Chapter 6: Genetics

1. Chapter 6:Genetics 18 Things You Should Know about Genetics

2. When told to, put the PTC paper on your tongue PTC, or phenylthiourea, is an organic compound having the unusual property of either tasting very bitter, or being virtually tasteless, depending on the genetic makeup of the taster. • The ability to taste PTC is a dominant genetic trait. T = Taster t = non-taster • If you can taste, you are either TT or Tt. • Those who can not taste are tt • About 70% of people can taste PTC, varying from a low of 58% for Aborginal people of Australia to 98% for Native Americans

3. Ever wonder why people resemble their parents &/or siblings? • How do farmers select the best plants or animals for breeding purposes? • How’d you like that PTC paper? • Why did some people in your class/family taste it and others didn’t?

4. How do we inherit our traits? Traits are distinguishing characteristics which we inherit from our parents and can pass on to our children. • PTC tasting ability ______________ • Tongue rolling ability ______________ • Hand preference _______________ • Eye color _______________ • Hair color _______________ • Dimples _______________ • Freckles _______________ What are you for these traits?

5. Dimples Widows peak Mid – digit hair Free earlobe Hitchhikers thumb Chin Dimple 2nd toe larger than 1st Straight pinkie finger

6. Genetics Studies the transmission of traits or characteristics from 1 generation to the next

7. Gregor Mendel(1822 – 1884)The Father of Genetics • Central European monk (Now the Czech Republic) discovered the basic underlying principles of heredity. • Mathematician who studied statistic Bill Nye

8. He used pea plants and controlled how they were bred over many generations • Saw that certain traits show up in offspring plants without any blending of parent characteristics. P Why all purple? Why not pink?

9. Mendel's work • Removed the male parts of the flower to prevent self- pollination 2. Used the pollen from a Purple flower producing plant and pollinated only flowers from other purple flower producers

10. 3. Observed generations for 2 years to be certain of Purebreds (a genetically uniform line – pedigrees) Purple X PurpleWhite X White Got all Purples Got all whites

11. 4. Crossed plants with contrasting traitsPurple X whitewhite X Purple Mendel expected to get something between purple and white but instead got all purples!! Did the white trait disappear forever?

13. Next, he took purple flowered plants from the First Generation (F1) offspring and crossed them. Would the white trait reappear? To Mendel’s surprise, the white trait reappeared in the Second Generation (F2) but only 25% of the flowers were white. 75% of the flowers were purple. Why?

14. Mendel didn’t just use the trait for flower color, he looked at other traits in pea plants and found a similar pattern. Every time he crossed on purebred with the contrasting purebred, only one trait ever showed. Then when he crossed the F1 offspring, the hidden trait reappeared.

16. Mendel’s conclusions • Traits (genes) are located on chromosomes and sexually reproducing organisms get two copies of a trait, one from each parent 2. Each parent only donates one gene per trait in their gametes. Gene from mom Gene from dad

17. Genes and chromosomes Eye color Hair color Skin color Nose size Nose shape Genes Eye shape hair texture Ear size widow’s peak Ear lobes Chromosome

18. Law of Segregation 3. During gamete formation (Meiosis), the two genes are separated. 50% of the gametes will contain one trait while the other 50% will contain the other trait In the example above, you can see that there are two parent chromosomes. In the same location on both chromosomes, one chromosome has a T gene while the other has a t gene for say being tail or being short. When the gametes are produced during Meiosis, the two genes will be separated, thus his Law of Segregation

19. More about how Mendel figured out more than he realized Mendel never said the term genes, but he did call them factors. These factors or genes, we now know are on the DNA and code for a particular protein. Each gene has a specific location or locus on a chromosome

20. Mendel said that there are different forms of a particular factor such as eye color. There are 3 different factors that determine our eye color • Blue • Green • Brown For hand preference, there are two factors for the hand preference trait • Left • Right

21. Allelesare the different forms of a trait/gene. There can be two such as hand preference or many such a hair color, blood type and eye color Allele for Allele for Allele for

