Download Microbiology bio 123

Module C-4
Genetics
All living things use DNA as their genetic material.
What does DNA do? They determine what enzymes an organism can make.
Phenotype – Characteristics that show, human (hair color, height, shoe size, etc.), Bacteria (what do the colonies
look like, shiny or dull, smooth edge or wavy, etc.), bacterium (rod or sphere or spirillium), can very with
environmental conditions. Phenotype is the result, or expression of the genotype.
Genotype – Actual genetic material that is their, whether it is displayed or not. (two brown eyed persons having
a blue eye child.), will not change with environment.
Genome – An organisms genetic information, in general.
Anabolism – putting together proteins, lipids, nucleic acids. Requires energy and Ligases.
DNA synthesis:
1. polymer – a very large molecule that is made up of the same kind of molecules.
2. Nucleotides – a nucleotide is a monomer that is put together to make the polymer.
1. Sugar – five carbon sugar, deoxyribose sugar
2. Phosphate – PO4
3. N Base
1. A – Adenine
2. T – Thymine
3. G – Guanine
4. C – Cytosine
4. Connected together by attaching a phosphate to a sugar, then to a phosphate and a sugar, each base is
attached to the sugar.
3. Double stranded – has two strands that complement each other. Base to base, held together by Hbonding.
4. Bases must bond to a set compliment.
1. A with T
2. G with C
5. In Eukaryotes, the DNA is separated into Chromosomes.
6. Base pairs – how long a DNA strand is, human is about 3,000,000,000 base pairs.
7. Bases of the DNA are anti-parallel – they have the five prime ends on the opposite sides.
8. Five prime end – the phosphate end of the DNA
9. Three prime end – the sugar end of the DNA
Complementary – the matching of the two pairs of bases, A-T and G-C
Cytosine has a single 8 point sugar
Guanine has an 8 point sugar bound to a 5 point sugar
Thymine has a single 8 point sugar
Adenine has as 8 point sugar bound to a 5 point sugar
T-A has a double H bond
G-C has a triple H bond
RNA
1. Two main differences between RNA and DNA
1. Uracil substitutes for Thymine,
2. Single stranded,
2. There are more than one kind of RNA, their structure is the same but their function is not.
3. Sugar base is different, still a five carbon sugar, but without the oxygen.
DNA Replication
1.
2.
3.
4.
DNA will replicate with cell division, for tissue growth, repair and for gamete production.
Is called semi-conservative because it reuses one half of the old strand for each new strand that is made.
Can only be made from the 5 prime end to the 3 prime end.
On the 3 prime end, the DNA strand is made in segments that are made from the 5 prime end to the 3
prime end.
5. The segment that are made are called Okasaki fragments.
Stages of DNA Replication
1. DNA double strands must be taken apart, or unzipped.
2. DNA is unzipped by an enzyme from the endonuclease family
3. nucleotides from the cytoplasm are used by a DNA polymerase enzyme and are attached to the unzipped
DNA strands.
4. DNA is put back together with Ligase enzymes.
Bacterial DNA replication
1.
2.
3.
4.
5.
6.
Bacteria have circular DNA
Endonuclease (restriction enzymes) enzymes snips the DNA apart.
DNA is unzipped and begins to form another circle.
As the DNA is unzipped the polymerase enzymes begin to make two more strands.
Results in two circular DNA strands being made.
Can also be replicated without snipping the DNA, just unzipping the DNA strands from each other,
therefore making two new strands.
Protein Synthesis
1.
2.
3.
4.
Is determined by the DNA,
the segment that is unwound to make a protein is called a gene.
There are to strands of DNA, a sense strand and an anti-sense strand.
The anti-sense strand is used to manufacture the RNA.
5. The RNA that is manufactured is called messenger RNA (mRNA).
6.
Protein Production,
1.
2.
3.
4.
5.
6.
7.
8.
