unit 6: dna/rna/protein synthesis€¦ · •translation: the process in which mrna is used as a...

UNIT 6: DNA/RNA/PROTEIN SYNTHESIS

TOPIC 1: DNA HISTORY & STRUCTURE

By the end of this topic , you should be able to…

• Identify the expe riments and s c ientis ts invo lv ed in the

dis cove ry of DNA

• Des c ribe the s truc ture of the DNA mole cule

REVIEW ☺

• Define monomer

• Define polymer

• What is the monomer of nucleic acids?

• Who discovered the structure of DNA and what is it’s structure?

REVIEW ☺

• Define monomer

• Building block (single unit)

• Define polymer

• Chain of repeating units

• What is the monomer of nucleic acids?

• Nucleotide

• Who discovered the structure of DNA and what is it’s structure?

• “Watson & Crick” – double helix

HISTORY OF DNA

HISTORY OF DNA

• Early scientists thought

protein was the cell’s

hereditary material because

it was more complex than

DNA

• Proteins were composed of

20 different amino acids in

long polypeptide chains

TRANSFORMATION

• Fred Griffith worked with virulent S and

nonvirulent R strain pneumonia bacteria

• He found that R strain could become

virulent when it took in DNA from heat-

killed S strain

• Study suggested that DNA is the cell’s

genetic material

GRIFFITH EXPERIMENT

HISTORY OF DNA

• Viruses are made of DNA

in a protein “coat”

• Experiments on viruses

by Hershey & Chase

supported the idea that

DNA was the cell’s

genetic materialRadioactive DNA was injected into bacteria!

BASICALLY…

• They us ed radioac tiv e marke rs on

pro te in and then DNA . The radioac tiv e

DNA was trans fe rred to the bac te ria ,

while the pro te in was not. The y

conc luded DNA is the he reditary

mate ria l of the ce ll.

DNA STRUCTURE

• Rosalind Franklin took

diffraction x-ray

photographs of DNA crystals

• 1950’s: Watson & Crick

used the x-ray diffraction

photo’s to come up with the

double helix model of DNA

ROSALIND FRANKLIN

WATSON AND CRICK

CHECK FOR UNDERSTANDING

Match the scientist with their contribution to the history of

DNA

Scientist

Franklin

Griffith

Watson

Crick

Hersey

Chase

Contribution

Built Model of DNA (Double Helix)

Worked with Bacteria, Confirmed DNA

was genetic information

Worked with viruses to confirm DNA is

genetic information

Took x-ray pictures od DNA

DNA STRUCTURE

THE BASICS

• DNA is a type of Nucleic Acid

• DNA: Deoxyribonucleic Acid

• Made of monomers called nucleotides

• Function: to store genetic information

DNA

• Two strands coiled called

a double helix

• Backbone made of a sugar

Deoxyribose bonded to

phosphate (PO4) groups

• Rungs made of nitrogen

bases bonded together by

weak hydrogen bonds

DNA DOUBLE HELIX

Nitrogenous

Base (A,T,G or C)

“Rungs of ladder”

“Legs of ladder”

Phosphate &

Sugar Backbone


Label a sugar,

phosphate and

base in the picture

to the right

DNA

•Double helix is formed by nucleotides linked to one another

•Nucleotide made of:

1. Phosphate group

2. 5-carbon sugar

3. Nitrogenous base

DNA NUCLEOTIDE

O=P-O

O

Phosphate

Group

NNitrogenous base

(A, G, C, or T)

CH2

O

C1C4

C3 C2

5

Sugar

(deoxyribose)

O

LABEL THE THREE PARTS OF THE NUCLEOTIDE IN YOUR NOTES

The process of specific

bases bonding together

to form the rungs of

the ladder is called

Complementary Base

Pairing

CHARGAFF’S RULE

• Adenine must pair with Thymine

• Guanine must pair with Cytosine

G CT A

DISCOVERY OF DNA STRUCTURE

• Erwin Chargaff showed the amounts of the four bases on DNA ( A,T,C,G)

• In a body or somatic cell:

A = 30.3%

T = 30.3%

G = 19.5%

C = 19.9%

QUESTION:

•If there is 30%

Adenine, how much

Cytosine is present?

