Transcription and Translation

Transcription and Translation

• Allows cells to read and express genetic instructions in DNA
• Main steps in gene expression

Transcription

• DNA is transcribed into a message
• Occurs in the nucleus
• RNA polymerase connects complementary RNA bases to the DNA template strand
• These bases bond to form a single-stranded mRNA
• mRNA is messenger RNA
• mRNA exits the nucleus into the cytoplasm to attach to a ribosome
• Ribosomes make protein and are made of rRNA (ribosomal RNA)

Translation

• tRNA (transfer RNA) carries an amino acid
• Amino acid is the monomer for a protein
• mRNA directs which tRNAs come in and which amino acids are transferred
• tRNA looks for complementary bases; when found on the mRNA, it transfers its amino acid
• Example: AUG, the tRNA contains the complementary anticodon → UAC
• tRNA with the UAC anticodon pairs with the mRNA's complementary AUG codon, transferring the amino acid
• Codon chart uses the codon on the mRNA, not the anticodon

Mutations

• Mutation refers to any change in the genetic material of a cell
• A source of new alleles
• Mutagens are substances that cause mutations

EM Radiation

• Ionizing radiation has high frequency and short wavelengths e.g., X-rays, UV, Gamma

Chemical Radiation

• Often causes mutations when individuals are subjected to prolonged or high intensity exposure

Intercalating Agents

• Chemicals that insert into DNA bases, creating a frameshift mutation and new reading frame

Base Analogues

• Chemicals structurally similar to nucleotide bases. May replace existing bases, resulting in an altered DNA sequence

DNA Relative Chemical

• Refers to chemicals that directly affect DNA, often disrupts bonds between DNA molecules
• Some DNA reactive chemicals may be involved in chemical reactions in the body to produce other compounds which cause mutations

Naturally Occurring Mutagens

• Viruses can interact with genetic materials in cells, changing the functioning of genes and triggering cancer
• Bacteria introduces free radicals that attack and damage DNA and inhibit DNA mechanisms, preventing cells from reconnecting

Point Mutations

• Substitution is where a nucleotide base is substituted for another
  • Silent Mutation: Base substitution occurs, but the same amino acid is coded for, and has no effect on the polypeptide
  • Missense: Base substitution occurs, but a different amino acid is coded for
  • Nonsense: Base substitution occurs, but a stop codon is produced which stops protein synthesis, and produces a short or no peptide
• Insertion is where a nucleotide base is inserted into the existing sequence
• Results in an incorrect polypeptide which is produced due to coding for different amino acids. Usually results in a non-functional protein
• Deletion is where a nucleotide base is deleted from the existing sequence
• Results in an incorrect polypeptide, usually resulting in a non-functional protein

Example of Point Mutation

• Missense Mutation Result: Sickle Cell Anemia
• Red blood cell has a ridged sickle shape instead of a donut shape
• Ridged and sticky vs. flexible and round
• Can get stuck in small blood vessels which slows blood flow and oxygen

Chromosomal Mutations

• Mutations that affect an entire extension of the DNA sequence
• Insertion: A section of a chromosome is detached from one chromosome and added to another chromosome
• Deletion: A section of the chromosome is removed or loss
• Duplication: A section of a chromosome is copied and reinserted into the chromosome
• Inversion: A section of a chromosome is removed, reversed, and reinserted
• Translocation: Two chromosomes swap sections of DNA
• Other chromosomal mutations cause an abnormal chromosome number
• Often caused by incorrect separation of Chromosomes during cell replication processes (nondisjunction)
• Trisomy: Three copies of a chromosome
• Monosomy: One copy of a chromosome

Somatic and Germline Mutations

• Somatic Mutations occur in the somatic cells, these cells are diploid and undergo mitosis
• New body cells involved in the growth and repair of an organism cannot be inherited by offspring
• Example: Development of Cancer: Mutation in the proto-oncogene leads to rapid uncontrolled division of the affected cells leading to the formation of a tumor
• Germline Mutations are mutations in germline cells/gametes, these mutations can be inherited from offspring
• Somatic Mutations
• Location: Body Cell
• Effect: Mutation affects all tissues and cells derived from the original cell
• Inheritance: Cannot be inherited
• Examples: Skin cancer, liver cancer
• Germline Mutations
• Location: Germ cells or gametes
• Effect: Mutation affects all cells in the offspring that inherit the mutation
• Inheritance: Can be inherited and may produce new alleles
• Examples: Cystic fibrosis

Causes of Genetic Variation

• Factor: Fertilisation
• How it creates genetic variation: Fusion of two random haploid gametes creates infinitely many possible combinations of genetic material resulting in genetically unique offspring
• Factor: Meiosis
• How it creates genetic variation: Crossing Over occurs where non-sister chromatids of homologous chromosomes exchange sections of their DNA during prophase I creating recombinant chromosomes (Independent Assortment)
• Each homologous chromosome pair separates randomly into the daughter cells during metaphase and anaphase I
• Both processes ensure meiosis produces genetically unique haploid cells
• Factor: Mutation
• How it creates genetic variation: New alleles are created from changes to DNA

