Molecular Genetics: Genetic Inheritance Analysis of D. Melanogaster

This report delves into the genetic inheritance of mutant characteristics, specifically cross-veinless wings (CV) and yellow body (Ye) in Drosophila melanogaster. It examines reciprocal crosses between mutant and wild-type strains to determine if alleles are sex-linked and to assess their dominance. The report includes Punnett square analyses, simulation data, and statistical tests to evaluate the significance of observed phenotypic ratios. Recombination frequencies are calculated to construct a linkage map of the genes involved. Furthermore, the report discusses the broader implications of understanding mutant characteristics, referencing their relevance to cancer research and the study of genetic inheritance patterns. The appendices provide supplementary simulation data and visual representations of the crosses performed. This document is available on Desklib, a platform offering AI-based study tools and a wealth of academic resources for students.

Running head: MOLECULAR GENETICS
Topic: MOLECULAR GENETICS
Name of the Student:
Name of the University:
Author Note:

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Answer 1:
a) Cross between mutant females with the wild type males
X+ Y Xm Xm
X+Xm X+Xm XmY XmY
Ratio: 1:1
It can be seen that that there is a ratio of 1:1 in the following cross between the mutant
females along with the wild type males. Half of the progeny in the F1 generation are mutant.
Half of the population are carriers for the following trait.
b) Cross between the mutant males and wild type females
X+ Y Xm Xm
X+Xm X+Xm XmY XmY
Ratio: 1
In the following cross between the mutant males and the wild type females there is
distribution of the mutant alleles. However all the progenies are normal and the females are
Xm Xm
X+ X+Xm X+Xm
Y XmY XmY
X+ X+
Xm X+Xm X+Xm
Y X+Y X+Y

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heterozygous with the mutant allele. That mean half of the population, the females have one
wild type allele and the other allele is mutant (Burgess & Thomsom, 2016).
c) Reciprocal cross between the two traits
+ +
m +m +m
m +m +m
Ratio:1
The reciprocal cross between the wild type along with the mutant alleles yields the
same genotype for the samples.
For the consideration of the dominant and recessive traits, the first cross should be
appropriate. The main characteristic of a sex linked allele is that it would be either expressed
in both the crosses or it would be absent. The mutant allele is dominant as the expression of
the alleles leads to the mutant phenotypes. Moreover it is present in one of the parents. Since
the cross between one mutant allele and one normal allele is not included, it cannot be
determined whether the allele is completely dominant. In X linked traits, males are usually
affected more than the females. This is a sex linked because as evident from the crosses, in
case of alleles the males from the crosses have the phenotypes of their mothers who are
homozygous and this is the fact for sex-linked alleles (Edwards, 2016).
Answer 2:
The cross between wild type female and mutant male with eye color sepia has been provided
in the Appendix 1 section.

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The genes are X linked as the alleles which are mutant are passed to the males of the F1
generation from those expressed by the mothers. Moreover, the genes are dominant as the
alleles are present in both the sexes and they are expressed phenotypically. However the
mutant types are not mentioned clearly and there are 0 flies with the mutant type (Farh et al.,
2015).
The cross between Wile type male and a mutant female with eye color sepia has been
presented in the Appendix 2 section.
Answer 3:
Here the two characteristics considered are cross veinless (CV) and Yellow body (Y)
For the cross
Wild type female Mutated male
Phenotype +++ CV, Y
Genotype +++ CVCV, YY
For the cross vein less characteristic
X+ X+
XCV X+XCV X+XCV
Y X+Y X+Y
Genotypic ratio: 1:1
Phenotypic ratio: 1

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For the yellow body characteristic
X+ X+
XY X+XY X+XY
Y X+Y X+Y
Genotypic ratio: 1:1
Phenotypic ratio: 1
+ +
CV CV+ CV+
Y Y+ Y+
Expected ratio: 1
Thus among the Punett square between the cross vein less and the yellow characteristic with
the wild type, it can be seen both are expressed but the wild type can be dominant if there are
no mutant progenies in the F1 generation. In both the crosses it can be seen that there is no
expression of the mutant alleles genotypically and phenotypically. Thus the wild types are
dominant (Hernendez et al., 2016). Simulation has been presented in the Appendix 3 section.
Answer 4:
Test cross between the fly’s scalloped (recessive allele) and ebony (recessive allele) and the
wild type and ebony where the scalloped and ebony characteristics have been taken and the
simulation has been presented in the Appendix 4 section below. Statistics of the average
distribution of the fly population with the scalloped and the wild type characteristics. The
significance value is less than 0.05 suggesting a difference between the characteristics. This

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means the alleles are dependent and the thus the wild type is dominant. Moreover further
association between the two characteristics cane be established through the linkage map
(Begerman et al., 2015).
Fig 7: The chi distribution table for the above statistics regarding the significance of the
phenotypes expressed by the dominant and the recessive alleles.
Answer 5:
Recombination frequency = Recombination /Total offspring *100
WT and F recombination frequency = 314+111/ (344+111+21+21+40+41+130+290) =
425/968 = 43%
YE and F= 43.38%
CV and F = 4.33%
Cv and Ye = 11.60%

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WT F Ye CV
This is the observed and the estimated linkage map of the given genes as shown by genetic
mapping.
Answer 6:
Detection of mutant characteristics has been important for the exploration of various
cancers among women. The mutant properties of the p53 gene have been important for the
process of metastasis. According to the studies by Golan, there has been an apparent
autosomal dominant pattern for the genetic transmission. The inheritance of the traits
controlled by genetic combinations and the alleles. Hereditary mutations has been inherited
through the parent and they are usually present virtually in the cells. Thus the mutations
inclusive of the germ line mutation s have been present in the cells of the parent. Earlier
studies have been on the role of mutation in genetics. However Mendel’s law of inheritance
do not encompass the factors affecting inheritance.

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References
Begemann, M., Zirn, B., Santen, G., Wirthgen, E., Soellner, L., Büttel, H. M., ... &
Eggermann, T. (2015). Paternally inherited IGF2 mutation and growth
restriction. New England journal of medicine, 373(4), 349-356.
Burgess, S., & Thompson, S. G. (2015). Mendelian randomization: methods for using
genetic variants in causal estimation. Chapman and Hall/CRC.
Edwards, A. W. F. (2016). Punnett's square: A postscript. Studies in History and Philosophy
of Science Part C: Studies in History and Philosophy of Biological and Biomedical
Sciences, 57, 69-70.
Farh, K. K. H., Marson, A., Zhu, J., Kleinewietfeld, M., Housley, W. J., Beik, S., ... & Hatan,
M. (2015). Genetic and epigenetic fine mapping of causal autoimmune disease
variants. Nature, 518(7539), 337.
Hernandez, D. G., Reed, X., & Singleton, A. B. (2016). Genetics in Parkinson disease:
Mendelian versus non‐Mendelian inheritance. Journal of neurochemistry, 139, 59-74.

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Appendix
Appendix 1:

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Appendix 2:

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Appendix 3:

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Appendix 4: