Unit 6 Biology Definitions

Asexual reproduction

produces new individuals that are identical to their parents

does not involve the fusion of gametes

Gamete

a specialised sex cell formed by meiosis

Runners

long shoots from plants, such as strawberries, that are used for asexual reproduction

Meiosis

cell division that forms daughter cells with half the number of chromosomes of the parent cell

DNA

nucleic acid molecules that contain genetic information and make up chromosomes

Chromosomes

long molecules found in the nucleus of all cells:made from DNA

Gene

part of a chromosome, made of DNA, which codes for a protein

Genome

all the genetic material found in an organism or a species

Polymer

a large molecule that is made up of many repeating units

Nucleotide

a molecule made of a phosphate group, a sugar and an organic base

Collagen

a protein found in connective tissue under the skin and in tendons

Mutation

a spontaneous change in the genetic material of a cell

Allele

an alternative form of a particular gene

Genotype

the combination of alleles an individual has for a particular gene, e.g. BB, Bb or bb

Phenotype

the physical expression of the genotype, i.e. the characteristic shown

Dominant

an allele that only needs to be present once in order to be expressed

represented by a capital letter

Recessive

an allele that will only be expressed if there are two present

represented by a lower case letter

Homzygous

when an individual carries two copies of the same allele for a gene, e.g. BB or bb

Heterozygous

when an individual carries two different alleles for a gene, e.g. Bb

Monohybrid inheritance

the pattern of inheritance shown when a characteristic is controlled by a single gene

Punnett square

a type of diagram used to work out the outcome of genetic crosses

Polydactyly

a genetic disorder caused by a dominant allele, where affected people have extra fingers or toes

Cystic fibrosis

a genetic condition that causes a build

Sex chromosomes

the pair of chromosomes that determine the sex of organism

Variation

differences between individuals of the same species

Evolution

a gradual change in a group of organisms over a long period of time

Natural selection

the survival of individual organisms that are best adapted to their environment

Fossils

the remains of animals / plants preserved in rock

Selective breeding

the breeding process used by scientists and farmers to produce organisms that show the characteristics that are considered useful

Genetic engineering

the process of moving a gene from one organism to another

Genetically modified (GM)

organisms that have had specific areas of their genetic material changed using genetic engineering techniques

Clone

an offspring that is genetically identical to the parent organism

Cuttings

a method of asexually reproducing plants, used by gardeners, by planting small lengths of plant shoots

Tissue culture

a method of producing large numbers of plants asexually by growing small parts of plants in a nutrient jelly

Surrogate

a female that gestates and gives birth to an organism that has not been produced from one of her own egg cells

Binomial system

the method of naming organisms by using their genus and species

Genus

a group of closely related species

Species

a group of organisms that can reproduce with each other to produce fertile offspring

Three domain system

a new classification system that divides organisms into three domains rather than five kingdoms

Extinct

describes a species that has died out

Speciation

where populations have become so different that successful interbreeding is no longer possible