Pick up the 2 handouts as you come in Pick up the 2 handouts as you come in!! Complete the Warm Up—on your notes Why do our bodies use mitosis? Why do our bodies use meiosis?

Genetics SB2c: I can analyze how biological traits are passed on to successive generations.

Guiding Questions: What determines an organism’s physical appearance? How do parents pass traits to their offspring? How can predictions be made about the genetics of an organism?

Genetics What is Genetics? Heredity The modern science that studies the mechanisms for the transmission of hereditary information in the resulting organism. Heredity Transmission of traits causing the offspring to resemble their parents.

What is genetics? Genetics: Is the science of heredity Mendel is considered the “Father of Genetics” Mendel was a monk who experimented with pea plants to study heredity Traits:Flower color, seed color, seed shape, pod color, pod shape, flower position, plant height

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

Genetics Definitions Genes - sections of chromosomes that code for a trait Trait - characteristic that can be passed from parent to offspring Allele - distinct form of a trait – one from each parent Dominant - fully expressed gene Recessive - gene expressed when not in the presence of a dominant allele Traits

What are examples of traits? 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

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

How do alleles determine what traits will show? Some alleles are dominant and others are recessive Do you have to remember which traits are dominant and which are recessive?... Dominant: A trait that will appear (show) * Represented with a CAPITAL letter Example: Tall (T), Black (B), Brown (B) NO… Punnett Square questions will give you clues or will tell you in the question! You HAVE TO READ! 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)

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

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. Tall is dominant over short t t Recessive Recessive Shows Short

Who is considered the “Father of Genetics”? Darwin Hooke Mendel Paquin Review Question #1 Who is considered the “Father of Genetics”? Darwin Hooke Mendel Paquin

Review Question #2 These plants were used in Mendel’s experiments because they grow & reproduce quickly: Peas Corn Wheat Roses

What is true-breeding? 2 parents reproduce offspring Review Question #3 What is true-breeding? 2 parents reproduce offspring 2 offspring with three parents Self fertilizing plants Cross pollinating plants

Tall is dominant over short Review Question #4 If a girl has Tt, she will show: Short Tall Both (a) & (b) 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! Same sized letters! Same sized letters! Same sized letters! Same Homo means: ________ 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! Different sized letters! Different sized letters! Different sized letters! Different Hetero means: __________ Think: Different SIZED letters

Allele Representation Homozygous Dominant Allele HH Homozygous Recessive Allele hh Heterozygous Dominant Allele Hh

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

What are some terms that will help with understanding Punnett Squares? Phenotype Characteristics you can see with your eyes! Multi color Butterfly Blue 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 HH GG bb Gg Hh Bb hh gg BB

Another term for heterozygous is: Review Question #5 Another term for heterozygous is: Allele Same Hybrid Pure

tt is an example of: homozygous heterozygous hybrid all of the above Review Question #6 tt is an example of: homozygous heterozygous hybrid all of the above

tt is an example of: phenotype heterozygous hybrid genotype Review Question #7 tt is an example of: phenotype heterozygous hybrid genotype

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

Tall is an example of: phenotype Heterozygous pure genotype Review Question #9 Tall is an example of: phenotype Heterozygous pure genotype

Total # of Students= ______ Trait Form 1 Form 2 Earlobe Dimples Chin Hairline Finger Hair Thumb

DAY 2 Take Out Notes from Yesterday!

Monohybrid Cross: The use of Punnett Square for 1 trait Punnett Square: A diagram used to predict the possible outcomes (offspring) of a particular cross or breeding. Monohybrid Cross: The use of Punnett Square for 1 trait (will have 4 boxes) A cross that studies one set on contrasting traits. Each cross produces a new generation. First generation: F1 Second generation: F2

Do the Punnett Squares to see the ratios. PP, pp

Explaining Mendel’s Results His results showed that inheritance follows a simple pattern. This pattern follows simple rules Law of Segregation: When an organism produces gametes, each gamete has an equal chance of receiving either one of the alleles.

