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202 Cards in this Set
- Front
- Back
Advantage to having small cells |
Larger sa:v allowing rapid absorption of substances/secretion of waste The smaller the cell the shorter the diffusion pathway across the membrane and around the whole cell |
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Why do epidermal transfer cells in broad beans/endothelium cells in the gut/arbuscles in plants have proliferations? |
Provide larger sa:v to allow substances to be absorbed quickly into the blood system/seed |
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Reasons for compartmentation in cells |
Maintain different environments to allow incompatible processes to occur simultaneously Keeps enzymes, toxic substances etc in separate locations Destruction of substances and organelles Cells secrete and internalise proteins in ER/Golgi |
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Examples of prokaryotes |
Bacteria and Archaea |
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Examples of eukaryotes |
Plants, protists, fungi and animals |
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Prokaryotes / eukaryotes which is unicellular /multicellular? |
Prokaryotes unicellular Eukaryotes multicellular |
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Genetic organisations in eukaryotes /prokaryotes |
Eukaryotes - linear, associates with Justine proteins to form chromatin =chromosomes Prokaryotes - circular and free without proteins in cytoplasm |
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Which type of cell has a cytoskeleton -eukaryotes or prokaryotes? |
Eukaryotes |
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What are the cell walls in eukaryotes /prokaryotes made of? |
Prokaryotes -Peptidoglycan =sugars and peptides Eukaryotes -cellulose or chitin |
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Which type of cells is flagellum present and what is it made of? |
Prokaryotes and eukaryotes Flagellin in prokaryotes Tubulin in eukaryotes |
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Method of cell division and what type of reproduction in eukaryotes /prokaryotes |
Asexual binary fission in prokaryotes using pilus Dominantly sexual mitosis /meiosis in eukaryotes |
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What is a capsule, its function and what type of cells is it found on? |
Polysaccharide layer coating prokaryotes hiding antigens used for sticking cells together and preventing phagocytosis |
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Function of glycosome and what type of cells is it found in? |
Lysosome/peroxisome involved in glycogen storage found in animal cells |
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Where is rRNA synthesised? |
Nucleolus |
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What does compartmentation of the genome from the cytoplasm allow? |
Gene expression to be regulated |
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How do small particles get transported across the nucleus? |
tRNA, signalling molecules etc use nuclear pores to diffuse passively |
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3 types of protein filaments consisting the cytoskeleton |
Actin - 2 intertwined helical strands Microtubules - long hollow cylinders made of tubulin which form the mitotic spindle that segregates chromosomes during mitosis Intermediates- rope like fibres coiled with keratin |
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Function of the cytoskeleton |
Anchorage for organelles, mechanical support providing rigidity holding the cell's shape, which is useful for animal cells since they lack cell walls Act as track ways to directly transport substances across the cell |
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Where is the cytoskeleton commonly found? |
Next to the RER where the necessary proteins are synthesised |
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Function of motor proteins, the different types and what direction they move in |
Allow vesicles etc to walk along the cytoskeleton to their destination Kinesin travels away from the nucleus (+) Dynein travels towards the nucleus (-) |
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Function of melanophores and how they work |
Pigments which allow crustaceans etc to change colour Motor proteins transport pigments in melanosomes across the cytoskeleton to the cell's centre (appears light) or dispersed (appears dark) |
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What processes so proteins undergo to enhance stability before secretion from the ER? |
Glycosylation -adding a carbohydrate Disulphide bond formation |
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How do proteins enter the ER and what is the function? |
Recognised by a translocator pore on the ER surface using signal proteins Makes sure that proteins are folded properly |
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How do vesicles transport themselves and what ensures that they reach the correct target membrane? |
Walk along microtubules in cytoskeleton Have a protruding protein that is specific to shape of target membrane |
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Function of protein bodies in animals and plants |
Animals - growth and development Plants - stored in vacuole to provide sulfur, carbon and nitrogen foe growth |
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Function of chaperone proteins |
Assist correct intracellular folding of polypeptides in ER |
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Autophagy |
Lysis and recycling of misfolded proteins Originates in cytoplasm |
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Functions of vacuole |
Storage of carbohydrates, respiratory organic ions Homeostatic devise ensuring hydrostatic pressure and cell turgidity is maintained Anti-herbivory using cyaogenic glucosides e.g. ricin |
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Why does the majority of mtDNA come from the mother? |
Egg cell is larger than sperm cell and so contains more genetic information |
