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Pedigree

Unit 9 Objective 3: Pedigrees, Incomplete Dominance, Co-dominance, Sex-linked Traits and Genetic Disease. Pedigree. A diagram showing the presence or absence of a trait within a family (parents, siblings, and offspring) Used to determine how a trait/disease is inherited (dominant or recessive).

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Pedigree

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  1. Unit 9 Objective 3:Pedigrees, Incomplete Dominance, Co-dominance, Sex-linked Traits and Genetic Disease

  2. Pedigree • A diagram showing the presence or absence of a trait within a family (parents, siblings, and offspring) • Used to determine how a trait/disease is inherited (dominant or recessive)

  3. Symbols Used in Pedigrees • Males are squares, females are circles. • A line between a square and a circle is a mating • Generations are connected by a vertical line • Children of a mating are connected to a horizontal line, the oldest on the left • Normal individuals are open squares or circles • Affected individuals are solid squares or circles

  4. What it is Incomplete Dominance One allele for a specific trait is not completely dominant over the other allele. This results in a phenotype in between the two homozygous forms. The dominant allele does not completely mask the recessive allele. Ex. Four o’clock Flowers

  5. What is co-dominance • Both alleles contribute to the phenotype. • Ex. Blood type • Ex. Cattle hair color

  6. Other Types of Complex Genetics • Multiple Alleles • An individual only has two, but more than two possibilities exist. • Polygenic Traits • Traits controlled by two or more genes • Skin color, Eye color, Hair color

  7. What is a Karyotype? • A map that shows the complete diploid set of chromosomes grouped together in pairs, arranged in decreasing size. • Normally contains 22 sets, (autosomes) of chromosomes and 1set of sex chromosomes for a total of 23 pairs

  8. Human Karyotype

  9. Sex Linked Traits • Two of our 46 chromosomes (pair #23) are known as sex chromosomes • Males have XY • Females have XX • Remaining 44 chromosomes are known as autosomes

  10. Sex linked Inheritance • Because the X and Y chromosomes determine sex, the genes located on them are called sex-linked traits. • Males always express the single allele they have. • Color-Blindness • Humans have three genes on the X chromosome for color vision. 1 in 12 males is color blind; 1 in 200 females are color blind. • Hemophilia • Duchenne Muscular Dystrophy

  11. Genetic disorders • An illness caused by abnormalities in genes or chromosomes • Mutations - changes in a gene’s DNA sequence. Can change proteins by altering the amino acid sequences which may affect the phenotype. • Non-disjunction – chromosomes don’t separate as they should during meiosis. • Result: gamete have abnormal number of chromosomes

  12. answers • 1. Normal Color Vision: A: 29,  B: 45,  C: --,  D: 26 • 2. Red-Green Color-Blind: A: 70,  B: --,  C: 5,  D: -- • 3. Red Color-blind: A: 70,  B: --,  C: 5,  D: 6 • 4. Green Color-Blind: A: 70,  B: --,  C: 5,  D: 2

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