Mendel and the Gene Idea Marie Černá
Mating in peas Carpel – ovules => female gametes Stamens – anthers (pollen grains) => male gametes
Mendel’s terms • character – a heritable feature (flower color) • trait – each variant for a character (purple or white for flower color) • hybrid - the result of breeding (hybridization) two different variants of a character monohybrid cross - only one character is studied dihybrid cross - two characters are studied simultaneously
Mendel’s experiments • P generation (parental) – self-pollinating their hybrid offspring: • F1 generation (first filial) • F2 generation (second filial)
Mendel’s experiment results • the law of hybrid uniformity in the F1 generation • phenotypic ratio of the F2 generation 3:1 • genotypic ratio of the F2 generation 1:2:1
The two fundamental principles of heredity: • The law of segregation • The law of independent assortment
The law of segregation the two alleles for a character are packaged into separate gametes the two alleles for each character segregate during gamete production
The law of independent assortment each pair of alleles segregates into gametes independently in polyhybrid cross, where pairs of alleles are on separate chromosomes
Genetics Science about heredity and variability of organisms Heredity and variability allow evolution of organisms on the Earth
Heredity The ability of parent organisms to pass theircharacters in form of talents (genes) on their descendants. It is manifested by reproduction. It allow to conserve characters of organisms. It allow continuing biological species.
Variability The ability of organisms to change their characters. It allow adaptation of organisms to certain environment. It allow evolution of biological species.
Gene (character) information for formation of certain organism’s biochemical character DNA region that codes information for formation of certain protein Gene expression - realization of genetic information - production of certain protein
Allele (trait) particular form (alternative version) of a gene is defined by nucleotide alignment in DNA is characterized by its own function activity For each gene, an organism inherits two alleles, one from each parent in the phenotype of a heterozygote: • dominant allele – is fully expressed • recessive allele – is completely masked
Organism’s status • Homozygous – having two identical alleles for a gene • Heterozygous – having two different alleles for a gene
Genetic terms • Genome – the complete set of genes in a species • Gene pool – the complete set of genes in a population • Genotype – the complete set of genes in an organism (defined by alleles) Phenotype – appearance of genotype
Literature Biology, eighth edition, Campbell, Reece Unit three: Genetics Chapter 14: Mendel and the Gene Idea Pages 262 – 271