DNA and Chromosome
Concepts and Approaches
Sept. 2024
Human is unique among living organisms
➢ Developed complicated languages
➢ Great civilizations
something special differentiates humans
from every other species
human life begins and ends at a fixed time
→ human species and all other forms of life must have
been created at a fixed moment
1
, 9/23/19
Theories of evolution 1858
Charles Darwin (1809-1882)
the various forms of life are not constant but continually give
rise to slightly different animals and plants, some of which
adapt to survive and multiply more effectively
The origin of this continuous variation?
evolutionary tree by Darwin, 1837
Cox et al., Molecular biology-Principles and practice, 2nd. 2015
Approach Mendelian Laws - Mathematics 1865
"hereditary particles"- genes
➢ traits
come in pairs, 1 parent contribute 1 copy
Gregor Mendel (1822-1884)
➢ different variants of a “gene” are called alleles
➢ one allele could mask the appearance of the other
hereditary particles maintain their separate identities across the generations
Nobody aware Mendel's work
– confirmed 16 years after Mendel’s death
Mendel’s first law (1865)
Watson et al., Molecular biology of the gene, 7th. 2013
2
, 9/23/19
1940s: What is the nature of the traits?
DNA isolated for the first time 1869
a vial containing nuclein
Friedrich Miescher Tübingen castle
(1844–1895)
Miescher studied proteins of leukocytes, collected from pus in
bandages of infected wound soiled bandages.
- Acidification of the solution precipitated a substance
- The substance is solubilized in alkali.
→ leukocyte nuclei isolation protocol
precipitated material differed from proteins → named nuclein
http://www.ralf-dahm.com/freepages/discovering-dna/
3
, 9/23/19
Approach Chromosomes and mitosis 1882
➢ Synthetic dye intensely absorbed by
granular structures in nucleus – chromatin
➢ Dividing cells split chromosomes to produce
Walther Flemming 2 identical halves - mitosis
(1843-1905)
→ nuclein and chromatin were the same
von Waldeyer-Hartz named thread-like structure
chromosomes (1888)
Flemming did not comprehend the relationship between cell division and heredity
Fry. Landmark experiments in Molecular biology. 2016
Nucleus is responsible for heredity 1902
Mendel's “factor” = chromosomes
Independently, the chromosome theory of heredity was reinforced by the Walter S. Sutton (1877-1916)
who was the first to show that chromosomes obey Mendel’s rules.
Grasshopper cells:
➢ During meiosis, chromosomes line up in pairs, same size and shape.
➢ Homologous pairs segregate so that each gamete receives one
chromosome from each pair.
➢ After fertilization, the resulting zygote had a full set of chromosomes
4
Concepts and Approaches
Sept. 2024
Human is unique among living organisms
➢ Developed complicated languages
➢ Great civilizations
something special differentiates humans
from every other species
human life begins and ends at a fixed time
→ human species and all other forms of life must have
been created at a fixed moment
1
, 9/23/19
Theories of evolution 1858
Charles Darwin (1809-1882)
the various forms of life are not constant but continually give
rise to slightly different animals and plants, some of which
adapt to survive and multiply more effectively
The origin of this continuous variation?
evolutionary tree by Darwin, 1837
Cox et al., Molecular biology-Principles and practice, 2nd. 2015
Approach Mendelian Laws - Mathematics 1865
"hereditary particles"- genes
➢ traits
come in pairs, 1 parent contribute 1 copy
Gregor Mendel (1822-1884)
➢ different variants of a “gene” are called alleles
➢ one allele could mask the appearance of the other
hereditary particles maintain their separate identities across the generations
Nobody aware Mendel's work
– confirmed 16 years after Mendel’s death
Mendel’s first law (1865)
Watson et al., Molecular biology of the gene, 7th. 2013
2
, 9/23/19
1940s: What is the nature of the traits?
DNA isolated for the first time 1869
a vial containing nuclein
Friedrich Miescher Tübingen castle
(1844–1895)
Miescher studied proteins of leukocytes, collected from pus in
bandages of infected wound soiled bandages.
- Acidification of the solution precipitated a substance
- The substance is solubilized in alkali.
→ leukocyte nuclei isolation protocol
precipitated material differed from proteins → named nuclein
http://www.ralf-dahm.com/freepages/discovering-dna/
3
, 9/23/19
Approach Chromosomes and mitosis 1882
➢ Synthetic dye intensely absorbed by
granular structures in nucleus – chromatin
➢ Dividing cells split chromosomes to produce
Walther Flemming 2 identical halves - mitosis
(1843-1905)
→ nuclein and chromatin were the same
von Waldeyer-Hartz named thread-like structure
chromosomes (1888)
Flemming did not comprehend the relationship between cell division and heredity
Fry. Landmark experiments in Molecular biology. 2016
Nucleus is responsible for heredity 1902
Mendel's “factor” = chromosomes
Independently, the chromosome theory of heredity was reinforced by the Walter S. Sutton (1877-1916)
who was the first to show that chromosomes obey Mendel’s rules.
Grasshopper cells:
➢ During meiosis, chromosomes line up in pairs, same size and shape.
➢ Homologous pairs segregate so that each gamete receives one
chromosome from each pair.
➢ After fertilization, the resulting zygote had a full set of chromosomes
4
