Biology Trials Flashcards
Transcription
The process of turning genetic information stored in the DNA into an intermediary molecule (mRNA)
- DNA polymerase binds to the ‘promotor’ which signals the DNA to unwind and allows enzymes to read the bases
- The mRNA molecule is built using the complementary bases
- The mRNA molecule detaches from the DNA strand
Translation
The process where genetic information encoded as mRNA turns into a polypeptide chain
Transcription carries the genetic code in the form of mRNA from the nucleus to the ribosome
- mRNA attaches to a ribosome
- the ribosome attaches the codons and anticodons together
- polypeptide chain forms and grows as amino acids are added
- once a stop codon is reached, the chain detaches
DNA replication
DNA replication is the process by which an existing DNA molecule is copied to produce 2 identical DNA molecules. The enzymes topoisomerase relaxes the DNA from its coiled structure. The enzyme helicase unwinds & unzips the DNA molecule at a particular point (an origin of replication) making two template strands of DNA available. The hydrogen bonds between the nitrogenous bases break. The enzyme primase synthesizes short RNA primers to start each new DNA strand or fragment. One of the strands is in the 3' to 5' direction, which is called the leading strand; the other is in the 5' to 3' direction and is called the lagging strand. The enzyme DNA polymerase catalyses' the synthesis of the new DNA strands. DNA Polymerase helps the DNA nucleotides (which are readily available in the cell) match up with their complementary base on the template DNA (A&T, C&G). DNA polymerase continues to bond free nucleotides to the exposed bases according to the complementary base pairing rule until there are no more exposed bases. DNA ligase (enzyme) seals the two strands of DNA into double strands. The final result of DNA replication is two identical DNA molecules, made up of one old and one new strand which automatically coil back into a double helix.
Mitosis model of cell replication
- The nuclear membrane breaks down and nucleolus disappear
- Chromatin condenses into chromosomes that have duplicated into two chromatids held together by a centromere
- Centrosome separate forming spindle
- Chromosomes move to the middle (equator)
- Chromatids pulled by spindle go to opposite poles, becoming chromosomes
- Nuclear membrane reforms
- Cytokinesis
- Two cells identical with the parent
Why is mitosis essential
for growth, repair and asexual reproduction
Meiosis model of cell replication
- The nuclear membrane breaks down and nucleolus disappear
- Chromatin condenses into chromosomes that have duplicated into two chromatids held together by a centromere
- Centrosome separate forming spindle
- Chromosomes move to the middle (equator)
- Homologous pairs come together and crossing over occurs
- Homologous pairs of chromosomes pulled apart by spindle go to opposite poles and cells become haploid
- Nuclear membrane reforms
- Cytokinesis
- Nuclear membrane breaks down
- Chromatin condenses into two chromatids held together by centromeres
- Centrosome separate forming spindle
- Chromosomes move to the middle (equator)
- Chromatids pulled by spindle go to opposite poles, becoming chromosomes
- Nuclear membrane reforms
- Cytokinesis
- Four haploid cells that are genetically unique
Why is meiosis essential
sexual reproduction, gamete production and genetic diversity
Progesterone role in pregnancy
A hormone that is important in pregnancy is progesterone. Progesterone is initially produced by the corpus luteum in the ovary and causes the endometrium to thicken, which helps to support and maintain the pregnancy in the first weeks when the placenta is still developing. The developed placenta then produces progesterone at significantly higher levels to maintain the pregnancy. Prior to birth progesterone levels drop significantly to facilitate labour.
Oestrogen role in pregnancy
Oestrogen support changes during pregnancy, such as the preparation of breasts for lactation and the uterus for contraction of childbirth
Oxytocin role in pregnancy
Oxytocin is the main hormone of birth and causes contractions of the uterus
Relaxin role in pregnancy
Relaxin is a hormone that plays a role in pregnancy and birth by relaxing the pelvis and joints to allow passage of the foetus
How is birth initiated
Birth is initiated because of stress to the foetus, the release of the corticotrophin-releasing hormone and the dominance of estrogen and progesterone
Nucleotide composition, hydrogen bonding and pairing
- DNA is a polymer made up of nucleotide monomers
A nucleotide contains a deoxyribose sugar joined to a phosphate group and a nitrogenous base - The sugar-phosphate chain forms an external backbone for the DNA strand and the nitrogenous bases radiate towards the centre of the helical molecule, joined to the sugar in the backbone
- Two purine bases: Guanine (G) and adenine (A) and two pyrimidine bases - thymine (T) and cytosine (C) - are the nitrogenous bases.
