BIOM 503 – HUMAN GENETICS
Introduction
Genetics is the branches of science that deals in genes and heritable characters; the
variation of the same offsprings; the variation of the same animals from the parent animal; the
variation of the same plants from the parent plants. It assists people to have an idea of how
characteristics are inherited in offspring and all that they need to know about the genes that are
involved in the process of growth and development of living organisms and how these organisms
are able to respond to various genetic and environmental stimulus.
Importance of Studying Human Genetics
The following reasons show the importance of studying human genetics:
1. Understanding Heredity: Human genetics gives explanations as to how certain
characters pass from the parents to the children and their generations. Detailed
information about such inheritance traits is important because through tracking the
patterns scientists are able to establish the genes linked to certain characteristics and even
certain illnesses.
2. Disease Prevention and Treatment: Mutations are associated with several diseases and
their genetic determination is crucial in preventing the diseases and finding cures for
them. Screening of the genetic blueprint assists in defining predispositions to definite
diseases, with targets for an individualized treatment most appropriate to address the
condition.
3. Advancing Medicine: There is he Human genetics research has brought about major
strides in the world of medicine and has made it possible to come up with well-targeted
therapies as well as personalized medicine. In this way, the scientist insinuates that doing
additional study about the genetic factors of disease can contribute to the creation of more
efficient drugs and methodologies of treating a disease, all depending on the genetics of
the individual.
4. Population Health and Public Policy: It is noble to emphasize that knowledge on
human genetics is essential while dealing with the prevention and control measures in the
public health and the formulation of policies. Understanding how genetic variation comes
about in a population is useful in combating diseases, determining where to invest in
health and which expensive gene related health services and products to provide for the
population..
5. Ethical Considerations: For the last few years the issues of the body genetic discovery,
genetic privacy, genetic discrimination, and gene editing technologies have turned into
more successful since they come to the for front of human discoveries. Scientific
techniques such as genetic profiling of human characteristics allow those individuals to
make the appropriate ethical choice with regard to these issues.
Basics of Genetics
Genes and DNA:Genes are part of DNA that dictate the blueprint for constructing the body and
its functions properly. Organic molecule or macromolecule which is composed of two long
chains of nucleotides coiled around each other in the form of a double helix and is the carrier of
genetic information or hereditary process. This helical structure is held together by sequences of
four nucleotides: Among these, the four letters or bases common in DNA are, adenine (A),
thymine (T), cytosine (C), and guanine (G). These nucleotides pair specifically; adeninest with
thymine and cytosine with guanine; they combine to form the rungs of the twisted ladder. The
sequence of these nucleotide pairs are distinct in a specific manner which composes the genetic
code – the blueprint of all forms and structure of life, beginning from bacteria to human – for the
production of proteins and life’s other processes.
Chromosomes: These are small long structure which has some portion of the hereditary
information of all forms of life including human beings, human have 23 pairs of this structure in
total there are 46 chromosomes in a human body. These are in the pairs, and therefore in each
pair there is Chromosome from the mother and other from the father, in aggregate, 23 from each.
This assessment also ensures that human is given all the DNA segment that maybe needed for
build up, growth, healthy physiological system in the body or any genetic code for other
attributes such as perceived traits as may be deemed necessary
Patterns of inheritance:
Mendelian inheritance: This deals with the chance of transmission of characters from one
generation to the next through the principle of dominance and recessiveness, as discovered by
the Austrian geneticist Gregory Johann Mendel in 19th century. This, however, contradicts
Mendel’s law of Dominance as it pointed out that dominant genes are only needed in one copy
for an organism to display the phenotype of the trait. This implies that if a person gets the
dominant allele from only one parent, the required gene trait will develop. For instance, if the
gene for brown eyes is dominant then a chromosome with a sequence of brown eye allele and the
other sequence containing blue eye allele will result in the brown eyed person. On the other,
recessive characteristics demand two dominant alleles, one sent by each rundown guardian, with
the intention that it would be knowledgeable about. A person who has only one recessive gene in
his body will be called a carrier and cannot exhibit the associated recessive characteristic but will
be able to pass the gene to his/her offspring. The simplest example is the genes responsible for
blue eye color: blue eye color is a recessive trait; thus, to develop blue eyes, a child has to inherit
two blue-eye alleles from the father and mother. These inheritance patterns constitute the
fundamentals of classical genetics, and they assist in showing how certain qualities or even
genetic disorders are inherited within families.