22. Next Principle is his Law of Dominance: – One factor “masks” the appearance of another factor. It prevents it from showing P = Purple flower color – Dominant allele P = white flower color – recessive allele • Dominant– trait that must show if present • Recessive – trait that will only show if in the pure form

23. More genetic vocabulary to learn • Genotype: Shows the actual genetic makeup. (Use symbols for genes) • PP or Pure dominant or homozygous (same genes) dominant • Pp or Hybrid or heterozygous (mixed genes_ • pp or Pure recessive or homozygous recessive Homozygous vs Heterozygous: Pure vs Hybrid (mixed)

24. Phenotype: • Tells appearance (describes the trait) Purple flower (if Pp or Pp) white flower (if pp) • NO HYBRIDS HERE!! • Describe what they look like • For Eye color: • Blue • Green • Brown • For Hair color; Red, Blonde or Brown

25. Vocabulary Review F Inheritable distinguishing characteristics – traits When present, this allele will show BB, Bb, or bb – Gene makeup Brown eyes, left handed… - Physical appearance Homozygous – both genes for a trait are the same Study of how traits are passed on Alternate form of a gene Allele which only shows when it is alone Two genes for a trait separate during meiosis One factor masks the expression of the other k) Hybrid – having two different alleles for a trait G • Genetics ___ • Allele ___ • Purebred ___ • Law of Segregation _ • Law of dominance __ • Genotype ___ • Phenotype ___ • Dominant ___ • Recessive ___ • Genes ___ • Heterozygous ___ E I J C D B H A K

26. Predict the likelihood of two individuals who are hybrids for having allergies (Having allergies is a dominant trait so we will use an “A” for the gene). A = Allergies a = No allergies Parent Cross: ___ x ___ A a Phenotype ratio What is the likelihood of these two parents having children with allergies to not having allergies? 3:1 or 75%:25% Genotype ratio What is the likelihood of having a child who is a purebred for allergies? Hybrid for allergies? Purebred for not having allergies? 1:2:1 Aa Aa Aa A a AA 25% Aa aa 50% 25%

27. Punnett Square Is a grid system for predicting all possible genotypes resulting from a genetic cross The axes will have the alleles found in the two parents which result from segregation of the alleles during meiosis

28. Trait: Hand Preference in humans. Being right handed is dominant to left hand preference. R = Right Hand preference r = Left Hand preference Cross two individuals with one being pure or homozygous dominant and the other being a hybrid or heterozygous for being right handed Parent Cross: ___ x ___ R R RR Rr Possible Phenotypes ____ Right handed ____ Left handed Possible Genotypes ___ RR ___ Rr ___rr 50% 50% R r RR RR 50% Rr 50% Rr 0%

29. For the same trait, cross a person who is pure for being right handed with a lefty. Parent Cross: ___ x ___ R R RR rr Possible Phenotypes ____ Right handed ____ Left handed Possible Genotypes ___ RR ___ Rr ___rr 100% 0% r r Rr RR 0% Rr 100% Rr 0%

30. Trait: Earlobe position: In humans, having free earlobes is dominant to having an attached earlobe F – Free earlobes f – Attached earlobes Cross a two people who both are hybrids x for having free earlobes. Parent Cross: ___ x ___ F f Ff Ff Possible Phenotypes ___ Right handed ____ Left handed Possible Genotypes ___ RR ___ Rr ___rr 75% 25% F f FF Ff 25% Ff 50% ff 25%

31. Back to Mendel’s work In pea plants, being a tall plant is dominant over being short plants. ___ = Tall allele ___ = Short allele Cross a Hybird tall with a homozgyous short Parent cross: ___ x ___ Possible Phenotypes ___ Tall ___ Short Possible Genotypes ___ TT ___ Tt ___ tt

32. 1. In humans, having a chin dimple is dominant to not having dimples. • Show the cross of two parents who are both hybrid for having dimples. • Give the expected Phenotype ratio and genotype ratio for this cross. ____ = Dimple gene ____ = Non dimple gene Parent cross ______ x ______ Phenotype ratio : Genotype ratio : • For the same trait, cross a hybrid with an individual who does not have dimples Parent cross ______ x ______ Phenotype ratio : Genotype ratio :

