Tuesday 3/6/12Aim: How does the genetic code get out of the

nucleus?

Do Now: Show the product after DNA replicates:

Homework:page 315 questions 19 and 20

Wednesday 3/7/12 pd 7

• AIM: how can we make an mRNA transcript from a DNA template?

• DO NOW: Explain the difference between replication and transcription.

• HOMEWORK: Internet project on the website due friday

How does a DNA strand become a protein? Name the processes.

Tuesday 4/5/11

• AIM: why is the primary transcript modified before leaving the nucleus?

• DO NOW: Explain what makes a skin cell different from a cardiac (heart) cell.

• Homework: Textbook Read page 306. reading check on page 306. analyze figure 13 on page 307. List the start codon and the 3 stop codons.

Before becoming a protein, name the molecule synthesized during

translation.polypeptide

Gene Expression• DNA only provides instructions.

• Gene expression is the process by which the information encoded in a gene is used to assemble protein .

• In you body, do all cells have the same genetic information?

• How come our cells in our stomach function differently than our skin?– Cells are differentiated meaning that different cells can

have very different structure and function due to the genes they express.

– Different cells listen to different instructions so that means they make different proteins

How do skin cells make proteins?

How do cardiac cells make proteins?

How is the information in DNA turned into Protein?

DNA template

• On the double helix, the sequence being transcribed is called the sense strand

• It holds the information to build the polypeptide

• The noncoding DNA strand is called the anti-sense strand

• The sense and anti-sense strands can switch and the cell makes a different polypeptide

The primary transcript is complementary to the DNA template (sense strand)

Thursday 3/8/12

• AIM:how does a mature mRNA molecule mirror its DNA template?

• DO NOW: Transcribe the following ATTCGTAGCATG

• Where does transcription take place?

• Homework: project DUE TOMORROW!

Primary transcript

• Rough draft mRNA• First mRNA

molecule made• It gets modified

before it leaves the nucleus

Transcription: DNA-RNA

Transcription (nucleus)• DNA-RNA• Step 1: unzip the DNA double helix

– Breaking the hydrogen bonds between Nitrogen bases

• Step 2: Attract ribonucleotides to the DNA template– Base pair rules

DNA RNA

A U

T A

C G

G C

Types of RNA

• mRNA: messenger RNA: carries the genetic code from the nucleus to the ribosome

• rRNA: ribosomal RNA: builds ribosomes

• tRNA: transfer RNA: carries amino acids to the synthesizing polypeptide

• The Three RNAs (mRNA, tRNA, and rRNA) all work together to turn the information in DNA into a beautiful, 3-dimestional protein!!!

Friday 3/9/12

• AIM: How is the primary transcript modified before it leaves the nucleus?

• DO NOW:Explain the difference between a codon and an anticodon.

• Transcribe the following:• Sense TACGGTACTGTAGGA• Antisense ATGCCATGACATCCT

POP QUIZ!

• Use the picture to answer questions 1-4

1-Name Enzyme A2- What is the function Of Enzyme B3- Name Strand 14- Why is strand 2

madeIn small fragments?

Enzyme A

Enzyme A

Enzyme B

Strand 1Strand 2

tRNA: Transfer RNA carries amino acids to the mRNA-ribosome complex

Ribosomal RNA builds ribosomes

• How does tRNA know• The mRNA which amino acid to

bring the ribosome• The mRNA holds the codons which

tell which amino acid

Transcription: DNA RNA

• DNA template used to create RNA

• Step 1: RNA polymerase attaches to promoter region, unzips DNA strand

Gene

Complementary DNA

Transcription: DNA RNA

• Step 2: As RNA polymerase unzips, it forms RNA strand with RNA nucleotides. 

• Only one DNA strand is transcribed at a time.

• Step 3: RNA polymerase continues until termination point.

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

Tutorial 12.1 Transcription

Transcription cont.• BUT BEFORE IT CAN LEAVE THE NUCLEUS,

THE PRIMARY TRANSCRIPT (immature mRNA) MUST BE MODIFIED (changed)

• WHY?• Make sure all the codons are in correct order• Get rid of junk DNA• Protect mRNA from degredation• Make sure mRNA recognizes and bonds to the

ribosome• Start codon (AUG) must recognize and bond to

the ribosome

• AIM: how do our cells make RNA from DNA templates

• DO NOW: how do you think RNA polymerase unzips the DNA double helix and why does the DNA double helix have to get unzipped?

• HOMEWORK: Quick Lab page 310 analysis questions 1-4 will be checked on Monday

• EXAM WEDNESDAYEXAM WEDNESDAY

Monday 3/12/12• AIM: How does the primary transcript

mirror the gene sequence?• DO NOW: Where are the instructions for all

of your physical characteristics located? (BE SPECIFIC)

• How do your physical characteristics develop? (from start to finish)

• Homework: page 314 questions 12 Write out the question followed by the answer!

• EXAM THIS THURSDAY DNA REPLICATION, TRANSCRIPTION and TRANSLATION Chapter 13 pages296-298,304-310

Transcription

• This animation shows the process of transcription

Translation RNA-Polypeptide

Transcription

• Promoter sequence: sequence of nucleotides on the DNA molecule that tells RNA polymerase to begin transcription– Start of the genes codons

• Terminator sequence: Tells RNA polymerase that transcription is over and to release the primary transcript

Primary transcript

• Immature Rough draft• Before it can leave the nucleus, must

be modified– Prevents degrading (break down)– Helps ribosome to recognize

Tuesday 3/13/12 pd 7

• AIM: How do genes develop into physical traits?

