Mitosis and Meiosis: Significance and Description

This academic report discusses the significance and description of mitosis and meiosis, including their stages and differences. It also covers the main sources of variation, such as crossing over and gene and chromosome mutations. Additionally, it explores the impact of Gregor Mendel on our understanding of genetics and his experiments on Pisum sativum.

Academic report

Table of Contents
MAIN BODY ..................................................................................................................................1
CONCLUSION .............................................................................................................................11
REFERENCES .............................................................................................................................13

MAIN BODY
Question 11.1: Give a description of mitosis and meiosis and discuss their significance.
Answer: All life on the planet starts and progress via a series of cellular phenomena. Cell
division is necessary to the growth, transformation and development. It is the generally
responsible to the growth of a living organism via the formation of the new cells or the
replacement of damaged, worn-out and old cells. Cell division is the constant procedure, that
continuously repeats in whole of the life cycle of living being. Renewal and cell division are the
buildings blocks of life at the end of this process, organism is inevitable to death. There two
process of cell division one is known as sexual process which is also called meiosis and another
is known as asexual process which is also called as mitosis (Ahluwalia, 2018).
 MITOSIS
In the mitosis process, nucleus of the living cell replicates and divides the original DNA
of the cells. It is the cell division process to replicate, differentiate and growth. It makes two
diploid daughter cells which are genetically similar as the parent. Mitosis is a six stage process
which are given below:
 Interphase: It occur before initiations of cell division. DNA replicates. Centrosomes or
centrioles appear. Organelles, ATP and proteins formed. It is not part of mitosis, it is only
the preparation for the mitosis.
 Prophase: in this phase, centrioles move to opposite sides of the cell. In nucleus,
appearance of chromosome occurs. Nuclear envelop disappear and DNA condensed and
visible to microscope. Centrioles attach to chromosomes.
 Metaphase: in this stage, spindles attach to the chromosomes and pull them to the centre
of the cell. Chromosome line up across the cell's equator (Berger, 2022).
 Anaphase: in this phase, chromosome split into two chromatid and migrate towards the
opposite poles of the cell and by microtubules it pulled towards centrosomes.
 Telophase: in this stage nuclear envelop initiate to regenerate around chromatids.
Chromatids unwind. Spindles starts break down and cell surface membrane initiate to
split from middle. Each half of the cell have similar DNA and single centrosome of
original cells.
 Cytokinesis: in this stage, four process occur that is, initiation, contraction, membrane
insertion and completion (Francomano, 2021).
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 MEOSIS
In this process of the sexual reproduction, there are two parents which give rise to an young one
with a specific combination of gene which are not similar to any parents but combine their DNA.
In this process somatic cells have two set of chromosomes that is, one set through each parent.
Meiosis produce four haploid cells which occurs through two stages that are meiosis 1 and
meiosis 2 .
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Illustration
1: Stages of mitosis
Source: https://www.sciencefacts.net/mitosis.html

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Illustration 2: Meiosis 1 & 2
source : https://biologydictionary.net/meiosis/

