Introduction to DNA and Genetics Assignment

Genetics

INTRODUCTION
Genetics refers to study of heredity of characters and traits which has been transferred
from the parental generation to the upcoming progeny. It consist study of genes those are the
factors containing specific features which get transferred from ancestors to new generation
(Kumar, Stecher and Tamura, 2016). The present report is based on case of parents of unborn are
both carriers of sickle cell in order to explain possible results of the same.
TASK 1
1.1 Structure of DNA, genes and chromosomes
DNA stands for deoxyribonucleic acid having structure of building block of DNA that
are nucleotides which are made of three parts such as deoxyribose sugar, phosphate group and
nitrogenous base. However, four types of nitrogenous bases are found in DNA i.e. adenine,
guanine, cytosine and thymine.
Gene is known as unit of hereditary information which occupies fixed location in
chromosome and direct synthesis of proteins. Genes are made up of DNA which can be
transcribed into RNA from DNA.
Chromosome is thread like structure found in nuclei of both plants and animals. They are
composed of protein and one molecule of deoxyribonucleic acid.
1.2 Mechanism and important of DNA replication
DNA replication can be described as duplication of DNA by specific process including
number of steps. Initially, replication fork formation by separating double stranded DNA into
single strands by DNA helicase enzyme. However, primer i.e. short piece of RNA that binds to
starting point for replication and primers are created by DNA primase enzyme. Moreover, DNA
polymerase generate new strand by elongation and add Okazaki fragments of DNA. Process of
replication is discontinuous as newly created fragments are disjointed (Ammerman and Cavalli-
Sforza, 2014). Additionally, final stage is termination include nuclease which remove all RNA
primer from original strands and proofreads newly formed DNA to remove errors. Furthermore,
DNA ligase join Okazaki fragments to for single unified strand and telomerase catalyse telomere
sequences at the ends of DNA and then parent strands & its complimentary strands coils into
familiar double helix. Finally, replication produce two DNA molecules, each one consist one
parents strand and one new strand.

The DNA Replication is very important because without this cell division is not possible.
Without replication, each cell lacks adequate hereditary fabric to give instructions for creating
proteins vital for body purposes.
TASK 2
2.1 Events of mitosis and meiosis
Mitosis is a kind of cell division in which a cell divides into two new cells which are
genetically identical to each other. It consist process of several events such as prophase,
metaphase, anaphase and telophase and then cytokine-sis. Meiosis is process of cell division in
which it reduces chromosome number by half for developing haploid cells that are genetically
different from parent cell (Civelek and Lusis, 2014). It consist Meiosis I and Meiosis II in which
Meiosis I include Prophase I, metaphase I, anaphase I & telophase I and Meiosis II involves
Prophase II, metaphase II, anaphase II & telophase II.
2.2 Comparison between product of mitosis and meiosis
The product of mitosis include formation of two daughters cell which are genetically
identical to parents cell and have two set of chromosomes. In comparison to this, product of
meiosis only consist one set of chromosomes.
2.3 Significance of meiosis in the generating variation
Genetic variation are commonly raised by meiosis, when the fertilization occurs in that
one gamete is the mother and other from father fuse and form zygote because of independent
assortment & recombination in meiosis, every gamete has their different set of the DNA. This
results to produce a specific combination of the genes and forms a zygote. In case of variation
meosis plays major role it leads to construction of gametes which will be with half of numbers of
chromosomes in any somatic body cell. Two gametes undergo fusion and get fused with the
each other that result in formation of new individual. These 2 gametes comes from different
parents one from father and one from the mother that along with it carries characteristics from
those two different individuals so this is primary source for the variation. Process of the
independent assortment occurs when metaphase 1 in which chromosomes from both the parents
line up on the same equator independently that means a few from the each of the parent on one
side and opposite on other (Lewis, 2016). Gametes formed and it has combine chromosome
mixture from parents's parent this mixture is known as secondary source to get variation. And

