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Wednesday 4/9/14

Wednesday 4/9/14. AIM: Why is Gregor Mendel the father of genetics? DO NOW: How many chromosomes do you have and where do they come from? What would happen if you had an extra chromosome and why? HOMEWORK: Text read pages 267-70. Reading check pages 267 and 268, q 1 and 2 pages 270.

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Wednesday 4/9/14

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  1. Wednesday 4/9/14 • AIM: Why is Gregor Mendel the father of genetics? • DO NOW: How many chromosomes do you have and where do they come from? • What would happen if you had an extra chromosome and why? • HOMEWORK: Text read pages 267-70. Reading check pages 267 and 268, q 1 and 2 pages 270

  2. What is genetics?

  3. Genetics • The study of inherited traits • Chromosomes are the units of inheritance • Chromosomes carry genes • Genes are the specific direction or code for your physical trait • Genes: code for proteins • Proteins cause chemical reactions • Chemical reactions lead to physical traits

  4. Where do your inherited traits come from? Your dads sperm and your moms egg

  5. Homologous chromosome • Similar in size shape and genetic content • Homologous chromosomes pair up at fertilization • n+n=2n

  6. Remember • Zygote gets one complete set of chromosomes from the egg • And one complete set of chromosomes from the sperm • Bringing together homologous chromosomes

  7. Haploid + haploid = diploid

  8. Human Chromosomes • Total we have 23 pairs • 2(23)=46 • 22 of those pairs are called autosomes • The 23 pair is the sex chromosomes

  9. XX female XY male Sex Chromosomes

  10. Y chromsome • Carries the SRY gene • SRY: sex determining region • If the SRY gene is turned on, then gonads develop into testis and fetus becomes male • If not then gonads become ovaries

  11. AIM: How does the structure of DNA relate to its function? • DO NOW: How many chromosomes do each of your cells have? • How many genes does each of your cells have? • How many nuclei does each of your cells have? • Homework: text read pages 293,296,297 and 299. Answer Reading questions 293,296,297

  12. Somatic or body cells have 46 chromosomes • Examples of somatic cells • Cardiac cells lung cells brain cells • Skin cells muscle cells gall bladder cells • Tracheal cells esophagal cells liver cells • Gametes or sex cells have 23 chromosomes • Male-sperm • Female-ova or egg • There are thousands of genes in each cell • There is one nucleus in each cell that houses the chromosomes which carry genes on them • Each cell expresses specific genes to make them specialized

  13. So how do we know anything about genetics and homologous chromosomes?

  14. Gregor Mendel • Father of genetics • Looked at the pea plant • Specifically 7 visible traits • Followed their inheritance over many generations • HE KNEW NOTHING ABOUT GENES!!!!!

  15. Mendel was lucky • Each of the 7 traits Mendel observed was only present in 1 of 2 possible forms • Ex: Plant color was either purple or white • Pea shape was either round or wrinkled • Mendel used this when performing his experiments.

  16. Thursday 4/10/14 • AIM: How did Gregor Mendel develop his basic laws of heredity? • DO NOW: What is genetics? How do we know anything about genetics? • HOMEWORK: Textbook read pages 276-277. do the reading check on page 277

  17. Genetics • The study of inherited traits • Chromosomes are the units of inheritance • Chromosomes carry genes • Genes are the specific direction or code for your physical trait • Genes: code for proteins • Proteins cause chemical reactions • Chemical reactions lead to physical traits

  18. AIM: How did Mendel develop his basic laws of heredity? • DO NOW: What is the difference between self fertilization and cross fertilization? • HOMEWORK: textbook read pages 267-270. 1-Explain the difference between true breeding and hybrid. • 2- Define P generation, first filial generation and second filial generation.’ • 3- Explain why Mendel studied pea plants

  19. Gregor Mendel’s experiments: Fertilization • Self-fertilization: egg in the flower is fertilized by the sperm of the same flower • Cross-fertilization: sperm from a foreign plant fertilizes an egg

  20. Gregor Mendel • Used both the processes of self fertilization and cross fertilization to experiment on pea plants • This helped him develop his basic laws of heredity

