Genetics and Evolution Flashcards
(157 cards)
Gregor Mendel
described the basic principles of hereditary, not the molecular foundations.
Thomas Hunt Morgan
associated a specific gene and its subsequent phenotype (eye colour in fruit fly) with a specific chromosome (the X chromosome)
Frederick Griffith
showed that cell extracts can transform bacteria, indicating biological macromolecules carry hereditary information.
Frederick Griffiths work
- made use of two strains of streptococcus pneumoniae in mice
- one lethal (smooth - S), the other less virulent (rough - R)
- tried to identify if changes (ie: adding heat) can make a difference in survival in mice.
What are the characteristics of the lethal streptococcus pneumoniae in Frederick Griffiths experiment on mice
- Smooth (S)
- presence of polysaccharide capsule
What are the characteristics of the less virulent (less lethal) streptococcus pneumoniae strain in Frederick Griffiiths experiment on mice
-Rough (R)
- lack of presence of polysaccharide capsule
What was found in Freddrick Griffiths experiment using two strains of streptococcus pneumoniae
-heat killed S strains were injected to mice and the mice were able to survive
-when heat killed S and R were injected mice died
-suggested that S can spread virulence to R even though it was heat killed
-unknown how R became virulent
Oswald Avery and Colin Macleod, Maclyn McCarry
- systematically and chemically destroyed each biological macromolecule in the extracts from dead S s.pneumoniae
- injected into mice with live R strain
- different scenarios(ie: no components destroyed, polysaccharide destroyed, lipids destroyed, RNA destroyed, Protein destroyed, DNA destroyed)
-mouse died in every scenario except when DNA was destroyed, suggesting that DNA was able to transform bacteria, and was the molecule of heritability that scientists had been looking for.
Alfred Hershey and Martha Chase experiment
- used phage T2 (virus that infects bacteria)
- grew two parallel cultures, one labeled P (contained radioactive DNA - due phosphorus in the backbone), one S (radioactive protein capsids were added due to the sulfur in methionine and cysteine containing sulfur atoms)
-infect new cultures - cultures centrifuged
- phages grown in radioactive P was transferred to bacteria host cells (confirming DNA was the hereditary material)
Phage ghosts
phage viroin that lacks nucleic acids
supernatant
liquid above solid residue (ie: after centrifuging)
Erwin Chargaff and DNA as hereditary information
in species DNA has consistent make up; human DNA is 30.9% adenine, 29.4% thymine, 19.9% guanine, 19.8% cytosine
Matthew Meselson and Franklin Stahl and DNA
showed that DNA replication is semiconservative; cellular DNA is copied during each cell cycle, and is therefore self-perpetuating and consistent
DNA vs other macromolecules and hereditary
DNA is not broken down in comparison to other macrmolecules such as carbohydrates and proteins and have a short half-life
Diploid Organisms (or cells)
have two copies of the genome in each cell
Haploid cells
one copy of the genome
sexual reproduction
- diploid zygote is produced by fusion of two haploid gametes (a haploid ovum and haploid spermatozoon) –>
- the zygote then goes through many mitotic divisions to develop into an adult with half the genetic material in each cell from each parent –>
- the adult female or male produces haploid gametes by meiotic cell division to repeat the life cycle once again.
zygote into adult
- require thousands of gene products
- encoded in the genome inherited from mother and father
- gene
- gene at locus
gene
a length of DNA coding for a particular gene product, fundamental unit of inheritance
locus
where every gene can be pinpointed to a specific location on a specific chromosome
can all physical traits of an organism be mapped to a single locus?
No. Every gene is located at a specific locus, but physical traits, particularly complex traits, like weight or height, can be controlled by many different genes and therefore do not map to a single locus, but to many
autosomes
non-sex chromosomes
allosomes
sex chromosomes (X, