Mendelian Genetics Module 8 December 5, 2013 Honors Biology Mendelian Genetics Module 8 December 5, 2013

Notebook Check Today Through Module 7 On Your Own questions Study Guide questions Module tests Lab book completed

Class Challenge

Quiz: Figure 7.6 Draw and label: Meiosis Stage I and Stage 2

Mendelian Genetics During 8 years of scientific work, Mendel studied breeding of pea plants. He noticed that pea plants had certain definable characteristics that seemed to change from plant to plant. Some pea plants were tall (6 feet high) Some were small (1 ½ feet high) Some flowers grew along the sides of the plants. (Axial flowers) While others grew on the top of the plant. (Terminal flowers) Some pea pods were green Some pea pods were yellow Some peas were wrinkled Some peas were smooth

True Breeding Figure 8.1 Mendel noticed that some plants bred so as to produce offspring with the same characteristic. Some tall plants would always give rise to other tall plants. When this happens, the tall plant has bred true. If an organism has a certain characteristic that is always passed on to its offspring, we say that this organism bred true with respect to that characteristic.

Figure 8.1 and Figure 8.2 Mendel developed the four principles of genetics that are still the foundation of science today. The traits of an organism are determined by packets of information called “factors.” Each organism has not one, but two factors that determine its traits. In sexual reproduction, each parent contributes ONLY ONE of its factors to offspring. In each definable trait, there is a dominate factor. If it exists in an organism, the trait determined by that dominant factor will be expressed.

As you study Figure 8.3 and 8.4 There are traits that a dominate trait (they are represented by a Capital letter) There are traits that are recessive ( they are represented by a lower-case letter)

Dr Wile’s CD Figure 8.2 Figure 8.3

Terms to Know Scientists do not use the term “factor” any more. We know that the packets of information are genes. We know that animals have homologous pairs of chromosomes, we know that genes come in pairs, with one gene on each homologous chromosome. Each gene that makes up one of these pairs is called an allele. Allele is one of a pair of genes that occupies the same position on homologous chromosomes.

Mendel’s “factors” are called Alleles Each definable trait has two alleles that help determine it, and they can each be represented by a letter. When we put two alleles together (for example Tt or tt), we are describing a genotype.

TT and Tt TT and Tt (genotype) will result in a tall plant. The allele T (tall) is dominant. The expression of an organism’s genotype is called a phenotype. It is what it looks like. (A tall plant)

There are two phenotypes possible Tall (TT, Tt) or Short (tt) When the genotype is composed of identical alleles (TT) or (tt) we say that the genotype is homozygous. When the genotype has mixed alleles (Tt) we say that it is heterozygous.

Dr Wile Example 8.1 Example 8.2

Dominant or Recessive Dominant allele: An allele that will determine phenotype if just one is present in the genotype. Recessive allele: An allele that will not determine the phenotype unless the genotype is homozygous in that allele.

A Restatement of Mendel’s Principles The traits of an organism are determined by its genes. Each organism has two alleles that make up the genotype for a given trait. In sexual reproduction, each parent contributes ONLY ONE of its alleles to its offspring. In each genotype, there is a dominant allele. If it exists in an organism, the phenotype is determined by that trait.

The reason that animals have two alleles for each genetic trait is because they have diploid cells. They have homologous pairs of chromosomes. In sexual reproduction, each parent contributes only one allele to the offspring. This is why meiosis takes diploid cells and makes them haploid. The process of meiosis separates the homologous pairs, separating the alleles from each other. Each gamete (sperm and egg) when fused will result with a zygote that has two alleles: one from the father and one from the mother.

Mendelian Genetics http://youtu.be/NWqgZUnJdAY Get your lab books out for questions found at 7:21 minute marker

A Beginner's Guide to Punnett Squares http://youtu.be/Y1PCwxUDTl8

Dr Wile Example 8.3

Identifying Traits in our class Hair color Eye color Ear lobes Tongue curls Hitchhikers thumb

Experiment 8.1 Object : To interpret your own pedigree with respect to earlobe attachment. Procedure:

Homework Read Module 8: MENDELIAN GENETICS (p. 247-257) Answer OYO question 8.1 – 8.7 Answer Study Guide questions: a-j and questions 2 – 9 4. Complete Experiment 8.1 Making your own Earlobe Pedigree. It will be graded on Dec 12. 5. Quiz: Mendel’s scientific contribution to the study of genetics. 6. Class challenge: