Do Now What does the term “heredity’ mean? Heredity is the passing of traits from parent to offspring How can you explain that the child has blue eyes like her mom but brown hair like Dad? Children inherit traits from both parents.

Heredity

Today’s Objectives Describe how sex of the offspring is determined. Determine the probability of a trait being inherited using Punnett squares.

Genetics Cells contain a nucleus Nucleus contains paired chromosomes Chromosomes contain genes Gene is a section of DNA DNA contains an organism’s information code to make a specific protein Proteins are needed for growth and repair of cells

How is sex determined? Your chromosomes!! The 23rd pair of chromosomes determines the sex of the fetus.

Tell me what I am ?????

What determines a boy or girl? Humans have 23 pairs or 46 chromosomes The 23rd pair can be either XX or XY In mammals if the sex chromosomes are alike, XX it results in a female. If the sex chromosomes are different, XY it results in a male.

Sex Determination

Sex Determination Female can contribute only a X chromosome towards the sex of their offspring. Male can contribute an X or a Y chromosome toward the sex of their offspring. Absence of an Y chromosome results in a the embryo developing into a female. Presence of an Y chromosome results in the embryo developing into a male.

So how are other traits determined? Brown Eyes Blue eyes

Gregor Mendel Austrian Monk Considered the “Father of Heredity” He conducted pea plant breeding experiments in their monastery garden. In 1865 he made his work public, units of inheritance. http://anthro.palomar.edu/mendel/mendel_1.htm

Mendel’s First Experiment Mendel crossed pure tall Pea plants with pure short Pea plants. Tall X Short  What do you predict Happened?

All the Offspring Plants were Tall! How can you explain this? One trait is dominant over the other or covers it up. The other trait is said to be recessive.

Does the recessive trait disappear? To test if the recessive trait was still there Mendel allowed the offspring from the first experiment to reproduce. Tall offspring X Tall offspring  What do you think happened?

The short trait reappeared! Not only did it reappear, but it was always in a three to one (3:1) ratio Three tall to every one short. (75% tall, 25% short) Why was this so predictable?

Mathematical Probability Lets apply letters to represent the traits T = tall t = short How many letters does the offspring get from its parents? 2! One from mom and one from dad

We now use something called a So the pure tall would be  TT and the pure short would be  tt TT X tt  ? We now use something called a Punnet Square to calculate the probability of the offspring

T T t T t T t t T t T t Punnett Square T T x t t Tall vs. Short Tall is Dominant over Short Pure tall crossed with pure short Tall allele = T Short allele = t T T t T t T t All Tt 100% will be Tall t T t T t

T t T T T t T t T t t t Punnett Square Tall vs. Short Hybrid Tall x Hybrid Tall T t x T t Tall is Dominant over Short The Short trait only appears when pure- Because it is Recessive Tall allele = T Short allele = t T t T T T t T 1TT: 2Tt: 1tt 3 Tall (75%): 1 Short (25%) t T t t t

DO NOW What determines if the offspring will be a male or female? 23 pair of chromosomes What are the chromosomes for a girl? Boy? XX girl XY boy

Do we all inherit the same variation of a gene? We do NOT inherit the same variation of the gene The different forms a gene may have for a trait are its alleles If the trait was ice cream, there would be 31 varieties at Baskin Robbins. Or 31 alleles.

How many alleles does the offspring receive for each trait? TWO! One from mom and one from dad. You can get same allele from each parent: Homozygous  Pure, two of the same alleles from each parent OR two different alleles: Heterozygous  Hybrid, two different alleles from each parent.

More terms… The alleles received from each parent is called the genotype What is expressed (shows up) is called the phenotype Ex: TT is the genotype Tall is the phenotype

Homozygous Tall x Heterozygous Tall Punnett Square Tall vs. Short Homozygous Tall x Heterozygous Tall T T x T t Tall is Dominant over Short Tall allele = T Short allele = t T T T T T T T 2TT:2Tt All Tall t T t T t

Homozygous Short x Heterozygous Tall Punnett Square Tall vs. Short Homozygous Short x Heterozygous Tall t t x T t Tall is Dominant over Short Tall allele = T Short allele = t t t T t T t T 2Tt:2tt 2 Tall: 2 Short t t t t t

