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CATALYST

CATALYST. Recall and Review: What are chromosomes? What are genes? What are alleles? How do these terms relate to DNA? How do these terms relate to the characteristics that you and I possess?. Chromosomes, Genes & Alleles. Human Chromosome Magnified. Chromosomes, Genes & Alleles.

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CATALYST

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  1. CATALYST • Recall and Review: • What are chromosomes? • What are genes? • What are alleles? • How do these terms relate to DNA? • How do these terms relate to the characteristics that you and I possess?

  2. Chromosomes, Genes & Alleles Human Chromosome Magnified

  3. Chromosomes, Genes & Alleles Human Chromosomes (Karyotype)

  4. DNA Fingerprintingyou will be able to: • explain how traits are passed on from parent to child. • Predict the probability for traits to be passed on to offspring. • Understand how paternity tests are performed.

  5. Heredity • Heredity: the passing of characteristics from parent to offspring • The study of how characteristics are passed from generation to generation is genetics. • Give three examples of inherited characteristics. • What characteristics can’t be inherited? • How do humans inherit genetic information?

  6. Heredity • Remember: Humans receive half of their nuclear DNA from their mother and half from their father. • Think: Where do we get our Mitochondrial DNA from? • So, for each gene that we posses we receive one allele (form) from mom and one allele (form) from dad.

  7. HeredityExample • For the trait pictured, Mom has two of the same alleles and Dad has two different alleles. Only one allele from each parent will be passed to their children. • Would these be the result every time?

  8. HeredityExample • One more time…

  9. HeredityExample • What is occurring in the image to the right?

  10. Alleles & Traits • Alleles can be expressed in different ways. • Some alleles are dominant. We represent these with a capital letter (i.e. A, B, T). • What does dominant mean? • Some alleles are recessive. We represent those with a lower case letter (i.e. a, b, t). • What does recessive mean?

  11. Alleles & Traits • If an individual has two of the same alleles they are said to be homozygous for that trait. • Can you think of two examples for eye color using the letter “Bb”. • If an individual has two different alleles they are said to be heterozygous for that trait. • Can you think of an example for eye color?

  12. Describe the genetic makeup for each individual pictured, use the letter “Aa” for the trait.

  13. Alleles & TraitsExample • Here is an example of how the dominant allele for Huntington’s disease (a rare neurological condition) is inherited. • A genotype is an individual allele combination • A phenotype is how the gene is expressed

  14. Alleles & Traits: The Punnett Square • If we know an individual’s genotype we can use punnett squares to predict the probability for offspring genotypes.

  15. Alleles & Traits: The Punnett Square • Humans have 3 alleles for blood type: • IA - Type A blood allele • IB – Type B blood allele • i – Type O blood allele **Both A and B are dominant (how we get AB blood type) • What are the possible genotypes for each blood type? (there are 6)

  16. Alleles & Traits: The Punnett Square • Using a Punnett Square, find the probabilities for the following: • Mom IA IA Mom IA IB • Dad IA IB Dad IA IB • Mom IA IA Mom IA i • Dad IB IB Dad i i Forensic Science: Fundamentals & Investigations, Chapter 7

  17. Heredity, Genetics & DNA Identification • Most of the human genome is the same in all humans, but some variation does exist does exist. • This variation results in DNA sequences of different length and base pair sequences. • These differences are called polymorphisms. • We can pass these differences onto our offspring.

  18. Paternity • Within the last two decades we have been able to improve techniques for identifying a child’s biological parents (in most cases fathers). • How is this possible? How would we go about doing this?

  19. Population Genetics & Forensics • Population genetics is the study of variation in genes among a group of individuals. • The proportion of people that have a particular trait is determined by the proportion of alleles available in the population gene pool. • Ex: Blue eye are rare in Asian populations, but common in northern European populations.

  20. Population Genetics & Forensics • We can compile databases for populations to determine a particular alleles frequency (percentage). • We then use this information we investigating forensic DNA samples. • Calculation are then made to determine the probability that a random person in the population would have the same alleles as a suspect or potential parent.

  21. Summarize • Summarize what you have learned (or reviewed) today in a 3-5 sentence paragraph.

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