Lesson Discussion: Self-Learning Module (SLM) General Biology 2
Lesson Discussion: Self-Learning Module (SLM) General Biology 2
Lesson Discussion: Self-Learning Module (SLM) General Biology 2
GENERAL BIOLOGY 2
Quarter 3 | Module 1 | AY 2021 – 2022
TEACHER: KRISTINE V. MASOLA, LPT
I. OBJECTIVES
1. Outline the process involved in genetic engineering (STEM_BIO11/12-IIIa-b-
6)
2. Discuss the applications of recombinant DNA (STEM_BIO11/12-IIIa-b-7)
LESSON DISCUSSION
GENES
DNA
Deoxyribonucleic acid or DNA is a genetic material
stored in the nucleus. The nucleus is a part of the
eukaryotic cell and contains nucleic acids and it is
responsible for protein production. Small segments of
DNA are called genes. Each gene holds the
instructions for how to produce a single protein. DNA is
a double-helix and has two strands running in opposite
directions. It is made up of building blocks called
nucleotides, which consists of three parts:
(1) A deoxyribose sugar(pentose sugar),
(2) A phosphate group, and
(3) A nitrogenous base
The nitrogenous bases are grouped into two: the two-ringed purines (Adenine-A and Guanine-
G) and the single-ringed pyrimidines (Cytosine-C and Thymine-T). In the double-stranded
DNA, the two strands run in opposite directions and the bases pair up such that A always pairs
with T and G pairs with C.
The figure below shows the difference between the DNA and RNA composition.
Gene is a portion of the DNA. In genetics language, the material found inside the nucleus which
makes up an organism’s complete set of genes called genotype must be expressed as an
observable characteristic or phenotype. The flow of genetic information is from DNA to
messenger RNA(mRNA) to protein. This series of processes of protein production is called
protein synthesis.
Your DNA, or deoxyribonucleic acid, contains the genes that determine who you are. How can
this organic molecule control your characteristics? DNA contains instructions for all the proteins
your body makes. Proteins, in turn, determine the structure and function of all your cells. What
determines a protein’s structure? It begins with the sequence of amino acids that make up the
protein. Instructions for making proteins with the correct sequence of amino acids are encoded
in DNA.
DNA is found in chromosomes. In eukaryotic cells, chromosomes always remain in the nucleus,
but proteins are made at ribosomes in the cytoplasm. How do the instructions in DNA get to the
site of protein synthesis outside the nucleus? Another type of nucleic acid is responsible. This
nucleic acid is RNA, or ribonucleic acid. RNA is a small molecule that can squeeze through
pores in the nuclear membrane. It carries the information from DNA in the nucleus to a
ribosome in the cytoplasm and then helps assemble the protein. In short:
DNA → RNA → Protein
The following steps describe the replication of DNA in both eukaryotic and prokaryotic cells:
1. The enzyme helicase starts to unzip the double helix as the nucleotide base pairs
separate. Each side of the double helix runs in opposite directions. At the same time,
replication begins on both strands of the molecules.
2. Free nucleotides pair with the base exposed as the template strand continuously unzip.
An enzyme complex-DNA Polymerase attaches the nucleotide to form a new strand
similar to each template.
3. A sub-unit of the DNA polymerase proofreads the new DNA and the DNA ligase
(enzyme) seals up the fragments into one long strand.
4. Two similar double-stranded molecules of DNA result from replication. The new copies
automatically wind up again DNA replication is semi-conservative because one old
strand is conserved and used and a new strand is made.
TRANSCRIPTION PROCESS
This process rewrites the genetic code in DNA into a messenger RNA (mRNA). Transcription
takes place in three steps: initiation, elongation, and termination.
Step 1: Initiation
It is the beginning of transcription. It occurs when the enzyme RNA polymerase binds to a
region of a gene called the promoter. This signals the DNA to unwind so the enzyme can
‘‘read’’ the bases in one of the DNA strands. The enzyme is now ready to make a strand of
mRNA with a complementary sequence of bases.
Step 2: Elongation
It is the addition of nucleotides to the mRNA strand. RNA polymerase reads the unwound DNA
strand and builds the mRNA molecule, using complementary base pairs. There is a brief time
during this process when the newly
formed RNA is bound to the unwound
DNA. During this process, an adenine
(A) in the DNA binds to uracil (U) in the
RNA.
Step 3: Termination
TRANSLATION PROCESS
It is the process that takes the information passed from DNA as messenger RNA and turns it
into a series of amino acids bound together with peptide bonds. It is essentially a translation
from one code (nucleotide sequence) to another code (amino acid sequence). The ribosome is
the site of this action, just as RNA polymerase was the site of mRNA synthesis. The ribosome
matches the base sequence on the mRNA in sets of three bases (called codons) to tRNA
molecules that have the three complementary bases in their anticodon regions. Again, the base-
pairing rule is important in this recognition (A binds to U and C binds to G). The ribosome moves
along the mRNA, matching 3 base pairs at a time and adding the amino acids to the polypeptide
chain. When the ribosome reaches one of the "stop" codes, the ribosome releases both the
polypeptide and the mRNA. This polypeptide will twist into its native conformation and begin to
act as a protein in the cell's metabolism.
