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Introduction to Genetics: Gregor Mendel and Inheritance Patterns

Learn about Gregor Mendel, the father of genetics, and his experiments with pea plants in the 1800s. Discover the fundamental principles of inheritance, including dominant and recessive traits, alleles, and Mendel's laws of segregation and independent assortment.

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Introduction to Genetics: Gregor Mendel and Inheritance Patterns

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  1. GENETICS 1

  2. How did the study of Genetics begin? Clip

  3. Gregor Mendel Geneticsis the branch of biology that deals with heredity. A great deal of what we knowabout genetics began with the work of a monk named Gregor Mendel, who experimented with sweet pea plants in the 1800s. 2

  4. 3 Mendel’s Work • Mendel studied the patterns of inheritance in pea plants. • He chose seven traits to follow.

  5. 4

  6. Mendel needed to make sure he had plants that always gave the same offspring-calledtrue breeding. • He “self-pollinated” plants until he got seeds that always gave the same offspring. 5

  7. Some plants can self-pollinate or cross-pollinate with another plant. 6

  8. Pollen X • He took a purple flower plant and crossed it with a white flower plant? • He called these the parent generation (P generation) • What do you think the offspring looked like? ALL PURPLE 7

  9. POLLEN F1 SAY WHAT??????? F2 8

  10. 9 Mendel concluded: 2. Something is being passed from parent to offspring. He called these “Factors” 3. Sometimes you can see “it” and sometimes you can’t see “it”. 4. If you can see it- it is dominant. 1. If it’s there and you can’t see it- it’s recessive.

  11. 10 5. There are two versions of these “FACTORS”. 6. To show the two version we use a capital letter for the dominant (S) version of the trait and a lower case for the recessive version (s) of the trait. ADD TO NOTES: Each Version is called an Allele.

  12. Each chromosome has many genes, but the alleles may be different 11 • Alleles are different versions of the same gene.

  13. 12

  14. Common Physical Human Traits- Different Alleles 13 Activity

  15. WHAT WE KNOW NOW 14

  16. Chromosome Anatomy 15

  17. We have two copies of all of our chromosomes Why? These are called Homologous Chromosomes 16

  18. Karyotype BOY OR GIRL? 17

  19. 18 DNA codes for Proteins

  20. 19 What is a gene? • A segment on the chromosome that codes for a protein. • People have two copies of each gene, one copy inherited from the mother and the other copy inherited from the father. • There are many versions of each gene-alleles

  21. Remember: Genes come in pairs. **One from your mother **One from your father.

  22. If the two alleles in the pair are identical, then the condition called homozygous.The term “purebred” issometimes used. 20.1

  23. If the 2 alleles are different,the condition is called heterozygous. The term “hybrid” issometimes used to refer to heterozygous. 20

  24. What the genes/alleles are …RR.…Rr 21 What the organism looks like…… Red…..White

  25. Genotype Phenotype

  26. 22

  27. How did you end up with the traits and genes that you got? During meiosis, each egg or sperm only gets one copy of each chromosome. Meiosis Review Animation 23

  28. 24 Mendel’s Laws Law of Dominance • States that the dominant allele will prevent the recessive allele from being expressed. • The recessive allele will appear when it is paired with another recessive allele in the offspring. • Remember: Genes Come in Pairs!

  29. Law of Segregation(separation) states that gene pairs separate when gametes (sex cells) are formed • Each gamete has only one allele of each gene pair. (haploid) Mendel’s Laws A b a B S Phase A b A b a B a B Makes a copy gene pairs separate 25 A b A b a B a B Goes through Meiosis

  30. 26 Mendel’s Laws Law of Independent Assortment states that different pairsof genes separate independently of each other when gametes are formed. Example: Just because you get the gene for brown hair does not mean you will get the gene for blue eyes. Animation

  31. 27 REVIEW • A trait is a characteristic an individual receives from itsparents. • Genes carry the instructions responsible for theexpression of traits. • A pair of inherited genes controls atrait. • One member of the pair comes from each parent. • Alternative versions of genes are known as alleles.

  32. REVIEWMendel’s Principles of Inheritance • Inherited traits are transmitted by genes which occur in alternate forms called alleles • Principle of Dominance - when 2 forms of the same gene are present the dominant allele is expressed • Principle of Segregation - in meiosis two alleles separate so that each gamete receives only one form of the gene • Principle of Independent Assortment - each trait is inherited independent of other traits (chance) 28 Peas in a pod- Genetics Clip

  33. Example EOCT Question: Earlobe shape is a human trait. Some people have free earlobes while others have attached earlobes. Two parents with free earlobes have four children. Three children have free earlobes and one child has attached earlobes. If these parents have another child, what is the probability that the child will have attached earlobes? A 25% B 50% C 75% D 100% 32

  34. Predicting possible outcomes of a genetic cross. 30

  35. Punnett Squares • Geneticist use punnett squares to determine the probability of a combination of alleles. • For example: If a heterozygous black rabbit is crossed with a heterozygous black rabbit, what are the chances the offspring will be black? 31

  36. B=Black b= Brown Genotypes? Phenotypes? 30

  37. 31 Claymation Clip

  38. Example EOCT question: In humans, a widow’s peak isdominant over a continuous hairline. Mary’s father has a widow’s peak, but Mary and her mother have a continuous hairline. What is the genotype of Mary’s father? A HH B Hh C hh D cannot be determined 33

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  40. Incomplete dominance is a cross between organisms with two different phenotypes produces offspring with a thirdphenotype that is a blending of the parental traits.  35

  41. Incomplete Dominance 36

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  43. 38

  44. Codominance With codominance, a cross between organisms with two different phenotypes produces offspring with a thirdphenotype in which both of the parental traits appear together.  DO NOT blend together. 39

  45. Codominance • Both phenotypes are expressed at the same time. • Example: Blood Types There are 3 alleles for blood type- multiple alleles 40

  46. CodominanceR = allele for red flowers W = allele for white flowers red x white ---> red & white spotted 41

  47. 42

  48. Polygenic traits Many traits are controlled by more than one gene. Ex: Skin Color 43

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