Genetics and Phenotype Variations

This assignment delves into the fundamental concepts of genetics. It examines gene interactions through various crosses, illustrating principles like dominance, recessiveness, and genotypic ratios. The discussion extends to independent assortment, highlighting its role in genetic diversity. Finally, the assignment analyzes how DNA and RNA variations can lead to phenotypic differences, emphasizing the impact of mutations on protein synthesis.

Biology 1
Biology
Name:
Course:
Professors Name:
University:
City / (State):
Date:

Biology 2
1.1 In mice, white far is dominant, what type of offspring will you expect in a cross between
heterozygous individual and the one with grey far
The genotypic ration is 2wg:2gg
For white fur Wg 1/4*100=25%
For grey far gg 1/4*100=25%
The resulting Phenotype white mice and grey mice
W g g g
Wg
gg
Wg gg

Biology 3
b. Haemophilia is a genetic disorder where the faulty gene is located on the X
chromosome. A female carrier has children with a healthy male. Explain using punnet square the
probability of having healthy, carrier or affected children. Can they have an affected daughter?
Can they have an affected son? Explain the difference
Xh X
X XhX X X
Y Xh Y XY
The ratio is 1 Carrier: 2 healthy:1 hemophilic
Probability of getting carrier is 25 %
Probability of getting healthy children is 50%
Probability of getting hemophilic is 25 %
From the above results, one daughter will be a carrier, one boy will be hemophilic, and
one boy and a girl will be healthy. One boy will be hemophilic. Being a carrier does not affect
the health meaning that the affected children are the ones who inherited the disease, these are the
two boys with the genes Xh Y. If the mother is a carrier, the son will receive one of the
chromosomes with haemophilia. Also, one daughter will receive one X chromosome with
haemophilia. Since the father is healthy, the X and Y chromosomes inherited by the children will
not be affected in any case (Ohno, 2013). In this case, the two boys will have Xh Y and XY
chromosomes while the daughters will have XhX and XX chromosomes.
A baby will inherit the X chromosome from with a dominant gene for a normal blood
clotting for the father hence she will not have haemophilia. Because the daughter got a
hemophilic gene Xh from mother, she will be a carrier meaning that she will be healthy and the

Biology 4
disease will not affect her. For sons, they only need one Xh to be affected by the disease (Ohno,
2013). This is because haemophilia is X linked genes disorder. The normal daughter did not
receive any hemophilic gene hence is not affected.
The ratio is 1 Carrier: 2 healthy:1 hemophilic
Hybrids
C. Both my parents have brown eyes but I have blue eyes. Explain how this can be using punnet
square. The mother is expectant, what is the probability that she has another boy with blue eyes.
Parents should have been carriers of the disease for the children to get affected by the
disease. Children inherit two genes from parents, one from the mother and the other one from the
father. In case if one of the parents have a mutated gene, some children will still have brown eyes
since they inherit the gene for brown eyes (Anderse et al., 2013). On the other hand, the
recessive gene which is for blue eyes will not be seen in other children. In some other cases, both
parents can have both dominant and recessive genes. In this case, children will inherit both genes
resulting to blue and brown eyes. In this case, mother and father had Bb and Bb genes. All of
them had brown eyes. When a cross is done keeping in mind that the genes representing brown
eyes are BB while the genes representing blue eyes are bb, the following result came out. The
genotypes of the parents are Bb,Bb
XB Xb XB Xb
XB XXBB XXBb XXBB XXBb
Xb XXBb XXbb XXBb XXbb
YB XYBB XYBb XYBB XYBb

Biology 5
Yb XYBb XYbb XYBb XYbb
Male with blue eyes= 2
Male with brown eyes= 6
Female with blue eyes=2
Female with brown eyes=6
The probability that mother will have a boy with blue eyes is 2/16 *100%= 12.5%
d. Parents A who are dominant homozygous for both body colour and eye colour is crossed
with parent B having recessive homozygous for both body and colour traits BB
BK BK bk bk
BK BBKK BBKK BbKk BbKk
BK BBKK BBKK BbKk BbKk
Bk BbKk BbKk bkbk bkbk
Bk BbKk BbKk bkbk bkbk
Phenotypic ratio for f1 is 12 brown eye and black body: 4 red eye and brown body

Biology 6
BK BK Bb Kk bk bk
BK BBKK BBbK BKKk BbKk BbKk
BK BBKK BBbK BKKk BbbK BbbK
Bb BBbK BbBb BKbk Bbbk Bbbk
Kk BKKk BKbk KkKk bKkk bKkk
Bk BbKk Bbbk bKkk bbkk bbkk
Bk BbKk Bbbk bKkk bbkk bbkk
Genotypic ratio is 2 BBKK:3 BBbK:3BKKk :5 BbKk:2 BbbK:4 BbKk:4 bbkk :4 Bbbk:4 bKkk:1
KkKk:1 BKbk:1 BbBb : 1BBbK: BKKk
1.2) Independent assortment
This is a principle which describes the way different genes independently separate from
each other during the development of reproductive cells. However, Gene linkage is a process
whereby certain genes are linked to certain chromosomes, for instance, hemophilic gene is sex-
linked genes (Davis Raboskyet al., 2016)
1.3) how variations in DNA/RNA can cause variations in phenotype
During cell transcription and translation, the mutation occurs. In DNA, base mutations
and deletions occur. Base mutations are where a new strand can be added to the DNA sequence.
Deletion is where a strand is a DNA sequence is removed. All these processes alter the makeup
of the DNA. Even though there is correcting mechanisms for these added or lost genes, it cannot
be achieved 100 percent (Muenke et al., 2015). However, during translation for RNA, genes go

Biology 7
through the same process but there is no correcting mechanism leading to a permanent change in
gene make up.

Biology 8
Reference list
Andersen, J.D., Johansen, P., Harder, S., Christoffersen, S.R., Delgado, M.C., Henriksen, S.T.,
Nielsen, M.M., Sørensen, E., Ullum, H., Hansen, T. and Dahl, A.L., 2013. Genetic analyses of
the human eye colours using a novel objective method for eye colour classification. Forensic
Science International: Genetics, 7(5), pp.508-515.
Davis Rabosky, A.R., Cox, C.L. and Rabosky, D.L., 2016. Unlinked Mendelian inheritance of
red and black pigmentation in snakes: Implications for Batesian mimicry. Evolution, 70(4),
pp.944-953.
Muenke, M., Kruszka, P.S., Sable, C.A. and Belmont, J.W., 2015. Molecular Genetics,
Principles of Diagnosis and Treatment. issues, 6.
Ohno, S., 2013. Sex chromosomes and sex-linked genes (Vol. 1). Springer Science & Business
Media.