3 Codominance Both alleles of a gene pair are equally dominant. Neither allele is dominant or recessive to the other and as a result both alleles are expressed in a heterozygous offspring.
4 CodominanceThe heterozygous offspring will express (show) both phenotypes
5 Punnett Square for Codominance XRRWWRWRRWRWRW100% mixed color carnations (RW)RWRWW
6 Punnett Square for Codominance XRWRWRWRRRWR25% red carnations (RR)50% mixed color carnations (RW)25% white carnations (WW)RWWWW
7 Incomplete DominanceOne allele of a gene pair is only partially dominant over the other.In these cases an intermediate form of the trait is expressed in heterozygous organisms.Often seen in flowers.
8 Incomplete DominanceThe heterozygous offspring will express (show) a blend of theParent phenotypes
9 Punnett Square for incomplete dominance XRRrrRrRR100% pink snapdragons (Rr)rRrRrRrRrr
10 Punnett Square for incomplete dominance XRrRrRrRRRRr25% red snapdragons (RR)50% pink snapdragons (Rr)25% white snapdragons (rr)Rrrrr
11 Investigating different patterns of inheritance Sex Linked Traits
12 Sex Linked TraitsTraits that are controlled by genes located on the sex chromosomes (X or Y)These traits are more common in males than females.Why???
13 Sex Linked Traits Girls = XX Boys = XY X Chromosome Larger and contains multiple genesY ChromosomeSmaller and contains no genesGirls = XXBoys = XY
14 Sex Linked Traits XB XB - Normal XB YØ - Normal Girls = XX Boys = XYColor blindness is a recessive condition inherited on the X chromosome:BB = Individual has normal visionBb = Individual has normal vision (carries the colorblind gene)bb = Individual is colorblindXB XB - NormalXB YØ - NormalXB Xb – Normal (carrier)Xb YØ – Color BlindXb Xb – Color Blind
16 Sex Linked Example Girls = XX Boys = XY Xb Xb XBXb XBXb XB XbYØ XbYØ Consider a case where a mother is color blind and the father has normal vision. What is the probability that this couple’s children will be colorblind?XbXbAll Daughters are carriers (XBXb ) with normal visionAll Sons are color blind (XbYØ)XBXbXBXbXBXbYØXbYØYØ
17 Sex Linked Example Girls = XX Boys = XY XB Xb XBXB XBXb XB XBYØ XbYØ Consider a case where a mother is a carrier and the father has normal vision. What is the probability that this couple’s children will be colorblind?XBXb50% the daughters will be carriers (XBXb ) but all will have normal vision.50% of the sons will be color blind (XbYØ) and 50% will have normal vision (XBYØ).XBXBXBXbXBXBYØXbYØYØ
18 Sex Linked Traits are more common in boys Girls = XX Boys = XYWhat is the only way that a female can inherit colorblindness?XBXbXBXbXbXbXbDad has to be color blind and Mom has to at least be a carrier of the trait!XBYØXbYØYØ
19 Investigating different patterns of inheritance Multiple Alleles
20 Multiple Alleles Traits that are controlled by three or more alleles. Even though more that two alleles exist for a particular trait, humans only carry two at a time.ABO Blood Type is a good example!
21 Blood Type - ABO Three alleles exist in the general population – A-B-O Humans only carry twoA and B are co-dominantO is recessiveLet’s see how this works!
22 Blood Type - ABO A and B are Co-Dominant and O is recessive What allele combinations are possible for A blood type?AA or AOWhat allele combinations are possible for B blood type?BB or BO
23 Blood Type - ABO A and B are Co-Dominant and O is recessive What allele combination is possible for AB blood type?ABWhat allele combination is possible for O blood type?OO
24 A O A O AO OO O AO OO O ABO Blood Type Consider the following genotypes:Father genotype = AO Father’s Blood Type = ________Mother Genotype = OO Mother’s Blood Type = ________AOAOWhat are the possible blood types for the children? What are the genotypes?50% chance of blood type A (AO)50% chance of blood type O (OO)AOOOOAOOOO
25 B O BO OO O BO OO O ABO Blood Type Consider a family where the father is blood type B, the Mother is blood type O, and their daughter is blood type O. What is the possibility that future children will have the following blood types?Why not BB?BOBlood type A _____%Blood type B _____%Blood type O _____%Blood type AB _____%BOOOO5050BOOOO