this finally crossing over that occurs also in the metaphase 1 in that genetic material exchanged
between the two homologous chromosomes. Entire parental chromosome transfers to the one cell
but instead of this mixture the paternal and maternal in one chromosome goes to the one cell and
the other opposite mixture go to another so variation occurs in individuals.
Variation during meiosis is very important to carry genetic material one generation to
other with help of parental genome. Such type of events happen when process of crossing over in
phase of prophase 1 in the meiosis. In the homologous chromosomes the pair forms and then this
exchange information which is genetic which helps in variation. In meiosis there are certain
phases which occurs and pair up with the homologous chromosomes and that is why variations
occurs. Passing of these genes one generation to the next generation which is progeny generation
which is known as heredity. Recombination occurs when prophase 1 takes place in that the
chromosomes which are homologous and from the parents pair with each other. To carry genetic
information which is required to transfer to the next generation, meiosis plays major role to
transfer genetic material one generation to the other. As given in case both parents who are
sickle cell carriers, in this case there are chances that their offspring will be affected with this
condition. As during meiosis genetic material of parent transfer to next generation.
TASK 3
3.1 Mono-hybrid inheritance and co-dominance
Other organisms & humans display the number of various traits expression patterns and
inheritance. Several different inherited characteristics, transmission of pattern is a mono-hybrid
inheritance in that these traits are observed by the one pair of alleles on the same locus. Knowing
and understanding mono-hybrid inheritance is difficult to understand genetics of different
medically traits in case of human beings (Sawcer, Franklin and Ban, 2014). Traits are transferred
to the families in various patterns, inheritance pattern of characteristics are considered dominant
thus it can observed in every generation. Each person who carries genetic code for characteristic
will show the proof of characteristic. There are various forms of genes which are called alleles,
these forms of genes are those which forms variations among humans. There are mainly two
types of allele they are recessive and dominant. For example gene which involves to form colour
of eye which is brown. Dominant colour is brown thus it will be represented by 'B' and blue is

recessive so it will be represented by 'b'. if mother has brown eyes and father has blue eyes there
are chances that their baby will get 50% brown eyes.
Co-dominance is nearly associated to the incomplete dominance, in that both alleles are
get expressed together in heterogygote (Renton, Chiò and Traynor, 2014. Number of the single
genes are known in human has their own role. Understanding of principles of monohybrid
inheritance and genetics provides large appreciation of things which are taking place in this
world. This field diseases which are genetic that gives idea of mono-hybrid inheritance provides
more personal application. One gene related disorders commonly comes under the autosomal
recessive, sex linked recessive, sex-linked dominant and autosomal dominant. Family history
allows the geneticists to determined that which inheritance mode is present for particular
disorder. Co-dominance is very peculiar term for the system in that allele from the every single
homozygote parent fuse together in the progeny and the future progeny together shows both
phenotypes. As given in case sickle-cell is inherited diseases which can transfer one generation
to the next with genetic material. According to mono hybrid it plays major role to express any
character from one generation to other. If parents are sickle-cell carrier there are 50% chances
that it will carry in offspring. The next offspring will be with sickle-cell, it can be explained with
the help of mono hybrid inheritance.
3.2 Multiple alleles role in inheritance of ABO blood groups
Multiple alleles are kind of non- Mendelian inheritance pattern that include alleles which
are more than two and normally codes for a specific character in humans. Multiple alleles gives
the meaning that there are alleles presents which are more than two in numbers and these are
with different and more than two phenotypes which are depend on recessive or dominant alleles
which are present in dominance pattern and trait person alleles follow when it combined with
each other. Mostly multiple alleles are for the attribute, mix types of pattern concurs which will
be dominance pattern. At times, ones of alleles are complete recessive to other & this will be
covered by allele that dominant to this. Alleles may be co-dominant with each other, can also
demonstrate traits equality in that phenotype of that specific person. In some cases the certain
alleles shows the total incomplete dominance during that particular time in which these set along
with each other in a genotype. Any person who is with such kind of the inheritance associated to
multiple alleles which can show the mixed phenotype and combine these both traits of alleles
with each other.