GENETIC ENGINEERING
Historical Development
The term genetic engineering initially referred to various techniques used for the modification or
manipulation of organisms through the processes of heredity and reproduction. As such, the
term embraced both artificial selection and all the interventions of biomedical techniques,
among them artificial insemination, in vitro fertilization (e.g., “test-tube” babies), cloning, and
gene manipulation. In the latter part of the 20th century, however, the term came to refer more
specifically to methods of recombinant DNA technology (or gene cloning), in which DNA
molecules from two or more sources are combined either within cells or in vitro and are then
inserted into host organisms in which they are able to propagate.
The process of genetic engineering requires the successful completion of five steps:
GMOs, or genetically modified organisms, are organisms whose genetic material has been
altered using genetic engineering. GMOs range from microorganisms like yeast and bacteria to
insects, plants, fish, and mammals. Genetically modified crops (GM crops) are those
engineered to introduce a new trait into the species. Purposes of GM crops generally include
resistance to certain pests, diseases, or environmental conditions, or resistance to chemical
treatments (e.g. resistance to an herbicide). Another purpose of genetic modification of crops is
to enhance their nutritional value, as seen in the case of golden rice.
The use of GM crops is widely debated. At the moment there is no known harm in consuming
genetically modified foods. GM foods are developed – and marketed – because there is some
perceived advantage either to the producer or consumer of these foods. This is meant to
translate into a product with a lower price, greater benefit (in terms of durability or nutritional
value), or both.
Some Potential
Benefits of Using GMOs Risks of Using GMOs Consequences to the
Environment Include:
1. a decreased use of pesticides and 1. potential 1. Unintended
insecticides development selection
2. reduced greenhouse gas emissions of allergens 2. Unwanted change in
3. increased nutritional values in foods 2. production of a toxic gene expression
4. contribute to an increase in the number substance to “non- 3. Unintended effect on
of functional foods or nutraceutical target” organisms non-GM weeds,
foods with added benefits 3. increased pests, or pathogens
5. better taste endocrine 4. Survival and
6. the faster output of cops disruption, persistence
7. more crops can be grown on less land reproductive beyond the
disorders, and intended zone
8. genetically modified animals have a
accelerated aging
higher resistance to disease and 5. Production of a toxic
overall better health 4. antibiotic resistance substance to 'non-
5. unknown effects target' organisms
6. soil and water 6. "Horizontal Gene
pollution transfer "
This has many uses in the society of today, from research and biotechnology to the medicine
stocked on the shelves of pharmacies. The ability to manipulate the creation of DNA with
technology has proven to be useful in various applications, as outlined below.
Food Industry
The process to manufacture cheese usually relies on an enzyme called rennet, which contains
chymosin. Traditionally, this substance is taken from the stomach milk-fed cows to manufacture
cheese. However, recombinant DNA of chymosin has been in use since 1990, and is genetically
and structurally identical to the original enzyme, but can be produced in larger quantities and a
lower cost.
A specific variety of rice, golden rice, is genetically engineered with recombinant DNA to
express enzymes that promote B-carotene biosynthesis. At present this is still in the process of
passing regulations, but has the potential to reduce prevalence of vitamin A deficiency
worldwide.
Pharmaceutical Industry
Diabetic patients often require injections of human insulin to help control levels of glucose, as
they have lost the ability to regulate blood glucose effectively. Using rDNA to create human
insulin rather than obtain it form animal sources allows their widespread use across the
pharmaceutical industry.
Recombinant human growth hormone is used to support normal growth and development for
patients with malfunctions in the pituitary gland. This offers a noticeable benefit, particularly
when contrasted to previously used methods of obtaining the hormone from cadavers, which
could pose serious negative health effects.
Blood clotting factors play an essential role in the management of patients that suffer from
hemophilia, a bleeding disorder involving lack of ability to produce enough blood clotting factor
VIII for blood coagulation to function as normal. The ability to manufacture recombinant blood
clotting factor VIII allows larger quantities to be used in practice and reduces the need for blood
donation to obtain the factor naturally.
Hepatitis B is an infection of the liver that can be prevented with the hepatitis B vaccine.
Recombinant DNA of the hepatitis B virus surface antigen is produced in yeast cells to be
included in the vaccine. This is beneficial as the hepatitis virus does not proliferate in vitro and
recombinant DNA provides a method to create the DNA needed to control hepatitis B.
Medical Research
Recombinant DNA has been used in the development of the most common diagnostic
techniques for HIV.
The antibody test uses a recombinant HIV protein to measure antibodies in the body that
proliferate when there is a HIV infection.
The DNA test uses reverse transcription polymerase chain reaction (RT-PCR) to detect
presence of HIV genetic material. This technique was developed using rDNA of
molecules and analyzing the genome sequences.
Agricultural Industry
Some commercial crops, such as soy, maize, sorghum, canola, alfalfa and cotton, are grown
with recombinant DNA that increases resistance to herbicides used in the agricultural process.