1. there are three possible phenotypes,
incomplete dominance or codominance
there are three possible phenotypes,

2. Incomplete Dominance (Blended Inheritance)
Meaning. In Mendel's pea experiment, dominance was essentially complete. Consequently, there was practically no difference between the homozygous and the heterozygous plants in the expression of a dominant character. For instancea (TT) tall pea plant was almost similar to a (Tt) tall pea plant. However, this is not true of all characters or organisms. There are characters or alleles that are not dominant or recessive. In such cases, both the alleles of the contrasting conditions of a character express as a blend (mixture).

3. With the result, the hybrid produced by crossing two pure individuals does not resemble either of them, but is midway between them. The expression of the traits of two pure parents as an intermediate condition or fine mixture in the Fi hybrids is known as incomplete or partial dominance. It is also called blended or intermediate or mosaic inheritance. It is due to -the fact that the dominant character or gene is not • ■ in a position to completely suppress the recessive \ one. With the result, the heterozygote has a dif-ferent phenotype (as well as a different genotype) -from homozygotes for either allele.

4. Andalusian fowl.

5. 1. Four-O'clock Plant (Figs. 5. 23 and 5. 24)
1. Four-O'clock Plant (Figs and 5.24). A cross between a plant pure for red flowers and a
      

6. lethal alleles
A mutant form of a gene that eventually results in the death of an organism if expressed in the phenotype. Most lethal genes are recessive;
Examples of diseases caused by recessive lethal alleles are cystic fibrosis, Tay-Sachs disease, sickle-cell anemia, and brachydactyly
The lethal alleles modify the 3: 1 phenotypic ratio into 3 : 0.
sickle-cell anaemia results from a recessive lethal gene that causes the production of abnormal and inefficient haemoglobin.

7. Dominant Lethal Allele - Quickly eliminated from the population, because usually causes death before the individual can reproduce.
In 1905, Lucien Cuénot observed unusual patterns when studying inheritance of a coat color gene in mice. After mating two yellow mice, he observed that the offspring never showed a normal 3:1 phenotypic ratio. Instead, Cuénot always observed a 2:1 ratio, with two yellow mice for every one non-yellow mouse (Cuénot, 1905; Paigen, 2003). Cuénot thus determined that yellow coat color was the dominant phenotypic trait, and by using test crosses, he showed that all his yellow mice were heterozygotes. However, from his many crosses, Cuénot never produced a single homozygous yellow mouse.

9. epistasis
Defination of epistasis - A double mutant where one mutation masks the phenotype of another mutation.
Note that epistasis is not the same thing as dominance. With epistasis a mutation in one gene masks the expression of a different gene. With dominance, one allele of a gene masks the expression of another allele of the same gene.

10. Duplicate recessive epistasis
9:7 phenotypic ratio
Flower Color in Peas
Complete dominance at both gene pairs; however, when either gene is homozygous recessive, it hides the effect of the other gene

11. Many years after Bateson first described this 9:7 phenotypic ratio in pea plants, researchers were finally able to determine the two genes responsible for it (Dooner et al., 1991). These genes control flower color by controlling pea plant biochemistry, in particular that related to pigment compounds called anthocyanins. In peas, there is a two-step chemical reaction that forms anthocyanins; gene C is responsible for the first step, and gene P is responsible for the second (Figure 2).

12. If either step is nonfunctional, then no purple pigment is produced, and the affected pea plant bears only white flowers. The dominant C and P alleles code for functional steps in anthocyanin production, whereas the recessive c and p alleles code for nonfunctional steps. Thus, if two recessive alleles occur for either gene, white flowers will resultt

13. Female Gametes Male Gametes CCPP CCPp CcPP CcPp CCpp Ccpp ccPP ccPp
Table 2: Results of the Cross Between Two Pea Plants with Genotype CcPp
Primula Petal Color
Female Gametes CP Cp cP cp
Male Gametes
CCPP
CCPp
CcPP
CcPp
CCpp
Ccpp
ccPP
ccPp
ccpp

14. dominant suppression epistasis
13:3 phenotypic ratio
Primula plant
Complete dominance at both gene pairs; however, when either gene is dominant, it hides the effects of the other gene

15. Table 3: Results of the Cross Between Two Primula Plants with Genotype KdDd
Female Gametes KD Kd kD kd
Male Gametes
KKDD
KKDd
KkDD
KkDd
KKdd
Kkdd
kkDD
kkDd
kkdd

16. Duplicate dominant epistasis
15:1
phenotypic ratio
Wheat Kernel Color
Complete dominance at both gene pairs; however, when either gene is dominant, it hides the effects of the other gene

17. Table :Results of the Cross Between Two Wheat Plants with Genotype AaBb
Female Gametes AB Ab aB ab
Male Gametes
AABB
AABb
AaBB
AaBb
AAbb
Aabb
aaBB
aaBb
aabb

18. In this cross, whenever a dominant allele is present at either locus, the biochemical conversion occurs, and a colored kernel results. Thus, only the double homozygous recessive genotype produces a phenotype with no color, and the resulting phenotypic ratio of color to noncolor is 15:1.

