genetics dna to the complexity of life genetics dna to the complexity of life
TRANSCRIPT
Genetics DNA to the Complexity of Life
I understand you claim that through adaptation, things evolve? but where in this processes of evolution do u think eyes began to form...
If it came about through evolution... should not their be organisms of lesser substance like bacteria have something near the representation of eyes...?
To suppose that the eye with all its inimitable contrivances ◦for adjusting the focus to different distances, ◦for admitting different amounts of light, and ◦for the correction of Spherical and chromatic
aberration…
…Could have been formed by natural selection, seems, I freely confess, absurd in the highest degree.
When it was first said that the sun stood still and the world turned round, the common sense of mankind declared the doctrine false!
Yet the old saying of Vox populi, vox Dei
"the voice of the people equal the voice of God”
• as every philosopher knows, cannot be trusted in science.
Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certain the case;
If further, the eye ever varies and the variations be inherited, as is likewise certainly the case; and if such variations should be useful to any animal under changing conditions of life
Then the difficulty of believing that a perfect and complex eye could be formed by natural selection, should not be considered as subversive of the theory."
How is it possible that this complex eye developed??????
We begin with DNA
Let us recap!
In prokaryotes (cells without a nucleus) DNA is located in the cytoplasm as a circular plasmid.
In eukaryotes (cells which have a nucleus), the DNA is stored inside this organelle (nucleus).
Where can the DNA be found?
When we unwind the chromosome supercoils found in the nucleus we
get a very long DNA chain
Let us look at an Object Scale(Click Picture for Web-link)
All 46 Chromosomes under Electron Microscope
Human Chromosomes
Chromosomes are only be seen in this x-like shape just before cell division.
Chromosomes are counted in pair of descending order
They are made up of two chromatid connected at the centre called the centromere
So how long is DNA really???
Its full length, the DNA molecule in a human chromosome would be between 1.7 and 8.5 centimeters long, depending on the chromosome
DNA - Structure
The backbone of DNA is made up of two molecules
1. Deoxyribose sugar2. Phosphate group
The Phosphate group is made of Phosphorus
and OxygenThis phosphate group can be drawn as an ion or with hydrogen atoms attached
Glucose Fructose Sucrose
So what is a deoxyribose (The D in DNA)?
It is a sugar!
simple sugars examples!
Glucose Sugar
Remember Glucose????
Glucose
Glucose Vs Ribose
Glucose has 6 carbon, Ribose has 5
Thus missing a OHCH
Deoxyribose Vs Ribose
Deoxyribose is missing the Oxygen at 2 prime
(Deoxy means “missing oxygen”)
The phosphate molecule and the deoxyribose sugar bind together to form the backbone of DNA
Before bonding together the phosphate starts as triphosphates
DNA - Backbone
Replace a phosphate group with the OH at 5
primeOH
Here is a single DNA backbone
Purines
PyrimidinesDNA - Bases
Another group of molecules
attach to Backbone
These are called Bases!
There are two groups
replace a base with OH at 1 prime
OH
DNA - Nucleotide
Nucleotides are molecules when the DNA backbone is
joined together with a Base,
DNA - Nucleotide
The nucleotides
build on top of each others
form bottom to top on the left
side and reverse on the
right side creating a
double stand DNA
DNA – Double Strand
Purines are attracted to the pyrmidines by forming hydrogen bonds
Adenine always matches up with thymine
cytosine always matches up with guanine.
Why is DNA a double helix???
The Hydrogen Bonding of the base pairs for stability.
As the base pair are built they contribute to the twisting shape.
Overview of DNA
Homework Textbook
Section 5.3 DNA and GenesRead pages 99 to 101
Complete the Over to you page 103
Questions 1 to 6 and 8
Protein SynthesisFrom DNA to Proteins
DNA is used for making messenger RNA (mRNA)
mRNA is used for making Proteins
DNA RNA Protein
DNA Transcription
From DNA to RNA
Transcription is the process of creating a complementary RNA copy of a sequence of DNA.
What is RNA?
Remember Deoxyribose Vs Ribose
Deoxyribose is missing the Oxygen at 2 prime
Instead of a Deoxyribose making the backbone, Ribose is used in RNA backbone
A number of enzymes are needed to bind with the DNA before
transcription can take place.
During transcription, a DNA sequence is read by
RNA polymerase
After the DNA is unwound, the polymerase molecule copies the DNA into RNA (in blue)
Transcription results in an RNA complement that includes uracil (U) in all instances where thymine (T) would have occurred in a DNA complement.
