REVIEW TUESDAY, WEDNESDAY, & THURSDAY AFTERSCHOOL FROM 2:45-3:45 TESTING 1 st : Wed. 5/13 and Thurs. 5/14 2 nd and 4 th : Fri. 5/15 and Mon. 5/18 Report to room D125 for testing!

I. Pioneer of genetics: Gregor Mendel Studied patterns of inheritance in pea plants Studied characteristics like: Flower color, seed color/shape, pod color/shape, height of stem

Mendel identified the role of complete dominance. (one trait is completely dominant over the other)

1. Trait: Specific characteristic (seed color, plant height) Generally controlled by 2 alleles of a gene

2. Gene: Factors that determine traits (Sections of DNA)

3. Allele Different forms of a gene

4. Genotype: Combination of alleles inherited from parents

5. Phenotype: Physical appearance of the genotype (adjective) Ex/ purple petals, white petals, freckles, blonde hair, brown hair, dimples

Genotypes and Phenotypes can be found by determining the alleles that were passed down from the parents

6. Dominant Allele: Produces a dominant phenotype in individuals who have at least one copy of the dominant allele Represented by a capital letter P = purple petal color

7. Recessive Allele For a recessive allele to produce a recessive phenotype, the individual must have TWO copies of the recessive allele Represented by a lowercase letter p = white petal color

GenotypePhenotype What possible genotypes would produce the phenotypes? P = purple p = white What possible genotypes would produce the phenotypes? P = purple p = white

8. Heterozygous: Organisms that have two DIFFERENT alleles for the same trait (hybrid) The presence of the dominant allele will produce the dominant phenotype

9. Homozygous: Organisms that have two IDENTICAL alleles for a particular trait (purebred) The phenotype will be determined by whether they have two dominant alleles or two recessive alleles

Let’s Practice! = b = B GENOTYPE PHENOTYPE

Can you predict the gentotypic and phenotypic outcome of a fertilization?

10. Following traits through generations: P : Parent generation F1: 1 st filial (1 st set of offspring from parents) F2: 2 nd filial (offspring of second generation)

11. Punnett Square: Grid that shows probable outcome of a genetic cross (fertilization)

A. One Factor Cross (Monohybrid Cross) Considers one trait Pea Pod Color Y = yellow y = green Freckles on face F = freckles f = no freckles yy x Yy Ff x Ff

B. Two Factor Cross (Dihybrid Cross): Considers two traits Ex/ Pea shape and pea color R = roundr = wrinkled Y = yellowy = green

Genotype Phenotype

For the crosses shown, draw a Punnett square and calculate the probability for the genotype and phenotype for the crosses. TraitDominantRecessive Seed coat shapeRound (R)Wrinkled (r) Pod colorGreen (G)Yellow (g) Seed coat colorBrown (B)White (b) Height of plantTall (T)Short (t) 1.Rr x rr 2.Rr x Rr 3.Cross 2 heterozygous green pod plants. 4.Cross a homozygous green pod plant with a heterozygous green pod plant. 5.Cross a homozygous tall plant with a short plant.

Practice Sheet –Investigating Human Inherited Traits Must be completed by the end of the block.

The presence of mid-digital hair is a dominant condition; therefore those lacking it are homozygous recessive.

Can you roll your tongue upward from the sides? If you can, you have the dominant phenotype (roller) If you cannot, you have the homozygous recessive trait (nonroller)

A distinct downward peak of the frontal hairline Having a widow’s peak is a dominant trait. Homozygous recessive individuals possess a straight hairline.

Is your earlobe attached or unattached? Free or unattached earlobe is dominant. The homozygous recessive condition is expressed as a direct attachment of the earlobe to the head.

The occurrence of natural indentations at the corners of the mouth (dimples) is controlled by a dominant allele. People without dimples possess the homozygous recessive genotype. **New research shows that environmental factors could also affect dimples!**

Hyperextensibility of the thumb is recessive. Those who cannot bend at least one thumb backward about 45 degrees are probably carrying the dominant gene. Sorry… But no hitchhikers thumb…

Can you taste the bitterness of the PTC paper? People who can taste the bitterness are either homozygous dominant (TT) or heterozygous dominant (Tt). People who cannot taste the bitterness are homozygous recessive.

12. Test Cross Done to determine the genotype of a phenotypically dominant individual (TT or Tt): Cross individual with a homozygous recessive individual T T t t T t t t

P = # of times an event occurs The total number of possible outcomes  Ex/ flipping a coin: ½ heads The larger the # of trials, the closer to the expected results Previous events have no effect on future outcomes

1. Law of Segregation Parental genes are randomly separated to the sex cells so that sex cells contain only one gene of the pair. Offspring therefore inherit one genetic allele from each parent when sex cells unite in fertilization.

2. Law of Independent Assortment Genes for different traits are sorted separately from one another so that the inheritance of one trait is not dependent on the inheritance of another Not everyone with blonde hair will also inherit blue eyes!

3. Law of Dominance (complete dominance) An organism with alternate forms of a gene will express the form that is dominant.

1. Incomplete Dominance One allele is not completely dominant over the other The heterozygous phenotype is somewhere in between the two homozygous phenotypes (blend)

2. Codominance Both alleles contribute to the phenotype “co-captains” 2 different alleles are dominant Blood Types are an example A- dominant (I A ) B- dominant (I B ) O- recessive(i)

TypeGenotypePhenotype A B O AB “A” Antigens “B” Antigens No Antigens Both “A” & “B” Antigens Universal Donor: O Universal Acceptor: AB RBC Plasma I A I A, I A i I B I B, I B i ii IAIBIAIB isohaemaglutinogen (AA), (AO) (BB), (BO) (OO) (AB)

Approximate distribution of blood groups and types in the U.S. population Blood TypeRh POSTIVERh NEGATIVEtotal O38%7%45% A34%6%40% B9%2%11% AB3%1%4% TOTAL84%16%100%

3. Sex-linked traits: Located on the X or the Y chromosome. Because the Y chromosome of many organisms contains little genetic information, most sex-linked characteristics are X-linked. Usually X-linked recessive Written with the X chromosome

Example: Colorblindness FemaleMale XBXBXBXB Normal female XBYXBY Normal male XBXbXBXb Carrier female XbYXbY Afflicted male XbXbXbXb Afflicted female B = normal vision b = colorblind

4. Pedigrees Displays a family tree, and shows the members of the family who are affected by a genetic trait Circles represent females and squares represent males A male and female directly connected by a horizontal like have married Vertical likes connect parents to their children. A darkened circle or square represents an individual affected by the trait being looked at

Mrs. Maida’s Family Pedigree

Sex-linked Recessive Pedigree

D – dominant (normal) d – recessive (muscular dystrophy)

Review: 1. A circle on a pedigree chart represents a: A. Male B. Female C. Person who expresses the trait 2. A shaded circle or square represents a: A. Person without the particular trait B. Female C. Person who expresses the particular trait

3. Which of the following pedigrees probably represents the inheritance pattern of a dominant trait? 4. Since the allele for colorblindness is located on the X chromosome, colorblindness: A. Cannot be inherited B. Is sex-linked C. Can only be inherited by females

5. A diagram in which several generations of a family and the occurrence of certain genetic characteristics are shown is called: A. Punnett Square B. Pedigree C. Family karyotype

There are 5 stations throughout the room! By 2:30, you must have completed the task at each station. Upon completion, please staple the worksheets in order, and hand in! YOU MAY CHOOSE TO WORK INDIVIDUALLY ON THIS, OR YOU MAY CHOOSE TO WORK WITH A PARTNER... (in which case you only need one worksheet per station!!)