Republic of the Philippines
UNIVERSITY OF EASTERN PHILIPPINES
University Town, Catarman, Northern Samar
COLLEGE OF EDUCATION
Secondary Teacher Education Department
2nd Semester SY: 2020-2021
Module in Major 7a: GENETICS
This module is prepared by:
Christine M. Adlawan, LLB, MPA
STEd Faculty
Module in GENETICS
Module
Prof. Christine M. Adlawan
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Genetics: The Science of Heredity
OVERVIEW
It is a common observation that seeds of mango trees germinate to
grow into mango plants, and dogs give birth to puppies only and not into the
young ones of any other animal. Humans give birth to human beings. The
tendency of offsprings to inherit parental characteristics is termed as ‗heredity‘
and the study of science of heredity and the reasons governing the variation
between the parents and their offsprings is called ‗Genetics‘.
Genetics seeks to answer questions like why two offspring of same
parents look different, why some people have dark, and others have fair
complexion. In other words, why is there variation among individuals of the
same kind? This module deals with genetics and the reasons behind the
variation among individuals of the same species. It also includes diagnostic
techniques to find out the bases for types of sex determination, inheritance of
blood groups in humans, hereditary disorders and gives an insight of the
human genome.
LEARNING PLAN
At the completion of this lesson, you should be able to:
1. define the terms heredity and genetics;
2. discuss the history of genetics;
3. explain the scope of genetics;
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4. determine the application of genetics studies to life and to the fields of
science; and
5. identify some important terminologies used in the study of genetics.
ACTIVITY
Traits of Our Class
This activity is designed to help students differentiate between
characteristics that are inherited versus characteristics that are not. It also
allows students to see the prevalence of certain traits by observing those
traits in their classmates or friends.
Instruction:
Identify whether the series of traits in the table are inherited or not
inherited. Put a check (⁄) mark if it is inherited, and a cross (x) mark if it is not
inherited. Give your own explanation or reason why such trait is inherited or
not.
Ask any of your classmates if he/she has any of the inheritable traits
listed in the table. If the classmate has some of the traits, write the
classmate's name next to your explanation. You may write as many names as
you can as long as they have the inheritable traits.
Series of Traits
Inherited
Not Inherited
Your Explanation
Name of
Classmate
Hair color
Shirt color
Height
Weight
Health
Dry skin
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Hair length
Skin color
Eye shape
Can roll his or her
tongue
Has detached
earlobes
Has a widow's
peak
Has a hitchhiker's
thumb
Has dimples
Has freckles
Has a widow's
peak
ANALYSIS
Answer the following questions briefly:
1. Which traits were hard to find from among your classmates?
___________________________________________________________
___________________________________________________________
________________________________________________________
2. Can you compare the percentage of the general population and
classmate/s that has each trait? Write them below.
___________________________________________________________
___________________________________________________________
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___________________________________________________________
________________________________________________________
3. Draw a conclusion from the above activity? Write them below.
___________________________________________________________
___________________________________________________________
___________________________________________________________
________________________________________________________
ABSTRACTION
A. What is Heredity and Genetics?
“Genetics is a field of science that includes the study of
inheritance and genetic variations by investigating the DNA, genes,
genome, chromosome and other components of it.”
It also pertains to ―the study of structure and function of DNA, genes,
chromosomes and related alterations‖.
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The term ―Genetics‖ was coined by William Bateson is 1905. The term
was derived from the Greek word ―genetikos‖ and ―genesis‖. Genetikos
means generative and genesis
means ―origin‖.
Heredity on the other hand,
refers to the genetic heritage
passed down by our biological
parents. It‘s the reason why we
look like them! More specifically, it
is the transmission of traits from
one generation to the next. These
traits can be physical, such as eye
color, blood type or a disease, or
behavioral.
For example, the hygienic behavior of honeybees that drives them to
remove sick larvae from the nest is an inherited behavior.
Hereditary traits are determined by genes, and a single gene can have
several variants called alleles. There are two copies of each gene in our cells
(with the exception of genes located on sex chromosomes). One of the copies
comes from the sperm, the other from the egg.
In an individual, these two copies (or alleles) are not necessarily
