Chapter 17 Campbell Reece

Front 1

Archibald Garrod

Back 1

One gene - one enzyme
Alkaptonuria - enzyme metabolism of alkaptans

Front 2

Beadle and Tatum

Back 2

Proved One gene - one enzyme hypothesis -Bread Mold mutations

Front 3

Central Dogma

Back 3

DNA -> RNA -> Protein
Transcription
Translation

Front 4

Transcription

Back 4

RNA synthesis under the direction of DNA in nucleus

Front 5

Translation
(Eukaryote)

Back 5

Polypeptide synthesis under the direction of mRNA at the ribosome(s) in the cytoplasm

Front 6

Gene

Back 6

programs protein synthesis via genetic messages in the form of messenger RNA

Front 7

Exon

Back 7

Expressed nucleic acid sequences

Front 8

Intron

Back 8

Intervening nucleic acid sequences

Front 9

Codon

Back 9

Triplets of nucleotides that represent a single amino acid

Front 10

Mutagen

Back 10

Physical and chemical agents that cause DNA mutation

Front 11

RNA processing

Back 11

modification of preMessenger RNA before genetic messages are passed to the cytoplasm

Front 12

Anti-codon

Back 12

nucleotide triplet on tRNA which base pairs with complementary codon on mRNA

Front 13

Promotor

Back 13

The DNA sequence where RNA polymerase attaches and initiates transcription

Front 14

Transcription Factors

Back 14

a collection of proteins that mediate the binding of RNA polymerase and initation of transcription

Front 15

Primary Transcript

Back 15

Initial RNA transcript for any gene (includes expressed and intervening sequences)

Front 16

Three stages of Transcription

Back 16

1. Initiation
2. Elongation
3. Termination

Front 17

Metabolic Pathway

Back 17

Cells synthesize and degrade most organic chemicals by sequences of reactions that are catalyzed by enzymes

Front 18

One gene - One Polypeptide

Back 18

Restatement of one gene one enzyme or one gene one protein

Front 19

Alkaptonuria

Back 19

A rare genetic inability to make the enzyme that metabolizes Alkapton

Front 20

messenger RNA (mRNA)

Back 20

carries genetic message specifying amino acid sequences from the DNA in the nucleus to the protein–synthesizing machinery (ribosomes) in the cytoplasm

Front 21

Ribosome

Back 21

Eukaryote Translation
coordinate the sequential coupling of tRNA molecules to mRNA codons

Front 22

Start codon

Back 22

where translation initiates
AUG

Front 23

Stop codon

Back 23

where translation terminates
UAA UAG UGA

Front 24

transfer RNA (tRNA)

Back 24

cloverleaf-shaped structure which carries the appropriate amino acid to the ribosome

Front 25

Two methods of post-transcriptional modification

Back 25

1. Alternation of mRNA ends
2. Splicing

Front 26

Template strand

Back 26

Strand of DNA that provides the template for ordering the sequence of nucleotides in an RNA transcript
NOTE: only one of the two DNA strands is transcribed.

Front 27

5' Cap

Back 27

a modified guanine nucleotide is added to the 5’ end of the transcript

Front 28

3' Poly-A Tail

Back 28

50-250 adenine nucleotides are added to the 3’ end of the transcript by poly-a polymerase (enzyme)

Front 29

Purpose of end modification

Back 29

1.Help export mature mRNA out of nucleus
2. Protect mRNA from degradation by hydrolytic enzymes
3. Help ribosomes attach to the mRNA

Front 30

Why Splicing?

Back 30

removes intervening sequences (introns) from the mRNA transcript

Front 31

Why splicing ? 2

Back 31

1. One gene can encode more than one polypeptide
2. Gets rid of evolutionary “junk DNA”

Front 32

Exon Shuffling (1)

Back 32

giving more room for crossover events between exons may increase chances for formation of beneficial new proteins,
NOTE: sexual traits in flies

Front 33

Reading frame

Back 33

The way a cell′s mRNA–translating machinery groups the mRNA nucleotides into codons

Front 34

Triplet code

Back 34

A set of three–nucleotide–long words that specify the amino acids for polypeptide chains.

Front 35

transcription initiation complex

Back 35

The completed assembly of transcription factors and RNA polymerase bound to the promoter.

Front 36

TATA box

Back 36

A promoter DNA sequence crucial in forming the transcription initiation complex.
a nucleotide sequence contain "TATA" about 25 nucleotides upstream from transcription start point

Front 37

RNA polymerase II

Back 37

used for mRNA synthesis in eukaryotes.

Front 38

sliceosome

Back 38

A complex assembly that interacts with the ends of an RNA intron in splicing RNA, releasing the intron and joining the two adjacent exons.

Front 39

Ribozyme

Back 39

An enzyme–like RNA molecule that catalyzes reactions during RNA splicing

Front 40

domains

Back 40

1. discrete structural and functional regions of a protein
2. correspondence to exons splicing

Front 41

Exon shuffling (2)

Back 41

allows for creation of proteins with multiple polypeptides and multiple structural and functional domains

Front 42

aminoacyl–tRNA synthetase

Back 42

An enzyme that joins each amino acid to the correct tRNA

Front 43

aminoacyl–tRNA

Back 43

An "activated amino acid"

Front 44

wobble

Back 44

A relaxation of the base–pairing rules so
third nucleotide of a tRNA anticodon can form hydrogen bonds with more than one kind of base

Front 45

Ribosomal RNA (rRNA)

Back 45

Plays catalytic (ribozymes) and structural roles in the ribosome.
Created in nucleolus

Front 46

P-Site

Back 46

holds the tRNA carrying the growing polypeptide chain
NOTE: peptidyl–tRNA site

Front 47

A-Site

Back 47

holds the tRNA carrying the next amino acid to be added to the chain
NOTE:aminoacyl–tRNA site

Front 48

E-Site

Back 48

place where discharged tRNAs leave the ribosome.
NOTE: EXIT site

Front 49

Three stages of Transcription

Back 49

1. Initiation
2. Elongation
3. Termination

Front 50

Transcription Initiation

Back 50

1. RNA Polymerase binds to the promoter
2. DNA strands unwind
3. RNA synthesis initiates at the start point of template strand

Front 51

Transcription Elongation

Back 51

1. RNA polymerase:
a.continues to untwist the double helix,
b. adds nucleotides to the 3′ end of the growing RNA molecule
2. the new RNA molecule peels away from its DNA template
3. DNA double helix re–forms

Front 52

Transcription Termination
(Eukaryote)

Back 52

the polymerase transcribes a sequence on the DNA called the polyadenylation signal sequence, which codes for a polyadenylation signal (AAUAAA) in the pre–mRNA

Front 53

Three stages of Translation

Back 53

1. Initiation
2. Elongation
3. Termination

Front 54

Translation Initiation

Back 54

1.small ribosomal subunit binds to both mRNA and a specific initiator tRNA
2.The small subunit then scans, downstream for the start codon

Front 55

Translation Elongation

Back 55

1. Codon Recognition
2. Peptide Bond formation
3. Translocation

Front 56

Translation Termination

Back 56

stop codon in the mRNA reaches the A site of the ribosome

Front 57

Polysome

Back 57

An aggregation of several ribosomes attached to one messenger RNA molecule
NOTE: Polyribosome

Front 58

post–translational modifications

Back 58

may be required before the protein can provide a specific function in the cell

Front 59

Bound ribosomes

Back 59

make proteins of the endomembrane system (the nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles, and plasma membrane) as well as proteins secreted from the cell

Front 60

Free ribosomes

Back 60

suspended in the cytosol and mostly synthesize proteins that dissolve in the cytosol and function there

Front 61

signal peptide

Back 61

A stretch of amino acids on a polypeptide that targets the protein to a specific destination in a eukaryotic cell

Front 62

signal–recognition particle (SRP)

Back 62

A protein–RNA complex that recognizes a signal peptide as it emerges from the ribosome

Front 63

translocation complex

Back 63

protein complex that has membrane pore and signal-cleaving enzyme

Front 64

RNA is multifunctional - Why?

Back 64

RNA:
1. Can hydrogen–bond to other nucleic acid molecules.
2. can assume a specific conformation by forming hydrogen bonds between bases in different parts of its own polynucleotide chain.
3. has functional groups that allow it to act as a catalyst (ribozyme).

Front 65

Small nuclear RNA (snRNA)
SNURPs

Back 65

structural and catalytic roles in sliceosomes

Front 66

SRP RNA

Back 66

component of signal recognition particle (SRP)

Front 67

Small nucleolar RNA (snoRNA)

Back 67

aids in processing of pre-RNA transcripts for ribosome subunit formation in the nucleolus

Front 68

small interfering RNA (siRNA) and microRNA (miRNA)

Back 68

involved in regulation of gene expression

Front 69

Mutation

Back 69

A change in the DNA of a gene, ultimately creating genetic diversity

Front 70

Point Mutation

Back 70

A change in a gene at a single nucleotide pair

Front 71

Genetic disease or disorder

Back 71

a mutation that has an adverse effect on the phenotype of an organism

Front 72

base-pair substitution

Back 72

the replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides

Front 73

base-pair substitution of third codon

Back 73

No effect to organisms Phenotype - rules are relaxed - wobble

Front 74

Missense mutation

Back 74

a base–pair substitution in which the new codon still codes for an amino acid

Front 75

Nonsense mutation

Back 75

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

Front 76

Insertion mutation

Back 76

A mutation involving the addition of one or more nucleotide pairs to a gene

Front 77

Deletion mutation

Back 77

A mutation involving the deletion of one or more nucleotide pairs to a gene

Front 78

Frameshift mutation

Back 78

number of nucleotides inserted or deleted is not a multiple of three, resulting in the improper grouping of the following nucleotides into codons