ABO blood type in humans is best example which can be given for multiple allele. Every
human contains RBCs which are type A, B or O(Libbrecht and Noble, 2015). The different 3
alleles fuse in the various ways followed the Mendel's Law of Inheritance. The outcome
genotype form either with type AB, A, B or O blood. The type A blood is formed by the
combination of two alleles these can be one one A and other one O, similar in type O blood, this
it combines with two recessive alleles that is O obtains type O and then type B blood forms by
combination of O or B allele. Followed by this the type AB blood is one of the examples for co-
dominance. Allele B and A are equal in the expressed and dominance accordingly. According to
the case multiple alleles are best example which can be shown with the help of inheritance of
ABO blood group. Blood group alleles combine and forms blood group in fetus. If the child's
parents are carrier of sickle-cell it may transfer to the offspring and the child can has risk of
sickle-cell anaemia.
3.3 Inheritance of sex chromosomes and sex linked characteristics
In case of humans, the biological sex is ascertained by pair of sex chromosomes that is
XY in males and XX in females. Genes present on X chromosomes are known as X- linked,
these have distinctive inheritance pattern due to presence in various numbers in males and
females. X- linked genetic disorder in human are more common in the males compare to females
because of X-linked inheritance pattern. Every human has two sex chromosomes Y and X, there
are 44 autosomes and Y and X do not carry same type of gene so are not homologous. Instead of
X and Y, human female has X chromosomes, these forms bona fide homologous pair. Because
the sex chromosomes do not involve in the homologous pairs the genes which they carry are
distinct and have unique pattern of the inheritance (Flint and Kendler, 2014). Chromosome in
human which are X and Y are important to decide the biological sex of any individual. It is due
to the gene which is called SRY, located on the chromosome Y and that encodes protein which
twist on the another gene needed for the development of any male.
Cell of human body consists forty six and 22 are homologous pairs and referred as
autosomes and the remaining two are sex chromosomes. There are some disorders which are
mainly sex chromosomes linked for example red green colour blindness. Commonly colour
blindness obtains in male child born to carrier female and normal male. Some traits are transfer
on sex chromosomes Y and X. several traits are carried on only x chromosome and some on Y.
sex linked traits considered traits such as colour-blindness and sickle cell anaemia. This is known

as linked due to the many male develops the traits compare to females because female has 2nd X
gene to the counteract recessive trait. Thus these traits are much seen in case of males. Traits
which are sex influenced are autosomal which can be influenced by the sex. In case of male, it
has one recessive allele then person can exhibit the trait by that they will contain two recessive in
case of the females.
CONCLUSION
This assignment is concluded as genetic material of parents plays a major role in next
generation. Transfer of genes can occur with the help of meiosis. DNA replication is major event
that helps to carry genome from one generation the other. Mono hybrid inheritance are important
for dominance the dominant character always appears in the next generation. The best example
for multiple allele is ABO blood groups this is why humans has different blood groups.

REFERENCES
Books and Journals
Kumar, S., Stecher, G. and Tamura, K., 2016. MEGA7: molecular evolutionary genetics analysis
version 7.0 for bigger datasets. Molecular biology and evolution. 33(7). pp.1870-1874.
Ammerman, A. J. and Cavalli-Sforza, L. L., 2014. The Neolithic transition and the genetics of
populations in Europe (Vol. 836). Princeton University Press.
Lewis, R., 2016. Human genetics: the basics. Garland Science.
Renton, A. E., Chiò, A. and Traynor, B. J., 2014. State of play in amyotrophic lateral sclerosis
genetics. Nature neuroscience. 17(1). p.17.
Libbrecht, M. W. and Noble, W. S., 2015. Machine learning applications in genetics and
genomics. Nature Reviews Genetics. 16(6). p.321.
Flint, J. and Kendler, K. S., 2014. The genetics of major depression. Neuron. 81(3). pp.484-503.
Sawcer, S., Franklin, R. J. and Ban, M., 2014. Multiple sclerosis genetics. The Lancet
Neurology. 13(7). pp.700-709.
Civelek, M. and Lusis, A. J., 2014. Systems genetics approaches to understand complex traits.
Nature Reviews Genetics. 15(1). p.34.