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Nucleotide |
Nitrogenous base Deoxyribose sugar Inorganic phosphate group |
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5' end |
Phosphate group end of DNA |
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3' end |
Hydroxy group end in DNA -OH |
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What forms DNA backbone? |
Neighbouring phosphate and sugar bonded together (covalent) Anti parallel held by hydrogen bonds |
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Purines |
Adenine and guanine 2 organic (carbon) rings |
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Pyrimidines |
Cytosine and thymine 1 organic (carbon) ring |
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Chargraff's rules |
Number of Adenine and Thymine bases equal Number if Cytosine and Guanine bases equal Base composition varies from species to species in relative base amounts |
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Semi-conservative replication |
Parent molecule with 2 complementary strands unwind Complementary strands separate Each daughter strand consists of one parental strand and one new strand |
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What sites does replication begin and how many are there in eukaryotes / prokaryotes? |
Origins of replication Where 2 DNA strands separate opening a replication bubble where replication occurs simultaneously in both directions Eukaryotes - many Prokaryotes - one |
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What is found at the end of a replication bubble? |
Replication fork where new DNA strands are being unwound |
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Topoisomerases |
Enzyme used in replication which corrects overwinding helping to relieve strain ahead of replication forks by breaking, swivelling and rejoining DNA |
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Helicase |
Breaks H bonds untwisting the double helix at the replication fork |
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Binding proteins |
Used in replication to stabilise single-stranded DNA preventing them from sticking back together again as they are being copied |
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DNA polymerase |
Catalyses the synthesis of a new DNA at a replication fork Requires a primer and a DNA template strand |
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Adding a nucleotide to a DNA strand |
Nucleoside triphosphates (dATP,dTTP etc ) add onto the free 3' end DNA replication occurs in the opposite direction to anti parallel helix so DNA strand inky elongates in 5'-3' |
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Lagging vs leading strand |
Leading strand =parental Lagging = new strand complementary to leading strand synthesised as a series of segments called Okazaki fragments |
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Okazaki fragments |
Segments of the lagging strand joined together by ligase which bonds together the sugar-phosphate backbone |
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Nucleosome and where is it found? |
DNA wound twice around 4 pairs of histone proteins supercoiled into the nucleoid |
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Looped domains |
Thick chromatin fibre formed by histone tail and linker DNA of nucleosomes |
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Difference between RNA and DNA |
Uses ribose sugar No thymine, uracil instead Single stranded |
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What is the difference in the way translation /transcription occurs in prokaryotes? |
DNA not segregated from ribosomes so translation can occur before transcription has finished |
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Triplet of nucleotide bases is called a |
Codon |
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Degeneracy |
More than one coin may specify a particular amino acid but no codon specifies more than one amino acid |
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What can be produced due to the universal nature of the genetic code |
Transgenic animals |
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Transcription unit |
Stretch of DNA that is transcribed into an RNA molecule |
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Terminator |
Sequence that signals the end of transcription |
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TATA box |
Promoter sequence which defines direction of transcription and indicates the DNA strand to be read Transcription factors recognise the box and bind to it before RNA polymerase 2 does to form the transcription initiation complex |
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Initiation of transcription at a eukaryotic promoter |
Transcriptional factor recognises TATA box and binds to the DNA. RNA polymerase 2 then binds too to form the transcription initiation complex |
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3 steps in transcription |
Initiation Elongation Termination |
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Termination step in transcription in eukaryotes |
RNA polymerase 2 transcribes the polyadenylation signal sequence in the pre-mRNA |
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Polyadenylation |
Used in termination of transcription Adds multiple adenine bases 3' end gets a poly-A tail |
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Untranslated regions |
Parts of mRNA that will not be translated into a protein |
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RNA splicing |
Removes introns and joins exons creating an mRNA molecule with a continuous coding sequence using a spliceosome |
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Spliceosome |
Excises pre -mRNA releasing the introns for degradation and splices the exons together |
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Alternative splicing and what this means |
Genes can encode more than one kind of polypeptide depending on which segments are treated as exons during splicing The number of different proteins that can be produced is grater than the number of genes |
