Genetics: Passing of Traits and Laws of Heredity

1. Genetics

2. Vocabulary GENE A or a (1 letter) ALLELE HOMOZYGOUS or Purebred AA or aa

3. Vocabulary Aa HETEROZYGOUS Or Hybrid AA or Aa (dimples) DOMINANT aa (no dimples) RECESSIVE

4. Vocabulary AA, Aa or aa GENOTYPE Dimples or no dimples PHENOTYPE PUNNETT SQUARE

5. What is genetics? heredity Gregor Mendel pea plants Law of Segregation Law of Independent Assortment • Genetics is the branch of biology that studies __________________ or the passing of traits from parent to offspring. • _________________ ___________________ (1822-1884) today he is considered to bethe father of modern genetics. Worked with _________________________. • Mendel’s findings led to two laws of heredity: • _____________________________________ - 2 alleles for a trait separate during meiosis (chromosomes separate) • _________________________________________________ - alleles for different traits separate independently from one another during meiosis. In other words inheritance of one trait does not influence inheritance of another. For example if you have blond hair you will not necessarily get blue eyes. These traits are inherited separately.

6. Nature vs. Nurture environment • Genes determine the physical trait, but ___________________can also play a role in how the trait is expressed.  • Example 1: Height and weight. Genes determine this trait, but environment can play a big role. If a person has genes for being very tall, but does not have the proper nutrition while growing up, then they may not be as tall as their genes would allow.  • Example 2: Fur color in some animals. Genes determine fur color, but some animals have fur that changes depending on the season. The arctic fox for instance has a white coat in the winter but a brown coat in the summer.

7. Now you practice identifying the genotypes and phenotypes using the following traits and symbols.

8. Complete the following table using the symbols and traits found above:

9. Write the correct symbols for the following genotypes. Circle those that are not possible. pure tall stems TT homozygous yellow seeds YYpure short stems tt pure green seeds yy homozygous terminal flowers aa hybrid round seeds Rr pure round seeds RR homozygous axial flowers AAhomozygous wrinkled seeds rr hybrid tall stems Tt Heterozygous wrinkled seeds ___ hybrid axial flowers Aa heterozygous short stems__heterozygous yellow seeds Yy heterozygous seed coat colorGg • Why are some of these not possible? You cannot have a heterozygous recessive organism. The only way to show a recessive trait is to have two small letters (yy). • Can I always identify the genotype if I know the phenotype? Explain your answer. No, If you know a plant is tall you don’t know if the genotype is TT or Tt.

10. How to Determine if a trait can be passed on to the offspring Probability Punnett square Monohybrid sperm Ee (__________ - Male genotype) (_________ Female genotype) Ee EE fertilization Ee eggs Ee ee • ________________ is the likelihood that an event will occur. • ________________________ are used to determine the probability that specific traits will be passed down from parent to offspring. • ____________________ cross- a cross that involves one pair of contrasting traits.

11. Practice Problem: In pea plants, tall is dominant over short. tt Tt T t 50% 50% t t Tt tt 0 2 2 2 2 Tt tt

12. Practice Problems RR rr R R 0 4 0 r r Rr Rr 4 0 Rr Rr Rr Rr R r 1 2 1 R r Rr RR 3 1 Rr rr

13. Practice Problems Gg gg G g 0 2 2 g g gg Gg 2 2 Gg gg

14. Practice Problems T t T T t t tt t t Tt Tt Tt Tt tt Tt Tt Parent genotypes must be Tt x tt A a A a Aa AA Parent genotypes must be Aa x Aa – both are heterozygous to get ¼ terminal flowers. aa Aa

15. Notes: Test Crosses Test Cross - Used to determine the unknown genotype of an organism. For example of a plant is tall you don’t know if it is TT or Tt. So you do a test cross to figure it out. You must cross the dominant organism with a _________________. Sample test cross: In dogs, there is a hereditary deafness caused by a recessive gene, “d.” A kennel owner has a male dog that she wants to use for breeding purposes if possible. The dog can hear, so the owner knows his genotype is either DD or Dd. If the dog’s genotype is Dd, the owner does not wish to spend the money to use him for breeding. Assume the male is DD Assume the male is Dd recessive

16. Test Cross - Used to determine the unknown genotype of an organism. For example of a plant is tall you don’t know if it is TT or Tt. So you do a test cross to figure it out. You must cross the dominant organism with a _________________. Sample test cross: In dogs, there is a hereditary deafness caused by a recessive gene, “d.” A kennel owner has a male dog that she wants to use for breeding purposes if possible. The dog can hear, so the owner knows his genotype is either DD or Dd. If the dog’s genotype is Dd, the owner does not wish to spend the money to use him for breeding. Assume the male is DD Assume the male is Dd recessive DD Dd Dd Dd Dd dd d d d d Dd Dd Dd dd Dd If any of the puppies are deaf, the male’s genotype MUST BE _______; but assuming a litter of at least about 4 to 5 puppies or more, if they can all hear, his genotype is MOST LIKELY _______. DD

17. Dihybrid Crosses • What letters would go in Box X? __________________ • What letters would go in Box Z? __________________ • What are the genotypes of the parent’s of this cross? ___________ _____________ • What percent of offspring are expected to have a white coat of fur? bbRR bbrr BbRr BbRr 4/16 = 25%