The newly synthesised RNA can now travel through the nuclear pore and into the Endoplasmic reticulum
It is in the endoplasmic reticulum that the messenger RNA gets translated into a protein process of TRANSLATION
Just as a book in a foreign language has to be translated to make sense, so does the mRNA
Want to see the DNA Transcription Animation?
Click Here
RNA Translation
From RNA to Proteins
The endoplasmic reticulum has these protein complexes, the many little orange dots, called Ribosomes, where mRNA gets translated into a protein.
3D protein model of ribosomes
mRNA binds to one part of the ribosome
The translation takes place by “reading” mRNA
three bases at a time.
Every three bases is called a CODON
The ribosome catalyses the peptide bond formation between the amino acids which are
carried by the transfer RNAs.
A U G G G C U U A A A G C A G U G C A C G U U
This is a molecule of messenger RNA.
It was made in the nucleus by transcription from a DNA molecule.
mRNA molecule
codon
A U G G G C U U A A A G C A G U G C A C G U U
A ribosome on the rough endoplasmic reticulum attaches
to the mRNA molecule.
ribosome
A U G G G C U U A A A G C A G U G C A C G U U
It brings an amino acid to the first three bases (codon) on the mRNA.
Amino acid
tRNA molecule
anticodon
U A C
A transfer RNA molecule arrives.
The three unpaired bases (anticodon) on the tRNA link up with the codon.
A U G G G C U U A A A G C A G U G C A C G U U
Another tRNA molecule comes into place, bringing a second amino acid.
U A C C C G
Its anticodon links up with the second codon on the mRNA.
A U G G G C U U A A A G C A G U G C A C G U U
A peptide bond forms between the two amino acids.
Peptide bond
C C G U A C
A U G G G C U U A A A G C A G U G C A C G U U
The first tRNA molecule releases its amino acid and moves off into the cytoplasm.
C C G U
A C
A U G G G C U U A A A G C A G U G C A C G U U C C G
The ribosome moves along the mRNA to the next codon.
A U G G G C U U A A A G C A G U G C A C G U U
Another tRNA molecule brings the next amino acid into place.
C C G
A A U
A U G G G C U U A A A G C A G U G C A C G U U
A peptide bond joins the second and third amino acids to form a polypeptide chain.
C C G C C G
A U G G G C U U A A A G C A G U G C A C G U U
The polypeptide chain gets longer.
G U C
A C G
The process continues.
This continues until a termination (stop) codon is reached.
The polypeptide is then complete.
Want to see the RNA translation Animation?
CLICK HERE
PROTEINS
Amino Acids Chains to Protein
Transporter protein molecule that regulators things going in and out of the cell
All Different kinds of shapes of protein
See the thing in the middle? Heme allow red blood cells
carry the oxygen
Lets Rotate it abit!
Remember the RNA polymerase?
The thing that copies the DNA into mRNA?
They are proteins too!
Remember what this process is called?
Transcription!
Remember the Ribosomes what did they do again?
They build animo acids into proteins
They themselves are made of proteins too!
You can see all the helix, folds and loops
The 20 amino acids are combined in different ways to make up the 100,000 or so different proteins in the human body.
Protein chains can be short or long.
Insulin is built from 51 amino acids and is one of the smallest proteins in the body.
Titin is the largest known protein uses in muscle fibres; Its human variant consists of 34,350 amino acids
Proteins can be found… in solutions in the bloodother fluids of the body (eg. saliva)in solid form as the framework of tissue, bone and hair. etc
Functions IncludeRegulatory: eg. enzymes, hormonesStructural: eg. keratin, collagenTransport: eg. HaemoglobinDestruction: eg. Toxins, Poison, AntibodiesSignalling: eg NTs
Scientists suggests that they make up about 75% of the dry weight of our bodies.
DNA Replication
DNA to MORE DNA
Just as DNA is copied into RNA, DNA also needs to be copied for cell division.
This ensures that the both cells have the same genetic information.
DNA - Replication
DNA replication occurs during Cell Division
There are two types
MitosisParent with 46 chromosomes split
into two daughter cells each with 46 chromosomes
MeiosisParent with 46 chromosomes split into two daughter cells called each
with only 23 chromosomes
Meiosis only occurs in Reproductive Cells
Egg and Sperm are sex cell we called Gametes
When the Egg and Sperm combine they create what we call a Zygote.
Though a Zygote can undergo mitosis like all cells, only it can undergo
meiosis for reproduction.
No other cells can undergo Meiosis!
Homework Textbook
Section 5.2Read pages 96 and 97Copy the mitosis and meiosis diagram (p96)
Complete the Over to you page 98
Questions ALL