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Which is junk DNA that is spliced out -introns or exons? |
Introns |
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Elongation step in transcription in eukaryotes |
Helicase untwists the double helix Nucleotide are added to the 3' end if the growing RNA molecule A gene can be transcribed simultaneously by several RNA polymerases, increasing the mRNA transcribed. This allows the encoded protein to be made in large amounts quickly in stressful situations |
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How is initiation in transcription different for bacteria |
RNA polymerase itself recognises and binds to the promoter No TATA box required |
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How is termination in transcription different in bacteria |
Polymerase stops transcription at the terminator RNA sequence |
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In which direction does both translation and transcription occur |
5'-3' |
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tRNA |
Used in translation 80 nucleotides held in place by hydrogen bonds into a clover shape Contains anticodons Recycled Picks up the designated amino acid in the cytosol and deposits it at the ribosome |
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Each amino acid is joined to the correct tRNA by |
Aminoacyl -tRNA synthetase (works as an enzyme and so is an active process) Each synthetase (20 kinds) has an active site specific for a particular amino acid Results in an aminoacyl tRNA |
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Wobble |
Flexible base pairing Anticodons of some tRNAs recognise more than one codon |
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Wobble |
Flexible base pairing Anticodons of some tRNAs recognise more than one codon |
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Ribosome structure |
Large and small subunit made of rRNA |
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P site on ribosome |
Peptidyl -tRNA Holds the tRNA that carries the growing polypeptide chain |
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A site on ribosome |
Aminoacyl tRNA site Space for enzyme to bind Holds the tRNA that carries the next amino acid to be added |
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E site in ribosome |
Exit site |
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3 stages of translation |
Initiation Elongation Termination |
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What can be produced due to the universal nature of the genetic code |
Transgenic animals |
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Promoter region |
Where RNA polymerase attaches to along with a primer in order to initiate transcription |
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Terminator |
Sequence that signals the end of transcription |
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Initiation of translation in eukaryotes |
Small ribosomal subunit carrying methionine binds to 5' cap of mRNA moving downstream until it reaches the complementary codon AUG Attachment of large ribosomal subunit using energy (GTP) forms translation initiation complex |
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Where is the initiator tRNA held |
P site of ribosome |
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Initiation of translation in bacteria |
Smal ribosomal subunit carrying methionine binds to mRNA at a specific RNA sequence just upstream of the start codon |
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Elongation of translation |
Amino acids are added involving elongation factor proteins 1. Codon recognition 2. Peptide bond formation 3. Translocation |
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Termination of translation |
When stop codon reached the A site of the ribosome a releasing factor binds to the stop codon causing hydrolysis of the hond between the polypeptide and its tRNA in the P site Polypeptide exits via exit tunnel Translation initiation complex dissassembles requiring GTP |
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Polyribosomes |
Used in translation to tail along the same mRNA to make many copies of a polypeptide simultaneously |
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Targeting polypeptides to specific locations |
Polypeptide has a signal peptide bound Signal recognition particle binds to this momentarily stopping translation Signal recognition particle leaves for ER and translation resumes Signal leaving enzyme cuts off signal peptide |
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If activator is degraded/represser binds to operator then transcription of lac operon is |
Blocked |
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Prokaryotic gene regulation when lactose is present |
Lactose binds to repressor causing a configuration change so that the repressor cannot hind to operator and so lac operon can be translated to produce lactase |
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What reduces lactose levels and makes the repressor change to its original shape What is this an example of? |
B galactosidase Negative feedback - as lactose levels decrease, b galactosidase levels imcrease |
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DNA isolation for microbes |
Heat or alkaline lysis |
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DNA isolation for higher organisms |
Salt, buffer and detergent to break open cell membranes |
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3 steps in PCR and their |
Denauration 94-98 Annealing = complementary primers to GOI (variable) Extension 72 = taq polymerase 5'-3' |
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PCR contents |
Template DNA Primers dNTPs Buffer Taq polymerase |
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Restriction enzymes |
Cuts palindromic sequences producing blunt/sticky ends |
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DNA ligation |
Enzyme which catalyses phosphodiester bonds between nucleotides using ATP |
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Cloning vectors |
