UNIT 8 – DNA & PROTEIN SYNTHESIS

The summary color on the following slides is green and the underlined words are vocabulary and hyperlinks are in blue!

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FIND SOMEONE WHO Sketch a simple DNA helix

and then find someone who:

1. Knows the meaning of DNA.

2. Knows the meaning of helix.

3. Knows the four letter “code” of DNA.

4. Knows how the word “gene” relates to DNA.

KNOWLEDGE CHECK

How does the nucleus

of the cell relate to

chromosome, the

double helix, and

then finally, genes? Turn and talk to

your neighbor.

http://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/uniquely-me/sci-media/images/cell-chromosomes-and-dna/464336-1-eng-NZ/Cell-chromosomes-and-DNA.jpg

DNA – CELL REVIEW

Zooming into DNA

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WHAT IS DEOXYRIBONUCLEIC ACID? All cells have genetic

material known as DNA (deoxyribonucleic acid).

prokaryotes, the DNA is loose within the cell.

eukaryotes, it is held within the nucleus.

Regardless of where, DNA is carries the instructions for every part of an organism.

http://library.thinkquest.org/06aug/01942/plcells/thinkquest/nucleus.jpg

REVIEW: NUCLEOTIDES

Remember the fourth group of biomolecules, nucleic acids, which include DNA and RNA, are molecules that carry genetic information in a sequence of nucleotides.

Nucleotides contain: 1 sugar 1 phosphate group 1 nitrogenous base, of which there are four:

Adenine Thymine Cytosine Guanine

http://rachelkahn3b.edublogs.org/files/2011/11/3_16nucleotide-1u53hy2.jpg

NUCLEOTIDES CONT. The nitrogenous bases are grouped in to

two categories, purines [adenine and guanine] and pyrimidines [thymine and cytosine].

They follow base pairing rules from the research of Erwin Chargaff.

NUCLEOTIDE HANDS With a pen:

Write a “P” on your thumb “S” on your palm Write an “A” on your 1st

finger “G” = 2nd finger “C” = 3rd finger “T” = pinkie

Now repeat on the other hand; invert your hands match up your fingers to create a model of the double helix.

CHARGAFF’S RULES

The lines between the bases represent hydrogen bonds. Chargaff researched the

biochemical percentages within DNA.

The bases will always pair up and bond as below: G will bond with C A will bond with T

The “GCAT” Rule Curvy letters

together, straight letters together.

KNOWLEDGE CHECK

How does the diagram show the research of Chargaff and the base pairing rules? Where is the sugar and the phosphate in the structure?

Turn and talk.

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HELICAL DNA

DNA is a twisted helix. Alternating sugar molecules

and phosphate molecules in the backbone of the helix with the nitrogenous bases within the center of the “ladder”. This was confirmed by the Rosalind

Franklins x-rays showing a helical pattern in 1951.

James Watson and Francis Crick used the information from Franklin to construct a model of the double helix in 1953 and were awarded a Nobel Prize in 1962.

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The sequence of nucleotides differs between species and is arranged in a different order, but the structure is the same.

The closer the relationship between two organisms [EX lions, tigers, and your house cat], the more similar the sequence.]

HELIX CONT.http

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3’ VERSUS 5’ The

complementary strands of the helix run in opposite directions.

A 3’ [three prime] end and 5’ [five prime] one.

The 3’ carbon is attached to a –OH group; the 5’ is attached to a phosphate. http://upload.wikimedia.org/wikipedia/commons/

e/e4/DNA_chemical_structure.svg

Reconstruction of Crick

and Watson’s 1953molecular model of

DNA,using the original

components.

© Science Museum/Science

and Society Picture Library

THE MODEL THAT STARTED IT ALL

DNA STRUCTURE CHART

Backbone Center

Nucleotides

Sugar

Phosphate

Nitrogenous Base

aa

aX

XX

Discuss the components of the DNA helix by using checks and X’s. Complete the structure chart. Turn and talk to your neighbor.

DNA REPLICATION Remember that during the S

phase in interphase, DNA is replicated prior to cellular division in the nucleus.

Using the “G-CAT” rule, half a strand of DNA can easily create the complementary strand.

DNA replication is semi-conservative, meaning the daughter cells receive ½ of the original strand and ½ of the newly synthesized strand of DNA.

This was confirmed by the Meselson–Stahl experiment was an experiment by Meselson and Stahl in 1958.http://bio.usuhs.mil/dna_replication2.gif

STEPS TO REPLICATION1. The enzyme DNA helicase “unzips” the DNA molecule.

This creates a replication bubble, AKA a replication fork.

