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Unit 2: Molecular Genetics - Coggle Diagram
Unit 2: Molecular Genetics
DNA Replication
Stage of DNA replication
Initiation
Elongation
Termination
Proofreading and Correction
Molecular Genetics
Nucleic Acids
Both DNA and RNA have a combination of 4 different nucleotides and that each nucleotide is composed of a five-carbon sugar, a phosphate group and one of four nitrogen-containing (nitrogenous) bases.
The bases found in DNA are A/T/C/G. In RNA the base U is found instead of T.
Structure of a nucleotide
A Pentose sugar. This is a 5 carbon sugar
The sugar in DNA is deoxyribose. The sugar in RNA is ribose.
A Phosphate group. Phosphate groups are important because they link the sugar on one nucleotide onto the phosphate of the next nucleotide to make a polynucleotide.
A Nitogenous base
Nucleic Acid and Heredity
In any DNA sample the amount of adenine is equal to the amount of thymine and the amount of cytosine is always equal to the amount of guanine. This constant relationship is known as Chargaff’s rule
Structure of DNA
DNA is a thread like natural polymer made up of nucleotides bound together in the shape of a double helix.
Base pairing - The Nitrogenous Bases pair up with other bases. For example the bases of one strand of DNA base pair with the bases on the opposite strand of the DNA.
DNA Molecule
A-T(U) C-G
This is because there is exactly enough room for one purine and one pyrimidine base between the two polynucleotide strands of DNA.
Nature/Role of the Genetic Material
It must contain, in a stable form, information encoding the organism’s structure, function, development and reproduction.
it must replicate accurately so progeny cells have the same genetic makeup.
it must be capable of some variation (mutation) to permit evolution. Ensuring the survival of a species.
DNA and RNA are polynucleotides
Both DNA and RNA are polynucleotides. They are made up of smaller molecules called nucleotides.
DNA is made of two polynucleotide strands.
RNA is made of a single polynucleotide strand: Has Uracil instead of Thymine.
Protein Synthesis
Transcription
In this process one strand of DNA that makes up a gene called the non-coding (template or anti-sense) strand acts as a template for the synthesis of a match (complementary ) RNA strand by an enzyme called RNA polymerase.
This strand is the primary transcript. In this process there are no Okazaki fragments, the process is similar to that of DNA replication involving the same enzymes, except DNA polymerase.
The primary transcript carries the same sequence information as the non transcribed strand of the DNA, sometimes called the coding (sense) strand.
Eukaryotes vs. Prokaryotes
Translation
This takes place in structures called ribosomes, which constructs polypeptides. Once the ribosome is attached to the mRNA and finds the start codon, it will travel rapidly down the mRNA, one codon at a time. Eventually a chain will be built that mirrors the sequence of codons in the m RNA.
The tRNA has three nucleotides sticking out at one end, the anticodon which can recognize just one or a few particular codons. The other end of the tRNA carries an amino acid. The amino acid that matches the codons on the mRNA.
Mutation
Chromosomal Mutations
This type of mutation can affect multiple genes, including genes located on sister chromatids. Portions of the chromosomes can be duplicated, lost during DNA replication; this can result in changes to structural or regulatory DNA sequences.
Another factor that can rearrange genetic material is the activity of transposable elements, known as jumping genes or transposons. These are short strands of DNA capable of moving from one location to another within the cell’s genetic material.
Changes in Chromosome
Changes in the structure can occur either naturally or due to exposure to radiation or certain chemicals. There are four means by which these changes can occur.
Deletion – when a portion of the chromosome is actually lost.
Inversion – this occurs when a certain gene segment becomes free from its chromosome segment momentarily before being reinserted in the reverse order.
Duplication – this occurs when a gene sequence is repeated one or more times within one or several chromosomes.
Translocation – this occurs when part of one chromosome switch positions with another part of the same chromosome or with part of another non-homologous chromosome.
Nondisjunction – this occurs when chromosomes or chromatids do not separate as they should during meiosis.
The inheritance of one chromosome is called monosomy
Mutation
Changes that take place at the molecular level within genes are an important source of genetic variation.
A permanent change in the genetic material of an organism is called a mutation.
All mutations are heritable in that they will be copied during DNA replication. Not all mutations will be passed on to future generations. Only changes that affect the genetic information contained in reproductive cells of an organism, called germ cell mutations, will be passed on to offspring.
Nonsense Mutation: this is a type of mutation that renders the gene being unable to code for any functional polypeptide.
Silent Mutation
This is a mutation that has no effect on the cell’s metabolism, this type of mutation results in nucleotide substitutions.
The change in nucleotide sequence has no effect on the polypeptide product.
Nucleotide Insertions and Deletions
The insertion or deletions of one or more nucleotides within a sequence of codons produces a second point mutation called frame-shift mutation.
Insertions or deletions cause the entire reading frame of the gene to be altered.
In some cases frame-shift mutations can be cancelled out where one insertion is compensated by one deletion along the coding sequence.
In most cases the frameshift mutation will result in a nonsense mutation.
Genetic Engineering
Human Genome Project (HGP)
This was completed in 2003 and it involved the knowledge of the base sequence of every chromosome making up the human genome.
Gene Therapy
This is the process of fixing genetic errors in organisms.
Cloning
A clone would posses the identical genetic make up from the parent donor, basically a diploid nucleus.
This diploid nucleus is transferred to the female gamete ( the original gamete nucleus is removed) and then inserted via in vitro fertilization ( this means fertilization takes place outside the body and the embryo is then inserted into the uterus).
Genetic Engineering
Selective Breeding
Breed only those plants or animals with desirable traits
Restriction Enzymes
Recombinant DNA
The ability to combine the DNA of one organism with the DNA of another organism.
DNA amplification
This is the process of producing large quantities of DNA from a sample.
Gel Electrophoresis
DNA sequencing
Transgenic Goat
Polymerase Chain Reaction
PCR allows scientists to make many copies of a piece of DNA.
Heat the DNA so it “unzips”.
Add the complementary nitrogenous bases.
. Allow DNA to cool so the complementary strands can “zip” together.
Gel Electrophoresis
This technology allows scientists to identify someone’s DNA!
“Cut” DNA sample with restriction enzymes.
Run the DNA fragments through a gel.
Bands will form in the gel.
Everyone’s DNA bands are unique and can be used to identify a person.
DNA bands are like “genetic fingerprints”.