• DO NOW: Transcribe A C G T A T C G C G T

• HOMEWORK: Practice Test questions 1-10

Modification of RNA

• The most important is RNA splicing (cutting out junk DNA gluing together important DNA)

• Addition of 5’cap and Poly-A tail

Modification of RNA: splicing

Tuesday 3/13/12

• AIM: How do genes develop into physical traits?

• DO NOW: Transcribe the following gene sequence

A C G T A T C G C G T

• HOMEWORK: Textbook Page 310 Quick lab questions 1-4

Transcription

• RNA polymerase continues until termination point.

• RNA molecule may become rRNA, tRNA, OR mRNA depending on what sequence was transcribed.

Why do we have to modify the primary mRNA

transcript?

Modification of RNA•5’ cap attached to the 5' end of the pre-mRNA

• Poly(A) tail attached to the 3' end of the pre-mRNA

• splicing is a modification of genetic information prior to translation

• Introns get cut out, and Exons get together

Splicesomes

• Enzymes capable of cutting out introns and pasting together exons

• Introns: noncoding sequences of nucleotides• Exons: coding sequences of nucleotides• Reading frame: sequence of coding

nucleotides that code for an amino acid sequence

• Codon: sequence of 3 nucleotides that specify one amino acid– The genetic word

Monday 4/8/13

• AIM: How is the mature mRNA transcript read once it is at the ribosome?

• DO NOW: transcribe and translate• Gene sequence:

TACCCTCAACTCTCAACT

• Homework: Textbook page 313 questions 8,9,10,12,13

Lets build a protein

Gene sequence: TACCCTCAACTCTCAACT

mRNA: AUGGGAGUUGAGAGUUGA

MET-GLY-VAL-GLU-SER

tRNA: UACCCUCAACUCUCAACU

• AUG: Start codon: tells ribosome to start translation

• UAA• UAG These are your STOP codons• UGA they tell the ribosome to stop

translating

HOW does tRNA know which amino acid to bring to the

ribosome?The mRNA codon which came

from the DNA gene

tRNA: Transfer RNA carries amino acids to the mRNA-ribosome complex

tRNA anticodontRNA anticodon• 3 base pair sequence 3 base pair sequence

complementary to the mRNA complementary to the mRNA codon codon • Anticodon-codonAnticodon-codon complex allows complex allows

amino acids to bond in proper amino acids to bond in proper sequencesequence

Tuesday 4/9/13

Animation of Translation

Amino Acid

• The R group gives the amino acid it’s unique properties

• Size, water solubility, electrical charge

• Skip to slide 63

How is DNA different from RNA?

DNA vs. RNA

Three big differences1.The sugar in DNA is deoxyribose; in RNA

it is ribose

2. The nitrogenous base uracil (U) is used in RNA in place of Thymine (T)

3. RNA is single stranded, DNA is a double helix

In your own words explain the central dogma of gene

expression

Types of RNA

• mRNA: messenger RNA: carries the genetic code from the nucleus to the ribosome

• rRNA: ribosomal RNA: builds ribosomes

• tRNA: transfer RNA: carries amino acids to the synthesizing polypeptide

• The Three RNAs (mRNA, tRNA, and rRNA) all work together to turn the information in DNA into a beautiful, 3-dimestional protein!!!

• Why is it important to modify the primary RNA before leaving the nucleus?– the splicing process can create many

unique proteins

Translation

mRNA Protein

• mRNA(or messenger RNA) contains the instructions to make 1 protein.

• After the mRNA is made, it is trimmed

down to a final size, and shipped out of the nucleus!

• When the mRNA gets into the cytoplasm, it is made into protein.

TranslationInitiation: 

• small ribosome scans along mRNA strand and finds binding site. 

• LARGE ribosome’s come in, with APE sites.  First codon aligned at P site. 

• tRNA carries amino acid and attaches it to the start codon. 

Translation

Elongation:  • Amino acid on P site transfers to A site.  • The growing polypeptide chains moves

to P site, tRNA brings new amino acid to A site. 

• Empty TRNA is ejected from E site.  The polypeptide grows off of P site. 

Translation

Termination:  • Stop codon on a site-release factor

release polypeptide chain.  Separation of machinery.   

• Transcription and translation

http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a3.html

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

How do errors in DNA replication effect an organism?– Errors in DNA replication may lead to the production of

the wrong protein.

Why are proteins important?• Proteins serve various functions in the body. The

structure of a protein determines its function. – Example:

» Antibodies: specialized proteins that defend our body

» Enzymes: proteins that facilitate biochemical reactions.

• If my DNA makes a mistake, how will the protein behave?

– The protein will have a different shape, and without its shape, it cannot function properly

– Proteins are shape specific

Example: Sickle Cell Anemia

• 1 base pair change leads to 1 change in the amino acid.

• This leads a change in the structure of hemoglobin, a transport protein.

– Why is the shape of the red blood cell important?• Because of the mutation in

the hemoglobin, decreases the cells' flexibility and results in a risk of various complications.