Bellringer-January 12, 2015

• DNA Complementary – ATG ATC ACC TAA

• DNA Template - • mRNA -

• Amino Acid Seq-

FILL IN THE DNA TEMPLATE, mRNA, and Amino Acid sequence (put the 3’ and 5’ to the DNA and mRNA sequences)

Protein Synthesis• 3 major processes: –Replication → DNA copied to form 2 new DNA

molecules• Nucleus

–Transcription → DNA info copied to RNA•Nucleus

– Translation → building a protein according to RNA instructions• Cytoplasm

RNA & TranscriptionFrom Gene to Protein (DNA RNA Protein)

Honors BiologyMs. Kim

DNA RNA Protein

• You are now familiar with DNA structure and how new cells are reproduced and DNA is replicated in this process

• We know DNA contains all the information necessary to make us who we are– But how??– We have genes…but how do they work?

• Now we will look into how DNA provides the necessary information to produce proteins.

The Flow of Genetic Information • DNA – information in a specific sequence (order) of

nucleotides along 2 DNA strands– Leads to specific traits by controlling the

synthesis of proteins• Gene expression includes two stages– Transcription: DNA RNA• “transcribe” = to copy into another form

– Translation: RNA polypeptide (proteins)

– “translate” = to change into another language

ProteinsProteins are the most versatile macromolecules in

living systems and serve crucial functions in essentially all biological processes such as: Function as catalysts Transport and store other molecules such as oxygen Provide mechanical support and immune protection Generate movement Transmit nerve impulses Control growth and differentiation.

How is Protein Made?

• Cells are controlled by a cellular chain of command–DNA RNA protein• Called the “Central dogma of biology”

• What are proteins made out of? –Amino acids• There are 20 different amino acids–building blocks of proteins

• All living things use the same 20 amino acids to make proteins!!!

Breaking down the genetic code

DNA

• Humans have 23 pairs of chromosomes

• These chromosomes are long chains of bases (A’s, T’s, C’s, and G’s)

• The bases make up the thousands of genes on each chromosome– So genes gives us specific traits based

up the sequence of A’s, T’s, C’s, and G’s – Genes are instructions on how to make

proteins which essentially control what we look like and daily functions

RNA

• Remember DNA cannot leave the nucleus, so we need something else to carry the information of the DNA from the nucleus to the cytoplasm of the cell

• It is RNA’s job to copy DNA’s information and then interpret it to make proteins

CENTRAL DOGMA

stored information

working copy functional molecule

DNA RNA Protein

Transcription Translation

Basic Principles of Transcription and Translation

Gene (portion of DNA) is copied• Transcription

– the synthesis of RNA from DNA (DNA mRNA)– Produces messenger RNA (mRNA). mRNA copies a portion of DNA

strand (gene)– Occurs in the nucleus of eukaryotes and leaves nucleus to direct

making of proteinThe mRNA is read to make specific amino acid sequences• Translation (happens later)

– Nucleic Acid information into Amino Acids. Each Amino Acid as a specific 3 base CODON that codes for it.

– actual synthesis of a protein (polypeptide. mRNA protein (polypeptide)

– Occurs on ribosomes

What is transcription?• Process of copying DNA

(the template strand) into a complementary RNA strand

• Occurs in the nucleus • Similar to DNA

replication, but Uracil (U) replaces Thymine (T)

Why RNA?• RNA – Ribonucleic Acid• How does DNA get out of the nucleus and go to

the ribosomes where the proteins are made?

– It can’t! DNA cannot leave the nucleus! – So, it copies itself into RNA and that leaves and

goes to the ribosomes• EXAMPLE – library book, photocopy

What are the characteristics of RNA?

• Ribose Nucleic Acid• Single stranded• Made of sugars (called ribose), phosphate groups and

nitrogen bases• Backbone= alternating ribose sugar/phosphates held

together by PHOSPHODIESTER BONDS• Made of RNA nucleotides• Contains bases:

• (A) Adenine• (G)Guanine• (C) Cytosine• (U) Uracil (replaces Thymine)

DNA vs. RNA: • Sugars = – DNA – deoxyribose – RNA – ribose

• Nitrogen bases =– DNA – A, C, G and thymine (T)– RNA – A, C, G and uracil (U)

• Location = – DNA – inside nucleus only– RNA – in and out of nucleus

• Stranded = – DNA – Double stranded– RNA – Single stranded

RNA: Ribose sugar

• Deoxyribose means deoxygenated (its lacks an oxygen)

• Ribose does not lack an oxygen

The 3 major types of RNA

• Messenger RNA (mRNA)• Ribosomal RNA (rRNA) • Transfer RNA (tRNA)

Type of RNA Function Job Picture

mRNA (messenger RNA)

Brings message from DNA (DNA instructions) to

ribosome to make protein

tRNA (transfer RNA)

Transfers/moves amino acids to

ribosomes

rRNA (ribosomal RNA)

Makes up part of the ribosomes

Messenger RNA • mRNA copies the DNA code and

carries it into the cytoplasm where protein synthesis happens

• Notice how the bases of mRNA are organized into codons

• A codon consists of 3 consecutive bases code for a specific amino acid

• Remember a chain of amino acids = a protein

• So….DNA codes for proteins!