Complex Inheritance: Patterned inheritance can be described as multiple influences by a
number of genes and rights inherited through the dominant or the recessive gene systems which
are known to bring complex features. Nonetheless, polygenic is the direct opposite of Mendelian
traits inherited from a single gene rather than one that is affected by the cumulative influence of
its multiple genes. These genes give a small measure to the total makeup of the phenotypes of
any given living item or organism. For example, some of those genes are simply involved in
determining fairly straightforward characteristics like the ability to roll one’s tongue or the extent
of hair curliness, while others are behind more complex inherent qualities such as height, skin
color, and intelligence, which depend on several genes at the same time.
Genetic variation
Mutations: These are changes that take place in the DNA sequence of a particular organism
which might help in the creation of new genes or can also contribute towards the occurrences of
various diseases and disorders. These changes are can be a point mutation, this is a change in
one nucleotide, or chromosomal which may be changes along segments of a chromosome.
Youths bring variation through mutations they carry in their genes; therefore, nobody has similar
genetic makeup as any other individual in the community. It may be bipolar, in the sense that
they may be transmitted from both parents, and they consist of germ cells – sperm and ova – and
are transmitted from generation to generation. They can also exist as genetic mutations –
inherited, germ cells, or somatic, when they develop in an organism at some certain point during
its growth due to certain stimuli, or errors that occur in the replication or mitosis processes.
Genetic mutations are classified as inherited or acquired mutations, inherited mutations are
present at birth while there are possibilities of them being inherited to the next generation. Such
mutation leads to he inherited genetic diseases for instance, cystic fibrosis or Huntington’s
disease depending on whether it is a point mutation or a frame mutations affecting single genes
or multi genes respectively. Although mutations can result from actions of specific agents which
increases the likelihood of such a change in an organism, they can also result from somatic cell
change at some point in an individual’s life. However, when mutations take place in somatic
cells then the defects may progress turns to juts like diseases, cancer inclusive.
Genetic disorders: This is a disease that is brought about by the dysfunctions of the
DNA of a person. These may include somatic gene mutation diseases where a single gene
mutation leads to disease for example: It is known that cystic fibrosis is genetically inherited;
this means it is as a result of a mutation in a single gene.
A single gene could cause disease for example in Huntington disease due to mutation of
single gene the disease occurs. There are some which are monogenic illness that are transmitted
from one generation to the other for example the sickle cell anemia or the Cystic fibrocosa and
others are Polygenic illness that is, have genetic and environment al imbalance like the
cardiovascular or diabetes. Some of the common congenital diseases that result from alterations
in chromosomal complexity include Down’s syndrome, which results from chromosomal
abnormalities. These diseases, of course, are not just one or two but many and each is unique in
terms of modes of genetic prevalence and its impact on the individual and families. In general,
individuals who are at risk of developing a certain disease, or those individuals who carried a
particular genetic disorder must seek the services of an expert physician in a bid to establish their
future prospects.
Research shows that there has been a massive advancement in human genetics and its
impacts have revolutionized the thought and application of genetics. The availability of the full
set of nucleotides of human DNA was the accomplishment that became possible after the
creation of the Human Genome Project in 2003. Since then, beginning with the improvements
that have been made specifically to DNA barcodes technologies, next-generation sequencing has
enabled the large-scale sequencing initiatives that are designed to find the genetic chips that are
linked to diseases and other characteristics. Some of these developments include the CRISPR-
Cas9 which has significantly advancing the kind of gene editing that is defined by changes of
some specific sequences in the DNA which could help in the fight against genetic disease.
