• DNA makes ____ makes ________.

• Proteins are the links between ___________ and ________________.

From DNA to Proteins Chapter 13

growing RNA transcript5’

3’5’

3’

direction of transcription

• The bridge between DNA and ________ synthesis is RNA.

• RNA differs from DNA

1. RNA contains _____as its sugar (not deoxyribose)

2. _______ replaces thymine.

AGTCAT becomes AGUCAU

3. An RNA molecule almost always consists of a _______strand.

___________ and ___________ are the two main processes linking gene to protein

Fig. 6.8a

This is an H in DNA

4 types of RNA

• ________ - carries info for protein production

• _______-transport amino acids in translation

• _______- part of ribosome, has role in translation

• ________ - splicing mRNA

UAA

AUGPre-mRNA

3. _____________

NH2 COO- Protein7. ________________

AUG

AAAAAA…..

D CA BE

7mG

UAA

F

4._________

Chromosome- 1.5 x 108 base pairs containing about 3000 genes

0.4% of a chromosome, containing 10 genes

ATGDNA

CB EDFTAA

= 1. ________________

= 2. ________________

5’3’

3’5’

+1 AATAAA

5. ______ 6. ____________

• ____________ - DNA is the template for RNA, usually __________ RNA (mRNA).

Fig. 17.2a

•____________________ - the information contained in the order of nucleotides in mRNA is used to determine the __________ sequence of a polypeptide.

-Translation occurs at ____________.

• The basic mechanics of transcription and translation are ________ in eukaryotes and prokaryotes.

• In the __________, three consecutive bases specify an amino acid, creating 43 (64) possible ________.

• The genetic instructions for a polypeptide chain are written in DNA as a series of three- __________words.

In the genetic code, nucleotide triplets specify amino acids

1. ___ of 64 triplets code for amino acids.

• AUG codes for the methionine and ____ of translation.

Fig. 17.4

•Three codons –___, ___ and

____ do not code amino acids but signal the termination of translation.

The genetic code

2. The genetic code is __________but not_ _________ .

• Typically several different codons specify a given amino acid

• Any one codon indicates _ __________ amino acid.

Know how to

read this chart!!

The genetic code (cont.)

A ______________ is established at the translation start

UUACGAUGGAUUCAAACGUCAGGGCCUAAGGCUAG

Start codon

AspStop

codon

Met AsnSer ArgVal AlaRNA

Summary- The genetic code uses_ ____________________, or codons, each of which is translated into a specific amino acid.

5’ 3’

Know how to

read this chart!!

• The genetic code is nearly ______________ , from bacteria to mammals

Thus, we can synthesize bacterial proteins in ______________

Exceptions do exist- they use slightly altered genetic codes:

1.single-celled eukaryotes like Paramecium.

2. certain mitochondria and chloroplast ____________

• Messenger RNA is transcribed from the template strand of a gene by ________________.

• __________________________ :

• separates the DNA strands

• bonds the RNA nucleotides as they base-pair along the DNA template.

DNA3’ 5’

5’ RNA 3’

What actually makes the RNA?

•Answer- Specific sequences of nucleotides called the _________ mark where gene transcription begins

What marks the start of transcription??

•In prokaryotes, RNA polymerase can recognize and bind ______________ to the promotor region.

•In eukaryotes, proteins called ___________ first bind the promotor region, especially a __________ , then RNA polymerase II binds

Transcript Modification

unit of transcription in a DNA strand

exon intron

mature mRNA transcript

poly-A tail

5’

5’ 3’

3’

snipped out

snipped out

exon exonintron

cap

transcription into pre-mRNA

3’ 5’

Transport to cytoplasm

UAA

AUGhnRNA

Transcription

NH2 COO- ProteinTranslation

AUG

AAAAAA…..

D

RNA SplicingpolyA tail,cap

CA BE

7mGmRNA

UAA

F

Regulatory DNA sequences

Chromosome- 1.5 x 108 base pairs containing about 3000 genes

0.4% of a chromosome, containing 10 genes

Overview of eukaryotic transcription/translation15.3

15.215.1

14

13.3

13.11211

11.111.2

12

13.113.213.3

14

15

21

2223.1

23.3

31.131.231.3

3233.133.334

35.135.3

35.2

33.2

23.2

13.2

ATGDNA

CB EDFTAA

= exon= intron

5’3’

3’5’

Template strand+1

AAUAAA

• _____________ (tRNA) - transfers amino acids from the cytoplasm’s pool to a ________________.

