Mendel and the Gene Idea Marie Černá

1865 – Gregor Mendel

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: F 1 generation (first filial) F 2 generation (second filial)

Dominant / recessive alleles

Mendel’s experiment results the law of hybrid uniformity in the F 1 generation phenotypic ratio of the F 2 generation 3:1 genotypic ratio of the F 2 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 their characters 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