PBL Week 2 Flashcards
How does DNA damage occur and how is it repaired?
DNA by exogenous factors (e.g raditiation, chemicals) or endogenous factors (e.g errors during metabolism, internal chemicals).
Types of repair include excision repair (where specific bases are fixed). Can be Base or Nucleotide excision repair (BER or NER). Mismatch repair is used when complementary bases aren’t correct and double strand break repair where breaks are repaired by Homologous Repair (HR) or Non-Homologous DNA End Joining (NHEJ). Furthermore, DNA polymerase can detect errors during DNA replication and remove any wrong bases.
What is the process of protein turnover?
When proteins are damaged, they must undergo turnover where it is hydrolysed into amino acids and resynthesised. This happens because some proteins only last minutes while others last weeks.
First, the protein is marked by covalently bonding to a smaller protein called Ubiquitin, allowing the protein to be transported to proteasome 26 (a large complex found in the cytoplasm that requires ATP), where it is broken down. Almost 1% of proteins are proteasome 26. The protein can then be reformed like normal.
Describe the normal development of the human embryo.
Week 1: fertilisation and implantation - when the sperm reaches the egg, the pronuceli fuse, forming a zygote. Cell division occurs until a Morula forms. Liquid inside this pushes the cells to the poles, forming a blastocyst which embeds itself into the uterine wall.
Week 2: Bilaminar germ disc forms (2 cell layers - epiblast and hypoblast), as well as amniotic cavity and primary yolk sac.
Week 3: Gastrulation occurs - formation of trilaminar germ disc (3 layers - endoderm, mesoderm and ectoderm). Also formation of primitive streak, motochord, neural tube and body axes.
Week 3-8: Organogenesis occurs. Trilaminar disc folds and cells differentiate into primitive versions of all major organ systems, neurulations (CNS), intraembryonic coelom (body cavity) and the muscoskeletal system.
Week 8-birth: foetal growth and maturation of tissues and organs.
What is epigenetics and how does it have an affect on health?
Epigenetics is the study of heritable changes in gene expression (active vs inactive) that doesn’t involve changes in the DNA sequence. Essentially, a change in phenotype without a change in genotype. Is due to difference in DNA methylation and histone modification. Epigenetics is responsible for DNA imprinting, where a paternal/maternal version of a gene is more likely to be expressed due to a difference in methylation. Epigenetics can also be affected by environmental factors, leading to incorrect gene expression and diseases such as cancers, developmental diseases and autoimmune diseases.
Describe the absorption, distribution and excretion of toxins in our body.
The skin, lungs and gut lining are the main barriers to toxins. Once past these barriers, a toxin travels around the body until it reaches the target tissue (the site where it causes damage). The toxcity of the substance can vary, with many factors affecting the removal/disposition of the toxin. These include the amount, whether it spreads past the target area, whether biotransformation makes it more or less toxic and the speed of the elimination of the chemical.
There are many pathways for toxins in the body:
- ingestion - through GI tract - excretion
- inhalation - into lungs then blood or lymphatics - back into lungs for exhalation/into liver + bile for excretion/into kidneys and excreted/into glands and excreted as sweat or saliva.
- accumulates in fat, skin, hair or bone from blood.
- enters through skin - passes into blood and excreted (soluble)/stored in fat (non-solubule).
How can normal foetal development be disrupted?
DNA damage is the main cause of disrupment. This can come from a variety of factors such as air pollution, smoking, drinking, insufficient nutrition, metabolism and ionizing raditation. Furthermore, reduced uteroplacental and umbilic blood flow can cause stunted growth or disrupted devlopment.
What is a teratogenic substance and how can we come into contact with them?
If a substance is teratogenic, it is a substance that may cause birth defects. Examples include thalidomide, mercury, alcohol and lead. Thalidomide was used as a anti-nausea medicine, however due to insufficient testing it was found to have catastrophic effects on foetal devlopment. Substances such as mercury and lead can come from the environment, alongside other harmful teratogens like certain pestisides. Finally, the foetus can be affected by alcohol consumption during pregnancy.
What is environmental health and what is the role of environmental health officers?
Environmental health is the monitoring or mitigating of factors in the environment that affect human health. Environmental health officers ensure that the environment we live in is safe and work to minimise risk from the environment. They work on environmental protection, food safety, public health, health and safety and housing communities.
Do science and technology generate a more or less toxic environment for our health?
Both - on one hand, advances in technology have allowed us to fix many issues we previously faced and made the environment safer for us to live in. On the other hand, the increased usage of the world’s resources has lead to new issues within the environment, such as climate change and pollution, which negatively affects our health.
