a day 3/14/2013 1. writing prompts at end of the table in a pile! if it’s not there then it’s a...

A day 3/14/2013• 1. writing prompts at end of the table in a pile! If it’s

not there then it’s a zero• 2. Replication quiz 2- take this time to review your

notes. If there are SPECIFIC questions now is the time to ask.

• 3. Mutations• 4. RNA• 5. How DNA codes for proteins! Part 1.• 6. HW: go to the HW website and check it out! YOU

NEED THE INTERNET. YOU HAVE today, Friday Saturday & Sunday to find a functioning internet access. You will need to print also. So make that happen!

Any difference in the DNA sequence will result in a difference in the amino acid sequence in a protein.

MUTATION: which are defined as any change in DNA.

A. Mutations are not all bad! 1. Most have no noticeable affect2. Some are beneficial 3. Some are harmful.

B. Mutations can be triggered by1. Environmental factors that affect the

structure of DNA2. OR simply be mistakes that occur during DNA

replication3. OR during the formation of egg and sperm

cells

1. What would a mutation in a sperm/egg cell cause???-A genetic mutation that effects every

cell in the body.B. Types of mutations:

there are many types of mutations but here are 2 examples

1. POINT: occurs at a single nucleotide in DNA. This type of mutation affects only a small

section of DNA called a Codon.

2. FRAMESHIFT: caused by the insertion of an extra nucleotide or the deletion of a nucleotide.

a. This type of mutation affects the entire section of DNA after the mutation.

So… How does DNA determine your unique characteristics???

• DNA is the instructions for making proteins.• DNA determines the structure and function of the

protein molecules that carry out:– your cell functions– your cell structures.

• YOU ARE YOUR PROTEINS! –Physical traits that you have that are different

from those around you are different because the structure of your proteins is different.

• So how do we get from DNA to proteins? The first step involves the other nucleic acid- RNA…

Quick review of RNA from your WPIV. The Structure of RNA

A. RNA is made of a SINGLE strand of NUCLEOTIDES. Each of these is composed of:

1. NITROGENOUS BASE2. SUGAR (RIBOSE)3. PHOSPHATE

i. RNA also has 4 possible nitrogen bases BUT instead of thymine, RNA has a nitrogen base called URACIL.

B. Additionally, there are also different types of RNA which fold into different shapes and have different functions:1. MESSENGER (mRNA): is a complementary

copy of DNA that leaves the nucleus to direct the making of proteins.

2. TRANSFER (tRNA): specialized RNA molecule that carries amino acids which are used to make proteins.

3. RIBOSOMAL (rRNA): makes up parts of the ribosomes which are the sites of protein synthesis.

RNA’s role in taking the information in DNA to create a protein is to copy (transcribe) the information from DNA into mRNA

Now, you will think about this process using a guiding worksheet!

Let’s review what we discussed from the worksheet & add a few details

The 1st part of going from DNA to protein: an mRNA copy of DNA is made through TRANSCRIPTION in the nucleus. *This is done because DNA can not leave the nucleus.

A. Steps:1. The enzyme RNA POLYMERASE separates the

2 strands of DNA.2. RNA polymerase then uses ONE strand of

DNA as template and adds complementary base pairs (Uracil instead of thymine)

3. When the end of the gene is reached, mRNA breaks off the DNA and leaves the nucleus.

4. DNA twists back up by reconnecting their hydrogen bonds.

The following diagram shows the strands of DNA unwinding and RNA nucleotides being added…

This diagram just shows how the RNA strand breaks off

from the DNA template…

• HW: Transcription web HW

A Day! 3/18/2013

• Review the WEB HW- please have it out on the table.

• Watch the animation of transcription.• http://www.hhmi.org/biointeractive/dna/DN

Ai_transcription_vo2.html

• Once we have the mRNA the information must be “translated” from the “language” of nucleic acids to proteins.

• As a table, pair (a person from your table), or individual you will read through the worksheet and answer the questions.