The Genetic Code

• It’s a table used that TRANSLATES RNA nucleotides (or mRNA “letters”) into one of the 20 amino acids–3 letter mRNA “word” = 1 amino acid–There are 4 different RNA “letters” that can be used• A, U, C, and G

Codons: Triplets of Bases

• Genetic information is coded as a sequence of base triplets, or codons• 3 letter mRNA “words” = codon–FOUND ONLY ON mRNA

• Codons must be read in the correct order – For specified polypeptide to be produced–Always read in the 5’ 3’ direction

THE

GENETIC CODE

Evolution of the Genetic Code

• The genetic code is nearly universal– Shared by organisms from the simplest bacteria to

the most complex animals• All organisms have SAME DNA “letters” and SAME

RNA “letters”

During transcription, a gene determines the sequence of bases

along length of mRNA.

DNAmolecule

Gene 1

Gene 2

Gene 3

DNA strand(template)

TRANSCRIPTION

mRNA

Protein

TRANSLATION

Amino acid

A C C A A A C C G A G T

U G G U U U G G C U C A

Trp Phe Gly Ser

Codon

3 5

35

Transcription• DNA RNA • RNA synthesis is done by RNA

polymerase• Forces DNA strands apart (breaks H

bonds btw bases) and hooks together RNA nucleotides

• Follows same DNA base-pairing rules, except in RNA, uracil substitutes for thymine –A = U (T on DNA = A in RNA)

–C = G

Synthesis of an RNA Transcript• Initiation– DNA strands unwind– RNA polymerase initiates mRNA synthesis at start point on

templates called promoters– RNA polymerase binds to promoter (certain base sequence (TATA

box))• Elongation– RNA polymerase moves downstream, unwinding DNA &

elongating mRNA transcript 5 3 direction. Makes complementary RNA strand to only one side of DNA.

– In wake of transcription, DNA strands re-form a double helix.• Termination– mRNA transcript is released at terminator signal– RNA polymerase detaches from the DNA

RNA is made in the 5’-3’ directionThe DNA template read in the 3’-5’ direction

Template strand = antisense strandCoding strand = sense strand

RNA Polymerase Binding and Initiation of Transcription

• Promoters (on DNA) starts RNA synthesis (BOTH prokaryotes & eukaryotes)

– RNA polymerase binds here then unwinds DNA– RNA Polymerase adds new FREE RNA nucleotides

to DNA template strand in 5’ 3’ direction– “TATA box” = start signal on DNA promoter

• Determines which strand is used as template only 1 side is used at a time!

Transcription Animation

• http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf

• V CELL

• http://highered.mheducation.com/sites/0072507470/student_view0/chapter3/animation__mrna_synthesis__transcription___quiz_1_.html

Elongation

RNApolymerase

Non-templatestrand of DNA

RNA nucleotides

3 end

C A E G C AA

U

T A G G T TA

AC

G

U

A

T

C

AT C C A A T

T

G

G

3

5

5

Newly madeRNA

Direction of transcription(“downstream”) Template

strand of DNA

Split Genes and RNA Splicing

• RNA splicing and RNA Modification–Removes introns and joins exons

• Introns = non-coding regions• Exons = coding regions that EXIT nucleus

Figure 17.10

TRANSCRIPTION

RNA PROCESSING

DNA

Pre-mRNA

mRNA

TRANSLATION

Ribosome

Polypeptide

5 Cap

Exon

Intron5 3Poly-A tail

Poly-A tail

Introns cut out andexons spliced together

Codingsegment

5 Cap

1 1463 UTR5 UTR

mRNA

Exon Exon

Intron

MaturemRNA

Pre-mRNA

RNA splicing is carried out by spliceosomes in some cases

RNA transcript (pre-mRNA)

Exon 1 Intron Exon 2

Other proteinsProtein

snRNA

snRNPs

Spliceosome

Spliceosomecomponents

Cut-outintronMature mRNA

Exon 1 Exon 2

5

5

5

1

2

3

Called small nuclear RNA +

proteins (ribonucleoproteins)

mRNA Codons

Lets Practice:CCAAGAGUGUGAAUG

Practice Coding

• DNA Complementary – A T C • DNA Template - A

G A • mRNA -

U A G• Amino Acid Seq- Ile-Ser-Stop

T C T

U C UT A GA U C

A T CT A G

The Ribosome

• Part of cell where translation (protein synthesis) occurs

• Where proteins are actually made

Ribosomal RNA

• Ribosomal RNA (rRNA) - ribosome attaches itself to mRNA

• Provides the stabilizing structure to hold all substances in position as the protein is synthesized.

• Contains the enzymes necessary for protein synthesis.

rRNA with attached mRNA and tRNA and forming protein

Transfer RNA• Transfer RNA (tRNA) -

reads the mRNA code and carries the amino acid to be incorporated into the developing protein– Notice the 3 bases at the

bottom of the tRNA which make up the anticodon• The anticodon base

pairs with the mRNA codon

– At the top an amino acid is attached to the tRNA