identical. If the two copies of a gene are identical, we say that the individual is
homozygous for that gene. If the two copies are different, the gene is
heterozygous.
The alleles of the same gene can have a dominant or recessive
relationship with one another. If both alleles are different (heterozygous) and
at least one of these two alleles is dominant, it is the dominant one that will be
expressed (i.e., that we will observe as a trait in an individual). Conversely, a
recessive allele (non-dominant) will not be expressed in an individual if both
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parents pass down the same allele (homozygote). As a result, even if a
recessive allele is present in a genotype (the genetic constitution of an
individual); it will not be observable in the phenotype (the set of observable
traits of an individual) if the other copy of the gene is a dominant allele.
During reproduction, the genes of biological parents combine to form a
new unique individual. This shuffling of genes is the reason all of us are
different.
B. The beginnings of Genetics
The history of genetics dates from the classical era with contributions
by Pythagoras, Hippocrates, Aristotle, Epicurus, and others. Modern genetics
began with the work of the Augustinian friar Gregor Johann Mendel. His work
on pea plants, published in 1866, established
the theory of Mendelian inheritance.
The
year
1900
marked
the
"rediscovery of Mendel" by Hugo de Vries,
Carl Correns and Erich von Tschermak, and
by 1915 the basic principles of Mendelian
genetics had been studied in a wide variety
of organisms — most notably the fruit fly
Drosophila melanogaster.
Led by Thomas Hunt Morgan and his fellow "drosophilists", geneticists
developed the Mendelian model, which was widely accepted by 1925.
Alongside experimental work, mathematicians developed the statistical
framework of population genetics, bringing genetic explanations into the study
of evolution.
With the basic patterns of genetic inheritance established, many
biologists turned to investigations of the physical nature of the gene. In the
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1940s and early 1950s, experiments pointed to DNA as the portion of
chromosomes (and perhaps other nucleoproteins) that held genes. A focus
on new model organisms such as viruses and bacteria, along with the
discovery of the double helical structure of DNA in 1953, marked the
transition to the era of molecular genetics.
In the following years, chemists developed techniques for sequencing
both nucleic acids and proteins, while many others worked out the
relationship between these two forms of biological molecules and discovered
the genetic code. The regulation of gene expression became a central issue
in the 1960s; by the 1970s gene expression could be controlled and
manipulated through genetic engineering. In the last decades of the 20th
century, many biologists focused on large-scale genetics projects, such as
sequencing entire genomes.
Ancient Theories
The most influential early theories of heredity were that of Hippocrates
and Aristotle. Hippocrates' theory was similar to Darwin's later ideas on
pangenesis, involving heredity material that collects from throughout the
body. Aristotle suggested instead that the form-giving principle of an organism
was transmitted through semen (which he considered to be a purified form of
blood) and the mother's menstrual blood, which interacted in the womb to
direct an organism's early development.
Ancient theories of pangenesis and blood in heredity
Although scientific evidence for patterns of genetic inheritance did not
appear until Mendel‘s work, history shows that humankind must have been
interested in heredity long before the dawn of civilization. Curiosity must first
have been based on human family resemblances, such as similarity in body
structure, voice, gait, and gestures. Such notions were instrumental in the
establishment of family and royal dynasties. Early nomadic tribes were
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interested in the qualities of the animals that they herded and domesticated
and, undoubtedly, bred selectively. The first human settlements that practiced
farming appear to have selected crop plants with favorable qualities. Ancient
tomb paintings show racehorse breeding pedigrees containing clear
depictions of the inheritance of several distinct physical traits in the horses.
Despite this interest, the first recorded speculations on heredity did not exist
until the time of the ancient Greeks; some aspects of their ideas are still
considered relevant today.
Hippocrates (c. 460–c. 375 bce), known as the father of medicine,
believed in the inheritance of acquired characteristics, and, to account for this,
he devised the hypothesis known as pangenesis. He postulated that all
organs of the body of a parent gave off invisible ―seeds,‖ which were like
miniaturized building components and were transmitted during sexual
intercourse, reassembling themselves in the mother‘s womb to form a baby.
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Aristotle (384–322 bce) emphasized the importance of blood in
heredity. He thought that the blood supplied generative material for building
all parts of the adult body, and he reasoned that blood was the basis for
passing on this generative power to the next generation. In fact, he believed
that the male‘s semen was purified blood and that a woman‘s menstrual blood
was her equivalent of semen. These male and female contributions united in
the womb to produce a baby. The blood contained some type of hereditary
essences, but he believed that the baby would develop under the influence of
these essences, rather than being built from the essences themselves.
Aristotle‘s ideas about the role of blood in procreation were probably
the origin of the still prevalent notion that somehow the blood is involved in
heredity. Today people still speak of certain traits as being ―in the blood‖ and
of ―blood lines‖ and ―blood ties.‖ The Greek model of inheritance, in which a
teeming multitude of substances was invoked, differed from that of the
Mendelian model. Mendel‘s idea was that distinct differences between
individuals are determined by differences in single yet powerful hereditary
factors. These single hereditary factors were identified as genes. Copies of
genes are transmitted through sperm and egg and guide the development of
the offspring. Genes are also responsible for reproducing the distinct features
of both parents that are visible in their children.
Preformation and natural selection
In the two millennia between the lives of Aristotle and Mendel, few new
ideas were recorded on the nature of heredity. In the 17th and 18th centuries
the idea of preformation was introduced. Scientists using the newly developed
microscopes imagined that they could see miniature replicas of human beings
inside sperm heads. French biologist Jean-Baptiste Lamarck invoked the
idea of ―the inheritance of acquired characters,‖ not as an explanation for
heredity but as a model for evolution. He lived at a time when the fixity of
species was taken for granted, yet he maintained that this fixity was only
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found in a constant environment. He enunciated the law of use and disuse,
which states that when certain organs become specially developed as a result
of some environmental need, then that state of development is hereditary and
can be passed on to progeny. He believed that in this way, over many
generations, giraffes could arise from deerlike animals that had to keep
stretching their necks to reach high leaves on trees.
British naturalist Alfred Russel Wallace originally postulated the
theory of evolution by natural selection. However, Charles Darwin‘s
observations during his circumnavigation of the globe aboard the HMS
Beagle (1831–36) provided evidence for natural selection and his suggestion
that humans and animals shared a common ancestry. Many scientists at the
time believed in a hereditary mechanism that was a version of the ancient
Greek idea of pangenesis, and Darwin‘s ideas did not appear to fit with the
theory of heredity that sprang from the experiments of Mendel.
The Work of Mendel
Mendel was the pioneer in experimenting and establishing the base of
genetics and hence Gregor Johann Mendel is known as the father of
genetics. During the period of 1856 to 1865, he experimented on pea plant
and discovered the phenomenon of ―inheritance of traits‖.
Through these experiments, Mendel saw that the genotypes and
phenotypes of the progeny were predictable and that some traits were
dominant over others. These patterns of Mendelian inheritance demonstrated
the usefulness of applying statistics to inheritance. They also contradicted
19th-century theories of blending inheritance, showing, rather, that genes
remain discrete through multiple generations of hybridization.
These traits are now known as genes that can be inherited from one
generation to another generation. In 1866, he published his research paper
describing the law of inheritance and independent assortment.
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Some of the milestone discoveries in the genetics are enlisted below:
 1842: Wilhelm von Nageli, a Swiss botanist, observed the plant cell.
 1866: Mendel‘s research work published under the title of ―experiments on
plant hybridization.‖
 1869: Friedrich Miescher discovered the nucleic acid.
 1888: Waldeyer identified the chromosome present in the cell.
 1889: Richard Altmann purified DNA from the protein.
 1905: William Bateson coined the term ―genetics‖.
 1908: discovery of Hardy-Weinberg‘s law.
 1910: Morgan T, explained that the genes are located on the chromosomes.
Also, they experimented on Drosophila Melanogaster and determined the
nature of sex-linked traits.
 1923: Griffith F, experimented on bacteria and postulated that the DNA is the
genetic material.
 1953: Watson and Crick identified the structure of DNA.
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C. The Scope and Significance of Genetics
In the last few decades, the science of genetics has pervaded all
aspects of biology so that it has assumed a central position of great
significance in biology as a whole. While on the one hand, genetics is used
for a study of the mechanism of heredity and variation, on the other hand it
has provided tools for the study of the fundamental biological processes
examined and taught in areas, like plant physiology, biochemistry, ecology,