9.
a specific gene is selected,
A endonuclease unzips the gene DNA,
A Ligases copies the anti-sense strand of DNA and manufactures mRNA,
mRNA leaves the DNA and goes to the Ribosomes, where it attaches between the little circle and bigger
circle of the Ribosome.
We use a source of Amino Acids (cytoplasm) (there are 20 of them) which is chosen by triplets from the
mRNA.
tRNA is used to gather the appropriate amino acid, it uses the anti-codon to gather the appropriate amino
acid.
The amino acids are put together with dehydration synthesis, they form a peptide bond which releases a
molecule of H2O when it is synthesized.
More than 1 Ribosome can use the same mRNA at the same time.
Terminator Codon, if the terminator Codon is misplaced and is somewhere in the middle of the mRNA,
the protein will be deficient in necessary amino acids.
Codon – triplets of m and tRNA outside of the nucleus.
Triplets – chains of three bases in the Nucleus. Sometimes there are more the one triplet for the same amino acid.
Transcription – when DNA is used to make mRNA
Translation – when mRNA is used to make protein
DNA→mRNA→protein
There are 20 different amino acids.
The control mechanism was first discovered in E. coli, and is called operons in bacterial cells.
Operons – a group of genes that are a unit of genes that are the control mechanism, consist of at least two genes,
the operator and repressor genes.
Mutations:
1.
2.
3.
4.
5.
6.
Simply a change in the DNA
They are inheritable.
They change the proteins that are made by the cell.
Mutations are not always harmful, most are neutral, some are beneficial, many are harmful.
Mutations occur naturally, but can also occur because of the environment.
Two major classes of mutations,
1. Point/base substitutions,
1. Occurs because of the change of one base in a codon,
1. AGT-CAG-CTA vs. ATT-CAG-CTA
2. Typically occurs when DNA replication occurs,
3. May or may not code for a different amino acid.
4. Many times the change makes no difference to the cell. On occasion, it is fatal.
2. Frame shift mutations,
1. Shifting, addition, or subtraction of one or several nucleotides which shifts the reading frame.
1. AGT-CAG-CTA vs. AGT-TCA-GCT-A, or
2. AGT-CAG-CTA vs. AGT-AGC-TA, or
3. AGT-CAG-CTA vs AGT-AGT-AGT-CAG-CTA
2. If it occurs close to the beginning, it is more serious than if it occurs closer to the end.
3. Typically these mutations are fatal to the cell.
4. When there is the addition of a complete codon, there is less possibility of it being fatal.
Mutagen – Anything that causes, or increases the rate of mutation. Most are also carcinogens.
1. Chemicals,
1. Pesticides,
2. Herbicides,
3. etc.
2. Transposons,
1. Jumping genes,
1. Indian corn,
2. Sweet corn,
3. Radiation,
1. X-rays,
2. Ultraviolet light,
Auxotroph – a nutritional mutant that is used in research. A mutant that is manufactured for use in laboratories.
They are engineered to be dependent upon a certain growth hormone, making it ineffectual in the real world.
Recombination – the new mixing of genes,
1. Natural genetic recombination,
1. Confugation,
1. Uses pilli to form a conjugation tube and allows plasmids to transfer DNA across he cell wall into
the second cell. Plasmids are where the resistance factors are usually stored in bacteria, thus the
quickness of bacteria to gain immunity to
2. Transduction,
1. Always involves a virus, bacteriophage, which infects the cell and modifies the bacteria's cell.
2. When the virus duplicates, it will sometimes take a particle of the host cells DNA with it, bring it
into the next cell.
3. Transformation,
1. When a cell dies, the cell wall begins to fall apart, living cells will pick up the pieces of the dead
cell's DNA, and therefore pick up new genetic material.
Recombinant DNA technology, major practical applications,
1. Safer vaccines,
2. Better diagnosis, by using DNA complementarity (sometimes bacteria),
3. Gene therapy,
1. E. coli makes human insulin,
2. clotting factors,
3. human growth hormone,
4. The most important and useful is the restriction endonucleases.