Mendelian Genetics presentation.ppt.pptx

Science 9 Lesson

1. GENETICS : THE STUDY OF HEREDITY ( What we inherit from our parents)

2. Mapping of Earth’s Features Mapping of Cells, Chromosomes, and Genes Cell Chromosome Chromosome fragment Gene Nucleotide base pairs Earth Country State City People GENETICS INVOLVES THE STUDY OF GENES

3. II. Gregor Mendel (1822-1884) FATHER of GENETICS Studied pea plants b/c: They grow rapidly Have 7 easy to observe, contrasting traits Can self-pollinate → Fertilize itself Cross-pollinate → Fertilize different plant

4. The 7 contrasting traits of pea plants Seed texture, seed color, seed coat color, pod texture, pod color, flower location, height

5. III. FLOWER STRUCTURE A. STAMEN – male part with pollen → sperm B. PISTIL – female part with ovary & ovules → (egg inside) Fertilization: Male & female reproductive cells join

6. What is the difference between self-pollination and cross-pollination?

7. IV. MENDEL’S EXPERIMENTS A. Self-pollinated plants (true-breeding)- sperm cells fertilize egg cells from within the same flower would produce offspring with identical traits to themselves (P) Purple X purple → All Purple (F 1 ) (P) White X white → All White (F 1 )

8. IV. MENDEL’S EXPERIMENTS B. Cross – pollinated plants- sperm from one plant used to pollinate female on different plant Offspring of these crosses are called hybrids (P) Purple X white * → All Purple (F 1 ) (P) Tall X short* → All Tall (F 1 ) * Trait seemed to disappear in the 2 nd , or F 1 generation.

9. * Trait seemed to disappear in the 2 nd , or F 1 generation.

10. 1 trait always disappeared in the 2 nd , or F 1 generation All the offspring had the characteristics of only one of their parents.

11. IV. MENDEL’S EXPERIMENTS cont. C. Self-pollinated F 1 plants → F 2 generation Purple (F 1 ) X purple (F 1 ) → ¾ Purple , ¼ white (F 2 ) Tall X tall → ¾ Tall, ¼ Short Missing traits reappeared

12. The trait reappeared in the 3 rd , or F 2 generation The white trait “skipped” a generation!

13. V. MENDEL’S CONCLUSIONS 1. Traits are controlled by genes , that occur in pairs.

14. DON’T COPY REMEMBER a GENE ? It’s a segment of DNA (bases) that codes for a trait DNA + Protein → Chromosome We have 23 pairs of homologous chromosomes Therefore, genes also occur in pairs.

15. 2. LAW OF DOMINANCE Some traits hide the effect of others. Allele – different form of a gene 2 alleles → Trait Alleles may be: Dominant – Hides the other trait Recessive – Trait seems to disappear Ex. Tall x short = All tall

16. This is not in the notes. DOMINANT ALLELES → capital letter of the dominant trait RECESSIVE ALLELE → lower case letter of the dominant trait Ex. Tall allele = T Short allele = t Round allele = _____ Wrinkled allele = _____

17. OTHER GENETIC TERMS HOMOZYGOUS = pure = organism w/ same alleles for a trait (TT,tt) HETEROZYGOUS = hybrid = different alleles for a trait (Tt) GENOTYPE – Alleles (genes) of a trait → (letters) Homozygous dominant - TT Heterozygous – Tt Homozygous recessive - tt PHENOTYPE – Physical traits →(description) Tall plant Tall plant Short plant

18. 3. LAW OF SEGREGATION Gene pairs separate → each sex cell only gets 1 allele

19. HOW CAN WE USE MATH TO FIGURE ALL THIS OUT? PROBABILITY – likelihood that a particular event will occur 1 out of 2 or 50 % that a flipped coin will land on heads Not dependent on previous result; You could flip heads 10 straight times PUNNETT SQUARE – chart used to predict probable outcomes in a genetic cross

20. HOW TO SET UP A PUNNETT SQUARE TALL X SHORT TT X tt HETEROZYGOUS TALL X HETEROZYGOUS TALL Tt x Tt

21. MONOHYBRID CROSS involves 1 pair of alleles → 1 trait FLOWER COLOR

22. TRY THIS ONE

23. GIVE THE GENOTYPIC RATIO & PHENOTYPIC RATIO

24. Tongue rolling (T) is dominant to non-tongue rolling (t) What is the probability of tongue rollers for the following crosses? 1) Homozygous dominant x Homozygous recessive 2) Heterozygous x homozygous recessive 3) Neither parent can roll their tongue

25. AUTOSOMAL Dominant/Recessive Diseases Dominant – Huntington’s disease Only 1 faulty allele needed Recessive – Cystic Fibrosis, PKU, Albinism, & Tay Sachs Require 2 faulty alleles

26. Huntington’s Disease A degenerative disease of the nervous system Caused by a lethal dominant allele No obvious effect until individual is about 35-45 years old Chromosome 4 is affected

27. Cystic Fibrosis Caused by 2 recessive alleles Mucus builds up on lungs Common among white people

28. PKU ( Phenylketonuria ) Caused by 2 recessive alleles Individuals with PKU cannot process a part of protein called phenylalanine, which is present in most foods. Will lead to cognitive disabilities if not treated properly.

29. Albinism Caused by 2 recessive alleles No pigment in hair, eyes, or skin Much be careful in sunlight More prone to skin cancer

30. Tay Sachs Caused by 2 recessive alleles Affects mostly Ashkenazic Jews Brain cells unable to metabolize gangliosides, a type of lipid. Lipids accumulate on brain and eventually cease to function…results in death (Usually by age of 4)

31. 4 . LAW OF INDEPENDENT ASSORTMENT http://www.sumanasinc.com/webcontent/anisamples/majorsbiology/independentassortment.html DIHYBRID CROSS → 2 pairs of alleles Ex. RrYy X RrYy (2 traits) Genes for different traits can separate independently during the formation of gametes

32. Dihybrid Cross Example R = round r = wrinkled Y = yellow y = green PHENOTYPIC RATIO = 9 ROUND YELLOW: 3 ROUND GREEN: 3 WRINKLED YELLOW: 1 WRINKLED GREEN