plant pathology, microbiology, etc.
Consequently
today
every
biologist should be bit of a geneticist.
Genetics, in fact provided the modern
paradigm (a prototype) for whole of
biology. The science of genetics also
had a tremendous impact in applied
areas including medicine, agriculture,
forestry, fisheries, law and religion. In
view of this, all newspapers often
address
questions
dealing
with
different aspect of genetics that may be of significance to common man, who
is not a geneticist or a biologist.
The recent upsurge of biotechnology has added further to the
significance of the science of genetics, so that the products of genetics have
also become a subject of discussion for Trade Related Aspects of Intellectual
Properties (TRIPs) under the aegis of General Agreement on Tariffs and
Trade (GATT). Patenting of life forms which may or may not be the product of
genetic manipulation is one such topic, which is receiving considerable
attention of both developed and developing countries.
Genetics can be broadly classified in the following three areas for the
convenience of a discussion on its scope and significance:
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(i)
Prof. Christine M. Adlawan
transmission genetics involving study of transmission of
genetic material from one generation to the other;
(ii)
molecular and biochemical genetics, involving study of the
structure and function of genes; and
(iii)
population and biometrical genetics, involving study of the
behavior and effects of genes in population, often using
mathematical models.
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The above classification is arbitrary, and the three areas are interrelated and even enter other areas of biology to answer some difficult
questions. Significance of genetics also stems from the fact that the genetic
material containing information for hereditary traits consists of nucleic acids
only, across the entire spectrum of life on the earth. More important of the two
types of nucleic acids, deoxyribose nucleic acid (DNA) and ribose nucleic acid
(RNA), is the former i.e. DNA, which has two unique properties:
(i)
it can replicate and produce its exact copies; and
(ii)
it carries the genetic information, necessary to give form to an
organism; this information is written into the sequence of four
monomers called nucleotides, which make the polymer
molecule, the DNA.
Genetic Diversity and Evolution Life of Earth exists in tremendous
array of forms and features that occupy almost every conceivable
environment. Life is also characterized by adaptation: many organisms are
exquisitely suited to the environment in which they are found. The history of
life is a chronicle of new forms of life emerging, old forms disappearing, and
exiting forms changing. Despite their tremendous diversity, living organisms
have an important feature in common: all use the same genetic system. A
complete set of genetic instructions for any organism is its genome, and all
genomes are encoded in nucleic acids-either DNA or RNA.
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D. Application of Genetics
Man has, without realizing it, exploited DNA for centuries but has only
in the last decade discovered how to manipulate the gene directly, and with
predictable results. Genetic engineering opens up almost unlimited potential
benefits. The production of food, fuel and chemicals may all be improved and
new approaches to the control of disease can be found. Nevertheless,
monstrous possibilities for the exploitation of these techniques, even for the
manipulation of the genes of man himself, spring to mind.
APPLICATIONS OF MENDELIAN GENETICS
Mendelian genetics treats genes as atoms, unsmashable balls which
can be mixed together and then sorted out in new combinations in breeding
and selection programs. This concept of particulate genes and the understanding of the patterns of their inheritance has enabled plant and animal
breeders to accelerate the process of domestication and the exploitation of
the living world by man. Various forms of domesticating selection have been
in use throughout human history. Planned breeding programs have included
the use of natural and artificial hybrids and the establishment of pure lines
with selection.
Other Applications of genetic studies are:
 Disease diagnosis and characterization
 Identification of pathogenic mutations
 Preserving biodiversity
 Identification and characterization of microbes
 Studying inheritance pattern
 Creating advanced plant species
 Creating genetically modified organisms
 Antibiotic resistance study and drug discovery
 Genetic/DNA medicines
 Genetic engineering
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 Crop improvement
 Animal and Plant Breeding program
 Infectious disease diagnosis
 Screening, prognosis, and diagnosis of cancer
 Disease diagnosis and characterization.
 Identification of pathogenic mutations.
 Preserving biodiversity.
 Identification and characterization of microbes.
 Studying inheritance pattern.
 Creating advanced plant species.
 Creating genetically modified organisms.
 DNA fingerprinting.
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E. Genetic Terminologies
The following are some important terms in the study of Genetics:

Allele
An alternative form of a gene that occurs at the same locus on
homologous chromosomes, e.g., A, B, and O genes are alleles.

Amorph
A silent gene that does not produce a detectable product (antigen),
e.g., O genes in the ABO BGS.

Aneuploidy
Having an abnormal number of chromosomes, i.e., not an exact
multiple of the haploid number. For example, Downs syndrome (three #21
chromosomes) or Klinefelter syndrome (XXY males).

Anticodon
A sequence of three bases in tRNA that is complementary to a codon
in mRNA. Enables tRNA to sequence amino acids in the order specified by
mRNA.

Antithetical
Alternative forms of the same antigen produced by allelic genes, e.g.,
K and k antigens in the Kell BGS or C and c antigens in the Rh BGS.

Autosome
A non-sex chromosome. Synonymous with somatic chromosomes
(chromosome pairs 1-22).

Balanced polymorphism
An equilibrium of two or more alleles that has remained constant over
long periods of time.

Beneficial gene
A gene that confirms a trait that is advantageous to survival and that
increases in frequency, e.g., the Fy gene that produces the Fy(a-b-)
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phenotype which makes West Africans resistant to certain types of malarial
parasites.

Chromosome
Rod-shaped structures within the cell nucleus that carry genes
encoded by DNA.

Cloned gene
A recombinant DNA molecule with the gene of interest. (Also see
recombinant DNA.)

Co-dominant
Genes are co-dominant if both alleles are expressed in the
heterozygous state, e.g., K and k genes in the Kell BGS.

Codon
A sequence of three bases in DNA or RNA that codes for a single
amino acid. Enables specific proteins to be made by specific genes.

Consanguinity
Having a common ancestor, i.e., being blood relatives. Mating between
two first cousins, for example, can be termed a consanguineous mating and is
indicated in a pedigree by a double bar between the two parents. Such
mating can result in an increased frequency of offspring who are homozygous
for a recessive autosomal trait possessed by both parents, e.g. cystic fibrosis
or the amorphic type of Rh null.

Crossing over
The exchange of genetic material between members of a pair of
homologous chromosomes. For example, if a mating between a male
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(MS/Ns) and a female (MS/MS) results in an offspring who is MS/Ms, the
recombinant child has occurred due to crossing over in the father.

Deletion
An abnormality in which part of a chromosome (carrying genetic
material) is lost.

Deleted phenotype
The condition in which antigens that are normally present are missing,
e.g., the Rh null phenotype in the Rh BGS. Deleted phenotypes can be
caused by inheritance of regulatory genes that do not allow functional
(antigen-producing) genes to make their products.

Diploid number of chromosomes
The number of chromosomes found in somatic cells, which in humans
is 46.

Dizygotic twins
Twins produced from two separate ova that are separately fertilized,
i.e. fraternal twins. Only dizygotic twins can exhibit blood group chimerism
(shown by mixed field agglutination when antigen typing red cells).

DNA
Deoxyribonucleic acid. Composed of nucleic acids, these molecules
encode the genes that allow genetic information to be passed to offspring.

DNA polymerases
Enzymes that can synthesize new DNA strands using previously
synthesized DNA (or RNA) as a template.

DNA probe
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A cloned DNA molecule labelled with a radioactive isotope (e.g.,
32
P or
35
S) or a nonisotopic label (e.g., biotin). Used in molecular genetics to identify
complementary DNA sequences by hybridizing to them.

Dominant gene
A gene is dominant if it is expressed when heterozygous but its allele
is not, e.g. in the Lewis system the Le gene is dominant (expressed in both Le
Le and Le le genotypes) and the le gene is recessive.

Functional genes
Genes that produce proteins, e.g., blood group genes that produce
antigens.

Gamete
A reproductive sex cell (ovum or sperm) with the haploid number (23)
of chromosomes that results from meiosis.

Gene
A segment of a DNA molecule that codes for the synthesis of a single
polypeptide.

Gene flow
Changes in gene frequencies that occur over long periods of time due
to migration in which different populations interbreed. An example is the
transfer of genes between racial groups, e.g., the "white" genes of the Duffy
blood group system (Fya Fyb) have an increased frequency in U.S. blacks
compared to African blacks.
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Prof. Christine M. Adlawan
Gene interaction
The situation in which genes inherited at different loci interact to
produce red cell phenotypes, e.g., Le le genes interact with Hh and Se se
genes to produce the various Lewis red cell phenotypes.