• The ribosome adds each amino acid carried by tRNA to the growing end of the _________________ chain.

codon in mRNA

anticodonin tRNA

amino acid OH

tRNA molecule’s attachment site for amino acid

How do proteins read the RNA molecule??

Answer-the ___________________

ribosome

tRNA

A tRNA molecule

• Is about ___ nucleotides long

• Contains attachment site for an amino acid.

• Contains a loop with the ___________

Fig. 17.13

The anticodon base-pairs with a complementary codon on mRNA.

If the codon on mRNA is UUU, a tRNA with a ______ anticodon and a tRNA carrying phenylalanine will bind to it.

5’3’

Translation can be divided into three ______ 1. initiation

2. _________

3. termination

1. Initiation

a. Small ribosomal subunit binds mRNA

b. Initiator tRNA (with methionine) is attached to start codon

Fig. 17.17

Translation

2. Elongation - Amino acid sequentially added

c. Translocation - the ribosome moves the tRNA with the attached polypeptide from the A site to the P site.

Translation

3. Termination occurs when ribosome reaches a _____codon.

• A ____________ binds to the stop codon and hydrolyzes the bond between the polypeptide and its tRNA in the P site.

Fig. 17.19

Translation

• Multiple ribosomes, polyribosomes, may trail along the same _______.

• A ribosome requires less than a ________ to translate an average-sized mRNA into a polypeptide.

Fig. 17.20

Other translation facts

OverviewTranscription

Translation

mRNA rRNA tRNA

Mature mRNA transcripts

ribosomal subunits

mature tRNA

Point mutations can affect protein structure and function• __________ are changes

in the genetic material of a cell (or virus).

• include large-scale mutations in which _____ segments of DNA are affected (translocations, duplications, and inversions).

• A chemical change in just one base pair of a gene causes a _______________

In sickle cell, a single T to A mutation changes amino acid from glu to val

•_________ - alterations of nucleotides still indicate the same amino

acids because of redundancy in the genetic code.

•Many other mutations cause no effect in function

• Other base-pair substitutions cause a readily detectable change in a protein.

• _______ mutations are those that still code for an amino acid but change the indicated amino acid.

• _______ mutations change an amino acid codon into a _____ codon, nearly always leading to a nonfunctional protein.

Fig. 17.24

• Insertions and ______ are additions or losses of nucleotide pairs in a gene.

• These have a _________ effect on the resulting protein more often than substitutions do.

• Unless these mutations occur in multiples of ____, they cause a ________ mutation.

• All the nucleotides downstream of the deletion or insertion will be improperly grouped into codons.

• The result will be extensive missense, ending sooner or later in nonsense - premature termination.

Fig. 17.24

______________Mutation

ARGININE GLYCINE TYROSINE TRYPTOPHAN ASPARAGINE

ARGININE GLYCINE LEUCINE GLUTAMATELEUCINE

mRNA

PARENTAL DNA

amino acid sequence

altered mRNA

BASE INSERTION

altered amino acid sequence

Really bad!!

• __________ are chemical or physical agents that interact with DNA to cause mutations.

• ________agents include high-energy radiation like X-rays and ultraviolet light.

__________ mutagens may operate in several ways.

• As base ____________ that may be substituted into DNA, but that pair incorrectly during DNA replication.

• Interfere with DNA replication by inserting into DNA and distorting the ______________.

• Cause chemical changes in bases that change their pairing properties.

Fig. 13.14, p. 210

TRANSCRIPTION Unwinding of gene regions of a DNA molecule

Pre mRNA Transcript Processing

mRNA rRNA tRNA

TRANSLATION

FINAL PROTEIN

Destined for use in cell or for trasport

Convergence of RNAs

Synthesis of a polypetide chain at binding sites for mRNA and tRNA on the surface of an intact ribosome

Cytoplasmic pools of amino acids, tRNAs, and ribosomal subunits

Mature mRNA transcripts

protein subunits

ribosomal subunits

mature tRNA