Meiosis 1:
 Prophase I: similar to mitosis prophase.
 Metaphase I : in this stage, homologues chromosome line-up on metaphase plate. Alleles
are separated.
 Anaphase I: chromosome pulled towards centrioles at each side of cell.
 Telophase I: new nuclear envelop develop plasma membrane separated.
Meiosis 2:
 Prophase II: resembles to prophase I. Nuclear envelop disappear and centrioles are
formed.
 metaphase II:chromosomes line up with centrosomes.
 Anaphase II: sister chromatid separate. Final division of DNA
 Telophase II:cytokinesis occurs (Lewis, and et. al., 2018).
Significance of mitosis and meiosis
SIGNIFICANCE
MITOSIS MEIOSIS
 Asexual process
 genetically similar
 production of diploid
cells.
 It is very crucial for
cell repair process.
 Vital for growth of
multicellular organism.
 It allow organism to
continue reproduce in
whole life
 Sexual process
 genetically different
 crossing over occur
 chromosomes comes
from the mother and
father.
 Random assortment of
maternal and paternal
gametes .
Question 21.1: Describe the impact of one geneticist on our understanding of genetics.
Answer: The basic or fundamental principle of heredity was discover by the Gregor Mendel.
Gregor Mendel discovered the basic principle of heredity in his monastic garden by the
experiments on Pisum sativum plants. Observations of Mendel became the basic of the study of
heredity and modern genetics. Gregor Mendel is also considered as the 'father of modern
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genetics'. In the 19th century people thinks that, traits were passed from the parent to the young
ones as mixtures of the characteristics of both parent. In that century concept of gene and
heredity was poorly developed. Mendel's experiments on pea plants were the first to concentrate
on the numerical relationships among all the traits seen in the offspring (Nikolova, Yordzhev,
and Peneva, 2022). According to the Mendel heredity undergo independent assortment and
segregation. Due to several reason Mendel select Pisum sativum:
 They grow too quickly
 They are easy to grow
 all the traits exists in two different forms
 Pisum have too much traits which are easy to observe.
Therefore, Mendel have observed and selected seven key traits in the Pisum sativum. That are
easily identified in one of two forms:
 Flower position - terminal or axial
 Flower colour - purple or white
 Stem length – short or long
 Seed colour – green or yellow
 Seed shape – wrinkled or round
 Pod colour – yellow or green
 Pod shape – constricted or inflated
Mendel performs the experiment on all these characters and and kept all the detailed of his
experiments and after completion of experiments find some results like in F1 generation all
offspring are similar to parents but in F2 generation they becomes different in ratio 3:1. thus,
this experiment of Mendel disproved the generally held belief that the young one would have a
“blend” of the parent traits. After the F2 generation evaluation, Mendel give the concept of
Inheritance (Panoutsopoulou, and Wheeler, 2018).
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Illustration 3: Cross pollination outcomes
Source: https://www.sciencedirect.com/topics/biochemistry-genetics-and-
molecular-biology/monohybrid-cross

Question 21.2: Demonstrate an understanding of monohybrid and dihybrid crosses including sex
links.
Answer: In the human males are heterogametic whereas female are homogametic. which means
males have two different sex gamete which are denoted by X and Y where as females have
similar sex gamete that are represented by X. As per this, all of the eggs carry X chromosome
where as only 50% of male sperm carry X chromosome and 50 % carry Y chromosomes. Which
means in human sex of the young one was decided by the male gamete (Song, and et. al., 2019).
Definition
Monohybrid cross Dihybrid cross
 The term monohybrid
is composed of mono
means one and hybrid
means made up of
different elements. So,
it is inheritance of
 The term Dihybrid
means two, therefore,
in the dihybrid crosses
two unrelated
characteristic's
inheritance are
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Illustration 4: inheritance of
humangametes
Source:
https://www.nature.com/scita
ble/topicpage/the-sex-of-
offspring-is-determined-by-
6524953/

single gene. examined.
cross  Monohybrid cross
occur between two
pure organism in
regard to study the
inheritance of one pair
of contrasting
characters.
 Dihybrid cross is occur
between two pure
organism in regard to
analyse the inheritance
of two pairs different
characters
Phenotypic ratio in F2
generation
 In monohybrid cross, it
commonly produces a
genotypic ratio which
is of 3:1 in the F2
generation of young
ones.
 In dihybrid cross, it
commonly produces a
genotypic ratio which
is of 9:3:3:1 in the F2
generation of young
ones.
Genotypic ratio in F2
generation
 In monohybrid cross it
generally produces a
genotypic ratio which
is of 1:2:1 in the F2
generation of offspring.
 In dihybrid cross it
generally produces a
genotypic ratio which
is of 1:2:1:2:4:2:1:2:1
in the F2 generation of
offspring.
Example  Example of
monohybrid cross
pollination is cross
between tall and dwarf
Pisum sativum plants.
 Example of dihybrid
cross pollination is
cross of Pisum sativum
plants having wrinkled
seeds and green and
round and yellow
seeds.
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Diagram
Question 21.3: Describe the main sources of variation, including crossing over and gene and
chromosome mutations.
Answer: Genetic variations is define as the difference in sequences of the DNA between
individuals within a population. Generally variation occurs in the germ cells means egg and
sperm and also in some somatic cells. There are several source of variation in which crossing
over and chromosome and gene mutations (Sussmilch, Ross, and Reid, 2022).
Crossing over Gene mutation Chromosome mutation
 It is defined as the
exchange of the DNA
between a paired
similar chromosomes
which occurs during
the growth of sperm
cells and egg cells. It
occur during the
pachytene stage of
 Gene mutation is the
permanent modification
in the sequence of DNA
which makes up a gene.
 Majorly it occur as
sequence differs.
 Gene mutation can
occur via two principle
ways that is :
 Chromosomal
mutation is the
modification of
chromosome which
can not be predicted.
 These mutation occur
due to the issue in
meiosis or by agent
like radiation ,
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Illustration 5: monohybrid
cross
com/2013/11/difference-
monohybrid-and-dihybrid.html
Illustration 6: Dihybrid cross
https://www.nagwa.com/en/ex
plainers/548187241602/

