The document summarizes the molecular basis of inheritance through DNA and protein synthesis. It describes the structure of DNA as a double helix made of nucleotides. DNA replication follows the semi-conservative model where each parental strand serves as a template for a new complementary strand. Genes specify proteins via transcription of DNA into mRNA and translation of mRNA into polypeptides on ribosomes. Genetic engineering techniques allow manipulation of genes through recombinant DNA and gene cloning.

1. The Molecular Basis of
Inheritance
Presented by:
Marlett Ann R. de los
Santos

2. Deoxyribonuccleic acid
(DNA)
• A nucleic acid
molecule that
contains the
genetic instruction
used in the
development and
functioning of all
living organisms.

3. Structure of a DNA
-DNA is a very large polymer
made up of monomers called
nucleotides. Each DNA nucleotide
consists of a phosphate group, the
sugar deoxyribose and a nitrogen
base. The only difference among the
four nucleotides of DNA is in their
nitrogen bases.

4. The four nitrogen bases of DNA are the organic ring
structures:
*adenine
*guanine
*cytosine
*thymine
Only the nitrogen bases of the nucleotides vary. And
the amounts of adenine and thymine nucleotides are
equal likewise the amounts of guanine and cytosine
nucleotides are equal too.

6. • The Watson-Crick model of DNA
has two strands. The phosphate
sugar chains form the backbone for
each strand. The nitrogen bases of
each strand pair with the other strand
by hydrogen bonding. Adenine (A)
always pair with thymine (T) and
guanine (G) always pair with

7. Because there are two strands
in a spiral, the shape of DNA
is described as double helix.
The DNA double helix is
sometimes compared to a
twisted ladder. The sides of
the ladder are the sugar
phosphate backbones. The
rungs are the pair of nitrogen
bases.

8. It is the order of these bases that
makes up the genetic code.
Differences in the order give
individuality to each organisms.
When a cell divides, the DNA
preserves this individuality by
passing exact copies of itself to each
new cell.

9. Ribonucleic acid (RNA)
- a nucleic acid of nucleotide
monomers that plays several
important roles in the processes that
translate genetic information from
DNA into protein products.

11. Roles of RNA
1. RNA acts as a messenger between
DNA and the protein synthesis
complexes known as ribosomes.
2. RNA forms vital portions of
ribosomes.
3. RNA acts as an essential carrier
molecule for amino acid to be used
in protein synthesis.

12. Structure of RNA
• Instead of the base thymine, RNA contains
the nitrogen base uracil (U). Uracil pair with
adenine pair with adenine just as thymine
does in DNA. Thus, RNA contains the four
bases adenine, uracil, cytosine and guanine.
• Like DNA, RNA is a nucleic made of
bonded nucleotides. However, there are
some important differences in the molecules.
DNA contains the sugar deoxyribose, but
RNA contains ribose, a slightly different
sugar.
• Whereas, a DNA molecule takes the shape

14. Types of RNA
There are three main kinds of RNA found in
organisms:
1. Messenger RNA (mRNA) – carries information
specifying amino acid sequences of proteins
from DNA to ribosomes.
2. Transfer RNA (tRNA) – serves as adapter
molecule in protein synthesis; translates mRNA
codons into amino acid.
3. Ribosomal RNA (rRNA) – plays catalytic
(ribozyme) roles and structural roles in
ribosomes.

15. How DNA replicates?
REPLICATION
- the process by which molecule is
copied.

17. A model for DNA
replication: the basic
concept
a. The parent molecule has
two complementary strands
of DNA. Each base is paired
by hydrogen bonding with
its specific partner, A with T
and G with C.
b. The first step in replication is
separation of the two DNA
strands.
c. Each parental strands new
serves as a template that
determine the order of
nucleotides along a new
complementary strand.
d. The nucleotides are
connected to form the sugar-
phosphate backbone of the
new strand and one new
strand.

