11–1 The Work of Gregor Mendel A. Gregor Mendel’s Peas Section Outline Section 11-1 11–1 The Work of Gregor Mendel A. Gregor Mendel’s Peas B. Genes and Dominance C. Segregation 1. The F1 Cross 2. Explaining the F1 Cross

2. What characteristics did he study? 11-1 Quiz? 1. Discuss who Gregor Mendel was and discuss his contribution to biology. 2. What characteristics did he study? 3. What is the P1, F1, F2 generation? 4. What are pure plants? Give one example of self-pollination and cross pollination. 5. How did Mendel determine which of each pair of traits was the dominant trait and which was recessive? 6. Although Tall plants appear to be tall, could they be considered “pure” for the tall trait? Why or why not?

Genetics This is the branch of biology which studies heredity. White Tiger - This type of tiger can have yellow parents. How can that happen? link What are some inherited traits for some dog breeds? (Physical and behavior) How do you keep producing a pure breed? Terms -alleles, hybrid, genes, purebred, traits

GREGOR MENDEL prezi Mendel was a monk who lived during the mid 1800’s in Austria. He was great in math and was a gardener at the monastery. He noticed various things about pea plants and their characteristics. He studied seven characteristics of pea plants and noticed what we today call inheritance or the passing of traits by heredity.

P1- pure parent cross contrasting traits Prezi Link F1 generation This generation showed only one trait from the parents that were crossed ( green pod, no yellow pod). Mendel allowed these to self-pollinate. This is called the F2 generation. Results of this pollination showed 3/4 were green and only 1/4 were yellow. The yellow pod trait had appeared to be lost in the F1 generation, actually reappeared in the F2 generation. How did Mendel determine which of each pair of traits was the dominant trait and which was recessive? Although Tall plants appear to be tall, could they be considered “pure” for the tall trait? Why or why not?

Principles of Dominance Section 11-1 P Generation F1 Generation F2 Generation Tall Short Tall Tall Tall Tall Tall Short

Figure 11-3 Mendel’s Seven F1 Crosses on Pea Plants Section 11-1 Seed Shape Seed Color Seed Coat Color Pod Shape Pod Color Flower Position Plant Height Round Yellow Gray Smooth Green Axial Tall Wrinkled Green White Constricted Yellow Terminal Short Round Yellow Gray Smooth Green Axial Tall

Conclusions of Mendel 1. Principle of dominance and Recessiveness One factor of a pair of alleles may mask the appearance of another. (Ex: blond hair is recessive to dark hair) 2. Principle of Segregation The two factors for a characteristic separate, during the formation of eggs and sperm. (B - Brown, b - blue) Which allele did you get? 3. Principle of Independent Assortment- Factors for different characteristics are distributed independently to sex cells. (curly fur /size of dog or tall plant /wrinkled seeds) Mendel’s most important decision was to study just a few isolated traits of the pea plants.

What do the numbers mean? What is the ratio of dominant to recessive? Section 11-1 Parents Long stems  short stems Red flowers  white flowers Green pods  yellow pods Round seeds  wrinkled seeds Yellow seeds  green seeds First Generation All long All red All green All round All yellow Second Generation 787 long: 277 short 705 red: 224 white 428 green: 152 yellow 5474 round: 1850 wrinkled 6022 yellow: 2001 green What do the numbers mean? What is the ratio of dominant to recessive?

11–2 Probability and Punnett Squares A. Genetics and Probability Section Outline Section 11-2 11–2 Probability and Punnett Squares A. Genetics and Probability B. Punnett Squares C. Probability and Segregation D. Probabilities Predict Averages Go to Section:

Punnett squares

Punnett squares

Tt X Tt Cross Section 11-2

Tt X Tt Cross Section 11-2 Go to Section:

Figure 11-10 Independent Assortment in Peas Section 11-3 Go to Section:

Section 11-3 Interest Grabber Height in Humans Height in pea plants is controlled by one of two alleles; the allele for a tall plant is the dominant allele, while the allele for a short plant is the recessive one. What about people? Are the factors that determine height more complicated in humans? Can you only be tall or short? Go to Section:

11–3 Exploring Mendelian Genetics A. Independent Assortment 1. The Two-Factor Cross: F1 The Two-Factor Cross: F2 A Summary of Mendel’s Principles C. Beyond Dominant and Recessive Alleles 1. Incomplete Dominance 2. Codominance 3. Multiple Alleles Polygenic Traits D. Applying Mendel’s Principles

Gene interactions(Recessive vs *Gene interactions(Recessive vs. Dominant) recessive genes do not produce the enzyme (protein) for a trait to be demonstrated. Incomplete dominance - hybrids are intermediates of the parents. (Ex red x white = pink). The recessive allele can not make any pigment at all so less pigment shows up (diagram) Codominance - both differing alleles of a gene are expressed at the same time. There is no dominance of one over the other. (Ex: roan cattle are a hybrid of a Red and White cross R xR’) Polygenic Inheritance - traits are controlled by two or more genes. (Ex Lab retrievers have two separate genes which determine coat color) Multiple alleles - numerous versions of a gene are possible. (eye color, blood type, etc.)diagram

Figure 11-11 Incomplete Dominance in Four O’Clock Flowers Section 11-3 Go to Section:

Different traits separate randomly Law of Independent assortment Section 11-3 Concept Map Gregor Mendel Different traits separate randomly Law of Independent assortment which is called the experimented with concluded that Pea plants “Factors” determine traits Some alleles are dominant, and some alleles are recessive Alleles are separated during gamete formation which is called the which is called the Law of Dominance Segregation Go to Section:

Section 11-4 Interest Grabber continued 1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis? 2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo? 3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have? Go to Section:

D. Comparing Mitosis and Meiosis Section Outline 11–4 Meiosis A. Chromosome Number B. Phases of Meiosis 1. Meiosis I 2. Meiosis II C. Gamete Formation D. Comparing Mitosis and Meiosis

Meiosis This is the division of chromosomes that creates new cells with half the number of chromosomes (haploid) This type of cell division occurs in sex cells egg, sperm, pollen, spores,etc. They have the chromosome number of 1n (1n + 1n = 2n) (Diploid) Two main parts of Meiosis: Meiosis I - Homologous Chromosomes separate into separate cells Meiosis II - Chromatids of each chromosome are segregated into separate cells.