provide the extra sequences required by the cloned genes to be replicated and expressed |
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Transformation of bacteria |
GOI put into cloning vector with ligation mixture and then heated onto a solid media allowing them to grow with selection OR Electroporation |
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Bacterial antibiotic selection |
If plasmid with resistance present then bacterium can multiply to form a colony |
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Nucleosome |
DNA wound round 8 histones resembling beads on a string Histone tails and linker DNA interact to form a fibre |
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Heterochromatin |
Condensed form of chromatin inaccessible to machinery responsible for transcription |
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Euchromatin |
Dispersed form of chromatin due to neutralised histone tails which drift apart Accessible to transcription machinery so contains genes to be transcribed |
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Gene regulation in transcription of eukaryotic cells Inactive Paused/stalled Elongation/active |
Inactive - RNA polymerase 2 not bound to promoter Paused- phosphorylated serine 5,RNA polymerase bound to TATA so transcription factors come into place Active - phorphorylated serine 5 and 2 |
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What is the advantage of double stranded hairpin small RNAs |
More stable |
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Which small RNA is used for repression of Gene translation |
miRNA |
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Which small RNA is used for promoting mRNA degradation |
miRNA |
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Which small RNA is used for repression of Gene transcription via chromatin remodeling and DNA methylation |
siRNA |
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Ubiquitin mediation degradation and what is used to do this |
Small RNAs = microRNA and siRNA Attach to protein to be degraded Recognised by a proteasome which unfolds the protein and sequestered it within a central cavity Enzymes in proteasome cut protein into small peptides to be degraded by other enzymes into cytosol |
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Functions of 5' end and poly-A-tail of mRNA ends |
Facilitates export of mature mRNA from nucleus after transcription Protects mRNA from degradation Helps ribosomes attach to 5' end to begin translation |
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Reporter construct |
Promoter region of gene fuses to visual marker to see whether GOI is switched on |
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3 types of reporter constructs |
GUS Fluorescent proteins Luciferase |
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GUS |
Reporter construct GOI binds to b glucronidase Blue stain shows enzyme activity seen by light microscope |
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Fluorescent proteins |
Reporter construct Jellyfish gene shown under UV Allows you to see no. of chromosomes |
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Luciferase |
Firefly gene binds to promoter Dark box and sensitive camera needed to detect chemiluminescence |
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2 ways of synthesis of insulin |
Bacteria - chains a and b produces from two plasmids whereby disulfide bonds form Eukaryote - proinsulin formed in yeast, disulfide bonds form then progressed used to purify it |
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What do black regions on a chromosome represent? |
Condensed heterochromatin |
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Cloning a genome |
Fragmented using REs Packaged into bacterial artificial chromosomes which can then be amplified |
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Finding the GOI |
Nucleic hybridisation based on complementary base pairing |
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Sickle cell anaemia |
Single nucleotide polymorphism mutation creates a polar, hydrophilic protein instead of a non polar, hydrophobic one creating a rigid discoid shape which melts as O2 is taken up |
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Feedback inhibition |
Final product can repress expression of the genes needed for all the enzymes needed for the pathway (long term) Enzyme can inhibit the activity of the first enzyme in the pathway (short term) |
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Tight junctions |
Holds plasma membranes in close proximity together Maintains polarity Restricts movement of ions and molecules |
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Physical communication between plant cells |
Plasmodesmata |
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Lipid bilateral membrane structure |
Phospholipid made up of non polar hydrophobic tail and polar hydrophilic head |
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Passive transport |
Molecule following concentration gradient, no energy required |
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Active transport |
Transport of molecule against concentration gradient requiring energy |
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Ion channel |
Ions pass down their electrochemical gradient without input if metabolic energy |
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Aquaporins |
Membrane channel for transport of water, glycerol, CO2 Allows osmosis |
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2 forms of ATP driven membrane transport |
P-type pump transports specific ions ABC transporters found everywhere on membrane transports lots of different substabces |
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Human chromosome |
23 pairs Diploid |
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Polyploidy |
Multiple sets More than two complete chromosome sets |
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Aneuploidy |
Incomplete number of chromosomes One or more chromosome has an extra copy or is deficient |
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Karyotype |