Genome
Term used to denote the entire DNA sequence (gene content) of a
gamete, person, population, or species.

Genotype
All of the alleles present at the locus (or closely linked loci) of a blood
group system, indicating chromosomal alignment if appropriate, e.g., AO in
the ABO BGS, CDe/cde in the Rh BGS, or MS/Ns in the MNSs BGS.
Genotypes are indicated by superscripts, underlining, or italics.

Haploid number of chromosomes
The number of chromosomes found in sex cells, which in humans is
23.

Hardy-Weinberg law
A law developed in 1908 independently by George Hardy (an English
mathematician) and Wilhelm Weinberg (a German physician) that is the basis
for calculations used in population genetics. The law is described by the
formula p2 + 2pg + q2 = 100%, where p is the frequency of one allele, q is the
frequency of the other, p2 and q2 are the homozygous frequencies, and 2pg is
the heterozygous frequency. The formula allows us to calculate the
frequencies of genes, phenotypes, and genotypes when the frequency of a
genetic trait is known.
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
Prof. Christine M. Adlawan
Harmful gene
A gene that confirms a harmful trait such that it is reduced to a level at
which it is maintained only by recurrent mutation, e.g., the gene for
hemophilia A, which has a mutation rate of 1 in 10,000.

Hemizygous
Inheritance of an X-linked gene in males, e.g. the Xga gene or the gene
for hemophilia A is said to be hemizygous in males since they have only one
X chromosome.

Heterozygous
The situation in which allelic genes are different, e.g. the Kk genotype
in the Kell BGS or the Fya Fyb genotype in the Duffy BGS.

Homologous chromosomes
A matched pair of chromosomes, one from each parent, e.g., two #6
chromosomes.

Homozygous
The situation in which allelic genes are identical, e.g., the KK genotype
or the Fya Fya genotype.

HUGO
Acronym
for
Human
Genome
Organization,
an
international
organization conceived in 1988 to co-ordinate the Human Genome Project.

Human Genome Project
A worldwide project to map and sequence the human genome. The
ultimate goal is to produce the complete nucleotide sequence of every human
chromosome. (Also see HUGO.)
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Prof. Christine M. Adlawan
Immune response genes
Name given to genes that appear to be able to control whether a
person is likely or unlikely to make red cell antibodies. Help explain why some
transfusion recipients are hyper-responders (make multiple alloantibodies)
and others, even when transfused with a very immunogenic antigen like D
from the Rh system, never produce antibodies. (About 30% of D-negative
people appear incapable of making anti-D.) The genes that regulate the
immune response may be linked to the genes of the major histocompatibility
complex (MHC) or may be the MHC genes themselves.

Karyotype
A photomicrograph (photograph taken through a microscope) of all the
chromosomes in a person, arranged in standard classification (from #1
chromosomes through to the sex chromosomes).

Linkage
Genes are linked if they are on the same chromosome within a
measurable distance of each other and are normally inherited together, e.g.,
Lutheran and Secretor genes are linked as are the Dd, Cc, Ee subloci in the
Rh BGS.

Locus
The location of allelic genes on the chromosome, e.g., A, B, and O
genes occur at the ABO locus. (Plural = loci)

Mapping of genes
A variety of processes that include discovering that a gene is linked to
another gene (which can serve as a marker for it), assigning genes to
particular
chromosomes,
assigning
genes
to
specific
regions
on
chromosomes, and determining nucleotide sequences on chromosomes.
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Prof. Christine M. Adlawan
Meiosis
The type of cell division that occurs in sex cells by which gametes
having the haploid number of chromosomes are produced from diploid cells.

Messenger RNA (mRNA)
Type of RNA polymerase using DNA as a template. Contains the
codons that encompass the genetic codes to be translated into protein.

Mitosis
Cell division that results in the formation of two cells, each with the
same number of chromosomes as the parent cells, i.e., cell division that forms
all new cells except sex cells.

Modifying gene
A regulatory gene (usually at a different locus than blood group genes)
that in some way alters the expression of the blood group genes. Also called
suppressor genes.

