Unit D 死记烂背 Flashcards
D1.1
16 Step Process of DNA Replication
- Occurs in S stage of interphase
- Semi-conservative
- Each strand of parent DNA used as template for synthesis
- Helicase separates strands and unwinds helix at replication origin
- Hydrogen bonds between strands broken
- RNA primer synthesised on DNA by DNA primase
- DNA polymerase III adds nucleotides to 3’ end
- Synthesised in 5’ to 3’ direction
- Complementary base pairing
- Adenosine-Thymine, Cytosine-Guanine
- Continuous on leading strand
- Discontinuous Okazaki fragments on lagging strand
- DNA ligase joins Okazaki fragments by forming phosphodiester bonds
- DNA polymerase I removes primers and replaces them with DNA
- DNA polymerase III removes mismatched nucleotides from the 3’ terminal and replaces it with a correct nucleotide
- Energy obtained from the double hydrolysis of deoxynucleoside triphosphate
DNA pol III has multiple domains, but polymerisation and proofreading ar
D1.1
7 Differences and 2 Similarities between Prokaryotic and Eukaryotic Genetic Material
Differences
- Associated with histones or not
- One vs many chromosomes
- Introns or not
- Replication points
- Circular vs Linear
- Plasmid or not
- In nucleoid vs in cytoplasm
Similarities
- Both are DNA
- Mitochondrial and chloroplast DNA similar to prokaryote DNA
Yes that has showed up in a markscheme before.
D1.1
7 Step Process of Polymerase Chain Reaction
- Denaturation - DNA heated to 95’C using thermal cycler ⇒ Hydrogen bonds disrupted, DNA helix unwinds
- Annealing - Cooling to 54’C for primer binding
- Elongation - Heating to 72’C for addition of nucleotides by Taq-polymerase, Polymerase adds nucleotides to 3’ end
- Final Elongation - Temperature maintained to ensure complete elongation
- Final Hold - Cooling to below 20’C for temporary storage
- The start and end of the DNA sequence are amplified
- The sequence of Denaturation, Annealing, and Elongation is repeated to amplify DNA
PCR is good because of its efficiency but is prone to error, as Taq does
D1.1
5 Step Process of Gel Electrophoresis
- Amplified DNA is fragmented using restriction endonucleases
- DNA sample is placed in well in agarose gel
- Negatively charged DNA is attracted to anode
- Fragments separate by charge and size
- Staining with ethidium bromide allows them to be seen under UV
D1.1
8 Step Process of DNA Profiling
- Unique minisatellite = non-coding regions of DNA with tandem repeats
- Tandem repeats (at one locus) vary in number of times sequence repeats / represent different
alleles for one locus - DNA sample cut by restriction enzymes into fragments;
- DNA are amplified at specific genetic sites with PCR;
- Fragments are separated bygel electrophoresis;
- fluorescent/radioactive label attached to different tandem repeats
- Combinations of
alleles are specific to an individual; - Use comparisons/similarities between fragment patterns to determine paternity/evidence match to a
suspect’s profile / other example of comparison/similarity
D1.1
Evidence of Semi-Conservative DNA Replication
Meselson and Stahl (1958)
* grow G1 bacteria in N-15 enviroment
* grow G2 bacteria in N-14 environment
* G1 is N-15 only
* G2 is N-15 + hybrid
* G3 is N-14 + hybrid
D1.2
11 Step Process of Transcription
- Antisense strand is used as template
- Regulated by transcription factor, eg. promoters and enhancers
- RNA polymerase and helicase separates strands of DNA
- Unwinding of double helix exposes 10-20 bases for pairing with RNA nucleotides
- RNA nucleotides match to complementary bases
- 5’ to 3’ direction
- Adenine with Thymine and Cytosine with Guanine, but RNA has Uracil instead of Thymine
- Hydrogen bonds between RNA nucleotide and complementary DNA base
- Energy obtained from the double hydrolysis of deoxynucleoside triphosphate
- Terminator sequence signals end of transcription
- mRNA detaches from DNA
D1.2
4 Types of Post-transcriptional Modification
- snRNP spliceosome splices introns and joins exons/ highly conserved sequences
- Alternative splicing produces different exon combinations from a single gene
- Terminal transferase binds to the 3’ of pre-mRNA and attaches the poly-A tail
- Modified guanine nucleotide attaches to 5’ (5’ cap)
Protects mRNA from enzymatic degradation and increases diversity
D1.2
Example of Alternative Splicing
In babies, troponin is spliced to give higher sensitivity to Ca2+ and higher tolerance to acdiosis. Alternative splicing of the pre-mRNA several weeks later results in lower senstivity and lower tolerance.
