Vocab Flashcards
Allele
An alternative form of a gene
Centromere
The point where the 2 chromatids are joined together
Chiasma
The point at which chromatids break and re-join in crossing over
Chromosome
A structure in the nucleus made up of DNA which holds the genetic information of an organism
Diploid
Full or complete number of chromosomes 2n/2 sets = 46 in humans
Homologous pair
A pair of chromosomes with the same genes but may have different alleles
Dominant
An allele that is always expressed if present - only one copy needed
Gamete
Sex cell. Egg or sperm in humans
Gene
A section of a DNA molecule that codes for a protein/characteristic
Gene Pool
The total variety of genes and alleles present in a sexually reproducing population available to be passed on to the next generation
Genome
All of an organism’s genes
Haploid
Half the normal number of chromosomes n/1 set = 23 in eggs or sperm
Heterozygous
Alleles are different eg. Tt
Homozygous
Both alleles are the same eg TT, tt
Linked
Genes that are located on the same chromosome
Locus
Position of a gene on a chromosome
Meiosis
Type of cell division producing four daughter cells each genetically different, with half the number of chromosomes of the parent cell = produces gametes
Crossing over
Exchange of genetic material between homologous chromosomes aka the inner chromatids during meiosis
Independent assortment
Each homologous pair of chromosomes are lined up randomly and are sorted independently of the other pairs during meiosis putting chromosomes/alleles into new combinations increasing genetic variation
Segregation
In meiosis the 2 members of the pair of alleles of a gene becomes separated into different gametes so the allele can join with a different allele of that gene at fertilisation
Mutation
A sudden change in the genetic base sequence of DNA in an organism
Phenotype
How the gene is expressed/what the organism looks like
Recessive
An allele that is only expressed when it is present in two copies - the dominant allele must be absent
Somatic cells
Body cells other than sex cells
Species
A group of organisms which can interbreed sexually and produce fertile offspring
Testcross
Finding the genotype of an individual showing dominant phenotypes by crossing them with a homozygous recessive individual and looking at the phenotypes of the offspring
Adaptation
A feature an organism has which helps it survive in its environment. It can be structural, behavioral or physiological
Allele frequency
The proportion of a particular allele in a gene pool, relative to the other alleles of the same gene
Evolution
Changes in the frequencies of alleles in a population over time
Natural selection
The process where individuals with favorable combinations of alleles are more likely to reproduce successfully and pass on these traits
Gene flow
The introduction of genes/alleles from one population to the gene pool of another - migration
Genetic variation
All the genes, alleles, and their combinations present in a population
Genetic drift
Random changes in allele frequencies in a population due to chance
Inbreeding
Mating of closely related individuals of the same species
Population
Members of the same species living in the same area at the same time
Environmental factors
Factors which select for or against particular phenotypes in the process of natural selection
Founders effect
Change in allele frequencies when a new population arises from only a few colonizing individuals. The new population will have reduced genetic diversity/smaller gene pool
Bottleneck effect
Recovery of a population after a catastrophic event, the range of alleles will decrease and the frequencies of alleles will change. The recovered population will have reduced genetic diversity
Sexual selection
Selection based on the choice of mating partners, usually female.
This leads to evolutionary change if choices are based on differences in inherited characteristics e.g tail length in peacocks
