Mendelian Genetics

Genetics Genetics is the study of heredity Heredity is the passing of traits from parent to offspring Gregor Mendel is considered the Father of Modern Genetics

Genetics Why did Mendel use pea plants? Easy to grow Make lots of offspring Can manipulate pollination

Genetics Peas can self- fertilize (pollinate flowers on same plant) Peas can cross- fertilize (pollinate flowers on a different plant)

Genetics Peas have several traits with only 2 contrasting forms

Mendel’s 3 Step Experiment Step 1: Produce the P (parent) generation Parents are true-breeding plants created by self- fertilization

Mendel’s 3 Step Experiment Step 2: Produce the F1 generation Cross 2 different parent plants together All F1 offspring looked alike

Mendel’s 3 Step Experiment Step 3: Produce the F2 generation Cross any 2 F1 plants together Offspring come out in a 3:1 ratio

Mendel’s Conclusions Parents transmit information about traits to their offspring using gametes, or sex cells Females make egg cells (ovum) Males make sperm cells

Where did your genes come from? Mendel’s Conclusions Each individual has 2 genes for each trait What is a gene? segment of DNA that codes for a trait Where did your genes come from? your parents

Mendel’s Conclusions If the 2 units you inherit are the same you are homozygous ex. purple & purple (P generation) If the 2 units you inherit are different you are heterozygous ex. purple & white (F1 generation)

Mendel’s Conclusions The different forms of a gene are called alleles (these are the trait choices) An individual’s alleles (genes) are its genotype

Mendel’s Conclusions The physical appearance that results from the alleles is the phenotype

Mendel’s Conclusions Not all alleles get expressed: the dominant allele is ALWAYS expressed when present  symbol is a CAPITAL letter (P) the recessive allele is covered up in the heterozygous condition  symbol is a lower-case letter (p)