ANSWER:

•There would be 20% Cytosine

•Adenine (30%) = Thymine (30%)

•Guanine (20%) = Cytosine (20%)

•Therefore, 60% A-T and 40% C-G

QUESTION

Write out the sequence of a strand complementary to

the following strand…

T T A G C A T G G

ANSWER

Original Strand: T T A G C A T G G

Complementary A A T C G T A C C

Strand:

LANGUAGE TARGET

• Match the scientist with their contribution

• Complete the DNA assignment

RECALL WARM-UP

• Draw and label a s ingle nuc leotide

• Prov ide the complementary bas e sequence for CAGGTA A CT.

• Prov ide a brie f description of the fo llowing s c ientis ts ’

achie v ements : Chargaff; Griffith; Wats on & Crick; Hers he y &

Chas e ; Franklin

• What makes up the backbone of DNA ?

• If a particular organis m contained 27% adenine , how much

guanine would be pre s ent?

• What bond ho lds the nitrogenous bas e s toge the r in a

mo lecule of DNA ?

TOPIC 2: DNA REPLICATION


• Identify the purpos e of DNA replication

• Identify and orde r the s teps invo lv ed in DNA

replication

• Explain the purpos e of mo le cule s (enzymes ) us ed in

DNA replication

DNA REPLICATION

REPLICATION FACTS

•DNA has to be copied before a cell divides•Why? Each daughter cell needs a complete genome

•DNA is copied during the S or synthesis phase of interphase

•New cells will need identical DNA strands

SYNTHESIS PHASE (S PHASE)

• S phase during

interphase of the cell

cycle

• Nucleus of eukaryotes

Mitosis-prophase

-metaphase

-anaphase

-telophase

G1 G2

Sphase

interphaseDNA replication takes

place in the S phase.

DNA REPLICATION

• Two strands open at origins forming

Y-shaped areas called a Replication

Fork (Y-shaped region)

• New strands grow at the forks

ReplicationFork

Parental DNA Molecule

3’

5’

3’

5’

LABEL THE REPLICATION FORK IN YOUR NOTES

STEPS OF DNA REPLICATION

1) Enzyme Helicaseunwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds


2) Primase gathers

nucleotides and brings

them into the

replication fork.

A “primer” is created to

start the new strand.


3) The enzyme DNA

Polymerase matches

free nucleotides with

the correct base pairs

on the template

(parent) strands.


4) The enzyme ligase connects any

“breaks” in the new strands and the

2 new strands rewind back together.

The Big Question: Why are there

“breaks” in the new strands at all?!

MAKING NEW DNA STRANDS

• The Leading Strand is built into the replication

fork

• The Lagging Strand is built in short sections in the

opposite direction (out of the fork)

• This causes the “breaks” in the strand.


• What enzyme is responsible for matching nucleotides to

the DNA strand?

• What enzyme is responsible for fixing any breaks in the

new DNA strand?

• Which strand can be continuously made? Which strand has

to be made in “chunks”?

• Label the DNA strand in your notes

DRAWING DNA REPLICATION

• Use the notes taken in class (the gray box) to

illustrate the process of DNA replication. You

need to show:

• The enzymes involved (helicase, ligase, primase, polymerase

• The original DNA molecule being unzipped

• The new DNA strands (lagging and leading) being built (be sure

to build in the correct direction)

• Nucleotides being dropped off at the replication fork (primase)

• Label all bases shown! Color code them as well

TOPIC 3: PROTEIN SYNTHESIS


• Des c ribe the diffe rence s be tween DNA and RNA

• Identify and orde r the s teps in prote in s ynthes is (trans c ription and

trans lation)

• Explain the purpos e of the mole cule s us ed in both trans c ription and

trans lation

• Use a codon chart to de te rmine a prote in sequence bas ed on an mRNA

code

• Compare and contras t gene and chromos omal mutations

WHAT CARRIES THE GENETIC MATERIAL OF THE CELL?

•DNA. However, why did early

scientists think that protein

carried this material?

• Compare the number of different

monomers protein has with the

number of monomers DNA (nucleic

acids) have.

SO WHAT ARE PROTEINS?

• Proteins are the “work-horses” of the cell…they do a lot of different jobs!

A) Antibodies – immune system (defense)

B) Structure – hair and nailsC) Speeding Up Reactions – enzymesD) Transport – hemoglobin (in blood)E) Movement – muscle

And the list goes on!

Question: Why do

these proteins all

have different shapes?

HOW DO OUR CELLS MAKE PROTEINS?

• DNA contains genes,

sections of nucleotide

chains

• Genes code for

polypeptides (proteins)

• Polypeptides are amino

acid chains

• DNA is found inside the nucleus, but proteins are made in ribosomes

• Predictions: So how do we get the message from DNA in the nucleus to the ribosomes?

THE SOLUTION?

• A molecule called RNA carries the message from the nucleus to the cytoplasm!

• Unlike DNA, RNA is small enough to fit through the poresin the nuclear membrane


• What organelle does DNA need to go to make a protein?

Where is that organelle located?

• Why does a copy of DNA need to be made?

• What is the copy of DNA called?

PUTTING IT TOGETHER

• DNA is responsible for controlling the production

of proteins in the cell, which is essential to life

• DNA→RNA→Proteins

• Chromosomes contain several thousand genes,

each with the directions to make one protein

• Do you remember the organelle where proteins are

produced?

WHERE ARE PROTEINS PRODUCED?

• Ribosomes!

• Ribosomes are where proteins are made

• Ribosomes are found in two places:

• – Free floating in the cytoplasm

• – Attached to Endoplasmic Reticulum (Rough ER)

• So…how does information needed to build the protein

get delivered from the DNA to the ribosomes???

• -With the help of RNA in a process called protein synthesis!

WHAT IS RNA?

• RNA stands for ribonucleic acid

• One subunit of RNA is a nucleotide

(just like DNA!)

• 1 - 5 carbon sugar (it’s ribose in RNA)

• 1 - phosphate group

• 1 – nitrogenous (N) base

• Three types of RNA

• mRNA, rRNA, tRNA

• First, we will look at mRNA!

A CLOSER LOOK AT RNA

• Looking at the mRNA to the right,

how is it different visually from

DNA?

• It is single stranded

• It is shorter and able to leave the nucleus

• The sugar is ribose

• There is a different base

• Uracil (U) takes the place of Thymine

(T)


• What is the RNA called that takes DNA’s mes s age to the

ribosome?

• What is the ribosome going to make with the mRNA?

• What nitrogenous base is different in RNA from DNA?

PROTEIN SYNTHESIS

• Protein synthesis is a two stage process

• Transcription and Translation

• In this process, a messenger molecule (mRNA)

carries instructions from DNA to ribosomes

• DNA cannot leave the nucleus; mRNA can!

• mRNA makes it possible for proteins to be assembled by

ribosomes outside of the nucleus

TRANSCRIPTION

• Transcription happens when DNA

is turned into mRNA

• This happens when proteins need

to be made in the cytoplasm!

• Since DNA cannot leave the

nucleus, it is transcribed into

RNA (DNA→RNA) • Transcribe: to copy (copy in the same

nucleic acid language, but only copy what

is needed)

HOW DOES IT HAPPEN?

• After an enzyme targets the portion of the DNA that should be

copied (initiation), the sections of DNA (genes) will

temporarily unwind to allow mRNA to transcribe (copy). This

will continue until an enzyme signals “the end”

• mRNA leaves the nucleus, travels into the cytoplasm and

attaches to a ribosome

• The “message” from DNA can now be translated to make a

protein

PROTEIN SYNTHESIS


• What does transcribe mean?

