleus

2. Protect mRNA from degrading

3. Help ribosomes attach to 5' end once mRNA is in cytoplasm

Front 37

A large complex of proteins and small RNAs that removes introns from pre-mRNA is called a ____________.

Back 37

A large complex of proteins and small RNAs that removes introns from pre-mRNA is called a spliceosome.

Front 38

Ribozyme

Back 38

an RNA molecule that functions as an enzyme, such as an intron that catalyzes its own removal during RNA splicing

Front 39

What three properties of RNA enable them to function as enzymes?

Back 39

1. Single-stranded: can form base-pair links within itself to have a certain structure

2. Some bases in RNA contain functional groups that participate in catalysis

3. RNA can hydrogen-bond with other nucleic acids (RNA or DNA) for specificity

Front 40

Alternative RNA Splicing

Back 40

a type of eukaryotic gene regulation in which different mRNA molecules can be produced from the same primary transcript depending on which RNA segments are treated as exons and which as introns

Front 41

Proteins are made of ___________, discrete structural and functional regions.

Back 41

Proteins are made of domains, discrete structural and functional regions.

Front 42

Transfer RNA (tRNA)

Back 42

an RNA molecule that functions as a translator between nucleic acid and protein languages by carrying specific amino acids to the ribosome, where they recognize the appropriate codons in the mRNA

Front 43

Describe the structure of tRNA.

Back 43

short length of RNA with anticodon (triplet of nucleotides that can base pair with mRNA strand) on one end and amino acid on the other; tRNA folds around itself and forms base-pair hydrogen bonds to form an L-shaped molecule

Front 44

Aminoacyl-tRNA Synthetase

Back 44

afamily of enzymes that join an amino acid to the appropriate tRNA

Front 45

Some tRNAs can bind to more than one codon because of __________. This is because base-pairing rules between the (first/second/third) nucleotide base of the codon and the corresponding tRNA anticodon are relaxed.

Back 45

Some tRNAs can bind to more than one codon because of wobble. This is because base-pairing rules between the third nucleotide base of the codon and the corresponding tRNA anticodon are relaxed.

Front 46

Ribosomal RNA (rRNA)

Back 46

RNA molecules that bind with proteins to make up ribosomes

Front 47

The most abundant type of RNA is _________.

Back 47

The most abundant type of RNA is rRNA.

Front 48

A ribosome consists of a(n) ________ binding site and three _________ binding sites, called ___, ___, and ___.

Back 48

A ribosome consists of an mRNA binding site and three tRNA binding sites, called A, P, and E.

Front 49

A ribosome's A site is used _________________, its P site is used ___________, and its E site is used _________________.

Back 49

A ribosome's A site is used to hold the tRNA carrying the next amino acid, its P site is used to hold the tRNA carrying the growing polypeptide chain, and its E site is used to discharge the spent tRNAs.

Front 50

What are the names for the P, A, and E sites on a ribosome?

Back 50

P = peptidlyl-tRNA binding site

A = aminoacyl-tRNA binding site

E = exit site

Front 51

Describe the steps for elongation of a polypeptide chain in translation.

Back 51

1. Codon recognition - anticodon of incoming tRNA base-pairs with mRNA codon in the A site

2. Peptide bond formation - RNA piece of large ribosomal subunit catalyzes formation of peptide bond between amino group from tRNA in site P with amino group from rRNA in site A

3. Translocation - ribosome moves the tRNA from site A to site B, pushing the other tRNA into site E and discharging it while pulling along the mRNA to expose the next codon for translation

Front 52

Describe the steps for termination of translation.

Back 52

1. Ribosome reaches a stop codon and a release factor binds to site A instead of a tRNA molecule

2. Release factor promotes hydrolysis of bond between tRNA in the P stie and the last amino acid in the polypeptide

3. Subunits and other components, including mRNA strand, dissociate

Front 53

Signal Peptide

Back 53

a sequence of about twenty amino acids at or near the leading end of a polypeptide that targets it to an organelle in a eukaryotic cell

Front 54

Signal-Recognition Particle (SRP)

Back 54

protein-RNA complex that recognizes a signal peptide and helps direct the ribsome to the ER and binds it to a receptor protein in the ER membrane

Front 55

Proteins that are part of the endomembrane system are produced (within the cytoplasm/in the ER).

Back 55

Proteins that are part of the endomembrane system are produced in the ER.

Front 56

Proteins that are destined for organelles or functions outside of the endomembrane system are produced (within the cytoplasm/in the ER).

Back 56

Proteins that are destined for organelles or functions outside of the endomembrane system are produced within the cytoplasm.

Front 57

Polyribosome (Polysome)

Back 57

a group of several ribosomes translating the same mRNA molecule

Front 58

Mutation

Back 58

a change in the nucleotide sequence of an organism's DNA or in the DNA or RNA of a virus

Front 59

Point Mutation

Back 59

a change in a single nucleotide pair of a gene

Front 60

Nucleotide-Pair Substitution

Back 60

a type of point mutation in which one nucleotide and its partner are replaced by another pair of nucleotides

Front 61

Silent Mutation

Back 61

a nucleotide-pair substitution that has no observable effect on the phenotype

Front 62

Missense Mutation

Back 62

a nucleotide-pair substitution that results in a codon that codes for a different amino acid

Front 63

Nonsense Mutation

Back 63

a mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein

Front 64

Insertion and Deletions

Back 64

mutations that include the addition or loss of nucleotide pair(s) in a gene

Front 65

Frameshift Mutation

Back 65

a mutation occuring when nucleotides are inserted in or deleted from a gene and the number is not a multiple of three, resulting in the improper grouping of subsequent nucleotides

Front 66

Mutagen

Back 66

a chemical or physical agent that interacts with DNA and can cause a mutation

Front 67

The direction of synthesis of an RNA transcript is (5'→3'/3'→5').

Back 67

The direction of synthesis of an RNA transcript is 5'→3'.

Front 68

Sequence logos are conventionally made from the (template/nontemplate/mRNA) strand.

Back 68

Sequency logos are conventionally made from the nontemplate strand.

Front 69

Knock-Out Mutation

Back 69

a mutation which leads to loss of a protein's function but not necessarily its complete absence