Gregor Mendel discovered the fundamental laws of inheritance through experiments breeding pea plants. He deduced that genes come in pairs and are inherited as distinct units, even without knowledge of DNA. The three Mendelian laws of inheritance are: the law of segregation which states offspring receive one allele from each parent; the law of independent assortment which states genes do not influence the sorting of alleles; and the law of dominance where the dominant allele will conceal the presence of the recessive allele.

1. Mendellian Laws of
Inheritance

2. Describe how Gregor Mendel came up
with the Laws of Heredity.
Gregor Mendor was known as the Father of Heredity because of
his great contribution in genetics. He discovered the fundamental
laws of inheritance through his experiment on pea plants. Mendel
grew over 10,000 pea plants and he observed its progeny number
and type. He deduced that genes come in pair and it is inherited
as distinct units. Even he did not recognize DNA and
chromosomes in the cell, he tracked the segregation of parental
genes and their appearance in the offspring as dominant and
recessive. The Mendelian Laws of Inheritance can be classified
into three such as Law of Segregation, Law of Independent
Assortment, and Law of Dominance.

3. Explain the following:
a. Law of Dominance
In Law of Dominance, an organism will express the
alternate forms of gene that is dominant. In this law, it
will express the allele that exerts greater influence than
the other allele. He explained based on his experiment
that each plant carried two traits with a dominant and
recessive allele. The dominant allele will conceal the
presence of another trait for the same characteristic but
it doesn’t mean it will not appear in other generation. It
will only be expressed if there is two copies of allele.

4. b. Law of Segregation
Law of Segregation states that a diploid
organism passes an allele for a trait to its
offspring. It denotes that an offspring will
receives one allele from each parent. The allele
that contains the dominant trait determines the
phenotype of the offspring. It also states that
copies of genes separate each gamete receives
only one allele.

5. c. Law of Independent Assortment
The law of independent assortment
states that genes do not influence each
other with regard to the sorting of
alleles into gametes. It can be illustrated
by the dihybrid cross wherein two
different traits will be crossed.

6. d. Sex Linkage
Sex linkage is Non-Medelian pattern of inheritance.
Also, it is the phenotypic expression of an allele that
is dependent on the sex chromosomes of an
individual. Sex-linked genes are genes found either
on X or Y chromosomes which are inherited either a
male or female. If it is X-linked gene, the X
chromosomes takes control. It is the same with Y-
linked genes.

7. 3. Solve the following problems in
genetics:

8. a. Two dogs are mated. One of the parent dogs is
long-haired (recessive allele). The puppies which
result contains two short-haired and three long-
haired puppies. What does the second parent
look like, and what is its genotype?
hh- long-haired (recessive allele)

9. h h
H Hh Hh
h hh hh

10. b. Gerald and Julia both have widow’s peaks (dominant).
Their first child also has a widow’s peak, but their
second child doesn’t. Gerald accuses Julia of being
unfaithful to him. Is he necessarily justified? Why or
why not? Work the genetics problem predicting the
frequencies of the versions of this trait among their
prospective children.
In this situation, I think window’s peak is dominant.
It means it can appear even there is only one allele that
carries it. For me, Mr. Smith is not necessarly be justified
because if we are going to compute it there is a chance
that both of them are heterozygous. Then, there 25% that
there child may not have a widow’s peak.

11. 75% widow’s peak
25% not
W w
W WWWw
w Ww ww

12. a.c. If a pure-breeding (homozygous) black (dominant),
long-haired (recessive) cat is mated to a pure- breeding
Persian, short-haired cat, and one of their male offspring
is mated to one of their female offspring, what is the
chance of producing a Persian colored, short-haired
kitten?
Black (dominant) BB
Long hair (recessive) hh
Persian bb
Short hair (dominant) HH
pure-breeding (homozygous) black (dominant), long-
haired (recessive) cat – BBhh
pure- breeding Persian, short-haired cat - bbHH

13. BBhh x bbHH
F1 offspring- BbHh
BH Bh bH bh
BH BBHH BBHh BbHH BbHh
Bh BBHh BBhh BbHh Bbhh
bH BbHH BbhH bbHH BbhH
bh BbHh Bbhh bbHh bbhh
There is only
1% chance of
producing a
Persian colored,
short-haired
kitten.
Ratio of 1:16

14. d. Jinky is married to Manny, and they have four
children. Jinky has a straight nose (recessive) and is
able to roll her tongue (dominant). Manny is also
able to roll his tongue, but he has a convex
(Roman) nose (dominant). Of their four children,
Julia is just like her father, and Daniel is just like
his mother. The other children—Kathrine, who has
a convex nose, and Empoy, who has a straight
nose—are unable to roll their tongues. Please
answer the following questions about this family.

15. What are the genotypes of Jinky and
Manny?
Jinky has a straight nose (recessive) and
is able to roll her tongue (dominant)-
nnTT
Manny can roll his tongue, but he has a
convex (Roman) nose (dominant)-
NNTT

16. Jinky’s father was a straight-nosed roller, while her mother
was a convex-nosed non-roller. What can you figure out
about their genotypes?
Jinky’s father was a straight-
nosed roller- nnTT
her mother was a convex-nosed
non-roller- NNtt

17. nnTT x NNtt
nT, nT, nT, nT Nt, Nt, Nt, Nt
NT Nt nT nt
NT NNTT NNTt NnTT NnTt
Nt NNTt NNtt NnTt Nntt
nT NnTT NnTt nnTT nnTt
nt NnTt Nntt nnTt nntt

18. The possible
genotype
that can
occur can be
seen above
with ratio of
9:3:3:1.
convex-nosed roller 1 NNTT
2 NNTt
2 NnTT
4 NnTt
9
convex-nosed non-
roller
1 NNtt
1 Nntt
1 Nntt
3
Straight nose roller 2 nnTt
1 nnTT
3
Straight nose non-
roller
nntt 1

19. • Manny’s father was a straight-nosed roller,
while his mother was a convex-nosed roller.
What can you determine about their
genotypes?
Manny’s father was a straight-nosed
roller - nnTT
his mother was a convex-nosed roller-
NNTT

20. f1 generation- NnTT
NT NT nT nT
NT NNTT NNTT NnTT NnTT
NT NNTT NNTT NnTT NnTT
nT NnTT NnTT nnTT nnTT
nT NnTT NnTT nnTT nnTT

21. The possible genenotyope of their offspring maybe
the following above with 12:4 or 3:1 ratio.
convex-nosed
roller
4 NNTT
8 NnTT
straight-nosed
roller
4 nnTT

22. Diagram the three described generations of this family in accepted pedigree form, including the
phenotypes for these two traits.