Replication occurs in the 5’ to 3’ direction.

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2. DNA polymerase travels down the strand, reading each base and using molecules made within the cell, builds the new strand.

Remember, A pairs with T, C pairs with G! The strand is built in pieces, called Okazaki fragments.

Each DNA molecule to go through replication has 1 “old”

strand and 1 “new”. Video 1 Video 2

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STEPS TO REPLICATION CONT.

http://test.classconnection.s3.amazonaws.com/763/flashcards/305763/png/bio_replication_bubbles.png

http://test.classconnection.s3.amazonaws.com/763/flashcards/305763/png/bio_replication_bubbles.png

3. Finally, DNA ligase connects the Okazaki fragments in the strand. Replication Animation

STEPS TO REPLICATION CONT.

https://wikispaces.psu.edu/download/attachments/54886630/DNA_replication_overview.jpg

KNOWLEDGE CHECK

How does the diagram

show the process of

DNA replication?

What enzymes are

involved? Turn and talk

to your neighbor. http://classes.midlandstech.edu/carterp/Courses/bio225/chap08/08-06_

Replication_1.jpg

THE CENTRAL DOGMA The Central Dogma of

biology states that genetic information within each cell flows from: DNA to RNA to Proteins With the help of

numerous enzymes, DNA information is translated into proteins.

https://cm.jefferson.edu/learn/dna_and_rna_files/central_dogma_of_molecular_biochemistry_with_enzymes.jpg

http://www.csun.edu/~cmalone/pdf360/Ch14-1gen%20code.pdf

WHAT ARE GENES? We know that DNA within cells is contained

within chromosomes in the nucleus. Sections of the DNA strand code for specific

information, called genes. These genes code for proteins.

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GENES CONT. Proteins (AKA polypeptides) are involved in many biological functions. EX fighting diseases

(antibodies) and speeding up chemical reactions in our body (enzymes).

Proteins also make up several structures in multicellular organisms like skin, hair, and muscles in animals, too.

http://www.virtualmedicalcentre.com/uploads/VMC/TreatmentImages/2437_dna_450_v2.jpg

DNA is held within the nucleus of eukaryotic cells; the message of DNA is carried in RNA.

RNA is single stranded, not double like DNA.

There are three types of RNA (mRNA, tRNA, and rRNA).

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FROM DNA TO RNA

RNA CONT. RNA is composed of nucleotides with:

sugar called ribose a phosphate group and 4 nitrogenous bases

Uracil replaces Thymine

Adenine Guanine Cytosine

http://i.livescience.com/images/i/000/053/587/i02/dna-rna-structure.jpg?1370549225

mRNA (messenger ribonucleic acid) carries a copy of the “message” to make proteins at the ribosomes (rRNA) of the cell.

mRNA is created in the nucleus in the process called transcription (or the process of copying genetic information from DNA into mRNA). Transcription happens in the

nucleus. http://www.tokyo-med.ac.jp/genet/mutation/nort.gif

TRANSCRIPTION

If the DNA code reads like this… ATC-GTA-CGC-AAT-TGC …Then the mRNA code reads like this… UAG-CAU-GCG-UUA-ACG The enzyme RNA polymerase separates two strands of

a DNA double helix and builds a strand of RNA using RNA nucleotides.

Remember, RNA coding: DNA: A T C G RNA: U A G C

“I wish I was adenine so I could pair with “U” “U a gansta child”

TRANSCRIPTION CONT.

Translation occurs when the cell uses the genetic information in mRNA to build proteins. The mRNA carries the

“code” (or instructions) to the ribosome [organelle in the cell which builds proteins];

Ribosome is made of ribosomal RNA (rRNA).

TRANSLATION – STEP 1 (THE RIBOSOME)

"Protein Synthesis." Science Online. Facts On File, Inc. Web. 18 Nov. 2013. 

The ribosome reads mRNA three bases at a time.

Three nitrogen bases (called a codon or a triplet; EX “AUG”) code for a specific amino acid; amino acids make up proteins. There is only one “start” codon (AUG) that

can begin the process [the amino acid, methionine].

UAA, UAG and UGA are 3 stop codons and signal the ribosome that the protein is complete.

TRANSLATION – STEP 2 (CODONS)

"Protein Synthesis." Science Online. Facts On File, Inc. Web. 18 Nov. 2013. 

Based on the mRNA code, transfer RNA(tRNA) carries amino acids to the ribosome. It is a single strand

of RNA that loops back on itself. On one end, a

three letter anticodon that matches the mRNA

The other end, an amino acid

TRANSLATION – STEP 3 (TRANSFER RNA)

"Elongation of Translation." Science Online. Facts On File, Inc. Web. 18 Nov. 2013. 

