This document summarizes the historical development of genetics from early concepts to modern understanding. It describes key figures and their contributions, including: - Mendel who established basic laws of inheritance through pea plant experiments. - Watson and Crick who discovered the double helix structure of DNA. - Chargaff who found regular proportions of DNA bases between species. - Nirenberg who helped discover the genetic code. - Berg who created the first recombinant DNA molecules. The document traces the progression of genetics from early theories to establishing DNA as the molecule of inheritance and cracking the genetic code.

1. Historical Development in
Genetics
Ariane Ruby B. Sogo-an
MST Biology

2. Recall:
What is Genetics?
- One of the discipline of Biology, is the science of genes,
heredity, and provides scientific explanation on the
concept of variation in living organisms.
- Genetics concerns the process of inheritance from
parents to offspring, including the molecular structure
and function of genes, gene behavior in the context of
a cell or organism (e.g. dominance), gene distribution,
variation and change in populations.

3. Note:
• Given that genes are universal to living
organisms, genetics can be applied to the
study of all living systems; including
bacteria, plants, animals, and humans.

4. Terms and Definition
• Genes
– Unit of information about specific traits and they
are passed by from parents to offspring.
Gametes
- sexual reproductive cell that fuses with another
sexual cell in the process of fertilization.

5. Terms and Definition
Allele – molecular form of a gene. (ex. AA, Aa or aa)
- Homozygous – pair of alleles are identical
- Heterozygous – having unidentical pair of alleles

6. Terms and Definition
• True Breeding lineage- when offspring of the
genetic crosses inherit a pair of identical
alleles for a trait.
• Hybrid offspring – having unidentical alleles
• Genotype – refers to a particular an individual
carries
• Phenotype – refers to individual observable
trait.

7. Old Concept
• Blending of traits from parent to offspring
– Father’s blob of information is blended with the
mother’s blob of information.
Charles Darwin – Natural
Selection
- through the
generations, the variation that
improve that chance of
surviving and reproducing will
occur with greater frequency
than those that do not.

8. Gregor Mendel
• Published “Experiments in
Plant Hybridization”
Why Peas? (Pisum sativum)
1. It is self Fertilizing
2. Easy to breed
3. Fast growth and
development

9. • First established the basic laws of inheritance
– Theory of Segregation
– Theory of Independent Assortment
– Incomplete Dominance

10. Mendel’s Protocol
1. Stamen are cut out from the plant leaving the
female reproductive part
2. Pollen from a plant is brushed onto another
floral bud. (to ensure cross breeding)
3. Cross fertilized seeds and each seeds are
allowed to grow onto new plant.
4. Observe traits.

11. Theory of Segregation
• Mendel’s hypothesis:
– In every generation, a plant inherits two (2)
“units” of information about a trait, one from
each parent.
Monohybrid crosses:
- insert picture of monohybrid cross
F1 – All heterozygous
F2 – 3:1

13. Independent Assortment
• Mendel attempted to explain HOW two pairs
of genes might be assorted into gametes

14. Dihybrid Crosses:

15. Incomplete Dominance
• One allele isnt completely dominant over its
partner, a heterozygous phenotype
somewhere in between the two homozygous
phenotypes emerges.
• Cross-Breeding of White and Red Snapdragon.
– All F1 came out as Pink. (still referred as
genotipically heterozygous )

16. Johann Friedrich Miescher
• Extraction of DNA.
• - At first, Miescher focused on the various
types of proteins that make up the
leucocytes.
• Miescher noticed that a substance
precipitated from the solution when acid was
added and dissolved again when alkali was
added
• He had, for the first time, obtained a crude
precipitate of DNA. Miescher stated that
“According to known histochemical facts, I had to
ascribe such material to the nuclei and he
decided to examine the cells’ nuclei more
closely.”

18. Walther Flemming
• Flemming investigated the process
of cell division and the distribution
of chromosomes to the daughter
nuclei, a process he
called mitosis from the Greek
word for thread.
• However, he did not see the
splitting into identical halves, the
daughter chromatids.
• He studied mitosis both in
vivo and in stained
preparations, using as the source
of biological material
the fins and gills of salamanders.

19. Boveri-Sutton
• The Boveri–Sutton
chromosome theory
(also known as the
chromosome theory of
inheritance or the Sutton–
Boveri theory) is a
fundamental unifying theory
of genetics which identifies
chromosomes as the carriers
of genetic material.

20. Boveri-Sutton
• It correctly explains the mechanism
underlying the laws of Mendelian inheritance
by identifying chromosomes with the paired
factors (particles) required by Mendel's laws.
It also states that chromosomes are linear
structures with genes located at specific sites
called loci along them.