Babies’ muscles are not very strong, which is why they need more sensiti
D1.2
4 Functions of Telomeres
- Protect against enzymatic degradation
- Prevent the loss of genes from the 5’ end during replication
- Prevent ends of DNA from attaching to each other (the cell would be killed otherwise)
- Recognition sites for telomerase allows telomeres to length and to regenerate upon cell division
Since prokaryote DNA is circular, they do not need telomeres.
D1.2
4 Examples of Non-Coding DNA
- Introns
- Telomeres
- Gene Regulators
- Genes for rRNA and tRNA
D1.3
13 Step Process of Translation
- Initiation, Elongation, Termination
- mRNA binds to small subunit, tRNA binds to large subunit
- Ribosome slides along mRNA to start codon
- met-tRNA binds to AUG start codon
- tRNA anticodon pairs with mRNA codon
- Complementary base pairing of RNA bases between codon and anticodon
- Second tRNA codon moves from A site into P site to pair with next codon
- Peptide bond forms between amino acid of P site tRNA and existing chain
- P site holds the tRNA attached to the polypeptide chain
- Ribosome moves along mRNA by one codon
- Movement from 5’ to 3’ direction
- tRNA without amino acid detaches from E site
- tRNA activating enzymes link amino acids to specific tRNA
- Until stop codon reached
D1.1
4 Types of Post-Translation Modification
- Removal of methionine
- Change of side chains
- Folding or cleaving
- Combination of domains and prosthetic groups to quaternary groups
D1.2
3 Step Example of Post-Translational Modification
- Signal peptide is cleaved from pre-proinsulin
- C peptide is cleaved from proinsulin
- Insulin is made of A and B peptides bonded by disulfide bonds
D1.2
3 Step Description of Proteasome
- Organisms maintain their proteome by diet
- Dysfunctional proteins can be recycled into amino acids by proteasome
- Proteasome hydrolyses peptide bonds between residues to supply ribosomes with amino acids
D1.3
4 Types of Mutations
- Substitution/ SNP
- Insertion
- Deletion
- Inversion
D1.3
7 Examples of Mutagens
- Mustard Gas
- Nitrous Acid
- Ethyl urethane
- Formaldehyde
- MMS and EMS
- UV radiation
- X-rays
D1.3
Neutral vs Silent Mutations
- Neutral: mutation in non-coding region - sequence is not translated
- SIlent: degeneracy of genetic code - codes for same protein
D1.3
5 Step Process of Gene Knockout
- Genetically engineers an organism wiht one dysfunctional gene so that its function can be observed
- Gene is replaced with non-homologous functional sequence
- The stem cell is fused with an embryo to create a chimera
- Adult organism is bred until a pure breeding offspring is produced
- Homozygous offspring are needed to study the gene’s function
D1.3
Example of Gene Knockout
The p53 gene on chromosome 17 synthesises cell cycle-regulating proteins
D1.3
5 Step Process of CRISPR Prime Editing
- CRISPR is a bacterial genomic record of viral attacks
- Single guide RNA identifies target sequence
- CRISPR RNA binds to viral sequence
- Cas9 makes a double cut in the sequence
- Reverse transcriptase transcribes a new sequence and replaces the target sequence
D1.1
4 Differences between RNA and DNA
- Single strand vs double helix
- Ribose vs deoxyribose
- Thymine vs uracil
- One form of DNA, but multiple forms of RNA
D1.3
4 Step Process: Carin’s technique to measure the length of DNA
I used the exact 2022 May TZ2 P2 markscheme.