Gene Flow and Genetic Drift

• Factor: Mutation
• Description: Changes to DNA
• Effect on Gene Pool: Creates new Alleles that are introduced to the gene pool
• Factor: Genetic Drift
• Description: Random events cause change in allele frequency as individuals are randomly eliminated
• Effect on Gene Pool: Removal of certain individuals and their alleles from the gene pool, causing random changes in allele frequencies within the gene pool
• Factor: Gene Flow
• Description: Individuals migrate to a population and spread their alleles
• Example: Bees pollinating flowers from different fields, mating of different dog breeds
• Effect on Gene Pool: Alleles of individuals that have migrated will enter the gene pool, increasing their frequency

Founder Effect

• Occurs when a small group of individuals break away to start a new population
• New population has less variation than the larger, original population as there are fewer alleles
• Example: Migration of humans out of Africa

Bottleneck Effect

• Sharp reduction in a population due to a natural disaster removes or greatly reduces alleles
• Example: A typhoon in the 18th century reduced the population of Pingelap island (Micronesia) to around 20 survivors leading to a high frequency of genetic disorders such as achromatopsia

Biotechnology

• Use of biological processes and manipulation of living organisms in products improve human life
• Biotechnology: Selective Breeding
• Organism Used: Wheat
• How the organism is used: Farrer used cross fertilization to select individuals with characteristics, used hand-pollination and pure breeding
• 1st Cross: Etauch (early ripen) x Fife (good baking properties) = Yandilla
• 2nd Cross: Yandilla x Purple Straw 14A (high yield, short, straw) = Federation
• Societal Impacts: Product increased yields and harvesting efficiency, Early ripening avoids rust infection and was more suited to shorter summers, Narrow leaves to reduce water loss - more suited to climate
• Biotechnology: Aquaculture
• Organism Used: GE Atlantic Salmon
• How the organism is used: Insertion of growth-hormone gene from chinook salmon and gene regulators from ocean pout causes GE salmon to continually produce growth hormone, salmon grows to market size in half the usual time
• Societal Impacts: Increased food supply, Alleviate overfishing of wild salmon populations
• Biotechnology: Insulin
• Organism Used: E. Coli
• How the organism is used: Insertion of the human gene for insulin into bacteria for mass replication
• Societal Impacts: Treatment of diabetes, prevent deaths
• Biotechnology: Bioremediation
• Organism Used: Genetically engineered microorganisms
• How the organism is used: Microorganisms are used to remove specific contaminants from the environment
• Examples: bacteria to clean up oil spills, Arabidposis plants for selenium polluted soils
• Societal Impacts: Cleaning up of the environment and reducing damage caused by human activities and pollution

Genetic Technologies that induce Genetic Change

• Technique: Selective Breeding
• Description: Deliberate crossing or mating between specific individuals with certain desirable traits from the same species
• Uses and Advantages: Produce animals with more muscle/meat, increased milk production and disease resistance, Produce plants with a higher yield, improved taste and pest-resistance
• Technique: Cloning
• Description: Creating copies of organisms or genetic material
• Uses and Advantages: Guaranteed expression of desired traits or genes

Transgenesis

• Inserting genes from one organism to another
• Creates new combinations of genetic material
• Used to produce desired proteins
• Used to express desired traits in organisms

Reproductive Technologies

• Artificial Insemination
• Processes: Extract sperm from a male, transport it and inseminate desired trait females
• Outcomes: Semen can be stored and transported for an extended time, semen from one, male can inseminate multiple ones reducing genetic diversity
• Artificial Pollination
• Processes: Transfer pollen from the stamen of a plant to the stigma to enable pollination and fertilisation
• Outcomes: Creates plant hybrids with desired traits, reducing genetic diversity

Cloning

• Type of Cloning: Whole organism cloning
• How it works: Plants-cutting(grafting)/tissue culture and Animals-somatic cell nuclear transfer/embryo twinning
• How effective: Varies, somatic less effective with death
• Type of Cloning: Gene cloning
• How it works: DNA is cut with restriction enzymes, gene of interest removed and inserted into plasmid. Plasmid is inserted into bacteria
• How effective: Effective, although the bacteria that take plasmid are selected

Somatic Cell Nuclear Transfer

• Involves 3 animals- a donor, egg donor and surrogate

1. Somatic cells are removed from animal cloning
2. Nucleus is removed from animals egg
3. Nucleus of cells is transfers to egg of animal where scientists’s inject with electricity
4. Nucleus inserted and Pulse given to induce division/ formation
5. Transfer to female to develop

Biotechnology on Biodiversity

• Increase in Biodiversity:

• New genetic combinations thanks to DNA recombinant

• Ability to breed world organisms, creating combo

• Decrease in Biodiversity

• Artificial selection of DNA via breeding

• Cloning organisms and genes

• Potential from organisms to be wild eliminating native species

Polymerase Chain reaction

• Used to amplify sequenced DNA form initial sample

• Method creating code by using denaturing, annealing and polymerase sequencing

• Steps:

1. Heat DNA so the strands separate
2. Cool to allow DNA binding
3. Primers added compliments region
4. Heat to add polymerase replicate strand
5. Cycle heating to amplify region