Complete: Word association. Use the description that best describes the term. This is practice for your vocab quiz. 1.a 2.e 3.c 4.d 5.b 6.f

Warm Up 1. The garden pea is a good subject for genetic study because it a. is easy to grow. c. produces many offspring. b. has characters in two clearly different forms. d. All of the above 2. Mendel first allowed each variety of garden pea to self-pollinate for several generations. This produced the a. F generation. c. P generation. b. F1 generation. d. filial generation. 3. What did Mendel find in the F1 generation? a. a ratio of 3:1c. 30 percent of the plants expressed the dominant trait. b. a ratio of 3:1:3d. 100 percent of the plants expressed the dominant trait. 4. Which ratio of plants expressing contrasting traits did Mendel find in the F2 generation? a. 3:1 c. 3:3 b. 3:1:3 d. 1:1 5. The trait that disappeared in the F1 generation a. reappeared in some plants in the F2 generation. c. reappeared in some plants in the P generation. b. reappeared in all plants in the F2 generation. d. was lost forever.

OBJECTIVES MENDELIAN TERMS Describe the patterns that Mendelian theory explains. Define and be able to use terminology associated with genetics; allele, gene, those below. Relate genotype to phenotype, using examples from Mendel's experiments with pea plants. Relate the terms recessive and dominant, with respect to Mendelian genetics. Relate the terms homozygous and heterozygous. Summarize the laws of segregation and independent assortment.

VOCABULARY Allele Dominant Recessive Genotype Phenotype Homozygous Heterozygous

EXPLAINING MENDEL’S RESULTS Mendel developed several hypotheses/theories to explain the results of his experiments. These hypotheses are collectively called the Mendelian theory of heredity, which form the foundation of modern genetics. Mendelian theory explains simple patterns of inheritance.  In these patterns, two of several versions of a gene combine and result in one of several possible traits.

MENDEL TERMS… COMMON TERMS Mendel Used: -Character -Factor We Use Now: -Gene -Allele

EXPLAINING MENDEL’S RESULTS/ MODERN TERMINOLOGY A gene is the most basic unit of heredity. It is found in DNA. An allele is a version of a gene. These are also found on the chromosome in DNA. A trait is what is seen on the outside of an organism as a result of the specific allele combination. Gene (hair color)  allele (brown)  trait (brown hair) To help, think of this analogy: Or Develop Your Own! When explainingGene  Category for unit of heredity Allele  One version of a specific gene Trait What is observed Analogy…Cakes: The category of food Chocolate cake recipe The finished cake

VISUAL CONCEPT: ALLELE Click above to play the video.

GENE  ALLELE  TRAIT For every gene we are given 2 alleles. One allele is from mom, one is from dad. The way these alleles interact give us a trait, which is observable on the outside. Allele Trait

ALLELES How do gametes end up with one allele? How do we end up with two alleles for each gene? Meiosis Fertilization Alleles interact to give us our traits. How do we end up with a trait?

HOW ALLELES INTERACT For “Mendelian Traits” alleles have one of two roles. An allele that is fully expressed whenever it is present is called dominant. This means this is the version of the gene that will show up. An allele that is not expressed when a dominant allele is present is called recessive. This allele cannot be seen if the dominant form is also present. A recessive allele is expressed only when there is no dominant allele present. The trait that results will be either dominant or recessive depending upon the combination of alleles makes it.

VISUAL CONCEPT: COMPARING DOMINANT AND RECESSIVE TRAITS Click above to play the video.

DEFINING ALLELES FURTHER Scientists use a code of letters to represent the function of alleles. A dominant allele is shown as a capital letter. This letter usually corresponds to the first letter of the word for the trait. A recessive allele is shown as a lowercase letter. This always relates to the dominant form. Offspring do not show a trait for every allele that they receive. Instead, combinations of alleles determine traits.

