DNA
DNA
A DNA (deoxyribonucleic acid) is a molecular polymer carrying genetic instructions for growth, reproduction, and function of all organisms, a genetic code that made them unique, with 2 chains coil together to make a double helix.
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Deoxyribonucleic acids (b.k.a. DNA)
Structure
Structure
DNAs are polymers made of 4 chemical bases: adenine (A), guanine (g), thymine (T), and cytosine (C).
Common DNAs called "double-stranded DNA" (dsDNA) are made of 2 polynucleotide chains coiled around each to form a double helix.
DNAs carry genetic instructions for developments, functions, growths and reproductions of any organisms and viruses.
DNA and ribonucleic acid are nucleic acids.
It's made of adenine (A), guanine (G), thymine (T), and cytosine (C).
(One in purple. One in yellow in the image)
Two polynucleotides make a DNA.
an unwinded strand of DNA
By unwinding DNA, it's shown that each strand is called a nucleotide, made of three components each:
a phosphate group
a deoxyribose sugar molecule
adenine (A)
guanine (G)
cytosine (C)
thymine (T)
Deoxyribose is called so as it's missing a hydroxide group at deoxyribose's second carbon is significant as it helps stabilize the DNA molecule.
James D. Watson
James D. Watson
James Dewey Watson is an American zoologist, molecular biologist, geneticist, and author who wrote books such as "DNA: The Secret of Life". He, Francis Crick, and Maurice Wilkins won the 1962 Noble Prize of physiology "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material".
Chemist superstar, Linus Pauling had found the exact arrangement of chains of amino acids/polypeptides fold up in proteins, naming it the a-helix/Alpha helix.
As soon as I returned to Copenhagen I read about Pauling a helix to my surprise his model wasn't based on a deductive leap from experimental X-ray diffraction data. Instead, it was Pauling's long experience as a structural chemist that that had encourage him to infer which type of helical fold would be most compatible with the underlying chemical features of the polypeptide chain. Pauling made scale models of the different parts of the protein molecule, working out plausible schemes in three dimensions. He had reduced the problem to a kind of three-dimensional jigsaw puzzle was that was simple yet brilliant. Whether the a-helix was correct- in addiction to being minor-was now the question.
Physicist Francis Crick who spent the war working on magnetic mines for the Admiralty. With end of the war, Crick planned to stay in military research, reading Shrodinger's What is Life? book, he moved to biology. Now he was pursuingg the 3D structure of proteins for his Ph D.
His endless questions as a child compelled his weary parents to buy him a children's encyclopedia, hoping that it wouldsatisfy his curiosity, only to made him insecure: he confided to his mother his fear that everything would have been discovered by the time he grew up, leaving him nothing to do. His. mother reassured him that there would still be a thing or twp for him to discover.
A great talker, Crick was invariably the center of attention in any gathering. HIs booming laugh was forever echoing down the hallways of the Cavendish. As the MRC Unit's resident theortician, he used to come with a novel insight at least once a month, and he would explain his lastest idea at great length to anyone willing to listen. The morning we met he lit up when he learned that my object in comping to Cambridge was to learn crystallography have a go at the DNA structure Soon I was asking Crick's opinion about using Pauling's model-building approach to go directly for the structure. Would we need many more years of diffraction experimentation before modeling would be practiable? To bring us up to speed on th the status of DNA structure studies, Crick invited his friend Maurice Wiklins from London for lunch. Wiklins believed that DNA's structure was a helix formed by several chains of linked nucleotides twisted around each other. All that remained to be settled was the number of cchains. At the time, Wiklins favored three based on his density measurements of DNA fibers. He was keen to star modemodel- buthe had run into a roadblock in the form of a new addition to the King's College BIophsics Unit, Rosalind Franklin.
In 1953, Pauling published a paper on the DNA structure. He proposed a three-chain model with sugar-phosphate backbones forming a dense central core, similar to a botched model a year earlier.
But it seemed to me, the biologist, that such hydrogen bonds required extremely acidic conditions never found in cells. With a mad ash to Alexander Todd's nearby organic chemistry lab my belief was confirmed: The impossible happened.
One of the best chemist had gotten his chemistry wrong: The subject was
deoxyribonucleic acid, but the structure he proposed was not even acidic; he knocked the 'A' off of DNA.
A geometry suggested that a helix was the most logical arrangement for a long string of repeating units like DNA's nucleotides, but what the helix looked like was unknown nor how many chains it had.
Bacteria
Bacteria
Classic experiments: DNA as the genetic material - Khan Academy
British scientist Fred Griffith studied the human bacterial agent, Pneumococcus. It has two strains, designated "smooth" (S) and "rough" (R). Injecting S into a mouse would kill it a few days later. It remains healthy if it receives R.
It is because S bacterial cells have a coating stopping the mouse's immune system from recognizing the invader.
R cells have no such coating and are therefore readily attacked by the mouse's immune defenses.
Curious, Griffith tested how different strains can interact with his unfortunate mice. By injecting heat-killed S bacteria and normal R bacteria (both harmless), it killed the mice days later.
The clue came when the Pneumococcus was isolated from the dead mice and found a living S bacteria. The R bacteria acquired something from the dead S variant, which allowed the R in the presence of the heat-killed S bacteria to transform itself into a living killer S strain. He confirmed that the bacteria bred true for the S type as any regular S strain would. A genetic change occurred to the bacteria injected into the mouse.
History
History
DNA wasn't deemed as possible for code-script bearers as permutations in the order of amino acids on the chain are roughly infinite, proteins could roughly readily encode the information underpinning life's extraordinary diversity, even if it was mainly seen on chromosomes and are known for almost 7 decades. In 1930, DNAs were known to be long molecules made of four different chemical bases: adenine, guanine, thymine, and cytosine.
underpinning: basic
But in Schrödinger's lecture, it's unclear how subunits (deoxynucleotides) of molecules were chemically linked and whether DNA molecules can vary in their sequences of the four bases.
