What were we when we were last together????

1. What were we when we were last together???? • Looking at chromosomes • Karyotyping – 22 autosomal pairs, 1 sex pair • Recognizing abnormalities in karyotypes

4. OK Now where do we go? • To genetics!!!! • What is a gene? • A gene is a unit of heredity that is passed down from parent to child. Genes are located on chromosomes that are in all of our cells, including the sperm and egg that make a baby. • Genes are made of molecules or chemicals called DNA. The pattern of DNA will determine if the gene is working properly. The DNA has to be in a certain pattern or order, like the numbers in a phone number.

6. What are our learning outcomes? • I can describe the evidence Mendel obtained for dominance, segregation, and the independent assortment of genes on different chromosomes. • I can summarize Mendel’s laws of segregation and independent assortment • I can calculate & compare ratios and probabilities of genotypes and phenotypes for genetic crosses with the following inheritance patterns: • - Dominant / Recessive-Testcrosses- Multiple Dominance / Multiple Alleles • - Incomplete Dominance- Codominance- Sex-Linked

7. I can use / interpret pedigrees which graphically illustrate the inheritance patterns above. • I can explain the effect that gene linkage and crossing over have on the variability of organisms. • I understand that traits can be controlled by one pair of genes or they may be polygenic meaning they are controlled by many genes (ex. skin colour, height)

8. Today’s Learnng Goals • What is genetics? • Who is Gregor Mendel (and what did he discover about passing on of traits)? • What are the basic genetic terminology that I need to know? • Phenotype • Genotype • Dominant • Recessive

9. Introduction to Genetics Genetics – the study of heredity which is the transmission of characteristics from parents to offspring

10. Heredity • the transmission or passing of traits from parent to offspring. • “Heredity: the thing a child gets from the other side of the family” – Marcelene Cox

11. Genetics Small sections of DNA are responsible for a “trait”. These small sections are called “Genes”. • Gene - A segment of DNA that codes for a specific trait • Trait - A characteristic an organism can pass on to it’s offspring through DNA

12. Gregor Johann Mendel • born on July 22, 1822 • to peasant parents in a small agrarian town in Czechoslovakia • In 1843 he entered an Augustinian monastery in Czechoslovakia • He was later sent to the University of Vienna to study

13. The pea flower The male part of the flower (stamen) was easily removed to prevent self-pollination. Pea flowers are easy to cross-pollinate (he could control the pollination) They were easy to grow. Mendel studied Pea PlantsWhy? Pistil Stamen

14. Dominant Recessive Mendel Isolated 7 pairs of contrasting traits.

15. In each case, one characteristic was dominant and one was recessvie

16. And the last 2 traits he selected: Flower postion: Axial is dominant over terminal Tall is dominant over short.

17. Mendel tested all 34 varieties of peas available to him through seed dealers. The garden peas were planted and studied for eight years. • Mendel's experiments used some 28,000 pea plants. • So just imagine what life would have been like living in the same monastery as Brother Gregor??

19. Genetic Terminology you will need to know: • Phenotype - Characteristics that can be observed. Tall and short are phenotypes • Genotype – Actual coding of the gene. • Examples of genotypes are: TT, Tt, tt • TT is tall, Tt is hybrid tall, tt is short • Allele – An allele is one of two or more versions of a gene. Tall and short are the alleles for height in pea plants. • Dominant – Tall is stronger over short so the tall allele will be expressed • Recessive – Short is the weaker allele and won’t show unless both alleles for short are present

20. More terms: • Homozygous – pure • a genotype in which both alleles of a pair are the same • Heterozygous – hybrid • a genotype in which the alleles of a pair are different

22. Alleles • two or more alternate forms of a gene. • The alleles are located at the same position on one of the pairs of homologous chromosomes

23. F1 Generation • Filial generation one • A term Mendel used for the first generation in his experiements.

24. F2 Generation • The second generation. • A term Mendel used for the offspring of the F1 generation.

25. Genotype • the alleles an organism contains

26. Phenotype • the observable traits of an organism that arise because of the interaction between genes

27. Punnett square • a chart used by geneticists to show the possible combinations of alleles in offspring AND • Used to calculate the probability of inheriting a particular trait • Probability – The chance that a given event will occur

28. Punnett Square Parent Offspring Parent

29. Y-Yellow y-white Genotype: 1:2:1 (YY:Yy:yy) Phenotype: 3 Yellow 1 White

30. You Try It Now! • Give the genotype and phenotype for the following cross: TT x tt (T = Tall and t = Short)

31. TT x tt Step One: Set Up Punnett Square (put one parent on the top and the other along the side) T T t t

32. TT x tt Step Two: Complete the Punnett Square T T t t

33. TT x tt Step Three: Write the genotype and phenotype T T t t Genotype: 4 – Tt 4:0:0 Phenotype: 4:0 tall 100% Tall Remember: Each box is 25%

34. Monohybrid cross • a cross that involves one allele pair of contrasting traits

35. When you study genetics, what are you examining? • When studying genetics you are examining the inheritance of biological traits which are passes from parents to offspring.

36. Explain how Mendel proved that the crossing of traits does not always produce or create a blend of those traits. • Mendel proved over and over that a blend is not always the result of the crossing of traits. He found that when he crossed two traits that one trait always dominated the other trait no matter what method of cross-fertilization he used. • For example, when he crossed a plant that produced round seeds with a plant that produced wrinkled seeds he always saw offspring with round seeds. • This was also proved true with other characteristics of the pea plant. He reasoned that factors (now known as genes) control the traits of plants and that there were alternate forms of these factors.

37. What does it mean when one trait is said to be dominant over another trait? • A dominant trait is the trait that is expressed most often. A dominant trait will overrule or mask a recessive trait. • For example, in garden peas purple flowers are dominant over white flowers. If a pea plant receives one allele for purple and one allele for white, the flower will be purple.

38. How are upper case and lower case letters used in genetics? • Mendel created a system of symbols he used to record the results of his experiments. Upper case letters are used for the dominant traits while lower case letters are used for the recessive traits. • For example, yellow seeds are dominant over green seeds so the allele for yellow seeds is represented by (Y) and the allele for green seeds is represented by (y).

39. What were the unexpected results Mendel saw when he crossed two hybrid parents? • A hybrid parent contains one dominant allele and one recessive allele. For example, a round hybrid parent would be (Rr). R is the allele for round while r is the allele for wrinkled. • Mendel discovered that when he crossed two hybrid parents 75% of the offspring expressed the dominant trait (round) while 25% expressed the recessive trait (wrinkled).

40. hybrid cross • Purple 75 % • White 25 % Genotype Ratio D:H:R 1:2:1 Phenotype Ratio D:R 3:1 Purple