Dominant Allele  Written as an uppercase  Corresponds (usually) to the first letter of the dominant allele/trait.  Examples.  Yellow (dominant)…Y  Purple flower (dom)…P  Round seed (dom)…R Recessive Allele  Written as a lowercase  Corresponds to the dominant allele  Examples.  Green (recessive)…y  White flower (rec)…p  Wrinkled seed (rec)…r ALLELES

PRACTICE ALLELES Black hair is dominant over red hair Brown eyes are dominant over green eyes Left thumb on top in hand clasping is dominant over right thumb on top. (Clasp you hands together. Which way does it feel natural?) Having a bent little finger is dominant over a straight little finger. (Put your hands on the table, relax you muscles and see if the last joint bends in towards your ring finger) Take 2 minutes and write a symbol for both the dominant and recessive alleles. As a follow up, if you show recessive for any of these traits examine your parents to see if they both show these came characteristics. (BTW…who should show them?)

POSSIBILITIES…THERE’S NO RIGHT OR WRONG ANSWERS HERE, JUST USE SOLID JUDGMENT. Dominant TraitDominant Allele Recessive traitRecessive Allele BlackBRedb Brown EyesBGreenb Left Thumb on Top L, TRight Thumb on Top l, t Bent Little Finger B, L, or FStraight Little Finger b, l, or f

MODERN GENETICS TERMS The set of specific combinations of alleles that an individual has for a character is called the genotype. These are given as a combination of letters that represent the allele. Alleles are on the chromosome so the genotype can only be determined by examining the combination of alleles. The observable trait that results from the genotype’s set of alleles is called the phenotype. This is observable. Your phenotype for your hair color is the color your hair is, based upon the alleles you were given. Thus, genotype determines phenotype. But phenotype is the thing that’s measurable.

VISUAL CONCEPT: GENOTYPE Click above to play the video.

MODERN GENETICS TERMS If an individual has two identical alleles of a certain gene, the individual is homozygous for the related character.  Homozygous means that the letters are the same!  They could be both the dominant or recessive allele!  Examples:  YY = two yellow alleles (both dominant)  yy = two green alleles (both recessive)  PP = two purple alleles (both dominant)  pp = two white alleles (both recessive)  Homozygous means purebred. If an individual has two different alleles of a certain gene, the individual is heterozygous for the related character.  Yy = one yellow and one green allele (1 dominant/1 recessive)  Pp = one purple and one white allele (1 dominant/1 recessive)  Heterozygous means hybrid.

1 Genotype 2 Phenotype 3 Genotype 4 Phenotype 5 Genotype 6 Phenotype PPPppp YYYyyy RRRrrr GGGggg

WHAT MENDEL DISCOVERED Mendel was able to establish three things based upon the evidence gathered from the pea plants. First thing was dominance and recessiveness. The second thing was that alleles end up in gametes according to the law of segregation. The law of segregation holds that when an organism produces gametes, each pair of alleles is separated and each gamete has an equal chance of receiving either one of the alleles. The 3 rd thing the law of independent assortment, that genes on different chromosomes end up in gametes independently from genes on other chromosomes. Since there are two for each gene, the chance is 50/50 on which allele ends up in any gamete. These alleles don’t affect the inheritance of alleles for other genes.

MEIOSIS OFFSPRING GAMETES The law of segregation states that each allele is separated giving each gamete an equal chance of receiving either allele. This gives multiple possibilities for offspring. There are 16 different possibilities with just these 4 alleles!

RECALL THAT A DIPLOID ORGANISM HAS 2 SETS OF CHROMOSOMES bB From Mom From Dad M m From Mom From Dad In these sets there are 2 chromosomes that carry the same genes, just different copies (sometimes) The different versions (the alleles) of each gene work together to give each trait seen on the outside. TRAIT1 TRAIT2

SUMMARY Mendelian theory explains simple patterns of inheritance. In these patterns, two of several versions of a gene combine and result in one of several possible traits. Genotype determines phenotype. In modern terms, the law of segregation holds that when an organism produces gametes, each pair of alleles is separated and each gamete has an equal chance of receiving either one of the alleles. In modern terms, the law of independent assortment holds that during gamete formation, the alleles of each gene segregate independently.

INDEPENDENT PRACTICE Complete the worksheet, front and back, practicing with Mendelian Genetics Terms.

END OF SECTION QUIZ In addition to the 10 multiple choice questions that are being handed out to you, answer these 5 questions in short answer form. 1.Describe the patterns that Mendelian theory explains. 2.Summarize the law of segregation. 3.Summarize the law of independent assortment. 4.Could a trait be heterozygous recessive? 5.What is the major flaw in Mendel’s independent assortment law? Homework follows…