• What is the first step in transcription?

• 2nd step?

• 3rd step?

BASE PAIRS

• Transcribing DNA to mRNA is very easy if you remember these

complementary pairs!

• C (in RNA) will attach to a G (in DNA)

• G (in RNA) will attach to a C (in DNA)

• A (in RNA) will attach to a T (in DNA)

• U (in RNA) will attach to a A (in DNA)

Try it!

• A piece of DNA reads: T A G C A T T C C G A U

• transcribe to mRNA:___________________________

• 1 side of DNA reads: A A G C G T A T C C C G

• Transcribe to mRNA: ___________________________

PRACTICE

• I will know that you know transcription because you can

correctly transcribe DNA into mRNA

TRANSLATION

• Translation: the process in which mRNA is used as a blueprint to form chains of amino acids

(RNA→Protein) • Amino acids linked together form a protein

• Translate: To change a sentence from one language (nucleic acid)

to another (amino acid)

• Every 3 letters on an mRNA chain = codon

• Each codon (3 DNA letters) = 1 amino acid

READING A CODON CHART

• Given the mRNA,

we can read a

codon chart to

translated into the

amino acid it codes

for

• Remember, 1 word

in nucleic acid

language is a

codon (three

nucleotides)

Think about it: What amino acid is coded for?

AUG ____________________

GUC ____________________

GCC ____________________

CGA ____________________

UAA ____________________

TRANSLATION

• Occurs in a ribosome in

ALL cells

• This process uses all

three forms of RNA

(mRNA, rRNA, and

tRNA)

• DNA is not directly

used!


• What are 3 nucleotides in an mRNA strand called?

• What does a codon make in a ribosome?

• What base pairs with “A”? What base in RNA pairs with

“A”?

STEPS OF TRANSLATION

1.The mRNA leaves the nucleus and lands on a ribosome (rRNA)

STEPS, CONT

2. tRNA (with the correct anticodon) lands on the ribosome opposite a

codon on the mRNA

STEPS, CONT

3. The tRNA leaves the ribosome, but the amino acid that it coded for

stays on the ribosome to wait for next codon to be read

STEPS, CONT

4. The ribosome moves to the next codon bringing in another amino

acid to the growing protein chain.


• What are the 4 steps of translation?

AN AMINO ACID CHAIN

• The amino acid chain will ALWAYS begin with the “START codon”

• AUG

• The tRNA will continue to add amino acids until it reaches a “STOP

codon” (UAA, UAG, UGA)

• When it reaches a stop codon, then a complete protein has been

built! The protein unattaches itself from the ribosome.

Think about it: Label the diagram of translation to the right with the following

terms!

ribosome

mRNA

tRNA

codon

anticodon

amino acid chain

PRACTICE

• Given the strand of DNA below, what would it’s complementary

DNA strand read?

ATC

• Now, transcribe the DNA to mRNA ________

• What amino acid does the codon code for? (use codon chart)

____________________

• What would the anticodon on the tRNA read? _______

PRACTICE

• Given the strand of DNA below, what would it’s complementary

DNA strand read?

TGA

• Now, transcribe the DNA to mRNA ________

• What amino acid does the codon code for? (use codon chart)

____________________

• What would the anticodon on the tRNA read? _______


• Complete the worksheet on translation

• You will demonstrate that you know this by completing the

steps necessary to translate 1 strand of DNA into a protein

MUTATIONS

• Changes to DNA are called mutations

• change the DNA

• changes the mRNA

• may change protein

• may change trait

DNA TACGCACATTTACGTACG

mRNA AUGCGUGUAAAUGCAUGC

aa aa aa aa aa aa aaprotein

trait

2 MAIN TYPES OF MUTATIONS

1.) Chromosomal Mutations

- a mutation involving many genes

2.) Gene Mutations

- a mutation that involves a few

nucleotides

Chromosomal mutation

Gene mutation


• What is a mutation?

• What are two types of mutations?

WHAT ARE CHROMOSOMES?

