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Chapter 5 section 2 notes


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Chapter 5 section 2 notes

  1. 1. Chapter 5: HereditySection 2: Genetics Since Mendel<br />Minersville Area School District<br />Mr. Motuk<br />Room 124<br />
  2. 2. Incomplete Dominance<br />Neither allele for a trait is dominant.<br />The phenotype produced is intermediate between the two homozygous parents. <br />This results in a blendingof the two traits.<br />Example:RR = Red Flowers<br />WW= White Flowers<br />RW = Pink flowers <br />
  3. 3. Incomplete Dominance<br />B= Allele for Black Fur<br />W= Allele for White Fur<br />So if we had incomplete dominance: <br />BB would be homozygous Black Fur<br />WW would be homozygous White Fur<br />BW would be heterozygous GREY Fur<br />
  4. 4. Multiple Alleles<br />More than two alleles that control a trait are called multiple alleles. <br />Traits controlled by multiple alleles produce more than three phenotypes. <br />An excellent example of multiple alleles is human blood type. <br />a. Blood types exist in four possible phenotypes: A, B, AB, and O. <br />
  5. 5. Blood Type Alleles<br />IA= type A blood<br />IB= Type B blood<br />i= Type “O” blood<br />A Blood is dominant over “O” blood (i).<br />B blood is dominant over “O” blood (i). <br />A blood is codominant with B blood. (both show up)<br />
  6. 6. Blood Type Genotypes<br />
  7. 7. Polygenic inheritance<br />A group of gene pairs acts together to produce a trait, which creates more variety in phenotypes. <br />Many human traits are controlled by polygenic inheritance, such as hair and eye color. <br />
  8. 8. Mutations<br />Mutations are genes that are altered or copied incorrectly. <br />A mutation can cause harmful, beneficial, or have no effect. <br />Chromosome disorders <br />Caused by more or fewer chromosomes than normal. <br />Down Syndrome is caused by an extra copy of chromosome # 21. <br />
  9. 9. Recessive Genetic Disorders<br />Both parents have a recessive allele responsible for the disorder and pass it to their child. <br />Because both parents are heterozygous they DON’T show any symptoms. <br />Cystic fibrosis is a homozygous disorder. <br />What is Cystic Fibrosis?(Journal Entry)<br />
  10. 10. Sex Determination<br />Chromosomes that determine the sex of an organism are XX in females and XY in males. <br />Females produce eggs with X chromosomes only. <br />Males produce sperm with either an X or a Y chromosome. <br />The male determines the sex of the offspring. <br />
  11. 11. Sex-linked Disorders<br />An allele inherited on an X or Y chromosome is a sex linked gene. <br />Color blindness is a sex linked disorder caused by a recessive allele on the X chromosome. <br />a. Color blindness is more common in men than women. Why?<br />A pedigree follows a trait through generations of a family. <br />
  12. 12. How to use a Pedigree<br />Males are represented by squares. <br />Females are represented by circles. <br />Completely filled in circle or square shows that the trait can be seen in that person. <br />A half colored in circle or square indicates a carrier. <br />Carriers are heterozygous for the trait, and the trait is not seen in that individual. <br />People represented by empty circles or squares do not have the trait and are not carriers. <br />
  13. 13. Example of a Pedigree<br />(Pedigree worksheet to follow)<br />