Monozygotic twins
Twins derived from a single fertilized ovum, i.e., identical twins.

Mutation
A permanent inheritable change in a single gene (point mutation) that
results in the existence of two or more alleles occurring at the same locus.
Blood group polymorphism has been caused by mutations occurring over
long periods of time.

Nondisjunction
The failure of two members of a chromosome pair to disjoin during
anaphase. For example, an offspring with the AB/O genotype can be
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produced if a group AB male mates with a group O female and nondisjunction
happens in the father.

Nucleic acids
Polymers of phosphorylated nucleosides, the building blocks of DNA
and RNA.

Nucleoside
The building blocks of RNA and DNA. Compounds consisting of a
purine (adenine or guanine) or pyrimidine (thymine or cytosine) attached to
ribose (in RNA) or deoxyribose (in DNA) at the 11 carbon.

Pedigree
A diagram representing a family tree.

Phenotype
The antigens (traits) that result from those genes that are directly
expressed (can be directly antigen typed), e.g., group A in the ABO BGS or
D+C+E- c+e+ in the Rh BGS.

Plasmid
Extrachromosomal
circular
DNA
in
bacteria.
Plasmids
can
independently replicate and encode a product for drug resistance or some
other advantage. Used in molecular genetics as vectors for cloned segments
of DNA.

Polymerase chain reaction
An in vitro method of amplifying DNA sequences hundreds of millions
to billions of times in a few hours. Developed in 1984-1985 by Mullis, Saiki, et
al.
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Prof. Christine M. Adlawan
Polymorphism
The existence of two or more different phenotypes resulting from two
or more alleles, each with an appreciable frequency. Most blood group
systems are polymorphic.

Polypeptides
Polymers of amino acids that form the building blocks of proteins.

Population genetics
The branch of genetics that deals with how genes are distributed in
populations and how gene and genotype frequencies stay constant or
change. Calculations are based on the Hardy-Weinberg law.

Proband
The family member whose phenotype leads to a family study. Also
called an index case.

Recessive
Genes are recessive if the phenotype that they code for is only
expressed when the genes are homozygous, e.g., le le genes, in the Lewis
system or h h genes in the ABO BGS.

Recombinant
A person who has a new combination of genes not found together on
the chromosome in either parent, e.g., an MS/Ns offspring whose parents are
Ms/NS and MS/MS. A recombinant results from crossing over in one parent.

Recombinant DNA
In molecular genetics, artificially made DNA composed of fragments of
DNA from different chromosomes (often from different species) that have
been joined together (spliced) by genetic engineering. For example,
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Module in GENETICS
Prof. Christine M. Adlawan
healthcare workers are routinely vaccinated with a recombinant hepatitis B
vaccine made by inserting a piece of the hepatitis B virus genome (the part
that codes for the HBsAg) into yeast cells via a plasmid. The yeast cells then
produce a large amount of HBsAg, which is purified into the vaccine and
stimulates the production of protective anti-HBs antibodies.

Regulatory genes
In the operon model, genes that inhibit an operator gene so that it
prevents its functional genes from producing proteins.

Restriction endonucleases
DNA enzymes of bacterial origin that can cleave DNA at internal
positions on a strand because they recognize specific sequences (usually 4-6
base pairs). The enzymes evolved in bacteria as defenses against the
invasion of foreign DNA in the form of viruses or plasmids and are used in
molecular genetics to chop up DNA at particular locations.

Restriction fragment length polymorphisms (RFLP)
Regions of DNA of varying lengths that can be cut out of DNA by
restriction endonucleases. Because the fragment lengths vary among
individuals, they are polymorphic and can be used as genetic markers.

Reverse transcriptase
An RNA-dependent DNA polymerase that synthesizes DNA from an
RNA template. Used by retroviruses like the human immunodeficiency virus
(HIV) to make proviral DNA from its RNA genome.

Ribosomal RNA (rRNA)
Type of RNA found in ribosomes, the site of protein synthesis in the
cytoplasm.
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Module in GENETICS
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Ribosomes
Complexes of rRNA and protein in cytoplasm that serve as platforms
for translation for mRNA into protein.

