Genetics

1. Genetics What is genetics? Study of how traits are passed from parent to offspring

2. Vocab • Trait: • Heredity: • Allele: • Dominant: • Recessive: • Pure breed: • Hybrid: Physical characteristic (hair color, eye color) Passing of trait from parent to offspring Different form of a trait (blue or brown eyes) The trait expressed when two alleles are present The trait hidden when two alleles are present Two of the same genes. 2 recessive or 2 Dominant One of each gene. 1 dominant and 1 recessive

3. heredity Transmission of characteristics from parent to offspring is called ___________________. The science that studies how those characteristics are passed on from one generation to the next is called ____________ Genetics

4. Different genes for a the same trait are called ___________. Eye color is an example ALLELES http://sps.k12.ar.us/massengale/genetics%20tutorial.htm

5. Method of Heredity • Heredity is possible due to Chromosomes. • Each chromosome contains hundreds of genes that carry the genetic code for traits • To make sure the species survives there are two ways to reproduce using Chromosomes. • Mitosis (making the exact copy of the cell) • Meiosis (cutting the chromosome number in half so when they join it will make a complete full set)

6. Chromosomes • 2 main jobs • Direct actions of cell parts • Allow cells to reproduce • Found inside the nucleus of the cells • Two types of cells • Body cells (liver, skin, stomach, muscle, etc.) • Have full set of chromosomes in pairs • Sex cells (egg and sperm) • Have a half of set of chromosomes 1 copy of each chromosome

7. Group of chromosomes

8. Chromosomes Continued • Because sperm and egg have ½ a set of chromosomes; when they meet they make a complete set.

9. Each chromosome is made of tightly coiled DNA strands.

10. Genes • Genes are the small sections of a chromosome that determine a specific trait • There are thousands of traits for every living thing. • Every gene has a pair on the other chromosome of the same pair.

12. Passing of trait on genes • Each sperm and egg have one copy of a gene from their original owner.

13. Gregor Mendel • father of genetics • studied the inheritance traits in pea plants. • Mendel showed that the inheritance of these traits follow two particular laws.

14. Mendel’s Experiments • Did his work with peas for four reasons: • Peas are simple plants with little number of traits • Peas are cheap to grow compared to humans • Peas have a quick life cycle • Peas were available for use

15. Mendel’s results Trait Dominant trait Recessive trait Total Color of pod Green-428 Yellow-152 580 Shape of pea Round-5474 Wrinkled-1850 7324 Color of pea Yellow-6022 Green-2001 8023 Flower color Red-705 White-224 929

16. Law of Segregation • The Law of Segregation states that when any individual produces gametes (egg or sperm), the copies of a gene separate, so that each gamete receives only one copy. • A gamete will receive one allele or the other. • In meiosis the chromosomes get separated and the alleles with the characters are segregated into two different gametes.

17. Law of Independent Assortment • Alleles of different genes assort independently of one another during egg and sperm formation. • So there is no relation, for example, between a cat's color and tail length. • This increases genetic diversity by producing different genetic combinations. • In independent assortment the chromosomes that end up in a newly-formed offspring are randomly sorted from all possible combinations of mother and father chromosomes. • Because gametes end up with a random mix instead of a pre-defined "set" from either parent, gametes are therefore considered assorted independently. • The offspring can end up with any combination of traits. • For human gametes, with 23 pairs of chromosomes, the number of possibilities is 2^23 or 8,388,608 possible combinations.

18. Review • Alleles are different expressions of a single trait (different eye colors) • Gregor Mendel is the first person who studied genetics using peas • He developed two laws • Law of segregation you only get 1 copy of a trait from each parent • Law of independent assortment each trait will separate randomly

19. Using these two laws and a little more information you can determine the possible outcome of offspring. • The possibilities are calculated in a tool called a punnett square.

20. DOMINANT Gene __________________ = An allele that is expressed in the presence of a weaker allele. __________________ = An allele that is not expressed in the presence of a dominant Allele RECESSIVE Gene

21. Homozygous= the same genes (AA or BB or aa or bb) it also means pure bred. • When an egg or sperm are made from a Homozygous trait it only has one type of gene to give both are the same. • Heterozygous= different genes (Aa or Bb) it also means hybrid. • When an egg or sperm are made from a heterozygous trait it can give either the dominant or recessive gene.