Mendel’s 1st Law Mendel’s 1st law: law of segregation -- a child inherits one allele from each parent Each gamete (sex cell) receives only one copy

Explaining Mendel’s Results Mendel looked for patterns and for a lack of patterns. The lack of patterns helped him develop Law of Independent assortment: Alleles of each gene are passed on independently during gamete formation. Ex. Round seeds may or may not be yellow. The traits are not linked. Inheritance of one trait has no effect on the inheritance of another trait

Mendel’s 2nd Law Mendel’s 2nd law: law of independent assortment - alleles of different genes are passed to offspring independently of each other during gamete formation Independent assortment means that new combinations of genes present in neither parent are possible

3rd Law: Degrees of Dominance Dominance occurs in varying degrees Complete dominance occurs when phenotypes of the heterozygous and homozygous dominant are identical Incomplete dominance the phenotype is somewhere between the phenotypes of the two parental varieties Codominance two dominant alleles affect the phenotype in separate, distinguishable ways

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… Mixes like paint! R R W RW RW W RW RW

Incomplete Dominance

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 BW BW W BW BW W

Codominance White = WW Red = RR Roan (spotted) = WR

Dihybrid Cross Involves two traits and two allele pairs. Yellow peas – Y Green peas – y Round peas – R Wrinkled peas – r So if I have a yellow, round pea; what is a possible genotype? YyRr or YYRR

Dihybrid Cross Since we have 4 alleles, our square is now going to have 4 boxes on each side.

Dihybrid Cross: The use of Punnett Square for 2 traits (will have 16 boxes)

Each gamete has only one allele for a trait because of: Review Question #10 Each gamete has only one allele for a trait because of: recessive Law of segregation dominance phenotype

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

In speckled chickens, both alleles are express because of: Review Question #12 In speckled chickens, both alleles are express because of: Co-dominance Law of segregation Law of Independent assortment Incomplete dominance

The cross with one trait is called: Review Question #13 The cross with one trait is called: Dihybrid Trihybrid Monohybrid All of the above

A dihybrid cross will have how many squares? Review Question #14 A dihybrid cross will have how many squares? 4 16 18 20

Patterns of Heredity READING A PEDIGREE Genetic disorder: a disease that is caused by a mutation in a gene Can be dominant or recessive

Genetic disorders caused by a recessive allele Recessive disorders Genetic disorders caused by a recessive allele Only shows up in people that are homozygous recessive EXAMPLES: Cystic fibrosis: thick mucus builds up in lungs and digestive system due to a defective protein in the cell membrane Tay-Sachs disease: certain lipid cannot be broken down and builds up in the central nervous system Phenylketonuria: phenylalanine amino acid cannot be broken down and builds up in the central nervous system

Genetic disorders caused by a dominant allele Dominant disorders Genetic disorders caused by a dominant allele Shows up in people that are homozygous dominant or heterozygous EXAMPLE: Huntington’s disease: certain parts of the brain break down  

Multiple alleles More than 2 alleles exist for a trait However, an organism can only have 2 of these alleles for a trait

Example: alleles for hair color are blond, brown, red Blood type is controlled by multiple alleles (A, B, and O) O is recessive, A and B are codominant

AA, AO or IAIA, IAi Type A blood BB, BO or IBIB, IBi Type B blood Genotype Phenotype AA, AO or IAIA, IAi Type A blood BB, BO or IBIB, IBi Type B blood OO or ii Type O blood AB or IAIB Type AB blood (A and B are codominant )

Sex determination Humans have 46 chromosomes 44 of these chromosomes are autosomes (do not determine the sex of an organism) 2 of these chromosomes are sex chromosomes (determine the sex of an organism) Sex chromosomes are X and Y Females are XX, Males are XY

Females can only make eggs with the X chromosome Males make sperm with the X or Y chromosome, so it is the males that determine the sex of a baby

Sex-linked traits Traits controlled by genes on the sex chromosomes, X or Y

Example: Hemophilia (h) is a recessive disorder in which you cannot clot your blood. Normal blood clotting (H) is dominant. These genes are located on the X chromosome.

For sex-linked traits, you must write genotypes like: XhXh : female with hemophilia XHXh : female carrier XhY : male with hemophilia XHY : normal male without hemophilia Example: XHXh x XhY

Example: Red-green color blindness: an individual cannot tell the difference between red and green XcXc : female with color blindness XCXc : female carrier XcY : male with color blindness XCY : male with color vision Example: XcXc x XCY

Key Vocabulary Allele Carrier Dominant Pedigree Genetics Codominance Genotype Incomplete dominance Heterozygous Polygenic trait Homozygous Sex chromosome Hybrid Sex linked trait Law of independent assortment Multiple alleles polyploidy Law of segregation Phenotype Recessive