BY5 Key Words

noahtattersall's version from 2015-06-15 10:28


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Semi-conservative theoryMolecules of DNA created with one strand made of entirely new material and the other made of entirely original material.
GeneLength of DNA on a chromosome normally coding for a particular polypeptide.
Triplet codeMade up of 3 bases.


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Degenerate codeAs most amino acids have more than one triplet code.
DNA helicaseActs on a specific region of the DNA molecule, the cistron, to break the hydrogen bonds between bases.
RNA polymeraseCopies a sequence of DNA to create RNA.
HaploidHalf the chromosome number.
Homologous chromosomesA pair of chromosomes, one maternal and one paternal, that have the same gene loci and determine the same features.


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ChromatidOne of the two copies of a chromosome that are joined together by a single centromere prior to cell division.
How meiosis creates genetic variationIndependent assortment of homologous chromosomes, Crossing over between chromatids of homologous chromosomes.
GenotypeThe genetic makeup of an organism.
Seminal vesicleProduces secretion which aids sperm mobility.
Prostate glandProduces alkaline secretion to neutralise acidity of urine as well as aiding sperm mobility.


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Seminiferous tubulesProduces spermatozoa
EndometriumA mucus membrane lining the uterus. It is part of the womb during pregnancy and is shed during menstruation.
SpermatogenesisThe formation of sperm in the testis.
OogenesisThe formation of eggs/ova in the ovary.
Sertoli CellsSecrete a fluid which nourishes the spermatids and protects them from the immune system of the male.


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Graafian follicleA mature follicle containing a secondary oocyte.
Corpus luteumProduces hormones during pregnancy but regresses if fertilisation doesn’t take place.
Zona pellucidaA clear membrane surrounding the secondary oocyte.
BlastocystA hollow ball of cells.
TrophoblastThe outer layer of the blastocyst which develops into two membranes, the amnion and chorion.


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Human chorionic gonadotropin (hCG)Secreted by the chorion in order to prevent the corpus luteum from degenerating.
Monoclonal antibodyMany copies of one type of antibody.
AntigenA non-self-protein that is recognised by the immune system and brings about an immune response.
In vitro fertilisation (IVF)Test tube baby
StamenMale part of the plant = anther + filament


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CarpelFemale part of the plant = stigma + style + ovary
Self-pollinationPollen from the anthers transferred to stigma on same flower or another flower on the same plant.
Cross-pollinationPollen is transferred from the anthers of one flower to the stigma of another flower on another plant of the same species.
Insect pollinated flowersColourful petals, scent, nectar, Anthers within flower, Stigma within flower, Small quantities of sticky pollen
Wind pollinated flowersSmall, green and inconspicuous, no scent, usually no petals, Anthers outside flower, Large, feathery stigmas, Large quantities of small, smooth, light pollen


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DehiscenceTo burst open releasing pollen grains.
ExineOuter wall of pollen grain
IntineInner wall of pollen grain
Double fertilisationMale gamete + female nucleus = zygote, Male gamete + two polar nuclei = triploid endosperm nucleus
Development of fruit and seedZygote → embryo (plumule, radicle and cotyledons), Triploid endosperm nucleus → food store, Integuments → testa, Ovule → seed, Ovary → fruit


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DicotyledonTwo seed leaves/cotyledons
MonocotyledonOne seed leave/cotyledon e.g. cereals
DormancyA period when active growth is suspended. Germination occurs when specific conditions are met.
Conditions for germinationSuitable temperature, Water, Oxygen
Mobilising food storesAmylase hydrolyses starch into maltose, Proteases convert proteins to amino acids


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AlleleOne of the different forms of a gene
GeneSection of DNA on a chromosome coding for a particular polypeptide.
PhenotypeAppearance of an organism.
Co-dominance Both alleles contribute to the phenotype.
Monohybrid inheritanceThe inheritance of a single characteristic. (two alleles involving a single gene)


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Dihybrid inheritanceThe inheritance of two separate genes.
Mendel’s first law of inheritanceThe law of segregation – “The characteristics of an organism are determined by factors (alleles) which occur in pairs. Only one of a pair of factors (alleles) can be present in a single gamete.”
Mendel’s second law of inheritance“Each member of an allelic pair may combine randomly with either of another pair”
ProbabilityRules of addition (getting heads plus tails = 0.5+0.5), Rules of multiplication (getting heads then heads again = 0.5x0.5)
Chi^2 (Chi squared)If significance is at or below 5%, the result is significant and something other than chance is affecting the result, If significance above 5%, the result is non-significant and is simply the result of statistical change.


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Expected values of Chi^2[Total number x ratio of them]/[Total number of types (ratio)]
Chi^2 formulaSUM OF [(O-E)^2]/E
Degrees of freedomOne less than the number of classes of data.
Sex-linked geneA gene located on a sex chromosome.
AutosomeA chromosome that is not sex-linked.