18. Does DNA replication follow
the conservative, semi-
conservative, or dispersive
model?
Matthew Meselson and Franklin Stahl cultured E.
coli bacteria for several generations on a medium
containing nucleotide precursors labeled with a heavy
isotope of 15N. The bacteria incorporated the heavy
nitrogen into their DNA. The scientists then transferred
the bacteria to a medium with only 14N, the lighter than
the parental DNA made in the 15N medium. They
distinguished the DNA by the difference in the densities
through centrifuging DNA extracted from the bacteria.

19. a. Semi-conservative model
- the two strands of the
parental molecule separate
and each function as a
template for synthesis of a
new, complementary
strand.
b. Conservative model
- the two parental strands
reassociate after acting as
templates for new strands.
c. Dispersive model
- each strand of both
daughter molecule contain
a mixture old and newly
synthesized DNA.

20. Meselson and Stahl concluded
that DNA replication follows the
semi-conservative model by
comparing their results predicted by
each of the three models.

22. Protein Synthesis
Genes specify proteins via transcription and
translation.
Transcription
-is the synthesis of RNA under the direction
of DNA.
Translation
-is the actual synthesis of a polypeptide,
which occurs under the direction of mRNA.

23. The resulting RNA molecule is a faithful
transcript of the genes protein-building
instructions. Messenger RNA carries the genetic
message from the DNA to the protein
synthesizing machinery of the cell.
The cell must translate the base sequence of
an mRNA molecule into the amino acid
sequence of a polypeptide. The sites of
translation are the ribosomes, complex particles
that facilitate the orderly linking of amino acid
into the polypeptide chains.

25. Why proteins could not
simply be translated
directly from DNA?
• It provides protection for the DNA
and its genetic information.
• Using an RNA intermediate allows
more copies of a protein to be made
simultaneously and be translated
repeatedly.

27. To summarize, cells are governed
by a molecular chain of
command:
DNA RNA PROTEIN

28. RECOMBINANT DNA or GENETIC
ENGINEERING
Genetic engineering
- the intentional production of new genes
and alteration of genomes by the
substitution or addition of new genetic
material.
Recombinant DNA
- a DNA resulting from the insertion of a
sequence of genes from one organism into
the DNA of another organism

30. Gene Splicing
is the cutting of DNA by
enzymes and insertion of a piece of
foreign DNA.
Gene Cloning
is the production of multiple
copies of genes.

31. How to extract DNA in
food?
• Materials needed: • Equipment needed:
Blender
Banana Coffee filter
Table salt Table spoon
Ethyl alcohol Graduated cylinder
Medicine dropper
Colorless shampoo
Test tube w/ cover
Distilled water Beaker
Ice cubes Bucket

32. • What to do?
Step 1.
* In a blender, mix a ratio of one banana per 250 mL of distilled
water.
* Blend for 15-20 seconds, until the mixture is a solution.
Step 2.
* In one of the 5 oz cups, make a solution consisting of 1 tsp. of
shampoo and two pinches of table salt.
* Add 20 mL of distilled water or until the cup is 1/3 full. Dissolve
the salt and shampoo by stirring slowly with the plastic spoon to
avoid foaming.
Step 3.
* To the solution you made in step 2, add the three heaping
teaspoons of the banana mixture from step 1. Mix the solution with
the spoon for 5-10 minutes.

33. Step 4.
* While one member of your group mixes the banana solution, another
member will place a #2 cone coffee filter inside the second 5 oz plastic
cup. Fold the coffee filter‘s edge around the cup so that the filter does not
touch the bottom of the cup.
Step 5.
* Filter the mixture by pouring into the filter and letting the solution drain
for several minutes until there is about 5 mL (covers the bottom of the
cup) of filtrate to test.
Step 6.
* Obtain a test tube of cold alcohol. For best results, the alcohol should be
as cold as possible.
Step 7.
* Fill the plastic pipette with banana solution.
Step 8.
* Add the solution to the alcohol.
* Let the solution set for 2-3 minutes without disturbing it. It is important
not to shake the test tube.

34. • EXPECTED RESULTS
You can watch the white DNA
precipitate out into the alcohol layer.
DNA has the appearance of white,
stringy mucus.

35. The End
thank you…