- Grow E. coli in radioactive thymidine in tritium
- Autoradiography and electron microscope
- Produced image of DNA and measured length of DNA
- All strands contained radioactive thymine
D1.3
4 Reasons for Highly Conserved Genes
- Genes are needed for basic cellular function and survival, eg. for protein synthesis
- Slower mutations rates
- Higher frequency of transcription means the sequence is proofread more often
D2.1
3 Steps of Animal Cell Cytokinesis
- Actin and myosin pull on plasma membrane
- cleavage furrow forms
- cells separate when cleavage furrow forms to the centre of the cell
D1.3
7 Differences and 3 Similarities between Unique and Repetitive Sequences in DNA
- variation between individuals
- sequence length
- proportion of genome
- whether translated or not
- genes or not
- exons vs introns
- number of times occurred
- satellite DNA is repetitive
- repetitive sequences are used for profiling
- prokaryotes do not usually have repetitive sequences
D2.1
5 Steps of Plant Cell Cytokinesis
- Microtubules assemble vesicle layer
- Vesicles form cell plate
- Vesicles build up on cell plate to form plasma membrane and plasmodesmatea
- Pectins form lamellae
- Cellulose deposited near lamellae to form cell wall
D2.1
4 Stage, 10 Step Process of Mitosis
- Prophase
- Heterochromatin forms by DNA supercoiling
- Microtubules form from Microtubule Organizing Centres
- Nuclear membrane dissolves
- Metaphase
- Microtubules attach to kinetochore
- Spindle fibre put under tension to test correct attachment to centromere
- Chromosomes align at equator (metaphase plate)
- Anaphase
- Cohesin loops cut
- Spindle fibre contraction, pulling chromosomes towards opposite poles
- Telophase
- Chromosomes are clustered and nuclear membrane reforms
- Euchromatin formation
D2.1
2 Processes Leading to Genetic Variation in Meiosis
- Crossing Over
- Independent Assortment
D2.1
3 Genetic Diseases caused by Non-disjunction
- Down Syndrome - trisomy 21
- Klinefelter’s Syndrome - XXY trisomy
- Turner’s Syndrome - X only
D2.1
6 Stages of Cell Cycle
- G0 - cell growth
- G1 - cytoplasm expansion, organelle replication, protein synthesis
- G1 Checkpoint - assess DNA damage
- S - DNA replication
- G2 - cell growth
- G2 Checkpoint - proofreading new DNA
D2.1
4 Cyclins
- Cyclin D - move from G0 to G1, and G1 to S
- Cyclin E - prepare S DNA replication
- Cyclin A - activates S DNA replication
- Cyclin B - promotes assembly of mitotic spindle
D2.1
2 Types of Genes in regulation of Cell Division
- Proto-oncogenes
- Tumour Suppression Genes
D3.2
4 Step Aetiology of Phenylketonuria
- mutation in autosome 12
- failure of phenylalanine hydroxylase
- phenylalanine accumulation and tyrosine deficiency
- cognitive impairment
D4.2
4 Measures of Ecological Stability
- Resistance - ability of an ecosystem to withstand negative impacts of disturbances
- Latitude - maximum disturbance a system can tolerate before tipping point
- Resilience - ability of an ecosystem to recover from negative impacts of disturbances
- Precariousness - how close the ecosystem is to tipping point
D4.2
4 Impacts of Plastic Pollution
- Disruption to marine food webs
- Reactions of polymers in animal digestive systems release toxins
- Wildlife entanglement and ingestion
- Habitat degradation
D4.2
5 Types of Succession
- Hydrosere = in a body of freshwater
- Halosere = in salt water marshes
- Psammosere = in sand dunes
- Xerosere = in dry regions (usually with arid climate)
- Lithosere = from bare rock
D4.2
4 Impacts of Succession
- Improved soil depth, mineral ion content, water retention
- More ecological niches
- Complex feeding relationships
- Ecological stability
D4.2
5 Steps of Eutrophication
- Nutrient enrichment of water bodies (agricultural runoff, sewage and wastewater discharge, and industrial activities)
- Algal bloom blocks light.
- Smaller plants which cannot access light and photosynthesize die. Accumulation of organic matter (positive feedback)
- Increased decomposition leads to higher bacterial reproduction. Aerobic respiration causes oxygen depletion.
- Collapse of aquatic ecosystem as other organisms cannot respire.
D4.3
8 Points for Enhanced Greenhouse Effect
- Greenhouse gases occur naturally
- Human activity produces greenhouse gases
- Incoming UV from Sun
- Reflection produces IR
- Greenhouse gases absorb and reemit radiation as heat
- Increased greenhouse gases causes abnormal rate of heat emission
- Global temperature increase threatens ecosystems
- There are natural fluctuations in temperature