• We will review this worksheet in 20 minutes.• Please be respectful of the class by remaining

focused and quiet (not silent) while we all work.• Think through the questions

A. As you know proteins are macromolecules that are composed of monomers called AMINO ACIDS.

1. There are 20 amino acids naturally occurring in living organisms.

2. Proteins are made by joining amino acids together into long chains.

3. The 20 amino acids can be joined together in any order and # so the possible number of different protein structures in virtually limitless.

4. The property of each protein is determined by the order in which different amino acids are joined together and THAT order is determined by DNA.a. If you change the order/# of amino acids

in the protein then its structure is changed. If its structure is changed then so is its function.

B. To get from DNA to protein, first the sequence of DNA nucleotides of one gene is transcribed into a sequence of mRNA nucleotides as we discussed above.1. The sequence of nucleotides in mRNA is the genetic

code. To determine the placement of amino acids in a protein, mRNA is “read” as a series of CODONS which is a set of 3 nucleotides.

2. Each codon specifies a singleamino acid that will be placed to form a protein.

http://www.hhmi.org/biointeractive/dna/DNAi_triplet_code.html

So the process basically works like this….

You can determine which amino acid is coded for by each codon by looking at the following table:

*Note: there is one codon (AUG) that is the start codon – this is present at the beginning of each gene that codes for a different protein. Also, there are 3 stop codons that do not code for any amino acid but signal the end of a gene.

Basic animation

• http://www.hhmi.org/biointeractive/dna/DNAi_translation_vo1.html

A. Translation begins when an mRNA molecule attaches to a RIBOSOME at the start codon.1. The ribosome moves along the strand of mRNA.

Start Codon

2. As each codon enters the ribosome a tRNA molecule, carrying the amino acid specified by the codon, binds to the mRNA.

a.Remember: tRNA carries a specific amino acid at one end. The other end of the molecule is sequence of 3 nucleotides called the ANTI-CODON or the complementary base pairs to the codon.

b.tRNA can only carry one specific amino acid.

Amino Acids

tRNA

Anticodon

*Thus the complementary base pairing of codon to anti-codon AND specificity of amino acids to particular tRNA is how the DNA instructions are followed & appropriate placement of the amino acids is accomplished creating the correct protein.

3. As each new tRNA moves into the ribosome and binds to its complementary codon, the amino acids they carry bond to one another forming the protein chain.

4. The process continues until a stop codon is reached.

5. The protein is then released from the ribosome.

This diagram shows a step by step of the beginning of translation…

1

2.

3.

4.

To make the process of translation faster and to make many copies of a protein, multiple ribosomes can move along mRNA

at once looking something like this…

Detailed animation

• http://www.hhmi.org/biointeractive/dna/DNAi_translation_vo2.html

Keep in mind…

• Genes don’t code for traits

• They code for proteins (or parts of proteins) that can affect traits

• i.e. they can code for a protein that makes eyes blue

1 Gene 1 Protein

• A gene gets transcribed into messenger RNA

• Messenger RNA is translated into a protein

Summary (Know this stuff)

• Transcription converts DNA code to mRNA– Occurs in nucleus

• Translation converts mRNA code into a protein– With help of tRNA in ribosome

• The structure and shape of the protein depends on the DNA sequence

• Differences in DNA determine differences in proteins = differences in physical traits.

BUT if ALL the DNA in our cells is EXACLY the same why aren’t all our cells identical???

– DIFFERENTIATION OF CELLS!– Each cell in our bodies is specialized for

the type of organ they are a part of (ex: heart)

– To be “different” and perform “different” roles “different” parts of the DNA are “turned on” and being expressed at any given time.

– Expressed gene is a gene that is being “read” for instructions on which protein to put together.

• HOMEWORK: It’s in the genes!• This worksheet will prepare you for

Wednesdays activity, Thursdays big quiz and could earn you some extra credit!