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Bio 233 Lab - Exercise 13 Heredity

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1 Bio 233 Lab - Exercise 13 Heredity
Gregor Mendel Born in 1822 in Czech Republic Priest who studied mathematics and science at the University of Vienna Spent the next 14 years working at a monastery and teaching high school Carried out his experiments on the side while working for the monastery.

2 Basic Mendelian Principles
Mendel’s ideas: Particulate inheritance: the determinants of inherited traits are discrete units that are passed between generations unaltered, not mixed together.

3 Why Pea Plants? The male gamete, equivalent to the sperm, is the pollen grain. The female gamete, equivalent to the egg, is the ovule. Pea plants are self-fertilizing–pollen (male sex cells) produced by one plant fertilize eggs (female sex cells) in that same plant Several true-breeding varieties of peas were available to him –if allowed to self-pollinate, they produced identical offspring Cross-pollination could be controlled by cutting away male parts and dusting flowers with pollen from other plants with a paintbrush One disadvantage –it took a year to grow each generation of plant

4 Monohybrid Cross We are first going to look at what happens when plants with different traits are crossed, then go through Mendel's explanation. Purple flowers vs. white flowers. The original parental lines are true-breeding, or pure-breeding. All offspring within the lines gave the same flower color for an arbitrary number of generations.


6 First Cross True-breeding purple x true-breeding white. All offspring are purple. The parent lines are the P generation; the offspring are the F1 (first filial) generation. All the F1's are purple regardless of which parent (father or mother) was purple and which was white. Note: no blending occurs. The purple F1 plants look exactly like the purple parentals. We say that purple is dominant because it appears in the F1 hybrid. White is recessive because it does not appear in the F1 hybrid.

7 Monohybrid Cross AA X aa Homozygous alleles A X a gametes
Aa first generation F1 Test for dominant or recessive alleles at one locus

8 Punnett-aquare method of predicting probable outcomes of genetic cross

9 Dihybrid Cross Test for dominant or recessive alleles at 2 loci
AABB X aabb parents AB AB X ab ab gametes AaBb F1 Hybrid offspring


11 Blood Types Determined by membrane proteins in the RBC cell membrane.
Called surface antigens (agglutinogens). Most common group: ABO blood group Two antigens: A and B ABO blood types: Type A: have the A surface antigen Type B: have the B surface antigen Type AB: have both the A and the B surface antigens Type O: have neither the A or the B surface antigen.


13 Blood Types Antibodies (agglutinins) to the surface antigens are in the plasma ABO group has anti-A antibodies and anti-B antibodies Type A: have anti-B Type B: have anti-A Type AB: has neither anti-A or anti-B Type O: has both anti-A and anti- B

14 Antibodies An antibody interacts with a specific antigen.
The ABO blood group has both anti-A and anti-B antibodies that react with the surface antigen A and the surface antigen B, respectively. The antibodies in your blood plasma do not recognize the surface antigens on your erythrocytes.



17 Blood Types Rh blood type Rh positive (Rh+): has the antigen
Based on another surface antigen Called either Rh or D Rh positive (Rh+): has the antigen Rh negative (Rh-): does not have the antigen

18 Some Readily Observable Human Traits
1-Mid-digital hair: Some people have hair on the back of the middle segment of some fingers. Individuals with hair on the middle segment of at least one finger are considered to have the trait mid-digital hair (H); other people have no mid-digital hair (N). Mid-digital hair is often used to illustrate basic genetics; the myth is that the presence or absence of mid-digital hair is controlled by a single gene with two alleles, and the allele for H is dominant.

19 2- Tongue rolling: Some people can roll their tongue into a tube, and some people can't. This is one of the most common traits that biology teachers use to demonstrate basic genetic principles. Alfred Sturtevant (one of the pioneers of Drosophila genetics) described tongue rolling as a simple two-allele character, with the allele for rolling (usually given the symbol T or R) being dominant over the allele for non-rolling (t or r) (Sturtevant 1940).

20 3- widow's peak Some people have a prominent V-shaped point at the front of their hairline, called a widow's peak, while other people have a hairline that goes straight across. Widow's peak is sometimes used to illustrate basic genetics; the myth is that it is controlled by one gene with two alleles, and the allele for widow's peak is dominant over the allele for straight hairline.

21 4- Earlobe Attachment Some people have earlobes that curve up between the lowest point of the earlobe and the point where the ear joins the head; these are known as "free" or "unattached" earlobes, as shown in the upper picture below. Other people have earlobes that blend in with the side of the head, known as "attached" or "adherent" earlobes, as shown in the lower picture.

22 5- Hitchhiker's thumb:  Some people have "hitchhiker's thumbs," which bend backwards with a large angle between the two segments (phalanges). The myth is that there are just two kinds of thumbs, straight thumbs (S) and hitchhiker's thumbs (H), and the trait is controlled by a single gene with two alleles, with the allele for S being dominant.

23 6- Relative finger Length
Some people have an index finger that is longer than their ring finger; we'll call this long index finger, or L. Others have an index finger that is shorter than their ring finger (S). This is said to be a sex-influenced trait. In males, the allele for S is said to be dominant, while the allele for L is said to be dominant in females. Thus SS and SL males will have short index fingers and only LL males will have long index fingers, while SS females have short index fingers and SL and LL females have long index fingers.

24 Terms used in Modern Genetics: Genes Diploid Mutation Alleles Hybrid Heterozygous Homozygous Dominant Recessive Gene expression Genotype phenotype

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