22. • It states simply that chromosomes, which are
seen in all dividing cells and pass from one
generation to the next, are the basis for all
genetic inheritance.
• The demonstration of the chromosomal basis
of inheritance gave rise to the modern science
of genetics.

23. William Bateson
• Described gene linkage
• Used Mendel’s work as his
basis for inheritance
principle.
• First suggest the term
Genetics 1905

24. • Bateson had close contacts with clinicians interested in
inherited disorders, notably Archibald Garrod, to whom
he suggested the recessive inheritance of alkaptonuria.
• . Bateson's views on human inheritance were far
sighted and cautious. Not only should he be regarded
as one of the founders of human genetics, but human
genetics itself should be seen as a key element of the
foundations of mendelian inheritance, not simply a
later development from knowledge gained by study of
other species.

25. Archibald Garrod
• Discovered
alkaptonuria, understanding
its inheritance.
• Discovery of genetically
inherited diseases. He was
one of the first scientists to
apply Mendelian genetics to
the study of human disease.

26. • Garrod treated a three-month-old
boy with alkaptonuria.
• Over the next several years Garrod
compiled data on this disease,
much of it gathered from
interviews with the families of 39
alkaptonuria patients.
• None of the parents of children
with the disease were affected;
however, every set of parents
turned out to be first cousins.

27. Pedigree

28. Conclusion:
- alkaptonuria was not caused by a bacterial
infection error triggered by the pairing of two
rare recessive genes. Individuals with both
recessive genes lack the enzyme needed to
break
Inborn Errors of Metabolism
Revised edition included: albinism and porphyria

29. Herman Muller
• Best known for his
successful induction of
mutations of genes in the
fruit fly by the use of X rays.
• He is known also for his dire
warnings concerning the
effects of nuclear radiation
on human genes.

30. • Muller frequently warned of the long-term
dangers of radioactive fallout from nuclear
war and nuclear testing, helping to raise
public awareness in this area.

31. • When he started working with Thomas Hunt
Morgan in the early 1900s, they would
occasionally find mutant flies (includes white
eyed flies).
• They already suspected that phenotypic
expression of the flies is caused by mutation.
• He based from a literature that X-Ray destroys
Chromosomes (however, it was not yet
established by that time that it can also cause
mutation).

32. • To test his theory, he made an experiment to
look for mutation induced by X-Rays.
• He used a special strain to female flies
carrying lethal recessive gene.

33. • In the first cross, female fly carrying a
recessive lethal gene was crossed with male
whose sperm had been bombarded with X-
Ray. He found that male flies that inherited
the lethal gene died.

34. • He also found that male in the 2nd cross that
inherited mutation induced by X-Ray gene also
died. Therefore, X-ray causes mutation.

35. Erwin Chagaff
• Regularity in proportion of
DNA in each Species.
• He began with the belief
that if DNA from different
species exhibited different
biological activities, there
should also be chemically
demonstrable differences
between the DNA.

36. Recall:
Chemical Structure of the DNA

37. 1. The first was the separation of the DNA
mixture into individual components by paper
chromatography.
2. The separated compounds were converted
into mercury salts.
3. The purines and pyrimidines were identified
via their ultraviolet absorption spectra.
Chargaff tested the method on several mixtures
of purines and pyrimidines and reported his
encouraging results in the Classic.

39. • Insights of the composition of DNA with the
scientific community:
• - Amount of Adenine relative to Guanine
differs from one species to the next.
• - The Amount of Adenine in DNA always
equals that of Thymine and the amount of
guanine always equals to Cytosine.
• Thus,
• A = T and G = C

40. Maurice Wilkins/
Rosalind Franklin
• Found that DNA was at least
a helix shape
• They took x-ray
crystallographic photographs
(x-ray diffraction) of protein
structures and found that
DNA was a helix.

41. Process: beam of x-rays is directed at a
molecule. The molecule scatters the beam in
patterns that can be captured of film. The
pattern itself consist only in dots and streaks.

42. Francis Crick
James Watson
• Crick determined that
DNA was a double helix
made of two
polynucleotide strands
• They looked at the photo
taken by Rosalind Franklin
closer and found that DNA
was a double helix and
that it was made of two
polynucleotide strands.

44. Chagaff Rule:

50. Marshall Nirenberg
• The Genetic code was
discovered; scientists are
now able to predict
characteristics by studying
DNA. This leads to genetic
engineering, genetic
counseling.

51. The Genetic Code

52. Paul Berg
• Creates first recombinant
DNA molecules.
• He was the first to
combine deoxyribonucleic
acid (DNA) molecules from
different organisms,
creating a hybrid known as
recombinant DNA.