During elongation, tRNA adds amino acids to the A [attachment]

site peptide bonds link those amino acids together mRNA slides through the ribosome to complete

to the growing protein until a stop codon is read.

TRANSLATION – STEP 4 (ELONGATION)

"Messenger RNA Translation." Science Online. Facts On File, Inc. Web. 18 Nov. 2013.

ANIMATED PROTEIN SYNTHESIS

COPY THE FOLLOWING DIAGRAM Complete the missing sections [shown with

question marks]. Turn and talk to your neighbor.

DNA mRNA Protein? ?

?

?

Nucleus

DNA mRNA Protein

Ribosome

Transcription

Translation

KNOWLEDGE CHECK The diagram shows a visual of the central

dogma; the process of creating proteins from the DNA code.

HISTORY OF AMINO ACIDS The link between amino acids and

proteins was first identified by the French chemist Louis-Nicolas Vauquelin [born in 1753] .

He identified the first amino acid in 1806, asparagine, from asparagus.

Over the next 100+ years, numerous scientists [chemists, biochemists, nutritionists] indentified the 20 amino acids on earth and studied the importance of amino acids to protein production and overall health. William Hyde Wollaston [1812] Henri Braconnot [1820] Sven Hedin [1895] Albrecht Kossel [1896] Edmund Dreschel [1899] Emil Fischer [1899] Frederick Gowland Hopkins [1901] Thomas B. Osborne and Lafayette B. Mendel

[1909] William Rose [1935]

http://media-2.web.britannica.com/eb-media/97/4897-004-98BB6704.jpg

HISTORY OF CODONS Researchers began to see the connection between the

mRNA code and each amino acid. In 1961, Francis Crick concluded that three nucleotide

bases on mRNA [a codon] code for a specific amino acid.

At the same time, Marshall W. Nirenberg and Heinrich Matthei created synthetic mRNA and identified the codon for phenylalanine (UUU), among others.

Nirenberg, Robert W. Holley, and Har G. Khorana were awarded a Nobel Prize for Physiology and Medicine in 1968 for codons and their “interpretation of the genetic code and its function in protein synthesis”.

The Nobel Prize in Physiology or Medicine 1968". Nobelprize.org. Nobel Media AB 2013. Web. 19 Nov 2013. 

READING AN AMINO ACID CHART An amino

acid chart helps to translate codons.

There are various types of charts.

Practice: GGA codes for….?

http://bioephemera.com/wp-content/uploads/2007/03/image003.jpg

First Letter

Second Letter

Third LetterU C A G

U

phenylalanine serine tyrosine cysteine U

phenylalanine serine tyrosine cysteine C

leucine serine stop stop A

leucine serine stoptryptopha

n G

C

leucine proline histidine arginine U

leucine proline histidine arginine C

leucine proline glutamine arginine A

leucine proline glutamine arginine G

A

isoleucinethreonin

e asparagine serine U

isoleucinethreonin

e asparagine serine C

isoleucinethreonin

e lysine arginine A

methioninethreonin

e lysine arginine G

G

valine alanine aspartate glycine U

valine alanine aspartate glycine C

valine alanine glutamate glycine A

valine alanine glutamate glycine G

"Genetic Code." Science Online. Facts On File, Inc. Web. 19 Nov. 2013. 

http://scienceofknowing.files.wordpress.com/2012/12/codon-chart.jpg?w=408

http://www.magrinscience.com/wp-content/uploads/2013/02/codon-chart.png

KNOWLEDGE CHECK

What determines the

sequence of amino acids in

the protein shown here?

Discuss the role of the mRNA

codon and tRNA anticodon in

your answer. Turn and talk to you neighbor.

http://upload.wikimedia.org/wikipedia/commons/thumb/3/38/Protein_primary_structure.svg/447px-Protein_primary_structure.svg.png

"Transcription and the Genetic Code." Science Online. Facts On File, Inc. Web. 19 Nov. 2013.

GENE EXPRESSION Multicellular organisms need a variety of cell

types to perform specific functions for the organism; therefore, individual cells differentiate and become specialized in structure and function. Differentiation happens due to selective

gene expression – some genes are turned off, some are turned on.

Internal and external environments can influence gene expression. EX hormones, sex EX temperature, nutrition

The arctic fox only has white fur during the

winter months, they have brown

fur during warmer

temperatures. This change in fur color is an

example of controlled gene

expression.Image

GENE EXPRESSION EXAMPLE