UPDATE | WITH COMPLETE SOLUTION.
Genes exist on linear chromosomes Answer - Mendel (1866): Genes control
phenotype (undefined substance)
• Walther Flemming (1882): Chromosomes exist and are passed down in cell
division
• Theodor Boveri (1890): Chromosomes must contain information for next
generation (Ascarids only keep all chromosomes in germline)
Thomas Hunt Morgan Answer - Genes must lie on chromosomes because
Drosophila eye color is a sex-linked trait and chromosomes are different
between sexes (1908).
Hypothesis of crossing over allows mapping of genes along chromosome
Answer - Linked traits must be closer together on physical chromosome
· First observation of chromosomes Answer - o Didn't know what the gene
physically could be but no idea on how chromosomes were connected to genes
o Walter flemming observed mitotic structures of chromosomes and had to
draw by hand that they copied themselves, divided into equal numbers and
passed things down during cell division.
· Genes exist on linear chromosomes
o Boveri Answer - § 1890
§ Looking at things, chromosomes might contain information for the next
generation by looking at ascarids proteins
,· Horse parasites that have a weird life cycle with all chromosomes in their
germ line, but cell throws away parts of DNA that it doesn't need
· Chromosomal material is less in chromosomes, but germ line contains the
same number of chromosomes
o Something needs to be passed down to the next generation
o Chromosomes might have something to do with inheritance and the nucleus
but don't know what a gene would physically be.
· Thomas Hunt Morgan Answer - o 2nd person ever to work with flies in his lab
o Discovered eye color was linked to gender and there's different looking
chromosomes between male and female
§ So he inferred that the gene laid on that sex chromosomes
Hypothesis of crossing over allows mapping of genes along chromosome
Answer - o Homologous chromosomes overlap and trade pieces of material
§ If this is true genes that are next to each other should be linked together
while genes far apart might be separated and be found more often
o From this able to map out how close the genes are on the fly traits
· Barbara McClintock mapped out corn Answer - o Could look at corn colors
and patterns and see what genes and traits were changed
o Flies are easy to work with and fast, whereas corn takes awhile.
Frederick Griffith Answer - o Tested to see how heredity transferred
o Took non virulent strains of Strep. Pneumoniae to become virulent when
mixed with heat killed pathogenic bacteria.
o Found that if you mixed 2 strains of strep together 1 was no virulent
§ Mice would live
,o One was virulent
§ Mice would die
o If kill bacteria with heat
§ Mouse lives
o If mixed the heat killed strain and the nonvirulent strain something would
transfer to the live bacteria that's normally not deadly and make the mice die.
o If you mix the heat killed strain and non variable strain, something would
transfer and cause the mouse to die
o If you mix the heat killed strain and non variable strain, something would
transfer and cause the mouse to die Answer - § This was the first evidence of a
"transforming principle"
· Information from one bacterial cell enters into another bacteria cell and this
leads to genetic engineering
We need an experiment that would let us test which component can transfer
heredity Answer - Frederick Griffith (1928): non-virulent strains of
Streptococcus pneumoniae became virulent when mixed with heat-killed
pathogenic bacteria.
A transforming principle in bacteria can carry genetic specificity
Avery, MacLeod and McCarty (1944): Used this Bacteria transformation to do
First Molecular Biology experiment in history Answer - Starting in 1940...Try:
Breaking down all the proteins (proteolytic enzymes)
Breaking down just the RNA (pancreatic ribonuclease)
Many other treatments, none of which worked
, Breaking down just the DNA (pancreatic deoxyribonuclease)
"Who would have thought?" (only published in 1944)
What Makes this "Molecular Biology"? Answer - Using tools produced by
biology (pancreatic enzymes)
Systematically manipulating components to see how they work instead of
watching the outcome of mating crosses
Viral genes are made of DNA Answer - Alfred Hersey and Martha Chase (1952):
The bacteriophage T2 carries the genetic information in the DNA and the
protein coat serves only as a shell.
· In 1940, Avery, MacLeod, and McCarty Answer - o Tried to figure out what
component of the mixture killed the mice from the previous experiment.
o This experiment they thought it was proteins so they used proteases and
chloroform or whatever could digest proteins and the mouse still died
o Tried to do beak down RNAs by using RNase enzyme to breakdown enzyme,
lipids, heating up, alcohol, and phenol, and the mouse still dies. Couldn't get rid
of what causes the bacteria to be virulent.
o Last experiment to DNase (degrades DNA) and then the mouse lives
§ DNA might be the genetic carrier
o This was the first molecular biology experiment in history
o This was the first molecular biology experiment in history Answer - § Makes
molecular biology because using tools for their experiment
· Using dna enzymes, and manipulating components to see how it works.
· Take away one thing and put in something new at a time to see what it does