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

But what color will the offspring show? 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 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)

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

Clicker 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 Clicker 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 Clicker 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

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

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

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

Tall is dominant over short Clicker 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 Clicker Question #9 Tall is an example of: phenotype Heterozygous pure 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? 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)

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? Mixes like paint! R R W RW RW W RW RW

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

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

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

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

When a woman is about 25 weeks pregnant… she can go to the doctor to determine the sex of her unborn child. What determines the sex of the child?

All eggs that female carries contain a X sex chromosome Sperm can either have a X or Y sex chromosome

To be a girl…. She has two x chromosomes.

To be a boy….. He has a X and Y sex chromosome.

There is 50% chance that you get either be a boy or girl There is 50% chance that you get either be a boy or girl. Its all depends on which sperm is the first to reach the egg.

Sex-linked Inheritance Definition: A gene carried on either the X or Y chromosome X-linked – only found on the X Colorblindness - recessive Hemophilia - recessive Y-linked – only found on the Y Hair on ears Can a female be born with this trait?

Man with hairy ears! http://www.ucm.es/info/genetica/grupod/mendelismo/Hairy%20ear01.jpg

Hemophilia Definition: disorder in which the blood does not clot Not fatal – just lots of treatments to keep blood volume levels appropriate

Xh = hemophilia allele XX or XY = normal XhX = carrier – only females XhXh or XhY = hemophilia

Why do men get hemophilia more than women? Because women will have to have both Xh gene in order to get hemophilia.

Pedigree Chart Pedigrees shows how a specific gene trait is passed down from one generation to the next.

Pedigree Chart How many female carriers for hemophilia are there? Can a male be a carrier? Could a male with hemophilia have a child who is not affected by or a carrier of hemophilia? How?

Karyotype Definition: Picture of the chromosomes from a person’s cell. How many pairs of chromosomes are there? What is the gender of the person in this karyotype? How can karyotypes be useful to doctors? http://www.contexo.info/DNA_Basics/images/karyotype1.gif

Normal Karyotype vs. Down Syndrome Karyotype. Which one is which? http://www.blackwellpublishing.com/korfgenetics/jpg/300_96dpi/Fig6-15.jpg http://sps.k12.ar.us/massengale/karyotype_male.jpg

Genetic Disorders Down’s Syndrome – extra chromosome on Pair 21 – happens because of Non-disjunction in Meiosis Turner Syndrome – Female – has only 1 X Chromosome – tend to be sterile, may not reach full sexual maturity Cystic Fibrosis – Recessive disorder – lungs and digestive system don’t work properly and thick mucous builds up in respiratory tract Kleinfelter’s Disease – male who is XXY – may have feminine-type characteristics Does not mean they are gay! Hemophilia – blood disorder Huntington’s Disease – Autosomal Dominant – Neurological Breakdown - fatal Sickle Cell Anemia – Autosomal Recessive – sickle-shaped blood cells – can’t move through bloodstream as easily – not fatal – typically found in African Americans

Genetic Disorders Tay-Sachs disease is a rare fatal inherited disorder that progressively destroys nerve cells (neurons) in the brain and spinal cord. Tay-Sachs disease becomes apparent in infancy. Infants with this disorder typically appear normal until the age of 3 to 6 months, when their development slows and muscles used for movement weaken.  Albinism – a genetic disorder characterized by the complete or partial absence of pigment in the skin, hair, and eyes. This is due to a lack of melanin production. Achondroplasia – an autosomal dominant genetic disorder that causes dwarfism Galactosemia – an autosomal recessive genetic disorder in which a person cannot digest the sugar galactose properly. Life threatening complications appear after birth such as lethargy, jaundice, liver damage, bleeding, cataracts, mental retardation..