meiosis process
(Twyman, and Wisden,
2018).
 In the male gamete
there are two types of
chromosome found.
one is X chromosome
and Other one is Y
chromosome but both
of the chromosome are
not equal in size . The
size of X chromosome
is longer as compare to
Y chromosomes.
 All other chromosome
present in except sex
chromosome are
known as Autosome.
 During pachytene stage
of meiosis process,
there are exchange of
genetic material which
is known as crossing
over.
 Which means genetic
information of two
offspring will be
unique due to this stage
of meiosis.
 Figure 6- of crossing
over mention below.
◦ Hereditary
mutations
◦ Acquired or somatic
mutations
 There are various types
of gene mutation:
◦ Hereditary or
somatic
◦ Polymorphism
◦ Mosaicism
◦ Spontaneous nature
chemical etc.
 it can change in
number of
chromosome or cell
structure.
 Breakage or
duplication is
responsible to these
mutation.
 Mainly five types of
chromosome mutation
occur:
◦ Translocation
◦ Deletion
◦ Duplication
◦ Inversion
◦ Isochromosome.
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 In crossing over, before
the split process of cell,
the similar pairs are
separate and divided
into two daughter cell
equally. This process is
known as segregation
which creates a huge
amount of variation.
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CONCLUSION
As per the above discussion, it has been concluded that meiosis and mitosis are the two
ways of cell division. Through which a new cell has been produced by sexual or asexual process.
As per this portfolio, it has also been concluded that Gregor Mendel play a vital role in the field
of genetics. They perform a lot of experiments on the Pisum sativum and give independent
assortment and segregation process. Finally, in this portfolio crossing over, chromosome
mutation and gene mutation has been discussed
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Illustration 7: Crossing over
over.html

REFERENCES
Books and Journals
Ahluwalia, K.B., 2018. Genetics. New Age International.
Berger, F., 2022. Which field of research would Gregor Mendel choose in the 21st century?. The
Plant Cell, 34(7), pp.2462-2465.
Francomano, C.A., 2021. Victor Almon McKusick: In the footsteps of Mendel and
Osler. American Journal of Medical Genetics Part A, 185(11), pp.3193-3201.
Lewis, C., Lennon, A.M., Eudoxie, G. and Umaharan, P., 2018. Genetic variation in
bioaccumulation and partitioning of cadmium in Theobroma cacao L. Science of the Total
Environment, 640, pp.696-703.
Nikolova, I., Yordzhev, K. and Peneva, I., 2022. On some stochastic applications to real world
problems. Asian-European Journal of Mathematics.
Panoutsopoulou, K. and Wheeler, E., 2018. Key concepts in genetic epidemiology. Genetic
Epidemiology, pp.7-24.
Song, C., Li, W., Pei, X., Liu, Y., Ren, Z., He, K., Zhang, F., Sun, K., Zhou, X., Ma, X. and
Yang, D., 2019. Dissection of the genetic variation and candidate genes of lint percentage
by a genome-wide association study in upland cotton. Theoretical and Applied
Genetics, 132(7), pp.1991-2002.
Sussmilch, F.C., Ross, J.J. and Reid, J.B., 2022. Mendel: from Genes to Genome. Plant
Physiology.
Twyman, R.M. and Wisden, W., 2018. Biological Heredity and Variation. In Advance Molecular
Biology (pp. 1-18). Garland Science.
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