Reproduction and variation

D.S.Q. 1. How often do hens (female chickens) lay eggs? 2. Can these eggs hatch into a chick? 3. Do hens lay eggs without the presence of a rooster (male chicken)? 4. How are chicken eggs fertilized? 5. What happens to the unfertilized eggs?

Activity Time

Discussion 1. Is a chicken egg an organism, organ, or cell? 2. What function do you think the yolk serves? 3. Do chickens reproduce sexually (DNA is received from both parents) or asexually (only one parent is involved, and the offspring is genetically identical to the parent)?

Heredity The passing of traits from parents to offspring For example: You have blue eyes because your mom does. However, what if you have blue eyes but both your parents have brown eyes? How does this happen?

Gregor Mendel He performed experiments that helped answer these questions and how inheritance happens. Mendel is known as the father of genetics Genetics is the study of how traits are passed from parents to offspring

Mendel’s Experiment His experiment was tested on a pea plant. http://study.com/academy/lesson/gregor-mendel-genetics-experiments-laws-discovery.html

True Breeding PLants When a true-breeding plant self pollinates, it always produces offsprings with traits that match the parent Ex. If a pea plant is wrinkled and self-pollinates, then it will only produce wrinkled seeds

Mendel’s Results Purple x Purple All white flowers White x White All Purple Flowers (True-breeding) White x White All white flowers

All purple flowers (hybrids) Mendel’s Result All purple flowers (hybrids) Purple x White After doing his experiment, he was wondering why when he mixed purple and white seeds that all of them came out purple flowers.

Second Generation (Hybrid) Crosses A hybrid plant is when a plant is produced from two true breeding plants with different forms of the same trait.

Mendel’s Conclusion There are two genetic factors control each inherited trait When organisms reproduce, each reproductive cell—sperm or egg—contributes one factor for each trait

Dominant & Recessive Traits All purple flowers (hybrids) Purple x White Why didn’t the flowers turn white? Mendel believed that the purple color is the only factor seen or expressed because it blocks the white factor

Dominant and Recessive Traits A genetic factor that blocks another genetic factor is called the dominant trait A dominant trait is observed when offspring have either one or two dominant factors A genetic factor that is blocked by the presence of a dominant factor is called a recessive trait A recessive trait is observed ONLY when two recessive genetic factors are present in the offspring

What is inheritance? Who do you look like? Your mom, dad, grandma, grandpa? What features do you have that are similar to them? A trait is a distinguishing characteristic of an organism During reproduction, traits are passed from one generation to another

What is inheritance? Inheritance is the passing of traits from one generation to another

Inheritance and DNA Organisms pass inherited traits to their offspring in one of two ways: Either asexually or sexually Asexual reproduction pass traits to their offspring by cell division and mitosis and are identical to their parents Sexual reproduction, produce offspring's that are similar to their parents

DNA & Genes Sexual reproduction requires DNA from a sperm cell and egg cell DNA is a molecule inside a cell’s nucleus.

DNA and Genes Gene: is a section of DNA that has genetic information for one trait Genes carry the information in the DNA IF you were to stretch out the DNA it would be 2 METERS LONG! Alleles are the different forms Of a gene

DNA and genes DNA fits in the nucleus because it is tightly coiled with proteins to form chromosomes A chromosome is a structure made of long chains of DNA

Chromosomes The number of chromosomes differ between every species. Humans have 23 paired chromosomes. We get 23 from the sperm cell (males) and 23 from egg cells (females)

Genotype and Phenotype What human trait can you observe?

Genotype and Phenotype Phenotypes are known as how a trait appears, or is expressed Genotype is when the two alleles that control the phenotype of a trait For example, the white plant in our previous example has two recessive alleles. The two alleles are its genotype and the WHITE flower is its phenotype

Symbols for Genotypes Uppercase letters represent dominant alleles Lowercase letters represent recessive alleles

Homozygous and Heterozygous When 2 alleles are the same, its genotype is HOMOZYGOUS. For example, AA or aa If two alleles of a gene are different, its genotype is heterozygous For example, Aa

2 ways of modeling inheritance Punnett Squares and pedigree can be used to predict the identify traits among genetically related individuals

Punnett Squares If the genotypes of the parents are known, then the different genotypes and phenotypes of the offspring can be predicted Punnett Square is a model used to predict possible outcomes for the offspring

Punnett Squares