19. 12:3:1 phenotypic ratio Dominant epistasis Fruit Color in Squash
Complete dominance at both gene pairs; however, when one gene is dominant, it hides the phenotype of the other gene

20. the gene symbols are W=white and w=colored
the gene symbols are W=white and w=colored. At the second gene yellow is dominant to green, and the symbols used are G=yellow, g=green. If the dihybrid is selfed, three phenotypes are produced in a 12:3:1 ratio. The following table explains how this ratio is obtained.

21. Dominant white allele negates effect of G allele
Genotype
Fruit Color
Gene Actions
9 W_G_
White
Dominant white allele negates effect of G allele
3 W_gg
3 wwG_
Yellow
Recessive color allele allows yellow allele expression
1 wwgg
Green
Recessive color allele allows green allele expression

22. Table 4: Examples of Digenic Epistatic Ratios
Description
Name(s) of Relationship (Used by Some Authors)
9:7
Complete dominance at both gene pairs; however, when either gene is homozygous recessive, it hides the effect of the other gene
Duplicate recessive epistasis
12:3:1
Complete dominance at both gene pairs; however, when one gene is dominant, it hides the phenotype of the other gene
Dominant epistasis
15:1
Complete dominance at both gene pairs; however, when either gene is dominant, it hides the effects of the other gene
Duplicate dominant epistasis
13:3
Dominant and recessive epistasis

23. Polygenic traits
Polygenic traits are the result of the interaction of several genes. For instance, phenotypes like high blood pressure (hypertension) are not the result of a single "blood pressure" gene with many alleles (a 120/80 allele, a 100/70 allele, a 170/95 allele, etc.) The phenotype is an interaction between a person's weight (one or more obesity genes), cholesterol level (one or more genes controlling metabolism), kidney function (salt transporter genes), smoking (a tendency to addiction), and probably lots of others too. Each of the contributing genes can also have multiple alleles.

24. Hair color in humans is a polygenic trait.
Eye color is, too.
Plant height in tobacco is controlled not by a single pair of genes but by a series of genes at multiple loci that each has a small additive affect on the phenotype of the plant. Assume three loci, each of which has two alleles. (A,a B,b C,c).

25. Imagine pure-breeding short plants are all aabbcc and tall plants are all AABCC and a situation where the height of the plant is determined entirely by the number of upper case alleles regardless of which locus the allele is at. Thus a plant with the genotype AaBbcc is the same height as a plant with genotype AabbCc.
There are 7 possible classes of plant heights depending on the number of upper case alleles.
0,1,2,3,4,5 or 6.

26. Pleiotropy
Pleiotropy is the effect of a single gene on more than one characteristic. An example is the "frizzle-trait" in chickens. The primary result of this gene is the production of defective feathers. Secondary results are both good and bad; good include increased adaptation to warm temperatures, bad include increased metabolic rate, decreased egg-laying, changes in heart, kidney and spleen.

27. Sickle-cell anemia is a human disease originating in warm lowland tropical areas where malaria is common. Sickle-celled individuals suffer from a number of problems, all of which are pleiotropic effects of the sickle-cell allele

28. MULTIPLE ALLELES
if there are 4 or more possible phenotypes for a particular trait, then more than 2 alleles for that trait must exist in the population.  We call this "MULTIPLE ALLELES".

29. An excellent example of multiple allele inheritance is human blood type. Blood type exists as four possible phenotypes: A, B, AB, & O. There are 3 alleles for the gene that determines blood type.

30. The ABO system in humans is controlled by three alleles, usually referred to as IA, IB, and IO (the "I" stands for isohaemagglutinin). IA and IB are codominant and produce type A and type B antigens, respectively, which migrate to the surface of red blood cells, while IO is the recessive allele and produces no antigen. The blood groups arising from the different possible genotypes are summarized in the following table

31. Genotype
Blood Group
IA IA A
IA IO
IB IB B
IB IO
IA IB AB
IO IO O