Chapter 11 Introduction to Genetics

With your group on a piece of paper answer the following questions What do you think of when you hear the word “genetics”? What are 3 examples of a trait? If a red flower and white flower reproduces, what color will the offspring be? Why? Assign one person to scribe, and one person to share with the class the answer to a question.

From whom did you get your traits? Parents Mom Dad

What kind of traits do you think you got from your parents? Eye color Hair color Height Nose shape

11.1 The Work of Gregor Mendel Genetics: Study of heredity and variation in organisms. Heredity: Passing of genetic information from parent to offspring.

Mendelian Genetics In the 1800s an Austrian monk studied plants. His name was Gregor Mendel. He is called the “Father of Genetics”. Mendel wanted to describe how traits were passed between generations.

Traits Traits: Variation of a particular character. Ex. Eye color, hair color, and nose shape.

What are some different traits? Tail length Hair color Ear direction

What happens when you cross red paint with white paint? Red mixed with white makes…. Pink If you crossed a red flower and a white flower… what color would the offspring be? Red, white, or pink

Pea Plant Traits 1. Flower color 2. Flower position 3. Seed color 4. Seed shape 5. Pod shape 6. Pod color 7. Plant height

Mendel’s Experiment Performed experiments using pea plants. Why pea plants? Easy to grow Have easy observable traits Reproduce quickly

Mendel’s Experiment Step 1: Looked at one trait, the flower color. Mendel allowed the pea plants to self-pollinate. This gave him purebred plants for the offspring. Fertilization: Male and female reproductive cells join. Purebred: Genetically uniform (identical). Hybrid: offspring of crosses between parents with different traits He called these plants the P generation (Parental).

Mendel’s Experiment Step 2: Cross-pollinated two P generation plants. Monohybrid cross: Parent plants differ in one characteristic. Flowers were all purple. He called these plants the F1 generation. F1 generation is the offspring of the P generation.

Mendel’s Experiment Step 3: Allowed F1 generation to self-pollinate. Produced a mix of white and purple flowers. He called this generation the F2 generation.

Overall

Genes and Alleles Genes: Factors that are passed from parent to offspring. For each inherited characteristic an individual has 2 forms of a gene. These copies are called alleles. Alleles are represented by letters. Ex. PP or Pp or pp

Alleles Principal of Dominant alleles: Will always be expressed with 1 or 2 uppercase letters. Ex. PP or Pp Principal of Recessive alleles: Will only be expressed with 2 lowercase letters. Ex. pp

Let’s Try Ex. Flower color Purple is dominant to white. What color is PP? Purple What color is pp? White What color is Pp?

Mendel's First Law Law of Segregation: Organism inherits two copies of genes, one from each parent. Alleles are separated during gamete formation. Gamete: Sex cells Where do you get your sex cells from? Mom and your dad

11.2 Applying Mendel’s Principal Probability: The likelihood that a particular event will occur. What is the probability of flipping a coin and landing on heads? What is the probability of rolling a die and landing on 6?

Punnett Squares Diagram that shows the probabilities of the possible outcome of a genetic cross.

Vocabulary Homozygous: When the alleles are the same. Homozygous Dominant: Alleles are both uppercase letters. Ex. PP or BB Homozygous Recessive: Alleles are both lowercase letters. Ex. pp or bb Heterozygous: Different. One uppercase and one lowercase letter. Ex. Pp or Bb

Genotype/Phenotype Genotype: Genetic makeup of an organism. Ex. PP or Pp or pp Phenotype: Physical characteristic expressed from the genotype. Ex. Purple, purple, white

Your mother is homozygous for black hair and your dad has blonde hair   Your mother is homozygous for black hair and your dad has blonde hair. Black is dominant to blonde.

Mendel's Second Law Law of Independent Assortment: Alleles for different genes separate independently of one another during gamete formation.

11.3 Other Patterns of Inheritance What happens when you cross red paint with white paint? Red mixed with white makes…. Pink If you crossed a red flower and a white flower… what color would the offspring be? Red, white, or pink

What is the offspring when you cross a Black chicken with a White chicken? x Blue chicken

This is called intermediate inheritance or incomplete dominance. Inheritance in which heterozygotes have an intermediate phenotype. Neither phenotype is expressed in offspring.

