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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. Theory of Heredity Inherited allele for purple P Inherited allele for purple P HOMOZYGOUSpurple flower PP

  11. Theory of Heredity Inherited allele for purple flower (P) Inherited allele for pink flower (p) HETEROZYGOUS purple flower (Pp)

  12. Theory of Heredity Inherited for pink flower (p) Inherited for pink flower (p) HOMOZYGOUS pink flower (pp)

  13. PREDICTING HEREDITY

  14. The likelihood that a specific event will occur Probability = # of 1 times event occurs number of possible outcomes Example: What is the probability that a tossed coin will be heads? ½ or 50% Probability

  15. The First Law of Probability: the results of the first trial of a chance event do not affect the results of later trials of the same event. In other words, no matter how many times a flipped coin lands on tails, every flip still has a ½ chance of tails. Probability

  16. Second Law of Probability: The probability of two or more independent events occurring together is the product of their separate probabilities. What is the probability that a couple will have four boys? ½ x ½ x ½ x ½ = 1/16 Probability

  17. Punnett squares can be used to predict and compare the genetic variations that will result from a cross. Punnett Squares!

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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

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

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

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

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

  27. 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

  28. 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

  29. 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

  30. 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.

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

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

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

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

  35. Pedigree for Colorblindness

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