Display of the chromosome pairs of a cell arranged by size and shape |
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Chromosome translocation |
Non homologous fusion |
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Chromosome deletion |
Part missing |
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Chromosome inversion |
Chromosome fragment in wrong direction /orientation |
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Dispermy |
Greater than 2 sets of chromosomes |
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3 forms of aneuploidy |
Nullisomy = both members of a chromosome pair missing Monosomy = one member of a pair is missing Trisomy = one extra chromosome |
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2 forms of chromosome inversion |
Paracentric - centromere excluded Pericentric - centromere included |
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Substitution mutation |
Code for same amino acid =silent/synonymous Code for different amino acid =replacement/nonsynonymous |
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Consequence of insertion/deletion mutation |
Shift in reading frame |
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Coding region mutations |
Substitutions Insertions Deletions |
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SNP |
Non coding region mutation Single Nucleotide Polymorphisms |
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Satellite DNA |
Very variable non coding DNA nearly always harmless sit used as a genetic marker i. e parent tests |
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Why garden pea (pisum sativum) is a model organism |
Readily available Short generation time Large number of progeny Easy to manipulate via cross pollination |
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Observation from Mendelian Genetics |
Alternative versions of a gene (allele) cause variation An organism inherits one allele from each parent Alleles can be dominant or recessive Alleles segregate during gamete production at random |
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Principle of segregation |
Two members of a gene pair segregate during meiosis at random. Half of the gametes carry one member of the pair and the other carry the other half |
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What would the blending hypothesis result in? |
Clones - genetically uniform |
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Independent assortment and what is the exception |
Alleles of different genes segregate from each other at random Recombination -crossing over When two genes are physically proximate on the same chromosome |
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If a disease only involves one gene it is known as |
Mendelian/monogenic |
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If a disease involves more than one gene it is known as |
Multifactorial |
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Which chromosome pairs are autosomal |
1-22 |
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Characteristics of autosomal dominant disease Affected person's parental genotype Sex of affected Transmitted by which sex |
At least one affected parent Affects either sex Transmitted by either sex |
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Characteristics of autosomal recessive disease Phenotype of affected's parents Affects which sex Increased incidence of |
Carriers/unaffected Affects either sex Inbreeding |
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Characteristics of X-linked recessive Affects which sex Carriers are which sex |
Affects mainly males Females only affected if father is affected and mother is a carrier Males cannot be carriers, can only be affected due to only having 1 X chromosome |
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Characteristics of X - linked dominant Affects which sex All female children of affected male are All male children of affected male are |
Both sexes Affected Unaffected |
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Characteristics of Y - linked disorder Affects which sex All sons of affected man are |
Only males Affected |
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Recombination occurs in what stage |
Meiosis prophase 1 |
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Recombination processes required |
Recombination enzyme to cut Ligase to anneal nicked ends into new combinations |
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Recombination fraction Units Equation Meaning |
Measure of distance between two genes Units = cM (centiMorgans) Number of recombinants/(no. of recombinant + non-recombinant) Higher recombination fraction means a higher frequency of recombinants/recombination that occurs |
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Evolutionary significance of recombination |
Produce potentially be fitter genotypes Speeds up rate of evolution in sexual organisms (asexual organisms so not recombine) |
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Double recombination evidence |
All offspring appear to be recombinant |
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Barr body |
Females inactive one of their X chromosomes in each cell to match the dosage found in men Inactive X chromosome condenses along the inside of the nuclear envelope |
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Why is recombination fraction never more than 50% |
Only 2 of the 4 chromatids recombine |
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Locus |
Physical position of a gene along a chromosome |
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Hardy weinburg assumption and requirements |
Gene frequency stays same in future generations Random mating No natural selection Large population size No migration No mutation |
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Selection coefficient |
Difference between the standard relative fitness (1.0) and fitness of genotype in question |
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When an allele increases in frequency it is said to be under what kind of selection? |
Positive |
