7. Phenotype vs. Genotype
3
1 1
2
1
Phenotype
Purple
Purple
Purple
White
Genotype
PP
(homozygous)
Pp
(heterozygous)
Pp
(heterozygous)
pp
(homozygous)
Ratio 3:1 Ratio 1:2:1
8.
9. DOMINENT AND RECESSIVE
The character that was expressed in
first generation is called DOMINENT
and the contrasting character, which
was not expressed called
RECESSIVE. Bb
12. MENDEL’S LAW OF
SEGREGATION
• Each organism contains 2 genes
• for each trait and these genes segregate during
the formation of gametes
• so that each gamete consists only one gene of
each trait.
• When fertilization occurs,
• the new organism receives 2 factors for each
trait one from each parent.
15. MENDEL’S LAW OF INDEPANDENT ASSORTMENT
•Members of one pair of genes
•segregate (assort)independently
•of members of another pair of genes.
Therefore, all possible combinations of
factors can occur in the gametes.
16. DIHYBRID CROSS
• For example, in pea plants seed shape is
controlled by one gene locus where round (R) is
dominant to wrinkled (r) while seed color is
controlled by a different gene locus where yellow
(Y) is dominant to green (y).
• Mendel crossed 2 pure-breeding plants: one with
round yellow seeds and the other with green
wrinkled seeds.
18. Mendelian Genetics
Dihybrid cross - parental generation differs in two traits
example-- cross round/yellow peas with wrinkled/green ones
Round/yellow is dominant
RY Ry rY ry
RY
Ry
rY
ry
What are the expected phenotype ratios in the F2 generation?
round, yellow = round, green =
wrinkled, yellow = wrinkled, green =
21. Incomplete Dominance
• Incomplete dominance occurs when neither allele in a heterozygous
individual is completely dominant over the other, resulting in an
intermediate phenotype.
• In other words, when two different alleles are inherited, they blend
together to produce a phenotype that is a combination of the two.
• This blending is often represented by a heterozygous genotype having
a phenotype that is "incomplete" or in-between the phenotypes of the
homozygous dominant and homozygous recessive genotypes.
22. • Example: One classic example of incomplete dominance is the
inheritance of flower color in snapdragons.
• There are two alleles involved: one for red flowers (RR) and one for
white flowers (WW).
• If you cross a red-flowered plant (RR) with a white-flowered plant
(WW), the offspring (Rr) will have pink flowers, which is an
intermediate phenotype between red and white.
23.
24. Codominance
• Codominance occurs when both alleles in a
heterozygous individual are fully expressed,
and neither is dominant or recessive over the
other.
• In this case, both alleles contribute equally
to the phenotype, often resulting in a distinct
pattern where both traits are visibly
expressed simultaneously.
25. • One example of codominance in plants is the inheritance of flower color in
certain varieties of four o'clock flowers (Mirabilis jalapa). These flowers
come in a variety of colors, including red, white, and pink, and they exhibit
codominance in their flower color inheritance.
• In this case:
• The "RR" genotype represents red flowers.
• The "WW" genotype represents white flowers.
• Now, when you have a heterozygous individual with one "R" allele and one
"W" allele (Rr), you don't get an intermediate pink color as seen in
incomplete dominance. Instead, you see both red and white pigments fully
expressed in the same flower, resulting in a flower with sectors of red and
white. T
28. • Multiple alleles can be defined as a series of forms of a gene
situated at the same locus of homologous chromosomes.
According to Mendel, each gene had two alternate forms or
allele morphs are being dominant and the other being recessive.
29. Multiple Alleles Characteristics
• Multiple alleles of a gene occupy the same locus on the chromosome.
• Multiple alleles are the alternative forms of the same gene so they influence the
same trait.
• The wild-type allele is mostly dominant over the mutant alleles.
• The wild type is considered the standard and all other alleles are considered
variants.
• Multiple alleles exist at the population level and an individual can have only two
alleles for the given gene.
• An individual can have only one type of allele (homozygous) or two different alleles
(heterozygous).
• A series of mutant alleles can exist in a population. They are generated by a
spontaneous mutation in the wild type and the mutant alleles.
• Multiple alleles lead to the formation of varied phenotypic traits for a character in
the population.
30.
31.
32. Rh Factor
• The Rh factor is a protein that can be found on the surface of
red blood cells.
• If your blood cells have this protein, you are Rh positive.
• If your blood cells do not have this protein, you are Rh-
negative.
• The "positive" or "negative" part of your blood type, such as O
positive or A negative, refers to your Rh status.
