Molecular Basis of Life Flashcards
Define autosome
Any chromosome other than a sex chromosome
Define allele
Alternative versions of the same gene (A or a)
Define backcross
A test cross in which an individual is crosses with its parental genotype
What is blending theory?
An ancient theory of heredity which predicted that progeny should show a mixture of parental genotypes
What human trait shows a distinct flaw in the blending theory of heredity
Gender
When humans reproduce, they produce males and females, with an average 50:50 ratio.
They rarely produce hermaphrodites, showing that gender cannot be blended.
What is a character?
Any measurable or observable property of an organism
Define chiasmata
Cross over structures formed by two chromatids in prophase 1 of meiosis
Define codominance
Each of two alleles of a gene are expressed so that each displays it’s own separate phenotype in the heterozygote
Define dihybrid cross
A cross in which the inheritance of two characters or genes is studied
What is a diploid?
A cell or individual organism with two complete sets of chromosomes
Define dominant
The member of a pair of alleles of a gene (A) that is expressed in the heterozygote
Define epistasis
An interaction of gene such as one disguises the effects of a second gene in the phenotype
What is a gamete?
A reproductive cell (such as sperm in humans or pollen in plants) that fuses with a partner gamete (egg cell) to form a fertilised zygote
What is a gene?
A genetic unit of function that determines a hereditary character
Define genotype
The genetic information or constitution of an individual organism or cell
Define haploid
A cell or individual organism carrying one set of chromosomes
Define heterozygote
A cell or organism that carries different alleles of a particular gene (Aa)
Define homozygote
A cell or organism that carries the same alleles of a particular gene (AA or aa)
Define incomplete dominance
Neither allele of a gene shows dominance to give an intermediate phenotype in the heterozygote
E.g. Pink carnation from White and red
What is an intercross?
A cross between two individuals
Define lethality of genes
A genotype that leads to the death of the cell or organism
Define linkage
Genes carried on the same chromosome tending to be inherited together
What is mapping?
The process of locating individual genes in their relative positions on a chromosome
Define meiosis
The process of reductive division of a cell leading to the halving of the diploid number of chromosomes
What is a monohybrid cross?
A cross in which the inheritance of one character or gene is studied
Define mutation
Any permanent heritable change in the genetic material (making the cell or individual a mutant)
What is a pedigree?
A diagram of a family tree showing the inheritance of a trait or traits down the generations
Define phenotype
The observable or measurable appearance of an organism or cell caused by it’s genotype, environment, and interactions of the two
Define recessive
The member of a pair of alleles of a gene that is not expressed in the heterozygote (a)
Define reciprocal
A pair of crosses, where the trait is carried by one sex in the first cross, and by the other sex in the second cross
Define recombination
A new association of alleles in the progeny caused by crossing over during meiosis
What is selfing?
When an individual is allowed to self fertilise to produce the next generation
Define sex chromosome
The chromosomes that determine the sex of an individual
Define sex influenced
An autosomal trait that may be expressed in either sex, but whose pattern of expression depends upon the sex of the individual
Define sex limited
An autosomal trait whose expression is limited to one sex
Define sex linked
A trait determined by a gene carried on sex chromosome
What is a test cross?
A cross test set up to determine the genotype of one parent by mating with a parent of known genotype
What is a trait?
One of the observable forms that a character may show
Define wild type
The common or reference form normally found in a natural population of an organism