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Balancing selection |
Form of natural selection where heterozygotes are fitter than homozygotes |
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What kind of populations have a lower chance of survival |
Small genetically homogeneous |
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In what kind of populations is inbreeding more likely to occur |
Small |
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Wright's inbreeding coefficient (f) |
Measure of degree of inbreeding in individuals Higher f = more inbred |
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Consequences of inbred populations |
High frequencies of homozygotes meaning that dangerous recessive alleles are easily revealed and thus less likely to be benefitted from (heterozygote advantage ) Less fit = inbreeding depression |
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Linked genes |
Genes on the same chromosome Normally close in proximity so that they are inherited together |
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2 models explaining human population genetics |
Multi regional Out of Africa |
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Multi regional model |
Homo erectus left Africa and dispersed over several continents (All humans derive from Homo erectus ) Gene flow between many populations - high genetic density |
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Out of Africa model |
Homo sapiens migrated out of Africa replacing all populations descending from Homo erectus without interbreeding African populations should have the greatest diversity |
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Evidence for Out of Africa model |
Negative relationship between genetic diversity and their geographical distance from Africa African populations are more polymorphic -> as first population moved this acted as a succession of genetic bottlenecks as they travelled further Humans emerged in Africa 120-140KYA, humans spread from Africa 30-80KYA |
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Our closest living relative and how we figured this out |
Chimpanzees Time to most common ancestor (TMRCA) |
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What is the best way to achieve accurate TMRCA |
Test non-recombining molecules e.g. mtDNA and Y chromosome |
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As humans migrated out of Africa how did they face the new climate Eumalanin - black/brown pigments Phaemelanin - red/yellow pigments |
Skin colour
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How do we know that humans and Neanderthals inhabited the same geographical regions |
Shared headlice |
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Effects of UV |
Sunburn Cancer Nutrient photodegradation Synthesis of vitamin D |
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Downside of having dark skin in bright environment |
Little vitamin D produced so high vitamin D diet is needed |
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Genome |
Complete set of genes in an organism |
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Difference between intergenic DNA and introns |
Both non coding DNA Introns = non - translatable Intergenic = non - transcribed |
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Pseudogenes |
Former genes that have accumulated mutations and are nonfunctional |
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Discontinuous phenotypic variation |
Discrete classes, no intermediates Not influenced by environment so Mendelian ratios observed |
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Continuous phenotypic variation |
No classes, intermediates present Influenced by environment so Mendelian ratios observed |
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Percentages of standard deviations from mean |
1 sd = 68% 2 sd = 95% |
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Threshold variation |
Appears discontinuous but is caused by a multi factorial continuous distribution Distribution called liability Phenotype depends on threshold |
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Quantitative trait locus |
Area of DNA containing genes (close together) for a phenotype due to continuous variation |
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Heritability |
Total variation within a population for a phenotype Add genetic variance and environmental variance (so long as the effects are independent ) |
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Broad sense heritability |
Proportion of phenotypic variation due to genotypic differences Genetic variance /(genetic variance and environmental variance) |
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How do inbreeding influence the heritability value |
More inbred =lower heritability |
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Vp equation with genotype-environment interaction |
Vp =Vg + Ve + Ve x g |
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Norm of reaction |
Curve indicating contribution of environmental variation to phenotypic variation |
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Difference between broad sense and narrow sense heritability |
Broad is specific to the population and environment in which it is measured Narrow is proportion of variation passed on to offspring |
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Multi niche polymorphism |
Different phenotypes for each niche within a species |
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Signs that natural selection is acting on a trait |
Heritable variation in trait Competition for resources Differences in fitness that depend on trait |
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Narrow sense heritability |
Predicts how trait will respond to selection Response to selection (change in mean per generation )/ difference between mean and selected group |
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Effect of selection of quantitative traits on genetic variance Directional Stabilising Disruptive |
Directional - same Stabilising - decrease Disruptive - increase |