Introduction to Genetics Chapter 11 Introduction to Genetics

Golden Doodle Blending Theory - offspring are a straight mix A Brief History In the past, people did not understand how traits were inherited, but there were many guesses based on things that could be observed. Two theories emerged…. Blending Theory - offspring are a straight mix Particulate Theory traits are inherited as "particles", offspring receive a "piece" from each parent, some pieces may hide the others Golden Doodle

Who was Gregor Mendel? GENETICS – study of heredity He was known as the “FATHER OF GENETICS” He discovered how traits were inherited GENETICS – study of heredity HEREDITY – the passing of traits from parents to offspring

Mendel’s Peas Mendel did his study on pea plants which have many traits tall/short purple /white flowers round/wrinkled seed

Genes and alleles Genes – sequence of DNA that determines a trait Alleles – one of a number of different forms of a gene

self-fertilized or cross-fertilized Pea plants can be self-fertilized or cross-fertilized (drawing) During sexual reproduction, male and female reproductive cells join in a process known as fertilization to produce a new cell. Plants can self pollinate so they have only one parent.

True-Breeding Plants always create plants that look like themselves (homozygous) Hybrids offspring of true-breeding plants (heterozygous) Tall x Short = Hybrid

Some traits are dominant over others. Tall x Short = all tall offspring (hybrids) *Tall is the dominant trait * Short is recessive

Mendel discovered that each trait is controlled by two factors (alleles) Genes – factors that determine your traits Genes are located on chromosomes

1. The “Father of Genetics” is ____________ Quick Check - What do we know so far? 1. The “Father of Genetics” is ____________ 2. Genetics is the study of _____________, which is how traits are passed from _________ to ____________ 3. Mendel studied what organism? ____________ 4. If one trait covers up another one, we say that it is ______________, the one that is covered up is ______ 5. A “true-breeding” plant is one that can only produce plants like itself a) true b) false 6. If a tall and a short plant are crossed, it will create a a) zygote b) gene c) hybrid

1. The “Father of Genetics” is Gregor Mendel Quick Check - What do we know so far? 1. The “Father of Genetics” is Gregor Mendel 2. Genetics is the study of Heredity, which is how traits are passed from parents to offspring 3. Mendel studied what organism? pea plants 4. If one trait covers up another one, we say that it is dominant the one that is covered up is recessive 5. A “true-breeding” plant is one that can only produce plants like itself a) true b) false 6. If a tall and a short plant are crossed, it will create a a) zygote b) gene c) hybrid

GENOTYPE  -  what genes, letters, the organism has (TT, Tt, tt) PHENOTYPE   - what it looks like (tall or short)

Mendel’s Experiments

Tracking Hybridization Parent – P generation Hybrid Offspring – F1 Generation Hybrid Cross – F2 Generation

Explaining the Cross When a parent makes sperm or eggs, their genes separate         (PRINCIPLE OF SEGREGATION) The GAMETES (egg or sperm) contain either a T allele (tall) or a t allele (short)

Punnett Square t Tt Tt Tt Tt Parents = TT and tt  F1 Generation – all tall T T t Tt Tt Tt Tt

Punnett Square F1 cross  F2 Generation: 3:1 ratio T t T t TT Tt Tt tt

The law of Independent Assortment How do alleles segregate when more than one gene is involved? Mendel had discovered the principle of independent assortment. The principle of independent assortment states that genes for different traits can segregate independently during gamete formation. Mendel’s experiment is known as a two-factor, or dihybrid, cross.

Summary of Mendel’s Ideas: The inheritance of biological characteristics is determined by individual units called genes, which are passed from parents to offspring.

Summary of Mendel’s Ideas: 2. Where two or more forms (alleles) of the genes for a single trait exist, some alleles may be dominant and others may be recessive.

Summary of Mendel’s Ideas: 3. In most sexually reproducing organisms, each adult has 2 copies of each gene - one from each parent. These genes segregate from each other when gametes are formed.

Summary of Mendel’s Ideas: 4. Law of Segregation: Alleles for different genes usually segregate independently of each other.

7. Genes are located on _______________ 8. Every gene is made of two Check for understanding 7.  Genes are located on _______________ 8.  Every gene is made of two a. genotypes b. alleles c. cells 9. The organism’s outward appearance, such as wrinkled seeds are referred to as the a) phenotype b) genotype

10. The letters (ex. RR) that represent the traits are referred to as the a) phenotype b) genotype 11. An organism that has two different alleles, or letters, such as Rr is: a) homozygous b) heterozygous 12. An organism that has two of the same alleles, or letters, such as RR is: a) homozygous b) heterozygous 13. Which of the following sets would represent Mendel’s Parent (P) generation? a) RR x RR b) Rr x Rr c) RR x rr 14. When two different alleles occur together, such as R r, the one that is expressed is a) dominant b) recessive

7. Genes are located on chromosomes 8. Every gene is made of two Check for understanding 7.  Genes are located on chromosomes 8.  Every gene is made of two a. genotypes b. alleles c. cells 9. The organism’s outward appearance, such as wrinkled seeds are referred to as the a) phenotype b) genotype

10. The letters (ex. RR) that represent the traits are referred to as the a) phenotype b) genotype 11. An organism that has two different alleles, or letters, such as Rr is: a) homozygous b) heterozygous 12. 7. An organism that has two of the same alleles, or letters, such as RR is: a) homozygous b) heterozygous 13. Which of the following sets would represent Mendel’s Parent (P) generation? a) RR x RR b) Rr x Rr c) RR x rr 14. When two different alleles occur together, such as R r, the one that is expressed is a) dominant b) recessive

What does this letter actually represent? 11. What is the diagram shown below called? What does this letter actually represent?

Check for understanding 1.  A one-eyed purple people eater is crossed with a two eyed purple people eater.  All of their offspring have two eyes.   Which trait is dominant?

2. If you use the letter E for this gene 2.  If you use the letter E for this gene.   What is the genotype of the offspring if the parents were EE x ee      3.  If you crossed the offspring with each other?  How many of the new offspring would you expect to have two eyes? EE = two eyes Ee = two eyes ee = one eye