53. • He selected the genes of simian virus 40 (SV40), a
monkey virus known to cause cancer in human
cells and in laboratory cultures. First, he
combined the DNA molecule of SV40 with the
DNA of a bacterial virus called lambda.
• He then planned to insert this hybrid molecule
into the bacterium Escherichia coli, where the
lambda virus would then attack the bacteria.

54. • Berg surmised that when the virus entered the
baterial cell, it would inject its own DNA—the
recombined SV40-lambda molecule. The bacteria
would then multiply, causing the alien gene to
replicate itself in large quantities.
• His genetic-engineering technique is used to
manufacture specific human proteins like
interferon, and has created the potential for
curing genetic defects.

55. Human Genome Project
• Human Genome Project
(headed by Charles
DeLisi), international scientifi
c collaboration that seeks to
understand the entire
genetic blueprint of a human
being.
• James D. Watson 1988-1992
replaced by Francis Collins in
April 1993.
• Project completed in 2003

56. Goal of HGP

57. • Through a process known as sequencing, the
Human Genome Project has identified nearly
all of the estimated 20,000 to 25,000 genes
(the basic units of heredity) in the nucleus of a
human cell. The project has also mapped the
location of these genes on the 23 pairs of
human chromosomes, the structures
containing the genes in the cell’s nucleus.

58. 1. The genome was broken into smaller pieces;
approximately 150,000 base pairs in length.
2. These pieces were then ligated into a type of vector
known as "bacterial artificial chromosomes", or
BACs, which are derived from bacterial chromosomes
which have been genetically engineered.
3. The vectors containing the genes can be inserted into
bacteria where they are copied by the bacterial DNA
replication machinery.
4. Each of these pieces was then sequenced separately as a
small "shotgun" project and then assembled. The
larger, 150,000 base pairs go together to create
chromosomes.
This is known as the "hierarchical shotgun" approach, because
the genome is first broken into relatively large chunks, which
are then mapped to chromosomes before being selected for
sequencing.

59. Key findings of the draft (2001) and complete
(2004) genome sequences include:
• 1. There are approximately 20,500 genes in human
beings, the same range as in mice.
• Understanding how these genes express themselves
will provide clues to how diseases are caused.
• 2. The human genome has significantly more
segmental duplications (nearly identical, repeated
sections of DNA) than other mammalian genomes.
These sections may underline the creation of new
primate-specific genes.

60. Field Contribution
Horticulture,
Animal Breeding
Scientists to alter a plant or animal to make it more
useful.
- GMO Fruits, Vegetables
- Livestock breeding
- Improve milk production
Economy Address food shortage
- Rice
Forensic Science Helped convict criminals via DNA test on semen, torn
out skin, blood, hair etc.
Medicine - Genetically alter bacteria so that they mass-produce
specific proteins, such as insulin used by people with
diabetes mellitus
- Human growth hormone (Chlorella) used by children
who suffer from growth disorders.

61. Contribution Controversies Outcome
The production of
medicines through
the use of
genetically altered
organisms
Critics of recombinant DNA
fear that the pathogenic, or
disease-producing,
organisms used in some
recombinant DNA
experiments might develop
extremely infectious forms
that could cause worldwide
epidemics.
National Institutes of
Health (NIH) in the
United States has
established regulations
restricting the types of
recombinant DNA
experiments that can be
performed using such
pathogens.
Production of
transgenic animals
to improve yield
and quality
(ex. fish)
Some experts fear that this
process may change the
characteristics of wild fish
in unpredictable and
possibly undesirable ways.
Currently under study

62. Contribution Controversies Outcome
Use of genetically
engineered bovine
somatotropin (BST) to
increase the milk yield
of dairy cows
Some critics
question the safety
of BST for both the
cows that are
injected with it and
the humans who
drink the resulting
milk.
Canadian Scientist
found out that:
BST caused
mastitis, lameness
and infertility to
cow but still safe
for human
consumption.
Transgenic plants to
improve crops and yield
(soybeans)
Allergens can be
transferred from one
food crop to another
through genetic
engineering.
Found out that it causes
allergic reaction to
humans
- Project was
canceled.

63. References:
1. BIOLOGY Concepts and Application 4th Edition Cecie Starr 2009
2. www. Wikipedia.com
3. American Society for Biochemistry and Molecular Biology 2013
(Online ISSN 1083-351X)
4. www.lucasbrouwers.nl
5. "The Discovery of the Molecular Structure of DNA - The
Double Helix". Nobelprize.org. Nobel Media AB 2013. Web. 30
Jun 2013.
6. 2002 - 2011, DNA Learning Center, Cold Spring Harbor
Laboratory
7. Department of Biology, Davidson College, Davidson NC 28035
8. National Center for Biotechnology Information, U.S. National
Library of Medicine

64. ARIBA ARIBA!!!
Thank you for Listening