chapter 13 by mrs. pires
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Proteins. Protein Synthesis. Chapter 13 By Mrs. Pires. Some background information…. Making Proteins. The human body is basically a bunch of proteins working together in a huge chemical reaction. DNA holds all the information (recipe) to make all the proteins in the body. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 13By Mrs. Pires
Proteins
The human body is basically a bunch of proteins working together in a huge chemical reaction.
DNA holds all the information (recipe) to make all the proteins in the body.
The DNA is located in the nucleus but the protein factory is the ribosome.
The DNA is too big and has too many responsibilities to leave the nucleus and go to the ribosomes to drop off a protein recipe.
DNA needs the help of a messenger!
Some background information….
The messenger RNA (mRNA) is like a disposable piece of DNA.
mRNA is assembled inside the nucleus from individual sugars, phosphates and bases that are floating around.
These pieces are put together in a specific order by copying a complimentary sequence of the DNA (which holds the protein recipe needed).
This is called transcription.
Some more background information….
After the protein recipe is copied down by the mRNA, the messenger RNA leaves the nucleus and heads to the ribosome’s protein-making factory.
Proteins are made in a process called Translation.
Characteristic DNA RNA
Shape Double helix Single helix
Location In Nucleus
In Nucleolus, cytoplasm, or ribosome
Sugar Deoxyribose Ribose
Types 1 type 3 types
BasesAdenine, Thymine,
Guanine, CytosineAdenine, Uracil,
Guanine, Cytosine
TYPEMessenger RNA
(mRNA)Transfer RNA
(tRNA)Ribosomal RNA
(rRNA)
Location nucleoluscytoplasm &
ribosome ribosome
Function
Copies the protein
recipe from the DNA strand
rewrites the recipe from the mRNA
into a language the ribosome will understand
part of ribosome structure
Shape Single helix
Cloverleaf, “hairpin”, inverted
“L” shape Globular shape
mRNA: tRNA:rRNA:
Every 3 bases in the DNA (and mRNA) is called a codon.
Every codon codes for one amino acid.
Amino acids link together to form protein like beads on a string.
There are 23 basic amino acids in the body.
DNA CODONSRNA CODONS
An enzyme called RNA polymerase unwinds a section of DNA to be copied.
One strand of the DNA double helix is used as a template (The template strand is also called the antisense strand)
RNA polymerase binds to the “start codon” (promoter) at the beginning of a desired recipe on the DNA strand.
The START (promoter) codon is TAC on the DNA strand.
The mRNA strand copies the
codons from the DNA using complementary base pairing until it gets to:
One of the STOP codons (ACT, ATT, or ATC).
These are also called repressors or terminator sequences.
The stretch of DNA that is transcribed into an RNA molecule is called a transcription unit.
TAC is the start codon
ACT, ATT, & ATC are the STOP codons
dna ATG CCG GTA CTT TCC CGT TAA
dna TAC GGC CAT GAA AGG GCA ATT
mRNA
tRNA
Amino acid sequence
This completed mRNA migrates from the nucleus to the cytoplasm and heads to the ribosome.
The strand of mRNA is called the codon sequence (codon language).
http://youtube.com/watch?v=OtYz_3rkvPk&feature=related
The mRNA gives the recipe to the ribosome to produce the protein. However, there is a problem.
The ribosome does not understand the codon language that the recipe is written in.
Never fear…help is on the way in the form of Transfer RNA!
tRNA
Transfer RNA (tRNA) is able to translate the codon language to the anticodon language so the ribosome can read it.
The ribosome binds to the mRNA at the start codon (AUG) that is recognized only by the initiator tRNA.
mRNA
The mRNA rolls between the two units on the ribosome.
< AUG
In this process, each set of 3 mRNA bases (the mRNA base triplet is called a codon) will pair with a complimentary tRNA base triplet (3 bases) called an anticodon.
http://biology.kenyon.edu/slonc/bio3/ribo/ribo1.html
http://www.sciencenetlinks.com/interactives/protein.html
http://www.youtube.com/watch?v=XuUpnAz5y1g&feature=related
Each tRNA is specific to an amino acid. As tRNA's are added to the sequence, the amino
acids begin to link together by peptide bonds as it grows.