Talking about complex traits and diseases, GWAS that involve scanning of SNPs across the
whole genome have presented discoveries on several genetic locations of interest which have
enhanced our understanding of the genetic factor in these disorders.
2. Historical Overview of Human Genetics
Early Understanding of Heredity
Heredity has roots that dates back even before the pagan ages of learning and as early as
Egyptian civilization they observed variation in the characteristics of plants and animals from
one generation to another. Some of the pre Socratic age of the early SOCration of the ancient
Greeks include Aristotle who also had some opinion to offer in the topic of heredity where he
noted that the children of an organism get the traits of their parents from the mixing of fluid at
their generation. This speculation however is very much of the early investment of the
investigation under examination While there was progression in this respect by the later part of
the eighteenth century, significant penetration towards formulating a much more scientific
approach towards the generation of an understanding of heredity only comes with the nineteenth
century.
Mendel's Experiments and the Laws of Inheritance
Genetics can be described as the science that studies the transmission of characteristics, or
traits, from parents to offspring. In the middle of the nineteenth century, a scientist named
Gregor Mendel, who was an Augustinian monk, conducted experiments on pea plants which to
this today, hold the groundwork for genes. Mendel evolved unique approaches, in which he
mated two pea plants who had different features, namely color and shape of the flowers and
seeds, and attempted to observe the law of transmission in the offspring. Through his
experiments, Mendel formulated the principles of inheritance, which are now known as Mendel's
laws: Mendel conducted some experiments on the inheritance and explained the laws related to
the inheritance which are called as Mendel Laws.
Law of Segregation: In particular, in the formation of gametes, alleles differ from each other
in such a way that only one of the alleles will become involved in a particular gamete.
Law of Independent Assortment: For two traits, if the alleles of one trait are located on one
set of chromosome and those of the other trait are located on the other set of chromosomes, then
such traits are said to be inherited independently of each other.
These laws did not receive any attention from the scientific fraternity as a whole when
Mendel was still alive, and it was only around the beginning of the twentieth century they were
again reviewed and became the corner stone of new fundamentals forming the subject of
genetics.
Development of Modern Genetics in the 20th Century
The 20th century as a whole can be considered the epoch-making period in the genetics
field due to remarkable discoveries and advancements in technology that are crucial for modern
genres researches. In this process the Chromosomal Theory of Inheritance was formally
proposed and later supported. Plekhnoff and other early geneticists realized that certain genes are
activated during certain times in a specific location and with the assistance of others such as
Thomas Hunt Morgan, substantial early evidence was found that genes are situated on
chromosomes. This discovery not only confirmed Mendel’s laws of inheritance but also laid
down the groundwork for the chromosomal theory for the transmission of heritable characters,
and hence became the foundational stone in the study of genetics.
In the course of world history in relation to genetics, one of the most significant events is
attributed to James Watson and Francis Crick who identified the DNA structure in 1953. Their
unraveling of the structural nature of the DNA molecule: which is indeed that this wholly
recognizable double helix formation has almost single-handedly revolutionalised what was
understood of where genetic material information is stored, how it can be replicated and
reproduced all over again. It also gave a ground for searching for more information on the
molecular mechanisms of hereditary and acted as an instrument needed to further study genetics.
Techniques of gene mapping as well as the DNA sequencing themselves developed with
more accuracy and directed purpose during the second half of twentieth century. Rapid
techniques such as restriction fragment length polymorphism (RFLP), polymerase chain reaction
(PCR), and DNA sequencing facilitated by these molecular maps and-marker assisted genome
atlas by the scientific community to chart and read the genetic makeup in record time. These
innovations marked the beginning of molecular genetic studies that were deemed to pave way for
future research where it was possible to look into the human genome and determine particular
Genes responsible for features or diseases independent of the latter.
