Inherited change - Yr 2 Flashcards
Gene
Section of DNA on a chromosome that controls a feature by coding for formation of one or more specific polypeptides or a functional RNA (including rRNA and tRNA).
Locus
The specific linear position of a particular gene on a certain chromosome
Alleles
Alternative forms of a particular gene with different base sequences, and therefore different codes
Homozygous
Situation or organism in which paired alleles are the same
Heterozygous
Situation of organism in which paired alleles are different
Dominant
An allele that expresses itself in the phenotype in heterozygous organisms
Recessive
An allele that does not express itself in the phenotype in heterozygous organisms
Co-dominant
Alleles which both contribute to the phenotype (i.e. produce a blended effect) in the heterozygous condition
Multiple alleles
If there are more than two alleles for each gene in the gene pool. NB. Only 2 chromosomes in a homologous pair so only 2 of the three or more alleles can be present in a single organism
Pure-breeding strain
Group of organisms in which a certain characteristic is unaltered for generations, indicating that organisms are homozygous for that feature
Monohybrid
Inheritance of a single pair of alleles
Dihybrid
Inheritance of two pairs of alleles
Haploid (n)
Cell or nucleus containing single, unpaired chromosomes
Diploid (2n)
Cell or nucleus containing pairs of homologous chromosomes
Phenotype
The observable or biochemical characteristics of an organism, resulting from both its genotype and the effects of the environment
Genotype
The combination of alleles present within the cells of an organism
Heritable
Features determined by genes (rather than the environment) and therefore passed on to offspring
Homologous chromosomes
A pair of chromosomes, one maternal and one paternal, that have the same gene loci and therefore determine the same features. They are not necessarily identical as may have different alleles. They are capable of pairing during meiosis.
Ratio
A measure of the relative size of two classes that is expressed as a proportion.
Sex linked
Any gene that is carried on either the X or Y chromosome.
Autosomal linkage
The situation where two or more genes are carried on the same autosome.
Autosome
A chromosome which is not a sex chromosome
Epistasis
This arises when the allele of one gene affects or masks the expression of another in the phenotype.