The amino acid (peptide chain) will continue to grow until it reaches the stop codon on the mRNA.
Since there is no stop anticodon (tRNA) to match the stop codon, the ribosomal complex falls apart.
The amino acid chain, now called a protein chain, is release into the cell.
www.wiley.com/legacy/college/boyer/0470003790/structure/tRNA/trna_intro.htm
1. Type in the link below:
2. Scroll down to page 2 where you will find the diagram below.
3. Click on “protein synthesis animation” under the diagram online.
4. Go through the Overview and Basic tutorials.
5. Complete the first two interactive activities dealing with the mRNA/amino
acid chart. Put your answers on the back of this paper.
DNA CAT TAT
mRNA CUC UAA
tRNA UAC GAU CUA
a.a. TRY
DNA: TAC GGA TCT GTA CTT ACG ACT mRNA: ___ ____ ___ ____ ___ ____ ___ tRNA: ___ ____ ___ ____ ___ ____ ___ a.a.: ___-____ -___ -____-____-____-___
* Remember: the chart is based on mRNA.
DO NOW!
Are heritable changes in genetic information
Two types: 1. Gene mutations (a.k.a. Point
mutations)2. Chromosomal Mutations
http://www.pbs.org/wgbh/nova/genome/media/2809_q056_13.html
Include: 1. Substitutions (one base is changed
into another)
2. Insertion results in a frameshift3. Deletion
This type of mutation is called a frameshift. Frame 1: AAU GCG GAC UAA --- asparagine ---- alanine ---- aspartate ---- stop Frame 2: A AUG CGG ACU AA ---methionine ---- arginine --- threonine--- Frame 3: AA UGC GGA CUA A
Four main types:◦ Deletion◦ Duplication◦ Inversion◦ Translocation
Lets take a look---------------------
Some or all of the genes on a chromosome become reversed.
THE CAT ATE THE FAT RAT could become….
THE TAC ETA EHT TAF RAT
Some or all of the genes on a chromosome are deleted.
THE CAT ATE THE FAT RAT could become….
THE CAT RAT
Some or all of the genes on a chromosome are doubled.
THE CAT ATE THE FAT RAT could become….
THE CAT CAT ATE THE FAT FAT RAT
Some or all of the genes on two different chromosomes either switch places like this:
1)THE CAT ATE THE FAT RAT2)THE RAT ATE THE HAT could become….
1) THE RAT ATE THE HAT RAT
2) THE CAT ATE THE FAT
or some genes from one chromosome transfer to another like this:
1) THE CAT ATE THE FAT RAT2) THE RAT ATE THE HAT could become….
1) THE CAT ATE THE…2) THE RAT ATE THE HAT FAT RAT
Brac 1: http://www.youtube.com/watch?v=4bGkUQBw1Rs
Sickle Cell and Malaria: http://www.pbs.org/wgbh/evolution/library/
01/2/l_012_02.html
Gene A
DNA: ACC GGT TAT
mRNA:
tRNA:
A.A sequ:
Trait:In this lab, the chart is basd on tRNA not mRNA
Gene A Gene B
DNA ACC GGT TAT DNA AGC CGA
mRNA mRNA
tRNA tRNA
a.a sequ. a.a sequ.
Trait Trait
Gene C Gene D
DNA TTT AAC DNA GGA CGC CGA
mRNA mRNA
tRNA tRNA
a.a sequ. a.a sequ.
Trait Trait
Gene E Gene F
DNA GGG AGG AAA CCC DNA ATC ATC CTA
mRNA mRNA
tRNA tRNA
a.a sequ. a.a sequ.
Trait Trait
Gene G Gene H
DNA DNA
mRNA mRNA
tRNA tRNA
a.a sequ. a.a sequ.
Trait Trait
DNA: TAC GGA TCT GTA CTT ACG ACT mRNA: ___ ____ ___ ____ ___ ____ ___ tRNA: ___ ____ ___ ____ ___ ____ ___ a.a.: ___-____ -___ -____-____-____-___
* Remember: the chart is based on mRNA.
DO NOW!
http://science.discovery.com/videos/creating-synthetic-life/