Humans have 23 pairs of chromosomes, with one chromosome from each parent.

The chromosomes are coiled up DNA.

Under normal conditions all of the chromosomes are inherited in tact.

When will a mutation be passed onto offspring?When it is in an egg or

sperm cell

CHROMOSOMAL MUTATIONS

•Any change in the structure or

number of chromosomes

•Large scale: Affect many genes

5 TYPES:

1. Deletion

2. Duplication

3. Inversion

4. Translocation

5. NonDisjunction

CHROMOSOMAL MUTATIONS

•Most chromosomal mutations

are lethal

• If the fetus survives: Tend to

cause wide-spread abnormalities

•Example: Down Syndrome


• What are the 5 types of mutations?

• On a separate piece of paper write them down and explain

them.

ONTO GENE MUTATIONS!

GENE MUTATIONS

•Small scale: one geneis affected

•Any change to the DNA sequence of a gene:

Nucleotides/Bases may be added, missing, or changed

GENE MUTATIONS: 2 TYPES:

POINT MUTATION (SUBSTITUTION) FRAMESHIFT MUTATION

TYPES OF MUTATIONS

• Changes to the letters

(A,C,T,G bases) in the DNA

• point mutation

• change to ONE letter (base) in the DNA

• may (or may not) cause change to protein

• frameshift mutation

• addition of a new letter (base) in the DNA sequence

• deletion of a letter (base) in the DNA

• both of these shift the DNA so it changes how the codons are read

• big changes to protein!

CAUSES OF MUTATIONS

• spontaneous

• occur during DNA replication

• Caused by MUTAGENS

• physical, ex: radiation from UV rays, X-rays or extreme heat

• or chemical (molecules that misplace base pairs or disrupt the

helical shape of DNA).

GENE MUTATIONS

•KEY IDEA: A mutated gene will make a mutated protein

•Mutant proteins are trouble!

•They do not go where they are supposed to go

•They do not do what

they are supposed to do

http://www.youtube.com/watch?v=xBynH-oCfJM

TOPIC 4 – GENES AND TECHNOLOGY


• Prov ide examples of the prac tical us es of

bio techno logy, inc luding ins ulin produc tion and cloning

GENETIC ENGINEERING=MANIPULATING DNA

• With present technology and knowledge of DNA structure,

we can extract, identify, modify, copy, and transfer DNA

sequences!

Genetic engineering allows scientists to create desirable traits

within organisms to meet specific needs without relying on

natural mutations.

USES OF RECOMBINANT-DNA TECHNOLOGY

• Advances in medicine

• Transgenic animals and plants that provide health benefits

• Transgenic animals used as test subjects

• Insulin or Human Growth Hormone production by bacteria

• Human Genome Project & Gene Therapy

• Agriculture

• Genetically modified plants and animals (their cells don’t

accept foreign DNA very well so you must infect plant and

animal cells with bacteria containing recombinant plasmids)

• Personal identification• DNA fingerprinting

• Paternity testing

• Forensic science

• Cloning • When humans clone, they use a

single cell of an adult organism to grow a new genetically identical individual

• They Inserts the nuclei from the blastula stage (hallow ball of cells after several divisions of a zygote) of an embryo into an adult cell

Ex. Dolly the sheep

HUMAN GENOME PROJECT

• The goal was to determine the

sequence of nitrogen bases in

human DNA. An entire set of DNA

from a body cell is considered that

organism’s genome.

• There are 3 billion base

pairs in the human genome

and approximately 25,000

genes.

• National Institute of Health (NIH) is

striving to cut the cost of

sequencing an individual’s genome

to $1,000 or less. Having one’s

complete genome sequence will

make it easier to diagnose,

manage and treat many diseases.


• How is genetic engineering useful

to people? (4 ways)

• What is it called when scientists

use DNA to identify a person?

• What is a genome?

COMPLETE THE LANGUAGE TARGET IN NOTES

unit 6: dna/rna/protein synthesis€¦ · •translation: the process in which mrna is used as a...

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