Deoxynucleotides ("deoxy" means to have less oxygen in a molecule than the compound it's derived from. + nucleotides) are the monomeric units of DNAs, the genetic material in all organisms, each made of three main parts: a phosphate group, a deoxyribose sugar molecule, and one of four nitrogenous bases: adenine, guanine, cytosine, or thymine.
monomeric: basic unit
Chromosomes
Chromosomes
Chromosomes are mostly represented with the letter 'x' and 'y' and have two parts
Autosomes (not-sex chromosomes)
Sex chromosomes indicate the organism's sex
To represent genes on chromosomes, smaller letters of the first mutant type are written on the top right.
E.g. 'w' is used to represent the mutant allele for white-eyed flies and add a white sign beside to indicate it is a wild type.
As genes are arranged like beads on a necklace string, a chromosome string, a break is statistically more likely to occur between two far genes than between two close genes. The rarer the reshuffling, closer the genes are.
The rediscovery of Mendel's work, and the breakthoughts following it, sparked a surge of interest in the social significance of genetics. While scientists and been grappling with the precise mechanisms of heredity through the 18th and 19th centuries, public concern had been mounting about the burden place on society by what came to be called the "degenerate classes" - the inhabitants of workhouses, and insane asylums.
Natural selection
Natural selection
Publication of Darwin's Origin of Species in 1859 brought these issues into sharp focus. Though Darwin carefully omitted to mention human evolution, fearing that do so would only further inflame an already raging controversy, it needed no big leap of imagination to use his idea of natural selection to humans. Natural selection is the force determining the fate of all genetic variations in nature, mutations like the one Morgan found in the fruit fly-eye-color gene, but also maybe differences in the abilities of humans to fend selves.
Natural populations have a huge reproductive potential, like fruit flies, with a generation time of just ten days, and females producing about 300 eggs apiece (half are females) starting with one fruit fly couple, a month after (3 generations after), 150³ will be born, more than 3 million flies.
Darwin chose a species from the other end of the reproductive spectrum: elephants are reckoned to be the slowest breeder of all known animals
Eugenics was an opportiunity for humans to control their own evolutionary destiny.
Darwin's famous example of the Galapagos Islands, those with genetic benefits, like the right size of beak for eating abundant seeds can survive and reproduce, a beneficial form that can be passed onto generations with beneficial mutation, eventually all members with that characteristic.
Darwin's cousin and friend, Francis Galton was inspired by The Origin of Species. He started a social and genetic crusade, "genetics", that would have grave consequences after Darwin's death.
Eugenics indicates the application of a highly gifted race by wise marriages in many human generations.
Today, eugenics is a dirty word linked to racism and Nazies, a dark forgotten phase of genetic history. It should be noted that eugenics wasn't always like that and deemed by many to help society and its people. It seems to be the answer to one of society's most continuous crises: a part of a population that can't exist outside an organization.
Galton instead preached what came to be called "positive eugenics," advising superior peoples to give birth, the American eugenics movement preferred to focus on "negative eugenics", preventing genetically inferior people from doing so. Each program's goals were mostly the same: human genetic stock's improvement, but these two ideas were different.
Origin of the word "Moron"
Origin of the word "Moron"
A 1912 study by psychologist and eugenicist Henry Goddard invented the word "moron", what he called the "Kallikak Family". "Kallikaak" a hybrid of two Greek words, kalos (beautiful) and kako (bad). Moron is used by Goddard to describe "feeble-minded" peoples. It's closely tied to the US involvement in eugenics, a scientific term meaning "well-born", describing the belief that the human population can be controlled by breeding to increase the occurrence of desirable heritable character characteristics. It focuses on eliminating unwanted ones singing out unmarried mothers, the poor and those with disabilities.
singing out: calling out, calling for
A report says that "moron" was from Goddard's fascination with intelligence and his desire to to measure what it was and what wasn't.
Most female organisms have xx chromosomes. Male have xy chromosome
Gender differences
Gender differences
Females have two copies of the X chromosome. Males have one copy and one of a much smaller.
The Fruit Flies Experiment
The Fruit Flies Experiment
Fruit flies (Drosophila Melanogaster) and humans have shockingly 60% of similar genes to each other. Fruit flies are used as model organisms.
Thomas Hunt Morgan is the father of experimental genetics using fruit flies to find something new, in early 1900s.
In a container of red-eyed fruit flies (normals), one was white-eyed (mutants). White eyed were mostly males.
F1 Generation
A female white-eyed and a male red-eyed breed gave birth to the F1 Generation, all were red-eyed offspring, showing that red-eye color is a dominant trait.
In basic terminology, F1 Generation refers to the first-generation of springs bred by parents. 'F' stands for 'filial. In short, F1 means 'first filial generation'.
dominant trait: traits inheritance that are mostly passed vertically from parent to child where both are affected by the trait related to the gene.
F2 Generation
For the F2 Generation, he excepted a phenotypic 3:1 ratio and a genotypic 1:2:1 ratio
(1. female red-eyed
2. male red-eyed
3. white-eyed female)
F2 Gen. resulting in a male white-eyed proved the Chromosomal Theory of Inheritance
phenotypic: organism with physical/observable traits, like height, eye color, and blood type
genotypic: genetic information/code inherited from its parent
dominant genes are dominating genes/higher chances of passing down to offspring than other (recessive) genes
recessive genes are genes that are being dominated/lower changes of passing down to offsprings
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