Mendel’s Laws of Heredity 10.1

Gregor Mendel An Austrian monk who studied heredity through pea plants “Father of Genetics”

Heredity The passing on of characteristics from parents to offspring Traits Characteristics that are inherited

Genetics The branch of biology that studies heredity Gametes Male and female sex cells (egg and sperm)

Fertilization The process in which the male gamete unites with the female gamete

Zygote The fertilized cell that develops into a seed, baby, etc.

Pollination The transfer of pollen grains from a male reproductive organ to a female reproductive organ in plants

Hybrid Offspring formed by parents having different forms of a trait Ex tall and short height

Monohybrid Cross Mendel crossed parent plants of different heights (mono = single trait)

Original parents (true breeding plants) are the P 1 generation Offspring of the parent plants are known as the F 1 generation (filial)

Cross two F 1 plants with each other and their offspring are known as F 2 generation

Alleles Different gene forms Come in pairs

Dominant The observed trait of an organism that masks the Recessive form of a trait

Dominant = capital letter Recessive = small case letter

Mendel’s 1 st Law of Inheritance Law of Segregation

Gametes receive only one allele for a trait from each parent

Phenotype The expression of a gene (The way an organism looks/behaves)

Genotype The actual genetic make-up of an organism (TT)

Genotypes… TT=the plant has 2 alleles for tallness Tt=1 allele for tallness and 1 allele for shortness

tt=2 alleles for shortness

Homozygous If the two alleles for the trait are the same

TT = homozygous dominant (for height) tt = homozygous recessive (for height)

Heterozygous The 2 alleles for a trait are different Tt=1 allele for tallness and 1 for shortness (for height)

Dihybrid Cross A cross where two different traits are used Di means two

Mendel’s 2 nd Law Law of Independent Assortment

Distribution of alleles for 1 trait into the gamete doesn’t affect distribution of alleles for the other trait

Punnett Square A shorthand way of finding the expected ratios of possible genotypes in the offspring cross

The gametes that each parent forms are listed on the top and left side of the square

Probability The likelihood that something will occur

Punnett Squares aren’t exact results because genetics is by chance (like flipping a coin)