  21. Definitions • True breed or pure breed: plants with a trait such as purple flowers that is always inherited by all offspring • Can only produce one type of gamete • HYBRID: • The offspring of a cross fertilization • 2 parents similar to sexual reproduction • Can produce different types of gametes

  22. Definitions continued • Monohybrid cross: tracks one trait at a time • Ex: flower color • Dihybrid cross:

  23. Self fertilized true breed parents for many generations All offspring gave the same results Cross fertilized true breeds to get an F1 generation Self fertilized the F1 and observed the F2 generation Mendel’s work

  24. Mendel’s Experiment Parent Generation (P1): Purple true breed X White true breed First Filial (F1) 100% Purple flowers Self fertilize Second Filial (F2) 75% Purple: 25% White 3:1 ratio

  25. Why were all the F1 generation flowers purple? Purple Trait is obviously dominant over the white trait The white trait was hidden but not gone

  26. Why were some of the F2 generation part purple and part white? The F1 parent was carrying the white trait but it was masked or hidden. White is recessive to purple

  27. Just from looking at these results, what can Mendel conclude?

  28. Mendel’s Conclusions from a monohybrid cross 1- Copies of inherited traits must be separated when gametes are formed 2- When present in 2 forms one form is dominant over the other 3- the recessive trait will show itself when present in two copies

  29. Tuesday 4/22/14

  30. From these experiments, Mendel concluded: • Traits are determined by physical unit that come in pairs (he did not know these would later be called alleles) • Gametes separate and carry only 1 allele(copy) for each gene • The particular allele that ends up in a gamete is caused by chance • One allele is dominant and one recessive • True-breeding organisms have the 2 copies of the same allele (homozygous)

  31. AIM: How can we predict the possible genotypes and phenotypes of offspring? • DO NOW: 2- if I cross fertilized a true breed green seed pea plant by a true breed yellow seed pea plant, what phenotypes do I expect to get? • HOMEWORK: Textbook read pages 272-273. answer questions 1,2,3 on page 275

  32. Create a list • 7 traits observed by Gregor Mendel 1- Flower color 2- Plant size 3- Flower position 4-Seed color 5- shape of pod 6- Pod color 7- Seed shape Each of these traits has a dominant and a recessive phenotype

  33. Seed color • Dominant phenotype: green • Recessive phenotype: yellow • Genotype Phenotype • GG • Gg • gg

  34. Mendel had no idea about the following • We know we get 2 copies of genes • 1 from sperm • 1 from egg • Allele: is a copy of a gene • Homologous chromosomes carry alleles

  35. Monohybrid Cross • Tracked one (mono) trait at a time

  36. Mendel’s work • Cross fertilized two true breed parents that displayed opposite traits.(P or Parental generation) • All First filial or F1 offspring were purple

  37. What happened to the white color?

  38. Self-fertilized F1 • Second filial or F2 generation yielded about ¼ white and ¾ purple • So the white flower color was not lost just masked

  39. Self-fertilized F2 • Saw that all white flowered F2 yielded all white F3 but the purple still yielded 3:1 ratio of purple to white • Therefore the white allele was not lost but rather hidden or masked by the purple allele

  40. From these experiments, Mendel concluded: • Traits are determined by physical unit that come in pairs (he did not know these would later be called alleles) • Gametes separate and carry only 1 allele for each gene • The particular allele that ends up in a gamete is caused by chance • One allele is dominant and one recessive • True-breeding organisms have the 2 copies of the same allele

  41. Thursday 4/24/14 • AIM: why did Mendel decide to perform a dihybrid cross? • DO NOW: Let A represent the allele coding for terminal flowers and a axial flowers. Complete the following table: • HOMEWORK: text read pages 274-275. answer questions 3 and 4 page 275

  42. Mendel’s Law of dominance • When two different alleles are present, the dominant alleles gives the resulting phenotype and masks the trait of the recessive allele • However the recessive allele is still present • Homozygous Dominant and heterozygous organisms display the same phenotype • Recessive alleles are only displayed when present in 2 copies • Homozygous recessive

  43. Mendel’s Law of segregation • Pairs of alleles on homologous chromosomes separate from each other during gamete formation • Gametes receive only one allele from a homologous pair. • Fertilization produces offspring with a copy of one allele from mom and one from dad

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