4.Patterns of Inheritance
Mendelian Inheritance Patterns
1. Autosomal Dominant Inheritance: The autosomal dominant means that a single
dominant allele is enough to cause the trait to appear in an individual. Those honestly
affected have an affected parent, and indeed possess equal probability of passing on the
trait to any offspring..
2. Autosomal Recessive Inheritance: The second possibility of the gene inheritance
relating to the disease is autosomal recessive inheritance, meaning a gene pair requires
two recessive alleles for an empathetic trait to occur. That is why heterozygous persons
who carry one allele of the concerned gene remain healthy, while the children born to a
heterozygous parent are affected irrespectively of whether they inherit two alleles of the
gene from the carrier parent.
3. X-linked Inheritance: About X-linked inheritance This is a kind of inheritance that
depends with an individual’s gene within an X chromosome. I personally know that X-
linked recessive trait is dominant in male children than female children because male
children have only one X chromosome while female children have two allele strands,
thus both must be affected in order to exhibit the trait, as mentioned in article by Larroca
and Hagerman (2014).
Non-Mendelian Inheritance Patterns
1. Codominance: Codominance means that both alleles are also expressed in the
heterozygous genotype of the individual in question. As such, no element of dominance
or recessiveness affects the two alleles, and they are equally expressed in the phenotype.
2. Incomplete Dominance: Incomplete dominance is the one where the dominant allele
does not overpower the recessive one but has a quantitative impact over the latter.
Heterogony is depicted whereby an organism possesses two alleles different from each
other and possessed by the organism without dominance by the other.
Multifactorial Inheritance
Autosomal dominant inheritance implies that a gene that controls a certain trait or
susceptibility to disease is located on any other chromosome than the sex chromosomes, and a
single copy of this gene is enough, or dominant, for the trait to be expressed. Inheritance patterns
that reflect many genes are called multifactorial and can result in many different variations of
something within a population such as the occurrence of diseases like diabetes or heart diseases,
height or weight etc.
5. Genetic Variation in Human Populations
Genetic Diversity and its Importance
The term has been defined as the variability of genotypes within a population or species
of organism. It serves as the wedge for natural selection for long-term survival and flexibility of
population genetics to occur. Who Has Higher Drying Genetic Diversity can also decrease
susceptibility to genetic drift, the effect of inbreeding detrimental on populations, and boosting
threat to the populations that select distinctiveness.
Genetic Polymorphisms
Genetic polymorphisms are defined as a variation in the DNA sequence that occurs in
one or more positions within a population. These could range from changes that are as basic as
the substitution of a single nucleotide (these are also called the single nucleotide polymorphisms
or single nucleotide changes), to insertion, deletion or other changes. Polymorphisms are
involved in determining the differences in the genetic makeup of individuals within the gene
pool for any population/group, and this can vary from anything that involves the susceptibility to
certain diseases, the body’s ability to metabolize drugs, to phenotypic variation.
Human Genome Sequencing Projects
Human genomic sequencing initiatives, including the Human Genome Project (HGP) and
other related endeavors, have the larger goal of identifying the full amount of nucleotide base
pairs that compose human DNA. These have frozen great understandings concerning human
genetic variation, evolution and genetic predisposition to diseases. Nowadays, it has become
possible to sequence the human genome quickly and affordably as the new-generation
sequencing technologies came into being, which has taken the scientific community nearer to
realizing person-centered care, genomics, and genetic information driven healthcare solutions.
6. Genetic Disorders
Overview of Genetic Disorders
Hereditary diseases are diseases resulting from mutation of the genes, that is, it is a disease
resulting from one or more than one gene which is mutated or in the event that there is imbalance
of the chromosomes. These disorders can be classified based on their inheritance patterns based
on the means of inheritance:
Autosomal Disorders: Resulting from changes in genes found in autosomes, that is,
chromosomes that are not categorized as ‘Sex Chromosomes’. These diseases are
classified according to the mode of inheritance which are autosomal dominant, autosomal
recessive and Xlinked.