- Hydrogen bonding results in the nitrogenous bases paring A-T and C-G
Aboriginal bush medicine
- A term used to describe the skills and practices used to maintain health, based on indigenous beliefs and practices.
- Use of native flora and fauna, traditionally prepared
- Preventative and diagnostic techniques, including treatments of mental illnesses
- Holistic view of health, emphasising the connections between physical, emotional, social and spiritual aspects of wellbeing
EXAMPLES - Tea tree oil
- Crushed leaves applied as a paste to wounds
- Strong antiseptic
- Used in western medicine to treat fungal infections and acne
EXAMPLES - Eucalyptus oil
- Infusions treat muscle aches, fevers and chills
- Used in western mouthwash and cough lollies
Aboriginal smoke bush
Conospermum, colloquially known as smokebush
- Endemic to south-west Western Australia
- Traditionally used and nurtured by Indigenous peoples of the region for it’s medicinal properties
- 1960s - US National Cancer Institute looking for cancer-fighting molecules, Western Australian Government grants them a licence to collect plant samples and screen them
- 1980s – AIDS epidemic, Smokebush screenedFound to contain conocurovone, a molecule able to combat the HIV virus in low concentrations
- US Department of Health and Human Services filed a patent for exclusive rights
- AMRAD gained exclusive licence to develop the patent
- WA government were paid $1.65 million to gain these rights
- Of the $100 million made annually from commercial use of the molecule, none was given to the indigenous population and no credit either
- No consultation of Indigenous community - No royalities or compensation, No acknowledgement
Vaccination antibodies concentration
After initial vaccination, a time delay occurs before antibodies are produced. The antibody level rise to peak then decreases to below the concentration required for immunity. A booster vaccination quickly increases antibody level and the remaining antibody level after a decline is sufficient to provide immunity.
A booster vaccine ensures the level of antibodies in the blood is high enough to provide immunity.
The memory B and T cells formed after an initial vaccination quickly recognise an antigen on re-exposure to it in a booster vaccine and so rapidly reproduce a large number of antibodies.
How can variation occur?
- Random segregation
- Crossing over
in the early stages of meiosis random segregation of each member of the homologous pairs of chromosomes results in haploid cells and produces highly varied gametes
Crossing over restructures some chromatids and may produce new combinations of alleles along a chromosome
Both processes result in new combinations of alleles in gametes
How mutagens work:
High-energy electromagnetic radiation
High-energy electromagnetic radiation includes gamma rays, X-rays and some ultraviolet rays
How mutagens work:
Electromagnetic radiation
Electromagnetic radiation passes through tissue to break DNA strands and chromosomes or alter nucleotide bases by changing atoms
How mutagens work:
Chemical mutagens
Chemical mutagens substitute bases and modify the backbone of DNA and often prevent them from replicating. some chemical mutagens break chromosomes
How mutagens work:
Naturally occurring mutagens
Naturally occurring mutagens include viruses, chemicals in plants (alkaloids) and moulds (aflatoxin) and change DNA structure
How mutagens work:
Reactive oxygen species (ROS)
Reactive oxygen species (ROS) interact with other mutagens to break DNA
Types of mutations:
Point mutations
Point mutations involve a change in one nucleotide base. They include:
- Substitution of a nucleotide may result in a different amino acid in a polypeptide chain
- Insertion or deletion of a nucleotide base results in a frameshift that has major harmful impacts on polypeptide synthesis
Types of mutations:
Chromosomal mutations
Chromosomal mutations result in whole sections of chromosomes being deleted, inserted, inverted or translocated to other chromosomes. These rearrangements are usually very harmful to organisms
Types of mutations:
Non-disjunction of homologous chromosomes
Non-disjunction of homologous chromosomes results in a change in chromosome number (aneuploidy) that is usually very harmful to fatal
Stomatic mutations
stomatic (body cell) mutation can result in diseases such as cancer but are not passed on to the next generation
