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Understanding Heredity: Genes and Traits

This text discusses the concept of heredity, including the role of genes in passing down physical traits from one generation to another. It also introduces Gregor Mendel and his experiments with pea plants, which helped establish the foundations of modern genetics.

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Understanding Heredity: Genes and Traits

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  1. Monday3/19/12 • AIM: What is heredity? • Homework: Handout Section 11.2 Read pages 288-291. Reading check on page 288. • 2- Use figure 11.7 and in your own words, summarize steps A-C • 3- Answer question 1 page 295 of the handout

  2. Transcribe and translateDNA: TACGTTTGCGACACCACT

  3. What do genes do? Units of heredity that are passed down from generation to generation Hold the code to build physical traits

  4. Where are genes located? On DNA which builds chromosomes which are in the nucleus

  5. How many codons are there in total? 64 How many amino acids are there in total? 20

  6. Why is it a good thing to have multiple codons specify the same amino acid? Because if the gene is mutated there is still a chance the protein therefore physical trait will be unaffected!

  7. If a person with brown eyes has a baby with a person with green eyes? What color eyes do you think their baby will have and why do you think that?

  8. What is Heredity? • The transfer of characteristics from one generation to the next

  9. Human heredity • Chromosomes are built from DNA wrapped around proteins • Genes are parts of DNA • Specific nucleotide sequences • Therefore genes are found on chromosomes • One chromosome might have 1000 genes on it • Your cells have more genes than chromosomes

  10. Thursday 3/22/12 • AIM: Why is Gregor Mendel the “father of Genetics”? • DO NOW: If a person with brown eyes has a baby with a person with green eyes? What color eyes do you think their baby wil have and why do you think that? • HOMEWORK: Text page 265 Inquiry Lab. Page 266 using words question 2

  11. What are Traits? • A characteristic that is determined by your genes • A pair of genes will determine the trait • Examples: • Tongue rolling • Earlobes • Widow’s Peak • Hair Whorl • Dimples

  12. What is genetics? • The science of how traits are inherited

  13. Who is Gregor Mendel? • “Father of Genetics” • Studied pea plants • He crossed pea plants with different characteristics and studied their offspring • He was able to determine how traits get passed on from generation to generation

  14. Gregor Mendel Father of genetics Looked at the pea plant Specifically 7 visible traits Followed their inheritance over many generations

  15. The pea plant displayed one of 2 possible characteristics for each trait

  16. How did Mendel experiment with the pea plant?

  17. Mendel’s pea plant Key feature: reproduction can be controlled and manipulated Self- fertilization and cross-fertilization were easily obtained

  18. 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

  19. Friday 3/23/12 • AIM: How did Gregor Mendel develop his 3 laws of heredity? • DO NOW: Explain the difference between self and cross fertilization. • Homework: Complete any assignment you missed this week • Last nights hw. 1- Page 265 Inquiry Lab • 2- page 266 Understanding words # 2

  20. Mendel’s work • At first Mendel self fertilized plants in order to create true breeds • True breed or pure breed has only one trait to pass on • Ex: Seed color • Yellow seed yellow seed • True breeds are homozygotes

  21. Monday 3/26/12 • AIM: How did Gregor Mendel develop his first two laws of heredity? • DO NOW: Explain why Mendel choose to work with pea plants • HOMEWORK: textbook read pages 267-269. questions 1 and 3 on page 270

  22. Mendel’s work • Mendel did not know anything about dominant or recessive behavior • He did know how to make pea plants reproduce

  23. Definitions • Genes: instructions to build physical characteristics • Chromosome: large unit of DNA and protein that carry genes on them • Human cells: • Somatic cells: body cells: diploid(2n) • Gametes: sex cells: haploid(n)

  24. Somatic Cells • ALL somatic (body cells) have the same 46 chromosomes • Each cell is different due to the genes that get turned on or off

  25. How is a cell’s DNA like a library?

  26. Wednesday 3/28/12 • AIM: How did Gregor Mendel develop his law of dominance? • DO NOW: Explain the difference between diploid and haploid and give an example of each • HOMEWORK: Textbook page 270 questions 2 and 4 • I AM CHECKING 1-4 TOMORROW

  27. Diploid (2n) vs haploid (n)

  28. Mendel’s work • He self fertilized plants for several generations to ensure that all were pure breeds • True breed or pure breed: plants with a trait such as purple flowers that is always inherited by all offspring • Only have 1 type of allele for a specific gene (homozygous)

  29. Mendel’s work Cross fertilized plants that were true breeding for 7 specific traits Hybrid: The offspring of a cross fertilization 2 parents similar to sexual reproduction Has genetic information from both parents

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

  31. Genetics vocabulary • Gene: part of DNa which holds the instructions to build a protein • Allele: copy of a gene • Specific directions • Genotype: genetic makeup of an organism • Phenotype; resulting physical characteristics

  32. What happened to the white color?

  33. Self-fertilized F1 Second filial or F2 generation yielded about ¼ white and ¾ purple

  34. Mendel’s conclusion • When the white flowered plants showed up in the F2 generation, Mendel concluded that the white characteristics must have been hidden in the F1

  35. 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

  36. From these experiments, Mendel concluded: Traits are determined by physical unit that come in pairs Pairs are separated during gamete formation Gametes only 1 allele each The particular allele that ends up in a gamete is caused by chance One allele is dominant and one recessive From Mendel’s Monohybrid cross he developed the law of dominance and the law of segregation

  37. 3/29/12 Thursday • AIM: how did Mendel develop his law of Independent assortment? • DO NOW: Explain why ALL of the F1 generation had purple flowered plants. • Homework: Textbook

  38. 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

  39. Mendel’s Law of dominance When two different alleles are present, the dominant alleles gives the resulting trait and masks the trait of the recessive allele However the recessive allele is still present

  40. Friday 3/30/12 • AIM: how did Gregor Mendel develop his law of independent assortment? • DO NOW: Explain the difference between genotype and phenotype

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