Homozygous Tall x Homozygous Tall Punnett Square Tall vs. Short Homozygous Tall x Homozygous Tall T T x T T Tall is Dominant over Short Tall allele = T Short allele = t T T T T T T T All TT All Tall T T T T T

Homozygous Short x Homozygous Short Punnett Square Tall vs. Short Homozygous Short x Homozygous Short t t x t t Tall is Dominant over Short Tall allele = T Short allele = t t t t t t t t All tt All Short t t t t t

Dominant Dominant Dominant Dominant Dominant Dominant Dominant

Homozygous Green x Homozygous Yellow Punnett Square Green Pea Pod vs. Yellow Pea Pod Homozygous Green x Homozygous Yellow G G x g g Green is Dominant over Yellow Green allele = G Yellow allele = g G G g G g G g All Gg All Green g G g G g

Homozygous Green x Heterozygous Green Punnett Square Green Pea Pod vs. Yellow Pea Pod Homozygous Green x Heterozygous Green G G x G g Green is Dominant over Yellow Green allele = G Yellow allele = g G G G G G G G 2 GG: 2Gg All Green g G g G g

Heterozygous Green x Heterozygous Green Punnett Square Green Pea Pod vs. Yellow Pea Pod Heterozygous Green x Heterozygous Green G g x G g Green is Dominant over Yellow Green allele = G Yellow allele = g G g G G G g G 1 GG: 2Gg: 1gg 3 Green: 1 Yellow g G g g g

Homozygous Yellow x Heterozygous Green Punnett Square Green Pea Pod vs. Yellow Pea Pod Homozygous Yellow x Heterozygous Green g g x G g Green is Dominant over Yellow Green allele = G Yellow allele = g g g G g G g G 2 Gg: 2 gg 2 Green: 2 Yellow g g g g g

Law of Segregation Allele pairs separate during gamete formation and randomly unite at fertilization. If there are 2 alleles for a trait the probability is always 50% for each allele.

Law of Independent Assortment Traits are transmitted to offspring independently of one another. Ex: Eye color and hair color sort independently. They are not connected.

Incomplete Dominance A form of inheritance in which one allele for a specific trait is not completely dominant over the other allele resulting in a combined phenotype (blending together) EX: Red and White snapdragon plants

Alleles are equally dominant What is co dominance? Alleles are equally dominant Both genes express themselves resulting in each color showing up separately.

Roan Cow

Multiple Alleles A trait that is controlled by more than 2 alleles Ex: Blood type A,B,O

Polygenic Inheritance More than one gene pair acts together to produce a single trait. Creates many variations Ex: Eye color, fingerprints

Who’s Baby is it? Mrs. Bright – AB Mrs. Light - A Mr. Bright O Mr. Light - A Baby – O Baby – A She got the wrong baby!!

The resulting plant will over White Flowers Chromosome from one plant Chromosome from the other plant The resulting plant will over White Flowers

What is a Mutation? Dramatically different from what is expected genetically Any permanent change in a gene or a chromosome of a cell Many are harmful, often causing death Some may be beneficial Some appear not to have an effect

Practice Quiz Mendel http://anthro.palomar.edu/practice/mendqui1.htm

Practice quiz probability http://anthro.palomar.edu/practice/mendqui2.htm

What is a pedigree chart? Pedigree charts show a record of the family of an individual They can be used to study the transmission of a hereditary condition They are particularly useful when there are large families and a good family record over several generations.

Symbols used in pedigree charts A marriage with five children, two daughters and three sons. The eldest son is affected by the condition. Eldest child  Youngest child Normal male Affected male Normal female Affected female Marriage

Example of Pedigree Charts Dominant or Recessive? Is this pedigree dominant or recessive?

Answer Dominant It is dominant because a parent in every generation have the disorder. Remember if a parent in every generation has the disorder, the disorder has not skipped a generation. If the disorder has not skipped a generation the disorder is dominant.

Example of Pedigree Charts Dominant or Recessive? Is this pedigree dominant or recessive?

Answer Recessive It is recessive because a parent in every generation does not have the disorder. Remember the disorder can skipped a generation if the disorder is recessive. The parents can be heterozygous and be carriers of the disorder but not have the symptoms of the disorder.

Pedigree Chart