22. HOMOZYGOUS/HETEROZYGOUS When alleles in the pair are the same the organism is called _________________ or ______ EX: ____ or ___ When both alleles in the pair are Different, the organism is __________________ or ___________ Ex: ____ HOMOZYGOUS PURE TT tt HETEROZYGOUS HYBRID Tt

23. DOMINANT/RECESSIVE Dominant _____________ allele is represented by a capital letter.(usually the first letter of the trait) ____________ allele is represented by the (SAME) lower-case letter. EX: Tall = ______ Short =______ Recessive T t NOT S for short

25. Dominant Trait Recessive trait

26. Expected and Observed results • Knowing the outcome of offspring an individual may have could be helpful • A punnett square is used to show all the possible combinations of offspring parents may have. • Knowing the genetic make up of the alleles is all you need to make it happen.

27. Reading a punnett Square • Two things can be read from a punnett square. • The actual genes that make up the trait • Ex: AA, or AaBb • The physical appearance of the trait • Ex: blue eyes, brown hair Genotype: Phenotype:

28. Punnett Squares • You can mathematically find the percent of off spring by using this method • You can figure out the chances of having a boy or girl • Using a punnett square with plants you can figure out what color flowers will bloom, or whether the plants will be short or tall.

29. Making Punnett Squares • The first step is to separate the parents genes (just like the egg and sperm) • If one of the parents is T T for Tall plant and the other parent has t t for a short plant • Place the genes on the outside of the box for the parents. • Then place the letters on the inside of the box. • The results inside the box are the possible offspring of the parents

30. A punnett square of multiple parents is on the sheet to the left. • The first Punnett square has been filled in for you. • Fill in the other 3 punnett squares into your notebook • For the first and last example: • 100% chance for a Homozygous Offspring. • For the second example: • 25% recessive • 75 % dominant T T T T T T T t T T T T T t t t T T T T t t t t T t T t t t t t

31. The punnett squares in the examples you just filled in where for one trait these are called Monohybrid Crosses • One = Mono • The next examples are for two traits or Dihybrid Crosses • Two = Di

32. Dihybrid crosses • We will look at two traits say Heterozygous Eye Color(A) and Hair Color (B) • Since there are more than one combination of gene you need to find out the four different combinations that can occur with the cross. • To find the correct combinations we use F.O.I.L.

33. F.O.I.L • First, Outer, Inner, Last letters of each letter. • The first parent has the following genotype: • A a B b • first combination is AB the First letter of each gene. • The second will be Ab the Outer letters of the parent. • The third combination will be aB the Inner letters. • The last combination will be ab the Last letters * * * * * * * *

34. F.O.I.L. Combinations • So the parents sperm and egg can make 4 different possible combinations of genes for two traits. • AB, Ab, aB, and ab • These combination get put onto the outside of the di-hybrid cross punnett square.

35. From here it is the same as the one trait cross. Place the two A’s into the box Then the two B’s Always place the A’s before the B’s AA AA Aa Aa AA AA Aa Aa Aa Aa aa aa Aa Aa aa aa BB Bb BB Bb Bb bb Bb bb BB Bb BB Bb Bb bb Bb bb

36. Practice problem 1 • Parent 1 is Heterozygous for trait (A) • Parent 2 is Heterozygous for trait (A) • What are the parents Phenotypes and genotypes? Phenotype ________ and _______ Genotype _____ and _____ • Fill in the Punnett square below Dominant Dominant A a A a A a A A A A a A a a a a

37. Practice problem 2 • Parent 1 is Homozygous for trait (a) • Parent 2 is Heterozygous for trait (A) • What are the parents Phenotypes and genotypes? Phenotype ________ and _______ Genotype _____ and _____ • Fill in the Punnett square below Recessive Dominant a a A a a a A A a A a a a a a a

38. Practice problem 3 • Parent 1 is Homozygous for trait (A) • Parent 2 is Homozygous for trait (a) • What are the parents Phenotypes and genotypes? Phenotype ________ and _______ Genotype _____ and _____ • Fill in the Punnett square below Dominant Recessive A A a a A A a A a A a A a A a a

39. Review • Chromosomes are threadlike parts of a cell that control traits • Body cells have 2 times as many chromosomes as sex cells • Dominant traits keep recessive traits from showing • An individual that is Heterozygous (Aa) can make two types of sex cells (A) or (a) an individual that is homozygous (AA) can make only one (A)

40. Review • The punnett square helps to predict the combinations of genes in all offspring • Expected results are predicted. While Observed results are what we see. • Mendel reported how traits were inherited in pea plants • Mendel explained the basic principles of genetics and inheritance.