The A Leve Biologist Hub Flashcards
Epigenetics meaning
Heritable changes in gene function whiteout changing the dna base sequence
Histone deacetylation meaning
Histone tell chromatic to compress DNA
Tightening of chromatin around histone, genetic material not accessible
Cancer cause
Switch off genes associated with rumour detection
Histone modification and deregulation of proteins that bind to DNA
What is RNAi (microRNA/miRNA/siRNA)
Mirna- complementary sequence to transcribed mrna- Upon binding of complex protein, Attached to target section of mRNA, blocking translation and speed up mRNA breakdown
Sirna interferes with translation by binding to mRNA and cleaving it. Prevents translation in the cytoplasm to produce polypeptide. Gene it codes for is not expressed
Dsrna-dicer-sirna-risc-mRNA change
What is siRNA
Short, double stranded fragments of RNA which binds and cleaves mRNA through a RISC. This is the same dicer processing enzyme and the risc complex formed in the mirna path because mirna and sirna share the same machinery after they’re synthesised
What are benign rumours
Local/cannot spread
Pose no direct health risk
Only require medical intervention (surgery)
Cannot spread through the bloodstream or lymphatic system but can put pressure on organs
What are malignant tumours
Metastasis(tumour cells can spread)
Basis of cancer/can cause cancer
Can spread/ cells break off and entered blood stream/lymphatic system
Can extend to bones/liver
Difference between benign/malignant?
Slow v fast growth
Capsule v lack of capsule
Lack of Necrosis v necrosis
Vessel invasion?
Examples of how cancer can be caused
Mutation/epigenetic changes to
Oncogenes becoming activated and tumour suppressor genes regulated/inactivated the cell cycle
Sex hormones(breast/prostate) promote cell division-
Breast cancer- variants of BRCA1 and BRCA2 gene-high oestrogen/progesterone found
Mutation inactivates tumour suppressor gene
Cells proliferate(divide)
Mutation inactivated DNA repair gene
Mutation of proto oncogene creates oncogene
Mutation inactivates several more tumour suppressor genes
Cancer
Describe the steps of sanger sequencing
Mix copies of your target DNA to be sequenced with radioactive nucleotides
These nucleotides also prevent further DNA lengthening, resulting in a mixture of different sequence DNA strands complementary to the template DNA
E.g. AATGGC creates TTACCG, TACCG, ACCG, CG and G
Run the DNA mixture on a gel to separate the different strands by size
Infer their sequence based on the results: the radioactive reading of the different bases alongside the sequence of the strands(smaller strands run further down the gel while larger strands stay towards the top, where they were loaded)
What are restriction endonucleases and how can dna be cloned?
Some microoorganisms have evolved enzymes that invade a host and chop its DNA up at specific sequences
DNA is denatured so 2 strands break apart, primers attach to the strands, DNA polymerase bonds to the primers and initiated the assembly of new DNA
What is in Vivo cloning
Involves stimulating bacteria to take up DNA by inserting it in plasmids
Plasmids also have antibiotic resistance gene, if taken up will enable growth on medium containing that antibiotic allows selection of plasmid which have taken up the DNA
Host cells are grown on a larger scale
In vivo advantages
- treat type 1 diabetes
- new ethical, financial and social issues resolved- social issues include genetic modification of human embryos- three partner babies,gm foods
- ## in gene based medicines for people who want to extort new technology for their immediate profit, results in a huge burden of treatment costs to patients or NHS
What are totipotent (totally powerful) stem cells
Can differentiate into any kind of cell
Unipotent cells
Can only propagate into one type of cell
What are cardiomyocytes
Contract to allow hearts pumping function, derived through multimedia (creates all other types of muscle including smooth or skeletal)
Humans and stem cells
Embryos possess
totipotent stem cells are cells which upon differentiation and development into the adult organism do not occur
Adults only have multipotent stem cells which have a limited range of cells they can change into
Deafness, blindness and infertility can be treated
Transcription factors can be used to grow different types of cell
Cardiomyocytes contract to enable hearts pumping function
Uses of genetic fingerprinting
Medicine
Criminology- crime scenes
Biodiversity
Paternity tests
Genetic fingerprinting technique
DNA undergoes PCR then cleavage at multiple sites with restriction endonucleases
The resulting many small fragments are tagged using a radioactive molecule
They’re separated using gel electrophoresis and viewed using a developed photographic film
What is a mutation/a silent mutation/missense mutation?
a random occurrence during dna replication and the rate of mutation is influenced by external factors such as UV radiation
Silent- degenerate code- polypeptide unchanged
Substitution in an intron is also a silent mutation
Nonsense- deletion/insertion- frameshift- early stop codon- truncated protein which may malfunction
Missense- substitution changes aa encoded. Doesn’t necessarily impact the overall protein, but may alter binding site and therefore it’s activity
What is meant by haploid
Has one set of chromosomes
Diploid is two sets of chromosomes
How does meiosis achieve genetic diversity
Genetic recombination by crossing over
Independent assortment of homologous chromosomes- in meiosis 1, anaphase 1,
Define chromosome non disjunction
Not assigning the expected chromosome or chromatid during meiosis/ results in a cell with a different number of chromosomes
Describe the structure of haemoglobin
- 4 protein/polypeptide chains
- 2 alpha chains and 2 beta chains
- each chain has haem group
- each haem group has one iron ion attached
- 4 oxygen bound=saturated haemoglobin
Haemoglobin fetches in lungs
Haemoglobin spits in respiring tissues
Role of valves in the heart
Av valves- Ensure no blood flows back into Syria from the ventricles
Semilunar valves- ensure no blood flows from the ventricles into the atria
Unit to measure stroke volume
Cm3 or ml
Stages of cell cycle
Prophase-chromosomes condense and disperse and are visible, nuclear envelope breaks down
Metaphase- microtubules connect to centromeres, chromosomes are lined at the equator of the cell by spindle fibres
Anaphase- chromatids split at their centromeres and are pulled towards opposite poles of the cell by shorterning spindle fibres
Telophase- nuclear envelope reforms around two new nuclei/ chromosomes decondense and become indistinguishable and spindle fibres spread out
Cytokinesis- cytoplasm of parent cell divides to complete cell division resulting in two new offspring cells
What is binary fission
Duplication of cells dna
No of copies of plasmids in each new cell is VARIABLE
Remember that bacteria do have a cell wall
