SINGLE TRAIT PUNNETT SQUARE Tt T t T t ¼ Punnett Squares

Genetics Genetics is the study of genes and inheritance Inheritance is how traits are passed on from generation to generation. Chromosomes are made up of genes, which are made up of DNA.

Gregor Mendel Austrian monk Experimented with pea plants He discovered that traits were carried from one generation to the next.

TERMS TO KNOW ALLELES DIFFERENT FORMS OF A TRAIT THAT A GENE MAY HAVE T,t HOMOZYGOUS AN ORGANISM WITH TWO ALLELES THAT ARE THE SAME TT, tt HETEROZYGOUS AN ORGANISM WITH TWO DIFFERENT ALLELES FOR A TRAIT Tt, Gg

TERMS TO KNOW HYBRID ONE OF EACH TRAIT (SAME AS HETEROZYGOUS) Tt, Gg DOMINANT A TRAIT THAT DOMINATES THE OTHER FORM OF THE TRAIT THE TRAIT THAT IS VISIBLE REPRESENTED BY AN UPPERCASE LETTER T OR G RECESSIVE THE TRAIT BEING DOMINATED OR COVERED UP BY THE DOMINATE TRAIT THE TRAIT IS NOT VISIBLE REPRESENTED BY A LOWER CASE LETTER t or g

TERMS TO KNOW PHENOTYPE THE PHYSICAL APPEARANCE OF AN ORGANISM (WHAT IT LOOKS LIKE) TALL, SHORT, GREEN, WRINKLED GENOTYPE THE GENE ORDER OF AN ORGANISM (WHAT ITS GENES LOOK LIKE) TT, GG, Tt, gg Gg, tt RATIO THE RELATIONSHIP IN NUMBERS BETWEEN TWO OR MORE THINGS (SAME AS MATH) 3:1, 2:2, 1:2:1

Mendel’s Experiment He chose to work with pea plants because –Readily available –Reproduced quickly –Traits were distinct

Mendel’s Experiment Mendel crossed true breeding plants that had two distinct and contrasting traits, like purple and white flowers. After the first cross, the plants self-fertilized.

Mendel’s Experiment P generation is parental generation. F1 generation is the first generation. F2 generation is the second generation.

Mendel’s Experiment He studied these seven traits

Mendel’s Phenotypic Conclusions In the F1 generation, all plants had the same trait. In the F2 generation, there was always a 3:1 ratio of a single trait.

Mendel’s Genotypic Conclusions In the F2 generation, The genotypic ratio is different. Remember P is dominant so the plants will be purple even with Pp.

TOOLS TO KNOW A PUNNET SQUARE IS A TOOL USED TO PREDICT THE POSSIBLE GENOTYPES FOR THE OFFSPRING OF TWO KNOWN PARENTS. PARENT’S GENES

HOW TO USE A MONOHYBRID (ONE TRAIT) PUNNETT SQUARE THE PARENTS’ ALLELES GO ON THE OUTSIDE OF THE SQUARE BB b b BB X bb

HOW TO USE A MONOHYBRID (ONE TRAIT) PUNNETT SQUARE THE PARENTS’ ALLELES GO ON THE OUTSIDE OF THE SQUARE BB b b BB BB UPPERCASE LETTERS SHOULD GO FIRST bb bb

HOW TO USE A MONOHYBRID (ONE TRAIT) PUNNETT SQUARE BB b b Bb WHAT DO THE RESULTS SHOW? B IS THE DOMINANT ALLELE FOR BLACK b IS THE RECESSIVE ALLELE FOR BROWN RESULTS: PHENOTYPIC: 100% BLACK 4:0 RATIO, BLACK TO BROWN GENOTYPIC: 100% Bb 4:0 ALL Bb Bb Bb

HOW TO USE A PUNNETT SQUARE Tt T t RESULTS: TT, Tt, Tt, tt PHENOTYPIC: 75% TALL 25% SHORT 3 TO 1 RATIO: TALL TO SHORT GENOTYPIC: 1TT: 2Tt: 1tt 1:2:1 RATIO 25 %TT, 50% Tt, 25% tt LET’S LOOK AT ANOTHER PUNNETT SQUARE AND PREDICT THE OUTCOME TT Tt Tt tt T IS THE DOMINANT ALLELE FOR TALLNESS t IS THE RECESSIVE ALLELE FOR SHORTNESS

Probability and Punnett Squares