Meiosis I Figure 11-15 Meiosis Interphase I Section 11-4 Prophase I Metaphase I Anaphase I Cells undergo a round of DNA replication, forming duplicate Chromosomes. Each chromosome pairs with its corresponding homologous chromosome to form a tetrad. Spindle fibers attach to the chromosomes. The fibers pull the homologous chromosomes toward the opposite ends of the cell. Go to Section:

Meiosis II Figure 11-17 Meiosis II Section 11-4 Prophase II Metaphase II Anaphase II Telophase II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells. Go to Section:

Meiosis I DNA replication has already happened.

Meiosis II No DNA replication has happened.

Egg and Sperm Formation Gametes - sex cells that have half the number of chromosomes as somatic cells (body) p. 278 Sperm are formed in the male sex organs through the process of meiosis. Four (4) new sperm are produced from this process from every “mother cell”. Eggs are formed in the female sex organs through meiosis. One egg cell or ootid and three (3) polar bodies are produced from every “mother cell”.

Genetic Variation Sexual reproduction - fusion of gametes with different genetic material. Offspring are genetically different than parents. Asexual reproduction - there is no exchange of genetic material. Organism is identical to parent. Binary fission, budding, cloning. How does genetic variety help organisms survive? Diploid numbers for various organisms: mouse 40 rat 42 hamster 44 guinea pig 64 dog 78 cat 38 frog 26 goldfish 94 garden pea 14 potato 48 corn 20 onion 16 house fly 12 grass hopper 24 What conclusion can you make from these numbers?

Crossing-Over of tetrads Section 11-4

FYI Reduction Division reduces the number of chromosomes per daughter cell by half. Prophase I – can last years. Human females have potential eggs which have entered prophase I by birth. Eggs remain “stuck” in this stage for decades. Oocytes – germ cells with potential to form eggs are in follicles, found in the ovary tissue. Each follicle has a single oocyte. All germ cells are in prophase I of meiosis by birth. Oocyte grows and is packed full of nutrients for a developing embryo. Oogensis – egg forms and follicle ruptures releases the egg. Ovulation occurs. Meiosis II is completed after the fertilization of the 1 egg. 3 polar bodies are produced and disintegrate. Synapsis – process of chromosome alignment in Prophase I. Synapsed pair of homologous chromosomes are called a tetrad. Crossing over can occur. Sperm – produced in seminiferous tubules from stages of cells. Spermatogonia primary spermatocytes spermatidsimmature sperm

Janssens (1909) predicted crossing over leads to genetic recombination/ which increases diversity of all life. Chiasmata- the points where two homologous chromosomes are in contact. Sites where crossing over takes place. Crossing over does not require the breakage and reunion of thick, compact chromosome pieces, but of individual DNA molecules (nucleotides+nucleotides). There are 223 combination possible in humans for to independent assort (8million possibilities) 1 in 70 million chance of having identical siblings in different pregnancies. Pleiotrophy – product of one gene can cause many problems. (Ex: cystic fibrosis) Epistasis – one pair of alleles (recessive) effect the genes or alleles at another loci (part of chromosome). Ex: Albinism

11–5 Linkage and Gene Maps A. Gene Linkage B. Gene Maps Section Outline Section 11-5 11–5 Linkage and Gene Maps A. Gene Linkage B. Gene Maps Go to Section:

What are some products that often come in packages containing several different colors and flavors? What happens if you want only one flavor? What else do you get besides the color or flavor you want? Linkage groups- these are “packages” of genes that tend to be inherited together. There is one linkage groups for every homologous pair of chromosomes. *A human cell has about 100 000 different genes attached in a single line on each chromosome. Crossing Over If genes for body color and wing size are linked, why aren’t they linked all the time? Sections of the chromosomes can cross, break and reattach during Meiosis I. (see diagram) Recombinants - individuals with new combinations of genes. It is believed that 2-3 cross-overs occurs on each pair of human homologs in sex cells.

Punnett Square - name after Reginald Punnett who studied genetics in the 1900’s. Sutton - (1902) His Chromosome theory of heredity states that genes are located on chromosomes and each occupies a certain place. Each chromosome contains a form of the gene called an allele. There can be two or more alleles for each gene. (see diagram) Linked genes - they are found on the same chromosome and do not undergo independent assortment. Discovered in fruit flies by Thomas Hunt Morgan.

What if there was no crossing-over in any organism? Gene Mapping Distance between genes (alleles) determines how often crossing over occurs. The farther apart- the more likely genes are to cross-over. This distance helps to “map” a chromosome and tell the probable place to find a certain gene on the chromosome. Genes located on one of the sex chromosomes is said to be sex linked. How is the sex of offspring determined? (Review)

Crossing-Over Go to Section:

Crossing-Over Go to Section:

Crossing-Over Go to Section:

Figure 11-19 Gene Map of the Fruit Fly Exact location on chromosomes Section 11-5 Exact location on chromosomes Chromosome 2 Go to Section:

Comparative Scale of a Gene Map Section 11-5 Mapping of Earth’s Features Mapping of Cells, Chromosomes, and Genes Cell Earth Country Chromosome Chromosome fragment State Gene City People Nucleotide base pairs Go to Section: