Mendelian Genetics

It began with Gregor Mendel He was an Austrian Monk who experimented with garden peas in the Mid 19th Century He noticed certain traits seemed to be passed from one generation to another He is known as the “father of genetics”

The father of what? Genetics is the study of heredity Heredity is the passing of traits from parents to offspring

What did Mendel work with? Mendel worked with peas He chose peas because they grew quickly, he could control how they reproduced, and the traits were easy to observe.

Austrian Monk 150 yrs ago “Father of Genetics” Pea plants because they grew quickly, were easy to observe, and he could control their reproduction

What was Mendel looking for? Mendel noticed how certain TRAITS were passed from generation to generation Traits are specific characteristics of an organism

Some of the traits Mendel studied were height, flower color, seed shape and color, pod shape and color and flower position.

Seed shape Seed color Seed coat color Pod shape Pod color Flower position Stem height Austrian Monk 150 yrs ago “Father of Genetics” Pea plants because they grew quickly, were easy to observe, and he could control their reproduction

P generation F1 generation F2 generation Parents F1 generation children Mendel did several crosses He called the first line of crosses the P generation P stands for Parent The offspring of the P generation were called the F1 generation F1 stands for First Filial, meaning 1st son When he crossed plants from the F1 generation, he called the offspring the F2 generation or 2nd son generation F2 generation grandchildren

Purebred purple X Purebred white = F1 generation Mendel’s Crosses Mendel’s P generation were PUREBRED plants Purebred plants are those that have been self-pollinated for a long time and have become GENETICALLY UNIFORM He crossed 2 types of purebred plants Purebred purple X Purebred white = F1 generation

Mendel’s Crosses Mendel then allowed members of the F1 generation to cross to produce the F2 generation The F2 generation included purple flowers and white flowers

Seed shape Seed color Seed coat color Pod shape Pod color Flower position Stem height Austrian Monk 150 yrs ago “Father of Genetics” (parental) Purebred Tall x Purebred Short (kids) = All Hybrid Tall Then cross 2 F1 plants Hybrid Tall x Hybrid Tall (grandkids)= 1 Pure Tall, 2 Hybrid Tall, 1 Pure Short ¾ tall and ¼ short Pea plants because they grew quickly, were easy to observe, and he could control their reproduction

Mendel found that these traits were linked to factors that are passed from generation to generation Today, we call these factors GENES Genes can have different forms called ALLELES For example, Height Gene has 2 forms, tall and short

bb Mendel’s Laws b Genes control traits Genes exist in pairs (alleles) Law of Segregation There are different forms of each trait called alleles. Parents have both alleles. Their sex cells will have one copy of each allele. Dad has blue eyes bb b Each Sperm has one allele Body cell

Principle of Dominance Mendel concluded that some alleles are dominant and others are recessive As long as the dominant allele is present, then it will show up The recessive allele will only be seen if a recessive allele is inherited from each parent In other words, you must have 2 recessive alleles to see them

= Principles of Genetics Seed shape Seed color Seed coat color Pod shape Pod color Flower position Stem height Austrian Monk 150 yrs ago “Father of Genetics” (parental) Purebred Tall x Purebred Short (kids) = All Hybrid Tall Then cross 2 F1 plants Hybrid Tall x Hybrid Tall (grandkids)= 1 Pure Tall, 2 Hybrid Tall, 1 Pure Short ¾ tall and ¼ short Pea plants because they grew quickly, were easy to observe, and he could control their reproduction Controlled by alleles which are different forms of a gene (mom/dad) Always expressed when the allele is present Is hidden whenever the dominant allele is present. = Principles of Genetics Individual factors (genes) must control inheritance of traits These genes exist in pairs known as alleles. You get one from your mom and one from your dad One gene in a pair can mask the other gene (dominant and recessive)

ALLELES Since alleles are inherited from each parent, they can be the same or different If an organism inherits 2 of the same alleles, it is said to be HOMOZYGOUS (true breeding) for that trait If an organism inherits 2 different alleles, it is said to be HETEROZYGOUS (hybrid) for that trait

Putting it all Together… GENOTYPE (HETEROZYGOUS) Tt = Tall ALLELE ALLELE PHENOTYPE

A punnett square can calculate the probability that offspring with a certain combination of alleles will be produced. Crossing 1 trait at a time For example, Mendel crossed a pure tall plant with a pure short plant For these crosses, we use a PUNNETT SQUARE This is a grid designed by Reginald Punnett to keep track of the alleles

Punnett Square Parent 2 – Pure Tall F1 Generation Parent 1- Pure Short

FINAL COUNTDOWN Name one name that Gregor Mendel is known by Name 2 reasons Mendel liked to work with pea plants Name 3 principles of genetics that Mendel discovered