Materials: none Catalyst: Beyonce and Jay Z are having another baby. Both parents are heterozygous for Hitchhiker’s thumb. Hitchhikers thumb is dominant to no Hitchhiker’s thumb. What are the possible genotypes and phenotypes of their offspring and in what percentages will they be seen?
Materials: none Catalyst: Compare and contrast Codominance with Incomplete Dominance. You may use a table or Venn Diagram to help you out.
Announcements Unit 3 Test this week (Thurs/Fri) If you do well you get to go to Six Flags in May!! Unit 3 Study guide due on Wednesday Can be found online at msnay.weebly.com LAST WEEK TO TURN IN LATE WORK FOR UNIT 3! No work/Mutant Makers projects will be accepted past Friday! Grades post tomorrow! Tutorial Today 3:15 – 4:30
Star Quiz 14
Objectives I can explain the concepts of codominance and incomplete dominance. I can determine the genotypes and phenotypes of codominant and incompletely dominant traits in offspring. I can explain the concept of sex-linked traits in mammals.
Codominance: (NOTES) RR’ BB’ Both alleles are expressed on different parts of the organism. Heterozygous = see both phenotypes CO means BOTH SHOW! RR’ BB’
Codominance Example: (NOTES) There are 3 alleles to classify blood type in humans (A, B, O). Blood type AB = codominant
Incomplete dominance: (NOTES) No dominant allele Blending of traits Heterozygous = blended phenotype
Example: snapdragon flower color: RR = red Rr = pink rr = white
How is Incomplete Dominance Shown on a Punnett Square? When the heterozygous genotype is shown, label it as having the “blended” phenotype. Ex: RR Rr heterozygous cross Rr rr Red= RR= 25% Pink=Rr=50% White=rr=25%
Silent Practice The color of pythons is a codominant trait. A dark brown python (BB) mates with a light brown python (B’B’). What are the genotypes and phenotype probabilities of the offspring?
Genetic Disorder Inheritance A heterozygote for a recessive disorder is a carrier. Disorders caused by dominant alleles are uncommon. (dominant)
Sex-linked traits Genes on sex chromosomes are called sex-linked genes. Y chromosome genes = male characteristics. X chromosome genes = many traits.
Male mammals have an XY genotype All of a male’s sex-linked genes are expressed. If a disorder is carried on the X chromosome, the male will express it.
Female mammals have an XX genotype Females must have 2 copies of a recessive sex linked trait to express the disorder.
Examples of Sex Linked Disorders Red – Green Colorblindness Recessive trait Found on the x chromosome Male Pattern Baldness Hemophilia
Sex Linked Disorders Summary (LISTEN) Males express sex linked traits more frequently than females. (XY vs. XX) If the gene is found on the X chromosome, it will be expressed in males no matter if it is dominant or recessive. For females, they must have 2 copies of the gene to express that disorder.
Classwork 3.11 Directions: complete the worksheet using your notes to correctly answer the questions. REMEMBER: Co means both show! Incomplete = blend When you are done, turn it in to the blue tray and work on your Unit 3 Study Guide!