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GENETICS

GENETICS. 1. Gregor Mendel. Genetics =the branch of biology that deals with heredity . A great deal of what we know about genetics began with the work of a monk named Gregor Mendel , who experimented with sweet pea plants in the 1800s. 2. Mendel’s Work.

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GENETICS

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  1. GENETICS 1

  2. Gregor Mendel Genetics=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

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

  4. Mendel needed to make sure he had plants that always gave the sameoffspring-called true breeding. • He “self-pollinated” plants until he got seeds that always gave the same offspring. 4

  5. Pollen X • He took a purple flower plant and crossed it with a white flower plant. • He called these the parent generation (P1 generation) • What do you think the offspring (the F1 generation) looked like? ALL PURPLE 5

  6. POLLEN F1 SAY WHAT??????? F2 6

  7. Mendel concluded: • Something is being passed from parent to offspring. • Sometimes you can see “it” and sometimes you can’t. • If you can see “it”- “it” isdominant. • If “it’s” there and you can’t see “it”- it’srecessive. 7

  8. Dominant alleles are shown using a capital letter (R) • Recessive alleles are shown using a lower case letter (r) Examples: R=red r=pink RR - ? Rr - ? Rr- ? Each version is called an allele. 8

  9. Alleles are locted on genes on chromosomes. 9

  10. Law of Dominance States that the dominant allele will prevent the recessive allele from being expressed. The recessive allele will only appear when it is paired with another recessive allele in the offspring. 10

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  12. WHAT WE KNOW NOW 12

  13. We have two copies of all of our chromosomes Why? 13

  14. BOY OR GIRL? 14

  15. 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 15

  16. If the two alleles in the pair are identical, then the condition called homozygous. If the 2 alleles are different,the condition is called heterozygous. The term “hybrid” issometimes used to refer to heterozygous. 16

  17. Genotype: the genes or alleles (RR, Rr, rr) Phenotype: an organisms physical appearance (Red, White) 17

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  19. 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. 19

  20. A b a B Law of Segregation (separation) states that gene pairs separate when gametes (sex cells) are formed, so each gamete has only one allele of each gene pair. A b a B A b a B A b a B A b a B 20

  21. Example: Just because you get the gene for brown hair does not mean you will get the gene for blue eyes. Law of Independent Assortment states that different pairs of genes separate independently of each other when gametes are formed. 21

  22. 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. 22

  23. 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) 23

  24. Punnett Squares • Used to determine the probability of a combination of alleles • Example: If a heterozygous black rabbit is crossed with a heterozygous black rabbit, what are the chances the offspring will be black? 24

  25. B=Black b= Brown Genotypes? Phenotypes? 25

  26. 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% 26

  27. 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 27

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  29. Incomplete dominance - cross between organisms with two different phenotypes that produces offspring with a thirdphenotype that is a blending of the parental traits. Ex. Red and White = Pink 29

  30. Incomplete Dominance 30

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  32. Codominance • a cross between organisms with two different phenotypes produces offspring with a thirdphenotype in which both of the parental traits appear together.  • Ex: Yellow and Orange = yellow with orange spots 32

  33. Codominance • Both phenotypes are expressed at the same time. • Example: Blood Types There are 3 alleles for blood type- multiple alleles 33

  34. CodominanceR = allele for red flowers W = allele for white flowers redxwhite---> red&whitespotted 34

  35. Polygenic traits Most traits are controlled by many genes, not just one. Examples: hair color and skin color. There are several genes that control them. This is the reason that there are so many different colors of hair and skin in humans. 35

  36. Sex Linked Traits Traits associated with particular sexes are called sex-linked or X-linked traits. These are usually carried on the X chromosome. Females = XX Males = XY 36

  37. 1st 22 are Autosomes, the last pair (XY) are sex chromosomes) Karyotype 37

  38. Charts that show relationships within a family Pedigree 38

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  41. Autosomal-Dominant 41

  42. SEX-LINKED 42

  43. SEX-LINKED 43

  44. Autosomal -Dominant 44

  45. Genetic Disorders 45

  46. Huntington’s Disease • Huntington's disease degenerative disease that causes certain nerve cells in your brain to waste away. • you may experience uncontrolled movements, emotional disturbances and mental deterioration. • The disorder was documented in 1872 by American physician George Huntington. • Fatal----ages:30-60 46

  47. Colorblindness • Sex-linked trait • Gene for color vision located on the X chromosomes. • Males are more likely to have colorblindness because they have only one X chromosome 47

  48. What do you see? What do you see? The individual with normal color vision will see a 5 revealed in the dot pattern. An individual with Red/Green (the most common) color blindness will see a 2 revealed in the dots. 48

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  50. TEST 50

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