Semester 2 Final Review Part 1 Genetics, Biotechnology, Protein Synthesis and Evolution

We’ve all heard of it, but … What is genetics? Genetics: the study of gene structure and action and the patterns of inheritance of traits from parent to offspring.

Mendel’s experiments

Mendel’s Principle Findings Dominant and Recessive – Certain characteristics are dominant to others – The dominant trait will mask another (recessive) trait, preventing it’s expression – The recessive trait “ disappears ” for a generation

Cross between varieties The dominant trait will mask another (recessive) trait, preventing it’s expression

Segregation – For each trait, organisms have 2 genes – Each pea plant got one gene from each parent – Genes segregate from each other during egg or sperm formation (meiosis) Mendel’s Principle Findings

Some terms … Trait: characteristics of an organism pass from generation to generation. – Eye color – Hair color and type – Height – Temperament – Symptoms for genetic diseases

Genotype Tells you the genetic makeup of the organism The genes the organism carries Written using symbols – Each allele is represented by a letter Tall = T dominant Short = t recessive – Capital letter designates the dominant trait and lower case letter designates the recessive trait. – Capital letter is always written first.

Homozygous An individual which contains one allele for a genetic trait – TT-- homozygous dominant – tt -- homozygous recessive

Heterozygous An individual which contains different alleles for a genetic trait – Tt heterozygote

Phenotype What the organism looks like Controlled by the genotype – TT tall – Tt tall – tt short

Example eye color gene Allele b (blue eyes) eye color gene Allele B (brown eyes) Paternal Maternal This person would have brown eyes (Bb) Phenotype Genotype

Punnett squares The probability the next generation will exhibit a certain trait can be shown with a punnett square. The genotype of the mother is shown on the top of the square (TT) The genotype of the mother is shown on the top of the square (TT) The genotype of the father is shown on the side of the square (tt) The genotype of the father is shown on the side of the square (tt) The various combinations of genes (genotypes) are shown in the squares. All of these offspring will be (T) Tall and carry the recessive (t) short allele. The various combinations of genes (genotypes) are shown in the squares. All of these offspring will be (T) Tall and carry the recessive (t) short allele. Tt Tt T T tttt

What happens if you cross a heterozygous plant (Tt) with a short plant (tt)? Punnett squares T t t Tt Tt tt tt t Tt Tt tt tt Two of the four will be Heterozygous (Tall) and the other two will be homozygous recessive (short) This is a 1:1 ratio

Monohybrid vs. Dihybrid Monohybrid crosses are crosses that examine the inheritance of only one specific trait. Dihybrid crosses are crosses that examine the inheritance of two different traits.

Mendel and Dihybrid Crosses Mendel studied dihybrid crosses. – He crossed a plant with yellow round peas with a plant with green wrinkled peas.

Mendel and Dihybrid Crosses Mendel began his experiments with purebred (homozygous) parent plants. RRYY x rryy – Remember each trait has 2 genes due to getting half your genes from mom and half from dad. How many gamete options do you have for RRYY?? RY rryy? ry These are the gametes from the “P” generation.

Mendel and Dihybrid Crosses “P” generation: RRYY x rryy RRYY rryy RY ryRrYy ryRrYy ryRrYy ryRrYy

Mendel and Dihybrid Crosses What is the genotypic ratio? 16 RrYy:0 anything else Phenotypic ratio? 16 Round Yellow: 0 anything else RY ryRrYy ryRrYy ryRrYy ryRrYy

Mendel and Dihybrid Crosses He then crossed two “F 1 ” organisms: RrYy x RrYy RYRyrYry RY RRYYRRYyRrYYRrYy Ry RRYyRRyyRrYyRryy rY RrYYRrYyrrYYrrYy ry RrYyRryyrrYyrryy RrYy

Mendel and Dihybrid Crosses What is the genotypic ratio for the F2 generation? 1 RRYY:2 RRYy: 2 RrYY: 4 RrYy: 1 rrYY: 2 Rryy: 2 rrYy: 1rryy: 1 RRyy RYRyrYry RY RRYYRRYyRrYYRrYy Ry RRYyRRyyRrYyRryy rY RrYYRrYyrrYYrrYy ry RrYyRryyrrYyrryy

Mendel and Dihybrid Crosses Phenotypic ratio for the F2 generation? RYRyrYry RY RRYYRRYyRrYYRrYy Ry RRYyRRyyRrYyRryy rY RrYYRrYyrrYYrrYy ry RrYyRryyrrYyrryy 9:16 Round Yellow, 3:16 Round Green, 3:16 Wrinkled Yellow, 1:16 Wrinkled Green

Mendel and Dihybrid Crosses 9:16 yellow and round, 3:16 green and round, 3:16 wrinkled and yellow, 1:16 wrinkled and green.

Genetics Vocabulary GeneLaw of Segregation Dominant Law of Independent Assortment RecessiveGenotype: Homozygous Dominant P Generation Homozygous Recessive F 1 Generation Heterozygous F 2 GenerationPhenotype TraitPunnett Square AlleleMonohybrid Cross Dihybrid Cross