Mendelian Genetics for Science 9.ppt.pptx

science Quarter 1 week 3

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

2. 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

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

4. 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

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

6. 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 )

7. 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.

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

9. 1 trait always disappeared in the 2 nd , or F 1 generation All the offspring had the characteristics of only one of their parents.

10. 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

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

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

13. 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.

14. 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

15. 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 = _____

16. 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

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

18. 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

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

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

21. TRY THIS ONE

22. GIVE THE GENOTYPIC RATIO & PHENOTYPIC RATIO

23. 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

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

25. 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

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

27. 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.

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

29. 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)

30. 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

31. 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