P RR x rr F1 Rr x Rr F2 1 RR 2 Rr 1 rr

Multiple Alleles Codominance: Both dominant alleles are expressed. For example blood. What are the four blood types? A B AB O

ABO Blood Alleles IA – dominant allele for type A blood IB – dominant allele for type B blood i – recessive allele for type O blood

ABO Blood Grouping Blood type Genotype A IAIA or IAi B IBIB or IBi AB ii NOTE: Blood type AB is also an example of codominance

Importance of Environment If a woman who is 6 ‘3’ and mates with a male who is 6 ‘7’… does that mean their son or daughter will be tall? Why? No, their offspring could be malnourished. Think of plants. Depending of the plant gets sunlight and water it affects how it will grow. Think of professional athletes and their parents.

Polygenic Inheritance Multiple genes affect a characteristic, the variation in phenotypes can become greater. Example. Humans height and skin color.

Environment Temperature can also effect the phenotype. Siamese cats usually have white fur but when there is cooler temperatures it changes the cats enzyme which makes the coat color darker.

11.4 Meiosis Homologous: Chromosomes in which one set comes from the male parent and one from the female parent. Diploid: 2 sets of chromosomes. Written as 2n. Haploid: One set of chromosomes. Written as n.

Twins Separated at Birth http://abcnews.go.com/blogs/headlines/2014/02/twins-separated-at-birth-find-each-other-on-different-continents/

Almost all human cells are diploid (2n) Almost all human cells are diploid (2n). They contain two homologous sets of chromosomes. Single set of chromosomes are called haploid (n). Gametes are sex cells (eggs and sperm) and are haploid. For humans n= 23. What is happening in this picture? Sperm (n) is fusing with an egg (n). This is called fertilization. The fertilized egg is called a zygote (2n).

Meiosis: Type of cell division that produces four cells, each with half the number of chromosomes as the parent cell. Mitosis - process by which the nucleus divides to form two nuclei, each containing a complete set of the cell’s chromosomes   Meiosis – two-stage form of cellular division that reduces the number of chromosomes per cell by one-half

Stages of Meiosis Meiosis 1 Prophase 1: Homologous chromosomes stick together. Form a tetrad. Paired chromosomes consist of four chromosomes. Chromosomes cross over. Crossing over: The exchange of genetic material between homologous chromosomes.

Metaphase 1 Tetrads line up in the middle of the cell and line up across the spindle.

Anaphase 1 Homologous chromosomes begin to separate and move away to opposite poles.

Telophase 1 and Cytokinesis Chromosomes arrive at pole. Each pole has haploid set of chromosomes. Nucleus reforms and cell divides.

Meiosis 2 Prophase 2: In each haploid daughter cell, spindle forms, attaches to centromere and more chromosomes.

Metaphase 2 Chromosomes line up in middle of the cell. Spindles attach to each sister chromatid.

Anaphase 2 Sister chromatids separate and move away to opposite poles.

Telophase 2 and Cytokinesis Chromosomes arrive at poles. Cytokinesis splits the cells one more time. Produces four haploid daughter cells.

Gametes to Zygotes Once the fertilization of both male and female gametes happen we create an egg called a zygote. Zygote: Fertilized egg.

Meiosis I Diploid cell 2N = 4 2 Haploid cells N = 2 Why does crossing-over occur? Crossing-over changes the combination of the genes on chromosomes.  allows for variation among organisms

Meiosis II 2 haploid cells N = 2 4 haploid cells N = 2

Meiosis

Genetic Linkage When genes are located on separate chromosomes, they sort independently of each other. When genes are located close to each other the greater the genetic linkage. Genetic linkage: The tendency for the alleles on one chromosome to be inherited together.

Mitosis vs. Meiosis MITOSIS MEIOSIS Why does it happen? Growth, repair, replace Make sex cells (gametes) Where does it happen in your body? When does it happen during your lifetime? Number of cells formed Number of chromosomes Number of cell divisions Types of cells formed Entire body EXCEPT………. Reproductive organs Fertilization  Death Males Puberty  Death Females Puberty  Menopause 1 cell  2 cells 1 cell  4 cells 46  46 2N  2N 46  23  23 meiosis I meiosis II 2N  N  N One Two All EXCEPT………………… Gametes (reproductive cells) Sperm cells Egg cells

Real life “Parent trap” http://www.people.com/article/twin-sisters-separated-birth-reunite-internet