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CarrierHas one normal gene and one potential harmful recessive gene. They are phenotypically normal.
LinkageWhen two different genes are located on the same chromosome. They are inherited together (as they move together during meiosis) and pass into the gametes together.
MutationsA change in the amount, arrangement or structure in the DNA of an organism. Can happen in two ways-DNA not copied properly before cell division, Chromosomes are damaged and break
Sickle-cell anaemiaGenetic disorder where red blood cells become sickle shaped and less able to transport oxygen.
Non-disjunctionA faulty cell division where one of the cells receives two copies of a chromosome while the other gets none.


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PolypoloidyAn increase in a complete set of chromosomes.
OncogeneA mutates gene that causes cancer
Selective advantageCharacteristic of an organism that enables it to survive and reproduce better than other organisms in a population in a given environment.
Intra-specific competitionCompetition between individuals of the same species.
Inter-specific competitionCompetition between individuals of different species.


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Selection pressuresAvailability of prey, Presence of predators, Environmental stresses, Competition with other species, Intra-specific competition
PopulationA group of interbreeding individuals of the same species, occupying the same habitat at the same time.
Gene poolThe total number of alleles in a population at any one time.
Allele frequencyThe number of times an allele occurs within the gene pool.
Genetic driftChance variations in allele frequencies in a population.


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Natural selectionA process that encourages the transmission of favourable alleles and hinders the transmissions of unfavourable ones and contributes to evolution.
IsolationOccurs when a barrier prevents two populations from breeding with one another. Geographical isolation → Allopatric speciation, Reproductive isolation → Sympatric speciation
SpeciesA group of similar organisms that can interbreed to produce fertile offspring.
DemeA breeding sub-unit
SpeciationThe evolution of new species form existing species.


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Behavioural isolationThe steps in the display of one subspecies, with elaborate courtship, fails to attract the necessary response in a potential partner of another subspecies.
Mechanical isolationThe genitalia of the two groups may be incompatible.
Gametic isolatione.g. sperm unable to survive in oviduct of partner
Hybrid inviabilityFertilisation takes place but development of the embryo may not occur. (e.g. chromosomes no longer match each other)
Hybrid sterilityIndividuals of a different species breed, the sets of chromosomes from each parent are different. Sets are unable to pair up during meiosis and so offspring are unable to produce gametes. Hybrid is sterile.


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CloneA group of genetically identical organisms formed from a single parent as a result of asexual reproduction or by artificial means.
Stem cellAn undifferentiated stem cell capable of dividing to give rise to cells which can develop into different types of specialised cells.
Totipotent cellsCells which can mature into a body cell.
MeristemGrowing points where cells divide rapidly by mitosis.
ExplantsSmall pieces of meristem.


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CallusMass of undifferentiated cells.
Human Genome ProjectRecords the complete base sequence of human DNA. Identifies genes formed by bases. Finds location of genes. Produces database of genes
Gene probeShort piece of DNA the sequences of which are complementary to the mutated sequence.
LiposomeMinute spheres of lipid molecules, capable of carrying DNA inside them.
Donor DNAA gene that is isolated for insertion.


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Restriction enzymeEnzyme which cuts DNA molecules between specific base sequences.
Reverse transcriptaseEnzyme used to synthesise DNA from mRNA in specific cells.
IntronPortion of DNA within a gene that does not code for a polypeptide.
PlasmidCircular loop of DNA found in bacteria. Known as a vector.
DNA ligaseEnzyme which joins together portions of DNA (plasmid to DNA)


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Recombinant DNADNA which results from the combination of fragments from two different organisms.
TransgenicAn organism that had its genotype altered producing a new strain of organism. (Genetically modified organisms)
ElectrophoresisExposing the fragments of DNA to an electric current in a gel trough.
PrimerShort sequence of nucleotides
Biological productivityPrimary productivity = the production of new organic matter by green plants, Secondary productivity = the production of new organic matter by consumers


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Photosynthetic efficiency (PE)The ability of a plant to trap light energy.
Gross Primary Productivity (GPP)The rate at which products, such as glucose, are formed.
Net Primary Productivity (NPP)The energy left over after respiration. (food available to primary consumers)
BiomassThe mass of living material present at a given time.
SuccessionThe change in structure and composition of species of a community over time.


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Climax communityA community that has reached equilibrium with its environment and no further change occurs.
SereStage in succession
ResistanceThe ability of an organism to survive exposure to a dose of that poison which would normally be lethal to it.
EcotourismThe responsible travel to natural areas that conserves the environment and improves the well-being of local people.
MonocultureThe simultaneous growth of large numbers of crop plants of similar age and type within a defined area.


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Soil erosionThe removal of top soil containing valuable nutrients.
CoppicingThe cutting down of trees close to the ground and then left for several years to re-grow.
Selective cuttingFelling only some of the largest trees, leaving the others in place
Long time rotationLeaving each part of the forest for many years before re-harvesting it.
Overfishing The rate at which fish are harvested exceeds the rate at which they reproduce.


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Drift nettingSuspending a net from floats stretched between two boats so that fish swim into it.
TrawlingDragging a large net through the water, catching whatever happens to be in the way.
EutrophicationThe artificial enrichment of aquatic habitats by excess nutrients, often caused by run-off of fertilisers, resulting in a reduction in the oxygen level of the water.
BiofuelAny type of fuel that is biological in origin e.g. wood, ethanol, sugarcane, corn, rapeseed