33. Probability What is the probability of flipping a head? What is the probability of flipping a tail? 50:50 chance of getting heads or tail if you toss one coin Coin Toss Activity: Flip one coin 10x. Keep track of the # of Heads and Tails you get. ____ Heads ____ Tails Did you get what we expected? Why or why not? **Need large numbers to get accurate predictions**

34. What happens when you toss two coins? • If you toss 2 coins 100 times, you should get: • 25 Heads/Heads • 50 Heads/Tails • 25 Tails/Tails • Asthe # of trials increases, the ratios predicted by the laws of probability get closer • Actual outcomes get closer to calculated predictions Now flip two coins 100 times and keep track of the number of combo you get.

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37. How could you tell if you were a hybrid right handed person or pure for the trait? You would need to mate with someone who is a lefty. • If any of your children are lefty, then you know you had to be a hybrid • Test Cross- • A cross between an organism with an unknown dominant genotype with an individual with the recessive phenotype

38. Is your black guinea pig pure for its coat color? In Guinea pigs: B = Black coat b = white coat Cross the (BB) guinea pig with a pure recessive (bb) Cross the (Bb) guinea pig with a pure recessive (bb) If:   BB x bb If: Bb x bb If any of the offspring are white coated, then we knew the black guinea pig was Bb

39. What happens when a red carnation is crossed with a white carnation? We would expect to get Red carnations. • WRONG!!! • We would end up getting all Pink carnations. • Neither the red allele nor the white allele are dominant to each other. Instead, their expression blends and we get hybrid pink carnations

40. How did this happen? P1: Red carnations(rr) x White carnations (ww) • F1: Pink carnations (rw) F1: Pink carnation (rw) x Pink carnation (rw) F2: 25% Red (rr) 50% Pink (rw) 25% White (ww) 1:2:1 phenotype ratio!! 1:2:1 genotype ratio!!

41. IncompleteDominance Heterozygous individuals will show a phenotype of something in between the other two phenotypes A green betta (gg) crossed with a steel blue betta (bb) gives a royal blue betta (gb)

42. Incomplete Dominance Hair color Eye color Height Face shape Wavy hair Pitch of male’s voice(tt – tenor, tb baritones, bb – low bass) Tay-Sachs Disease - • Inability to produce the enzyme hexosaminidase A.  • Causes fluid pressure on brain then breakdown of brain. Starts a ~ 6 months w/ death by 2 – 3 years.   • Most common among the descendents of Eastern European Jews (Ashkenazi Jews). • Tt individuals produce 40-60% of enzyme

43. Crosses: 1. Cross a Round faced person with an square faced person 2. Cross a Black with a white horse 3. Cross a Wavy haired person with a curly haired person

44. Codominance Condition in which both alleles of a gene are expressed or active • Roan horses: Red is codominant with white.

45. Roans

46. Blood types in humans A is codominant with B resulting in AB blood A type blood has the A proteins on their RBCs B type has the B proteins on its RBC Both A and B are dominant to O A= B >o As you can see, AB blood is a mixture of both A and B proteins. Animation

47. Problems • Figure out what blood type two parents must be in order to have 4 children, each with a different blood type. 2. Who could be the father? A woman with O type blood has a child with B type blood Man #1 is A type blood Man #2 is AB blood 3. What could be your blood type?

48. Polygenic Inheritance • Some human traits are controlled by more than one set of genes that determine the expression of the traits. • Ie. Eye color , hair color, height, body weight, skin color, etc…

49. How is sex determined? Below is a Karyotype (a picture of all the chromsomes in a cell) of the two different individuals. Can you see a difference between the two.

50. Sex Chromosomes Both have 22 pairs of Autosomes(Body Chromosomes) • Sex Chromosomes are the big X & little Y chromosome • The female on the left has two X (XX) chromosomes while the male on the right has an X and a Y (XY)