Germ-line mutations
Germ-line mutations can be passed on to offspring and thereby alter allele frequency in the gene pool. Many chromosome mutations in the germ-line result in sterility
Mutations in ‘Coding’ DNA
‘Coding’ DNA segments result in the production of polypeptides so mutations may result from the failure to produce a functional polypeptide
Mutations in ‘non- coding’ DNA
‘Non-coding’ DNA segments may have no known function or regulate gene expression. If regulatory, mutations may result from the failure to produce a functional polypeptide
Genetic variation relating to fertilisation, meiosis and mutation and the effect of the mutation, gene flow and genetic drift on the gene pool of populations
- Fertilisation and meiosis result in recombinations of existing alleles
- Mutations produce new alleles and have the potential to change the gene pool and influence evolution
- Mutation increases variation in the gene pool
- Gene flow from immigrants can increase genetic diversity
- Genetic drift is a random change that mainly impacts. very small populations
Incidence definition
Incidence is the number of new cases of a disease at a. given time
Prevalence definition
Prevalence measures the number or proportion of cases of a disease at a given period
Antivirals treatment
treat a narrow range of viruses and include drugs for the treatment of influenza, HIV, herpes, Hepatitis B and C
Antibiotics treatment
target bacterial pathogens. antibiotics do not work against viral infections such as the cold or influenza
morbidity vs mortality
morbidity refers to the rate of disease in a population
mortality refers to the number of deaths in a population
How Prions cause disease
- Proteinaceous infectious particle
- Abnormally folded protein, transmits misfolded
protein state to other cellular proteins
e.g: Mad cow disease
How viruses cause disease
- non-cellular
- Nucleic acid + protein envelope
- Replicate inside living cells
e. g: COVID-19
How bacteria cause disease
- single-celled, prokaryotic organism
- Reproduce by binary fusion
- Secrete toxins, invade cells, form biofilms
e. g: Tuberculosis
How Protozoa cause disease
- single-celled, eukaryotic organism
- Absorb nutrients from hosts
- Secrete toxins, invade cells, form biofilms
e. g: Malaria
How Fungi cause disease
- Eukaryotic, may be multicellular
- Reproduce by spreading spores
E.g: Athletes foot (tinea pedis)
Macroparasite
- Visible to naked eye
- Ectoparasites – live on organisms
- Endoparasites – live in organisms
E.g: Tapeworm
Robert Koch description
Robert Koch (1843 – 1910)
- German microbiologist
- Identified microbial origins of anthrax, cholera and tuberculosis
- Developed a procedure for isolating and identifying microbes causing disease
- Postulates: links microbial growth as causative agent for disease
Koch’s postulates
- In all organisms with the disease, the microorganisms must be present
- Microorganisms must be isolated, and grown in pure culture
- When a healthy organism is inoculated with the pure culture, it develops the same symptoms as the original sick organism
- Isolate and re-grow microorganisms from newly infected organism. If same, congrats, that’s the cause of the disease
Lous Pasteur description
Louis Pasteur (1822 – 1895)
- French microbiologist
- Disproved theory spontaneous generation
- Proposed germ theory of disease (all things come from pre-existing things)
- Also pasteurization to sterilize food, medical equipment etc
Swan-necked flask experiment
- Take flasks with bent (swan) necks. Particles in the air cannot travel through these necks without getting stuck. Fill with broth
- Apply heat to both flasks, bring to boil. This sterilizes the contents of the flasks
- Break the neck of one flask
- Observe the growth of microorganisms in broth
• Flask with broken neck = microbe growth
• Flask without broken neck = no growth
daptions of different pathogens that facilitate their entry into and transmission between hosts
Cell wall degrading enzymes: Break down cell walls to release intracellular nutrients
Effector proteins: Proteins secreted to suppress host
defences, and aid
entry into cells
- e.g. T3SS
Toxins
- Damage host tissues
- Disable immune system
- e.g. botulinum
Adhesion to host cells:
Adhesion molecules help pathogens stick around cells and colonise tissues and organs