18. Complex Genetics

19. inComplete dominance • In carnations, incomplete dominance can be seen in flower color: • red (RR) pink (Rr) white (rr) • Cross two pink carnations. • Write the genotypes of the parents • Genotypic ratio: • Phenotypic ratio: • What percent of the offspring are pink? _______ Rr x Rr R r R r RR Rr Rr rr 1RR : 2Rr : 1rr 1 red : 2 pink : 1 white 50%

20. Cross between 2 sickle cell carriers • Sickle cell anemia is another example of incomplete dominance. Carriers of the allele have a much milder form of the disease. • Normal - (HAHA), Carrier - (HAHS), Sickle cell - (HSHS) • Complete a punnett square to determine the chances of two sickle cell carriers having a homozygous normal child? Genotype of parents: ________ x ___________ HAHS HAHS HA HS HA HS HAHA HAHS HSHS HAHS 25% chance of a homozygous normal child

21. codominance • The allele for red hair (HR) is codominant with the allele for white hair (HW) in cattle. Cattle that have the genotypes HRHW are called roan because their hair is a mixture of red and white hairs. • Red (HR HR) Roan(HRHW) White (HW HW)

22. Codominance Practice Problems • HRHR = Red HRHW = roan HWHW= White • Cross a red cow and a white bull: _______________ X __________________ • What is the genotypic ratio of the offspring? ____________ • What is the phenotypic ratio of the offspring? ___________ • What percent of the offspring are roan? HRHR HWHW HR HR HW HW HRHW HRHW HRHW HRHW 0 HRHR : 4 HRHW : 0 HWHW 0 red: 4 roan : 0 white 100%

23. Blood Types TWO Multiple Alleles - A gene that has more than ________ alleles (or forms of a gene). In other words, not just one dominant and one recessive allele (i.e. R and r). Use the same common letter with superscripts to show only one gene is playing a role. O No antigens A A antigen B B antigen AB Both A & B antigens

24. Blood Typing Practice Problem #1 1. A man with type O blood marries a woman with type AB blood, what are the possible blood types of their children? i i IA i IAi IB i IBi IA IB 50% 50% 0% 0%

25. Blood Typing Practice Problem #2 2. Is it possible for a man with type A blood and a woman with type B blood to have one child with type O blood and another child with type AB Blood? Why or why not? Show your work!!! IA i IB i Yes, if both parents are heterozygous. IA IB IBi IA i ii

26. Notes: Polygenic Traits many genes • Polygenic Traits are controlled by ________________ . See lots of variety • Ex: ________________________________________________________ Eye, skin, hair color, height, weight,

27. If two parents have a medium skin tone (AaBbCc), their children could have: _____________________ __________________________________________ • By looking at the graph, we can see that it is most likely that their kids will have ___________ skin tone. A wide variety of skin colors – light to dark medium

28. In humans, other examples of polygenic traits:

29. Sex-Linked Traits linked X • Genes which are located on the sex chromosomes are said to be sex-______________ or ______-linked. • Sex-linked traits occur more frequently in ________because they have only ______ X chromosome. • Sex-linked traits include: color blindness, hemophilia and muscular dystrophy. • XNXN = Normal Female XNY = Normal Male • XNXn = Normal Female Carrier XnY = Male with disorder • XnXn = Female with disorder males 1

30. __________________ (Xn) is a very common sex-linked trait and is recessive to normal vision (XN). More males have this disorder than females. COLOR BLINDNESS XNY XNXn ¼ = 25% XN Y XN Xn XNXN XNY XNXnXnY ½ = 50%

31. Hemophilia practice problem In humans, hemophilia is a sex-linked trait located on the X chromosome. Normal blood is dominant (XH) to hemophilia (Xh). A heterozygous female is referred to as a carrier. Cross a carrier female with a male with hemophilia. ___________________ X __________________ What percentage of this couple’s sons will have hemophilia? __ What percentage of this couple’s daughters will have hemophilia? ______ What percentage of this couple’s kids will have hemophilia? ______ XhY XHXh Xh Y XHXh XHY XhXhXhY XH Xh 50% 50% 50%

32. Well-known Autosomal Genetic Disorders:

33. Well-known Sex-Linked Genetic Disorders:

34. Notes: Pedigrees & Genetic Disorders Biologists use charts called pedigrees to study the pattern of phenotypic inheritance in individuals and their family. Some of the most common symbols used:

35. Pedigrees • Pedigrees – family trees that follow a trait/disorder • Symbols – square = ___________, circle = ____________ • Shaded individual – person has the disorder/trait. • Roman numerals - __________________ MALE FEMALE GENERATIONS

36. Determining Inheritance Patterns Using Pedigrees • Tips to determining pattern of inheritance in a pedigree: • Autosomal - about ___________ males and females shaded • Sex-linked – more ____________ are shaded in. • Dominant – for every child with the disease at least one parent is shaded • Recessive – if one set of parents are _____________________________________ parents but kid has the disease. HALF MALES NORMAL (NOT SHADED)

37. Pedigree 1 Circle one in each pair: Autosomal or Sex-linked Dominant or Recessive B/c same # of males and females have it. B/c there are unaffected parents but a child with the disease

38. Pedigree 2 Circle one in each pair: Autosomal or Sex-linked Dominant or Recessive B/c in more females. B/c for every child with the disease at least one parent has the disease.

39. Pedigree 3 Circle one in each pair: Autosomal or Sex-linked Dominant or Recessive B/c in more males. B/c there are unaffected parents but a child with the disease