Genetics Unit 6

What is genetics? Genetics : Is the science of heredity Genetics began with Mendel Mendel is considered the “Father of Genetics” Mendel was a monk who experimented with pea plants to study heredity

What is a trait? Trait : Is a notable feature or characteristic in an organism Physical traits – Examples - Hair color, eye color, & height Behavioral traits – Example – Sheepdog has herding instincts Medical conditions – Examples – Cancer, Sickle cell, cystic fibrosis

Why did Mendel study peas? Peas reproduce and grow quickly They had easy to observe traits Can reproduce using 2 different plants or using 1 plant – True-Breeding : Can produce offspring with only 1 parent Cross Pollination – 2 parents self-fertilizing/true-breeding

What are alleles? Allele : Alternative form that a single gene may have for a particular trait. (huh?) A gene in a particular place on a particular chromosome will express a particular trait….like flower color Chromosome from MOM Chromosome from DAD But what color will the offspring show? Purple is an Allele coming from mom White is an Allele coming from dad

How do alleles determine what traits will show? Some alleles are dominant and others are recessive Dominant: A trait that will appear (show) * Represented with a CAPITAL letter Example: Tall (T), Black (B), Brown (B) Recessive: A trait that is masked (hidden) if a dominant allele is present, but will show if both alleles are recessive * Represented with a lower case letter Example: short (t), blond (b), blue (b) Do you have to remember which traits are dominant and which are recessive?... NO… Punnett Square questions will give you clues or will tell you in the question! You HAVE TO READ!

I do you know a trait will show or not? Rule #1: If there is a dominant trait present, it will always show that trait. T Dominant Tall is dominant over short T t DominantRecessive Shows Tall Capital “T” bosses the little “t”

I do you know a trait will show or not? Rule #2: If there is NOT a dominant trait present, then the recessive trait will always show. t Recessive Tall is dominant over short Shows Short

Clicker Question #1 Who is considered the “Father of Genetics”? a.Darwin b.Hooke c.Mendel d.Paquin

Clicker Question #2 These plants were used in Mendel’s experiments because they grow & reproduce quickly: a.Peas b.Corn c.Wheat d.Roses

Clicker Question #3 What is true-breeding? a.2 parents reproduce offspring b.2 offspring with three parents c.Self fertilizing plants d.Cross pollinating plants

Clicker Question #4 If a girl has Tt, she will show: a.Short b.Tall c.Both (a) & (b) d.None of the above Tall is dominant over short

Before we start Punnett Squares, we have a few more things to learn…

What are some terms that will help with understanding Punnett Squares? Homozygous : Organism with 2 of the same alleles for a particular trait. Also called “pure”. Examples – TT tt DD dd Same sized letters! Homo means: ________ Same Think: Same SIZED letters

What are some terms that will help with understanding Punnett Squares? Heterozygous: Organism with 2 different alleles for a particular trait. Also called “hybrid”. Examples – Tt Dd Gg Bb Different sized letters! Hetero means: __________ Different Think: Different SIZED letters

What are some terms that will help with understanding Punnett Squares? Phenotype : The observable characteristic or outward expression of an allele pair Characteristics you can see with your eyes! Think: Phenotype -- Physical Blond Hair Red Hair Black Hair Brown Hair

What are some terms that will help with understanding Punnett Squares? Phenotype Characteristics you can see with your eyes! Blue Butterfly Multi color Butterfly White Butterfly Orange Butterfly

What are some terms that will help with understanding Punnett Squares? Genotype : The organism’s allele pairs Characteristics you can NOT see with your eyes! Think: Genotype – Genetic Code GG Gg gg BB Bb bb HH Hh hh

Clicker Question #5 Another term for heterozygous is: a.Allele b.Same c.Hybrid d.Pure

Clicker Question #6 tt is an example of: a.homozygous b.heterozygous c.hybrid d.all of the above

Clicker Question #7 tt is an example of: a.phenotype b.heterozygous c.hybrid d.genotype

Clicker Question #8 If a boy has tt, he will show: a.tall b.short c.both (a) & (b) d.none of the above Tall is dominant over short

Clicker Question #9 Tall is an example of: a.phenotype b.Heterozygous c.pure d.genotype

What is Mendel’s Law of Segregation? Law of Segregation: States that the two alleles for each trait separate during meiosis. During meiosis, the alleles separate During fertilization, the alleles unite into a pair again

What’s the difference between monohybrid ?& dihybrid crosses? Monohybrid Cross : The use of Punnett Square for 1 trait (will have 4 boxes) Punnett Square : A diagram used to predict the possible outcomes (offspring) of a particular cross or breeding.

Punnett Square Video

What’s the difference between monohybrid ?& dihybrid crosses? Dihybrid Cross : The use of Punnett Square for 2 traits (will have 16 boxes)

What’s the difference between monohybrid ?& dihybrid crosses? Law of Independent Assortment : Mendelian law stating that two alleles for each trait separate during meiosis During Dihybrid crosses: The random assortment of alleles results in four possible gametes…each of which is equally likely to occur I will show you this when I show dihybrid crosses

Sometimes two traits can be dominant at the same time

What’s the difference between incomplete dominance and co-dominance? Incomplete Dominance : Complex inheritance pattern in which the heterozygous phenotype is intermediate between those of the two homozygous parent organisms…huh? RR W W RW Mixes like paint!

What’s the difference between incomplete dominance and co-dominance? Co-Dominance : Complex inheritance pattern that occurs when neither allele is dominant and both alleles are expressed. B B W W BWBWBWBW BWBWBWBW

Clicker Question #10 Each gamete has only one allele for a trait because of: a.recessive b.Law of segregation c.dominance d.phenotype

Clicker Question #11 When a white flower & a red flower have pink offspring, this is because of: a.Co-dominance b.Law of segregation c.Law of Independent assortment d.Incomplete dominance

Clicker Question #12 In speckled chickens, both alleles are expressed because of: a.Co-dominance b.Law of segregation c.Law of Independent assortment d.Incomplete dominance

Clicker Question #13 The cross with one trait is called: a.Dihybrid b.Trihybrid c.Monohybrid d.All of the above

Clicker Question #14 A dihybrid cross will have how many squares? a.4 b.16 c.18 d.20

Lets start Punnett Squares!