X-linked Disorders: Depending on the genetic makeup of the disease, it is caused by
mutations on the X chromosome. As expected, the x-linked disorders are more likely to
affect males since they do not possess the second X chromosome.
Chromosomal Disorders: Caused by Structural chromosome changes like aneuploidy
(one or more missing or extra chromatids) or chromosomal deletions/duplications.
Common Genetic Disorders
1. Cystic Fibrosis: The cystic fibrosis is a genetic disease, which transmits according to the
autosomal recessive pattern and resulting from mutations in the CZTTR gene. It impacts
the disease of the respiratory tract, digestive system, as well as reproductive tract, and
causes thick, viscous mucus in the respiratory and digestive track.
2. Sickle Cell Disease: Sickle cell disease also referred to as sickle cell anemia, is a
hereditary disorder whose gene locus lies at chromosome 11, the gene responsible for the
mutation being hemoglobin. Mosseri adds that it causes red blood cells to dialect an
arched selling, leading to blood vessels becoming blocked and complications arising in
the form of such things as pain crises and organ related problems among others.
3. Down Syndrome: Down syndrome is a form of mental retardation characterized by a
chromosomal abnormality whereby, instead of having 46 chromosomes, an individual is
born with one additional chromosome 21. Down Syndrome is related to low intelligence,
distinct facial build, and increased susceptibility to some illnesses like the heart
complications and leukemia.
Genetic Testing and Counseling
Genetic testing refer to a test done on a certain person’s genes with the aim of identifying
whether or not that person has had a mutation or change in his or her genes that are associated
with certain diseases or have a tendency of developing certain diseases. In detail, it may be
acceptable when needed for diagnosing illnesses, in assessment of risk, in intention to check
potential carriers of a certain disorder, in prenatal examinations, and for pharmacogenomic
purposes. Genetic counseling can be defined as the science of informing people or families
about specific inherited diseases, the manner in which they are inherited or the possibility of
arranging a genetic test. For instance, it helps a person make a choice about genetic testing,
procreation, specific treatment and living with an illness.
7. Genetics and Disease Risk
Genetic Factors in Common Diseases
1. Cancer: Researchers agree that cancer has genetic causes to an extent. Change in
oncogenes, tumor suppressor genes, and DNA repair genes play an imperative role in the
starting of cancer and its’ further advancement. Patent gene mutations are linked to
specific hereditary cancers; for example, women carrying the BRCA1/2 mutations are
more susceptible to develop the breast and ovarian cancers.
2. Cardiovascular Diseases: Original genes are associated with various conditions that lead
to cardiovascular diseases which include coronary artery disease, hypertension and
stroke. Factors related to lipid metabolism, genetic factors relevant to blood pressure
regulation, and variations affect the individual’s susceptibility to these conditions.
8.Advances in Human Genetics Research
Genomic Technologies
1. CRISPR-Cas9: CRISPR-Cas9 is new gene editing tool used in cells as well as in the
organisms it manipulates the genetic material directly. The CAS9 has taken the face of
genetic engineering and biomedical research through the change that it brought in the use
of the CRISPR tool which able to achieve gene editing tasks in a shorter time and
accuracy.
2. Next-Generation Sequencing (NGS): They have advanced into higher levels to make it
possible for NGS techniques to sequence the genome and the genetic variability. Mainly,
these throughputs have been indispensable for whole-genome sequencing as well as large
scale genomic studies becoming relatively cheaper and more feasible, and have further
helped to support detailed study of human genetics and genomics.
Human Genome Project and its Impact
The postscript of the Human Genome Project (HGP) can be boasted as a great
achievement enshrined in the book of molecular genetics because it established the first map of
the human genome while paving way to genetics and genomics. It has further spread to several
sectors, starting with reinforcing genetic science and information databases, and going up to
being instrumental in revealing critical findings in genomics and informatics, and gave
substantial tool boxes for deciphering vast genomics databases. In addition, it has contributed to
advancements within the HGP and has encouraged essential investigation that has funnelled to
discovering disease linked genes and is also the premise for precision medication. Most
noteworthy, the project had a significant focus on cooperation throughout the participation of the
various teams involved in the different corresponding work streams, which all also addressed
aspects of going global and data sharing; thus, emphasizing a realm of common purpose in
genomic science and the possibilities of change with regards to human health.
