Mendel ’ s Principle of Dominance or Recessiveness Traits found in humans Modified by Mrs. Snyder January 2015

What is the relationship between DNA and your physical appearance? Take a moment to think about what you know about DNA, chromosomes, and ribosomes. Write down several ideas. Now, look at the image to the right. What are genes? See page 111

What are genes?

If genes control traits, then we need to find out how they do this. Two alleles exist for each gene (because chromosomes are paired.) (page 111) alleles For now we will keep things simple. The presence or absence of an allele impacts an organism’s appearance. The terms dominant, recessive, homozygous, and heterozygous are important for you to understand.

Terms defined Dominant – page 109 Recessive – page 109 Homozygous vs heterozygous Homozygous vs heterozygous How are alleles represented? Probability: pages

Explore 1 Fundamentally Genetics You and your groups will be looking at each other to determine whether you are dominant or recessive for the following traits.

More terms Genotype phenotype

Tongue Rolling

Earlobes

Earbump Often called Darwin ’ s Ear Bump Dominant - Having a small bump on the ear Recessive - Not having the bump

Widow ’ s Peak

Hitchhiker ’ s Thumb

Cleft Chin

Clockwise Hair Whorl

Here is the link to the lab we are going to dolink Obtain a lap top when directed. Create an excel chart It should have 8 columns Label as directed

Period 3 Lab: Partners – randomly generated John, Rebecca Laura, Ilana Tae, Jessie Alex, Gino Kylie, Maria Grace, Justin Andrew, Robert Nia, Gianna DJ, Cooper You are a team of scientists. You are studying the random distribution of traits (this occurs during meiosis) and will use your traits as an example. One person is the “mother” and one is the father.

Period 7 Partners – randomly generated You are a team of scientists. You are studying the random distribution of traits (this occurs during meiosis) and will use your traits as an example. One person is the “mother” and one is the father.

Period 8 Partners – randomly generated You are a team of scientists. You are studying the random distribution of traits (this occurs during meiosis) and will use your traits as an example. One person is the “mother” and one is the father.

Explore 2 Punnett Squares You will be able to predict the outcomes of crosses by completing this next activity.

Mendel & The Gene Idea Explain

Mendel and Genetics Answer the following questions as we explain the concepts surrounding basic genetic

It All Began with Mendel (FYI) Gregor Mendel was born in Called the “ Father of Genetics ” Late 1800 chromosomes and the process of meiosis were unknown. Mendel ’ s work was considered obscure and unimportant until 1900 Walter Sutton proposed the Chromosome Theory and people began to listen to his ideas. Chromosome Theory – specific genes are located on specific chromosomes

Three Conclusions to His Research 1. Principle of Dominance and Recessiveness One allele in a pair may mask the effect of the other 2. Principle of Segregation The two alleles for a characteristic separate during the formation of eggs and sperm 3. Principle of Independent Assortment The alleles for different characteristics are distributed to reproductive cells independently.

Mendelian genetics Character (heritable feature, i.e., fur color) Trait (variant for a character, i.e., brown) True-bred (all offspring of same variety) Hybridization (crossing of 2 different true-breds) P generation (parents) F 1 generation (first filial generation)

Genetic vocabulary……. Punnett square: Gene: point on a chromosome that controls the trait Allele: an alternate form of a gene A or a Homozygous: identical alleles for a character Heterozygous: different alleles for a gene Phenotype: physical traits Genotype: genetic makeup Testcross: breeding of a recessive homozygote X dominate phenotype (but unknown genotype)

How can the Chances of an Offspring ’ s Traits be Determined? BY USING A PUNNETT SQUARE Get out your Punnett Squares Problems In groups of two come to the board and complete the given monohybrid problems.

Bb X Bb Phenotypic Ratio 3:1 Genotypic Ratio 1:2:1 B b B b B B B b b B b b

Exploration 4 What about two traits? Complete the second half of your Punnett Square Problems

What about 2 Traits? BbTt x BbTt The Gametes contain one of each of the alleles. (BT). Each of the offspring contain four alleles exactly like the parents.(BbTt). Notice the number of possible offspring has increased. The phenotypic ratio is 9:3:3:1

BbTt x BbTt BTBtbTbt BT BBTTBBTT BBTtBbTTBbTt BtBBTtBBttBbTtBbtt bTBbTTBbTt bbTTbbTT bbTt btBbTtBbttbbTtbbtt

Exceptions to Mendel ’ s Rule

Incomplete Dominance The phenotype of the heterozygote is intermediate between those of the two homozygotes. Ex) Snap Dragon Color Red, Pink, White

Co-dominance Phenotype of both homozygotes are produced in heterozygotes individuals. Both alleles are expressed equally. Ex)Roan Cattle White-feathered birds are both homozygotes for both B and W alleles

Multiple Alleles Ex )Blood type Blood type A and B are co-dominant, while O is recessive. Forms possible blood types of A, B, AB, and O.

Blood Also Shows Codominance

Sex-Determination Chromosome pairs 1-22 are autosomes Chromosome pair 23 are sex chromosomes They determine the sex of an individual XX = femaleXY = male

Sex-Linked Inheritance Traits that are only found on the X chromosome Colorblindness and Hemophilia are examples of sex-linked traits. These genes are recessive and found only on the X chromosome.

Polygenic Inheritance Inheritance pattern of a trait that is controlled by two or more genes. Gene may be on the same chromosome or on different chromosomes. Ex) Skin color and Height

ELABORATION 1 Exceptions to the Rule Punnet Squares: Dihybrid, Sex-Linked, Multiple Alleles, Co-Dominance, Incomplete Dominance

Elaboration 2 Who ’ s the Parents? Upon completion of this lab, you will: determine the ABO blood types of two sets of parents and two newborn children examine the genetic relationships possible between the parents and children match the “ mixed up ” children with their proper parents.