RNA
Ribonucleic acid. Nucleic acids that are formed using DNA as a
template. Similar to DNA except has ribose in place of deoxyribose and uracil
in place of thymine. (Also see messenger RNA, ribosomal RNA, and transfer
RNA.)

Sex chromosomes
The chromosomes that determine sex. XX in females and XY in males.

Sex-linked
An outdated term for genes on the X chromosome. Historically
synonymous for X-linked since, apart from genes essential for male sex
determination, the Y chromosome appears to have few recognized gene loci
.

Somatic chromosome
A non-sex chromosome (soma=body). Synonym is autosome.

Syntenic
Genes are on the same chromosome but are not close enough for
linkage to be demonstrated.

Transcription
Synthesis of single-stranded RNA by RNA polymerase using DNA as a
template. The process in the nucleus whereby DNA is transcribed into mRNA.
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Module in GENETICS
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Prof. Christine M. Adlawan
Transfer RNA (tRNA)
Type of RNA that facilitates translation of mRNA into protein. Contains
anticodons that provide the molecular link between the codons of mRNA and
the amino acid sequences of proteins.

Transient polymorphism
A temporary polymorphism in which an allele (harmful gene) is
disappearing or an allele (beneficial gene) is increasing in frequency.

Translation
The process of translating the codon sequence in mRNA into
polypeptides with the help of tRNA and ribosomes
.

Trans position
Genes in the trans position are on opposite chromosomes of a pair of
homologous chromosomes. In the genotype CDe/cde, for example, D and c
genes are in the trans position.

X-chromosome
The sex chromosome present in double dose in females (XX) and in
single dose in males (XY).

X-linked
Genes on the X chromosome, e.g., genes for hemophilia A, hemophilia
B, and Xga blood group genes.

Y-chromosome
The sex chromosome present only in males (XY).
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Module in GENETICS
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APPLICATION
From the discussion above, answer the following questions briefly:
1.
What do you think are the advantages and disadvantages of genetic
testing?
2.
Do our genes determine who we are?
3.
If a behavior or trait is genetically based, does that make it morally
acceptable—or at least excusable? Share your thoughts about it.
ASSESSMENT
This test will be given through Google forms. Make sure to be ready on
the scheduled date of the assessment.
FEEDBACK
Do you have any question relative to our topic? Write them below.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
___________________________________________________________
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Module in GENETICS
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SUMMARY
To aid you in reviewing the important concepts in this module, here are
the highlights.

Genetics is a field of biology that studies how traits are passed
from parents to their offspring. The passing of traits from
parents to offspring is known as heredity; therefore, genetics is
the study of heredity.

Genetics is built around molecules called DNA. DNA molecules
hold all the genetic information for an organism. It provides cells
with the information they need to perform tasks that allow an
organism to grow, survive and reproduce. A gene is one
particular section of a DNA molecule that tells a cell to perform
one specific task.

Heredity is what makes children look like their parents. During
reproduction, DNA is replicated and passed from a parent to
their offspring. This inheritance of genetic material by offspring
influences the appearance and behavior of the offspring. The
environment that an organism lives in can also influence how
genes are expressed.

Genetics as a scientific discipline stemmed from the work of Gregor
Mendel in the middle of the 19th century. All present research in
genetics can be traced back to Mendel‘s discovery of the laws
governing the inheritance of traits.

Genetics are classified into three areas: transmission genetics,
molecular and biochemical genetics and population and
biometrical genetics.
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REFERENCES
 Reece, JB., Campbell, N.A, Urry, L.A, et.al., Campbell Biology. 11th
edition.
 A.J.S. McMillan. Introduction to Genetics.1st Edition. Hardcover ISBN:
9781483229140. eBook ISBN: 9781483282510
 https://sites.ualberta.ca/~pletendr/tm-modules/genetics/70genterm.html
 Ayala, F.J. and J.A. Kiger, Jr. 1984. Modern Genetics (2nded or latest
edition). Benjamin Cummings Pub. Co., Inc. Calif.
 Burns, G. and P.J. Bottin. 1989. The Science of Genetics. MacMillan
Pub. Co., N.Y.
 Etienne-Decant, J. 1988. Genetic Biochem: From Gene to Protein. Ellis
Harwood Ltd., Great Britain.
 https://www.whatisbiotechnology.org/index.php/science/summary/Gen
etics
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