9. Ethical, Legal, and Social Implications (ELSI) of Human Genetics
Genetic Discrimination
It also referred to as gene-based mal-treatment which is a process of treating an
individual ill based on their genetic profile. Genetic discrimination concerns involvement stems
up in different facets in employment, health insurance and education or housing among others.
There is need to enact legislation and laws that will protect people’s genetic information, and
injuries from discrimination and assure them of their privacy and Privilege.
Privacy Concerns in Genetic Testing
Privacy concerns with respect to genetic testing are related to the freedom of persons to
have their genetic information protected at physical and family planning levels. A few of the
issues ratable to privacy concerns or infringing personal or organizational rights because of
disclosure of individual’s genetic information. Chapters in the same regard also show the
importance of legal and regulatory framework and information protection mechanism to ensure
the individuals’ right in privacy and self determination particularly to those who are reasonably
likely to be genetically tested.
Ethical Issues Surrounding Gene Editing and Designer Babies
The use of the genome editing tools such as CRISPR-Cas9 has opened a way to edit the
human germline, meaning modify the human gamete cells, which brought up the question of the
permissibility of this activity. This is coupled with some disadvantages like inability to guess
likely side effects, health impacts of multiple positive hits and other latent effects of altering
characteristic genes or traits. Police persons have admitted that the case presented by the pro
gene editing by designing babies where offspring are personally created to be ordered for a
purpose of having one or more of the genes available for heritable advantageous traits—that is,
being born with certain desirable attributes—raises some very serious questions of ethical
considerations in the whole policy of gene editing.
10. Future Directions in Human Genetics
Precision Medicine Initiatives
Precision medicine on the other hand tries to address healthcare in a more distinct manner
taking into consideration an individual’s genetics, surroundings, and behavior. Further
developments of the concept of genes will concentrate on the use of genetic information for
managing patient care for preventing, diagnosing, and treating diseases. This is done by
constructing phenotypes and genotypes through the identification of prognosis and diagnostics,
and the bioscriptions employing genetic data for enhancedpatients’ performance.
Potential Applications of Gene Editing Technologies
Gene editing technologies hold promise for a wide range of applications, including:
However, there are areas many domains where gene editing technologies can be applied:
To determine the possible explanations on the utilization of gene editing to correct wrong
mutations in human body or other diseases for therapeutic solutions.
Relatively more life threatening type of cancer called glioblastoma multiforme with
specific regard to diagnosis and therapy with an emphasis on immune cell engineering in
the field of cancer immunotherapy and stem cell based regenerative medicine.
Conclusion
Over the years, there has been a tremendous progress in human geneticsIn enabling the
society explicate on cause of sicknesses and even healthy construction. From the identification
of the ‘markers’ meaning appropriate genes which define certain diseases or conditions, to the
‘personalized’ approach to a patient claiming that patient has individual genetic makeup and that
has to be taken into consideration when treating a particular patient, this area has changed the
medicine and the ways of treatment. At the same time, however, it has been demonstrated how
the subject still holds enormous potential and how there exists today numerous approaches that
are still to be discovered. This is because it may be the case future research might uncover other
genetic data that were not evident early on or even improve the approach used in diagnosing such
disorder, not mentioning the discovery of better ways of treating such disorder. Moreover as
science unravels the secrets of the workings of the physical human genome, it can map out the
new road to advances in health and human prosperity in the broadest sense. Science is still
continuing the search for discovery in genetics about human beings and the next upcoming
discovery awaiting for us is another revolution in the medical field and an improvement on the
health of individuals.