Extremophiles: Pathogens may be able to survive in hostile environments to help their survival inside of organisms
adaptions of different pathogens that facilitate their entry into and transmission between hosts
Protective coverings
- Bacterial capsules: tightly packed polysaccharides giving an extra protective layer
- Viral envelopes: allow longevity outside of host cells and avoidance of immune system
Vectors - Increase efficiency of transmission - Carry pathogens from host to host - E.g. Anopheles mosquitoes for transmission of Plasmodium protozoa, causing malaria
Reservoirs
- Sites both living and non-living where pathogens lay dormant for long periods between outbreaks
- E.g. animals may be reservoirs of human diseases (rabies, cholera)
Rapid species evolution - High rates of mutation during replication allow pathogens to rapidly evolve - Increases pathogenicity - Increased ability to evade host immune responses
Components of the first line of defence
Cilia
Hair-like projections - Line airways
Move in a wave-lie motion to push pathogens away from lungs
Mucous membranes - Cells lining openings of body secrete mucous - Traps pathogens and particles
Secretions
Fluids secreted from sweat glands, hair follicles, urinary tract Flush out pathogens
- antimicrobial
chemical barriers
- stomach acid
- Alkali contents of small intestine
- enzymes in mouth
Skin
- protective layer
- pores secrete anti-microbials
- Outer layer of skin is constantly shedding
The second line of defence
The lymph system
Inflammation
Phagocytosis
Cell death to seal off pathogens
Major Histocompatibility Complex (MHC)
Glycoproteins present on every single cell specifically reserved for presentation of molecules such as antigens and identification
There are TWO TYPES: I and II
MHC I
o Present on all nucleated cells
o Presents the normal proteins it makes AND abnormal ones
o Presents to Tc cells (CD8)
MHC II
o Present on antigen- presenting cells (APCs) ONLY
o Presents the abnormal, pathogenic antigens
o Presents to Th cells (CD4)
Explain how the immune system responds after primary exposure to a pathogen, including innate and acquired immunity
Pathogen enters body detected as foreign due non-self antigens on its surface
2. Inflammation allows increased blood flow to the site
3. Non-specific responses Phagocytosis
4. Macrophages
• engulf pathogens which they encounter
• release cytokines to call other immune cells to the site of infection
• present the foreign antigens on their surface
5. B cells and T helper cells which are recruited to the site by interleukins (cytokine)
6. B and T cells bind to antigen presented on macrophage MCHII molecule
1. B cells via antibodies, T cells via T cell receptors (TCRs)
7. CLONAL SELECTION: Cells selected by binding affinity to antigens
8. B cells differentiate into plasma cells
• secrete pathogen-specific antibodies to immobilise the foreign cells
9. Cytotoxic killer T cells attack pathogenic cells by releasing cytotoxins (e.g. perforin)
10. Memory B and T cells are produced
11. Pathogen is cleared from the site
12. Suppressor T cells dampen the immune response
13. Memory B and T cells remain circulating in the blood to provide long-term immunity.
• Investigate and analyse the wide range of interrelated factors involved in limited local, regional and global spread of a named infectious disease
-Local
1. Immunisation • Herd immunity 2. Personal Hygiene • Washing hands • Covering coughs • Cleaning surfaces 3. Safe Health Practices • Staying home when you’re sick • Contraceptives 4. Public Health Information / programs • Schools • Workplaces
• Investigate and analyse the wide range of interrelated factors involved in limited local, regional and global spread of a named infectious disease
-Regional
1. Monitoring environmental conditions • Sanitation facilities • Food and water supplies • Combatting climate 2. Improving swift identification • Surveillance • Recognition • Diagnosis 3. Creating appropriate responses
• Investigate and analyse the wide range of interrelated factors involved in limited local, regional and global spread of a named infectious disease
-Global
1. Quarantine • Isolating / banning individuals travelling from certain countries 2. Communication • World Health Organization 3. Monitoring affected / potentially affected individuals • Travel cards / documents used to track this data 33
