Plan for the Day  Seating Chart & Group Cards  Notes: Introduction Genetics  Activity: Class Trait Variation  Exit Ticket: In class assessment  Homework = Bring Your Text book.

How does an organism pass its characteristics on to its offspring? Chapter 11

Learning Targets I can describe where an organism gets its unique characteristics. I can describe how the different forms of a gene are distributed to offspring.

Genetics The scientific study of heredity

Section How it all began Gregor Mendel ( ) Known as the father of genetics Worked with pea plants

Mendel’s Pea Plants He observed 2 traits for each part of the plant.

Mendel’s Pea Plants He came up with the concept of alleles. He noticed that alleles are hereditary, and that you can predict the probability of the offspring having certain alleles.

Mendel’s Pea Plants He observed that some traits dominated over others For instance, if you “crossed” a round seed-pod plant with a wrinkled seed-pod plant you generally get a round seed-pod plant. Mendel Video

Mendel’s Pea Plants

What does “crossing” the pea plants mean? It means to mate a plant with another plant by pollination. Garden peas are both self-fertilizing and cross-fertilizing. self-fertilizing – a plant’s pollen grains fertilize its own egg cells in the ovary. cross-fertilizing – a plant’s pollen grains fertilize another plant’s egg cells in the ovary.

Genes and Dominance The offspring of crosses between parents with different traits are called Hybrids When Mendel crossed plants with different traits he expected them to blend, but that’s not what happened at all. All of the offspring had the character of only one of the parents

Mendel drew two conclusions 1. Inheritance is determined by factors that are passed from generation to generation – today we call these factors genes

Alleles (uh LEELZ) Different forms of a gene Plant Height –One form produced tall plants –Another form produced short plants.

Mendel’s 2 nd conclusion 2. The Principal of Dominance Some alleles are dominant and some are recessive

dominant Covers up the recessive form Ex.) T = tall

recessive Gets covered up in the presence of a dominant allele Ex.) t = short

Quick Lab Period 6 Trait Survey Feature Dominant Trait Number Recessive Trait NumberTotal A Free ear lobes 29Attached ear lobes 534 B Hair on fingers 22 No hair on fingers 1234 C Widow’s peak 7 No widow’s peak 2734 DCurly hair17 Straight hair 1634 ECleft chin2 Smooth chin Copy the data table into your notebook. 2.Write a prediction. 3.We will collect our data together starting with Trait A. 4.Those with free ear lobes move to the left side and those with attached to the right. 5.Count the number in each group and record. 6.Repeat for B to E.

Quick Lab Period 4 Trait Survey Feature Dominant Trait Number Recessive Trait NumberTotal A Free ear lobes % Attached ear lobes 032 B Hair on fingers 26 81% No hair on fingers 6 19% 32 C Widow’s peak 10 31% No widow’s peak 22 69% DCurly hair 16 50% Straight hair 16 50% 32 ECleft chin 4 13% Smooth chin 28 87% 32 1.Copy the data table into your notebook. 2.Write a prediction. 3.We will collect our data together starting with Trait A. 4.Those with free ear lobes move to the left side and those with attached to the right. 5.Count the number in each group and record. 6.Repeat for B to E.

Segregation Mendel wanted to answer another question Q: Had the recessive alleles disappeared? Or where they still present in the F 1 plants? To answer this he allowed the F 1 plants to produce an F 2 generation by self pollination

P 1 Parental TallShort All Tall F1F1 F2F2 3 tall : 1 short 75% tall 25% short

The F 1 Cross The recessive traits reappeared! Roughly 1/4 of the F 2 plants showed a recessive trait

Explanation of the F 1 Cross The reappearance indicated that at some point the allele for shortness had been separated from the allele for tallness Mendel suggested that the alleles for tallness and shortness in the F1 plants were segregated from each other during the formation of sex cells or gametes When each F1 plant flowers, the two alleles segregate from each other so that each gamete carries only a single copy of each gene. Therefore, each F1 plant produces two types of gametes – those with the allele for tallness and those with the allele for shortness

Segregation Segregation is the process of alleles separating from one another during gamete formation.

In Your Notebooks: 1a. What did Mendel conclude determines biological inheritance? 1b. What are dominant and recessive alleles? 1c. Why were true- breeding pea plants important for Mendel’s experiment? 2a. What is segregation? 2b. What happens to alleles between the P generation and the F 2 generation? 2c. What evidence did Mendel use to explain how segregation occurs?