Genetics Flashcards
(28 cards)
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).
The specific linear position of a particular gene on a certain chromosome
Locus
Alternative form/variation of a particular gene with different base sequences, and therefore different codes
Alleles
A pair of homologous chromosomes carrying the same alleles for a single gene
Homozygous
Heterozygous
A pair of homologous chromosomes carrying teo different alleles for a single gene
An allele that always expresses itself in the phenotype in heterozygous organisms
Dominant
Recessive
An allele only expresses if no dominant allele is present
Co-dominant
Alleles which both contribute to the phenotype (i.e. produce a blended effect) in the heterozygous condition. Both alleles are equally dominant and expressed in the phenotype
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. More than two alleles for a single gene
Multiple alleles
Pure-breeding strain
Group of organisms in which a certain characteristic is unaltered for generations, indicating that organisms are homozygous for that feature
Inheritance of a single pair of alleles. Genetic inheritance cross of a characteristic determined by one gene
Monohybrid
Dihybrid
Inheritance of two pairs of alleles. Genetic Inheritance cross for a characteristic determined by two genes
Cell or nucleus containing single, unpaired chromosomes
Haploid (n)
Diploid (2n)
Cell or nucleus containing pairs of homologous chromosomes
The observable or biochemical characteristics of an organism, resulting from both its genotype and the effects of the environment. The expression of a gene and its interaction with the environment
Phenotype
Genotype
The combination of alleles present within the cells of an organism. The alleles an organism has for a gene
Features determined by genes (rather than the environment) and therefore passed on to offspring
Heritable
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. Have the same genes
Ratio
A measure of the relative size of two classes that is expressed as a proportion.
Any gene that is carried on either the X or Y chromosome. A gene whose locus is on the X chromosome
Sex linked
The situation where two or more genes are carried on the same autosome/chromosome.
Autosomal linkage
A chromosome which is not a sex chromosome
Autosome
Epistasis
This arises when the allele of one gene affects or masks the expression of another in the phenotype. When one gene modifies or masks the expression of a different gene at a different locus
Carrier
A person carrying an allele that is not expressed in the phenotype but can be passed on to the offspring
