inheritance, variation and evolution

• polydactyly is a condition where an individual is born with extra fingers or toes due to the presence of a dominant allele
• recessive describes an allele that is only expressed in the absence of a dominant allele (represented by smaller letters)
• phenotype is an organisms observable characterisitcs sue to interactions of the genotype and the enviroment
• selective breeding is the process by which humans artifcially selected organisms with desirable characteristics and breed them to produce offspring with desirable phenotypes
• linnaean system is the classification of organisms into kingdom, phylum, class, order, family, genus and species, as developed by carl linnaeus
• classification is the organisation of organisms into groups based on their characteristics and structure
• DNA is a double-stranded polymer wound to form a double helix which carried the genetic code
• the genome is the complete genetic material of an organism
• an allele is a version of a gene
• embryo screening is a procedure used to determine the presence of faulty genes in an embryo produced by IVF, a few embryonic cells are removed and screened for defective alleles
• GM crops are crops that have had their genomes modified by the insertion of a desired gene from another organism
• cystic fibrosis is a cellular membrane disorder resulting from the presence of a recessive allele
• MRSA is a type of bacteria that is resistant to the antibiotic, methicillin
• binonial system is the universal system of naming organisms using their genus and species
• sex chromosomes are a pair of chromosomes responsible for the determination of gender:
• natural selection is the process by which the frequency of advantages traits passed on in genes gradually increases in a population over time
• adaptation is a feature of an organism that increases its chance of survival in its enviroment. such features maybe behavioural, structural or functional
• inbreeding is the formation of offspring from the breeding of closely related individuals
• extinction the death of all members of a species
• asexual reproduction is a form of reproduction involving a single parent and creates genetically identicle offspring
• dominant described an allele that is always expressed
• variation is the differences between individuals due to genes, the enviroment or a combination of both
• species is a group of similar organisms that are able to breed with one another to produce fertile offspring
• heterozygous is when someone has two different alleles of a gene
• homozygous is when someone has two identicle alleles of a gene
• genetic engineering is a modification of the genome of an organism by the insertion of a desired gene from another organism, enabling the formation of organisms with benefical characterisitcs
• gametes are sex cells with half the chromosomes
• fertilisation is the fusion of the nucleus of the male and female gametes
• the genotype is an organisms genetic composition describes all alleles
• a vector is a carrier used to transfer a gene from one organism to another
• the three-domain system is a method of classification in which organisms are categorised into three groups archaea, bacteria and eukaryota
• a mutation is a randome change in DNA which may result in genetic variants
• an evolutuonary tree is a diagram which illustrates the evolutionary relationships between organisms
• evolution is the gradual change in the inherited traits within a population over time and occurs due to natual selection
• population is all organisms of the same species living with one another in a habitat
• a species is a group of similar organisms that are able to breed with one another to produce fertile offspring
• a punnet square is a grid used to predict the potential outcomes of a genetic cross
• Nucleotides consist of , a sugar, a phosphate
• The genome is the entire genetic material
• Nucleotides are attached to each sugar on the opposite strand