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Genetics and Heredity

Genetics and Heredity. Traits and Genes. A trait is a specific characteristic, such a eye color or height, that varies from one individual to another Today scientists call the chemical factors that determine traits genes. Are these inherited traits?. Your eye color.

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Genetics and Heredity

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  1. Genetics and Heredity

  2. Traits and Genes • A trait is a specific characteristic, such a eye color or height, that varies from one individual to another • Today scientists call the chemical factors that determine traits genes

  3. Are these inherited traits? Your eye color Your hair color and texture Your height

  4. Are these inherited traits? Your personality Your musical, athletic, and artistic abilities

  5. Think about this…. • “My parents have brown eyes, why are mine blue?” • “My brother is tall. Why am I short?” • “Why does my sister have blonde hair while mine is brown?”

  6. Alleles • The different forms of a gene are called alleles. For example, the alleles for a tall plant could be TT or Tt • The principle of dominance states that some alleles are dominant and others are recessive.

  7. These are questions that Gregor Mendel tried to answer.. • Born in 1822 in Austria • 1843 – Studied Theology • 1846-Studied Science at the University of Vienna Father of Genetics

  8. Dominant (H) Homozygous (HH or hh) Genotype (HH, Hh or hh) Purebred (HH or hh) Recessive (h) Heterozygous (Hh) Phenotype (blonde, brown, red) Hybrid (Hh) Mendel’s studies led to:

  9. Fertilization- during sexual reproduction, male and female reproductive cells join True breeding- when allowed to self-pollinate, they would produce offspring identical to themselves. Mendel’s studies led to:

  10. PREDICTING HEREDITY

  11. A a AA A Aa a Aa aa Monohybrid Cross:a cross that shows the possible offspring for one trait Aa x Aa A: White fur a: Brown fur Genotypic Ratio: 1:2:1 Phenotype: 3 white:1 brown

  12. A A A a Practice! Cross a HOMOZYGOUS dominant female with a HETEROZYGOUS male using the same trait. What is the genotypic ratio? AA AA 2:2 or 50% What is the phenotypic ratio? Aa Aa 4 white fur

  13. BR Br bR br BR BBRR BBRr BbRR BbRr Br BBRr BBrr BbRr Bbrr bR BbRR BbRr bbRR bbRr br BbRr Bbrr bbRr bbrr Dihybrid Crosses:cross that shows the possible offspring for two traits BbRr x BbRr • This shows a cross between parents hybrid for two traits: BbRr x BbRr Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth

  14. BR Br bR br BR BBRR BBRr BbRR BbRr Br BBRr BBrr BbRr Bbrr bR BbRR BbRr bbRR bbRr br BbRr Bbrr bbRr bbrr Dihybrid Crosses Phenotypic Ratio: # dom/dom : # dom/rec : # rec/dom : # rec/rec • How many of the offspring would have a black, rough coat? (#dom/dom) • How many would have a black, smooth coat? (#dom/rec) • How many would have a brown, rough coat? (#rec/dom) • How many would have a brown, smooth coat? (#rec/rec) 16 Phenotypic Ratio: 9:3:3:1

  15. BR Br bR br BR BBRR BBRr BbRR BbRr Br BBRr BBrr BbRr Bbrr bR BbRR BbRr bbRR bbRr br BbRr Bbrr bbRr bbrr Dihybrid Crosses • If mouse #1 were crossed with mouse #16, what would their offspring look like? 1 16

  16. More Complex Patterns of Heredity • Incomplete Dominance • Codominance • Multiple Alleles • Polygenic Traits • Sex-Linked Traits

  17. Incomplete Dominance RR WW RW One allele is not completely dominant over the other. The heterozygous phenotype is somewhere in between the two.

  18. Codominance:two dominant alleles are expressed at the same time CRCR CWCW CRCW

  19. Codominance • Sickle-Cell Anemia is another codominant trait. NA NA NSNA NSNA NS NA=Normal RBC NS=Sickle Cell RBC NANA NANA NA

  20. Multiple Alleles:traits with more than 2 alleles • Blood type has 3 alleles: A, B, O • A and B are codominant over O • O is recessive

  21. Polygenic Traits Often show a wide range of phenotypes. For example, the wide range of skin color in humans comes about partly because more that for different genes probably control the trait. Traits controlled by two or more genes

  22. What are Sex-Linked Traits? Traits that are located on one of the sex chromosomes (XY) Hemophilia: Failure of blood to clot Alix and Nicholas II Muscular Dystrophy: wasting away of muscles

  23. Can I inherit a sex-linked disease? Fathers (XY) can only pass disorders to daughters (XX) Mothers (XX) can pass disorders to both sons (XY) and daughters (XX) Most disorders are carried on the X chromosome, so males are more likely to inherit them.

  24. How can I tell if I have a genetic disorder? • Karyotypes are a “map” of all 46 (23 pair) of chromosomes.

  25. What’s wrong with this Karyotype? Is this a male or a female?

  26. Pedigree Analysis A pedigree shows inheritance of genetic traits over several generations Marriage male female Female Carrier Offspring

  27. Royal Hemophilia Pedigree http://www.sciencecases.org/hemo/hemo.asp

  28. Pedigree for Colorblindness

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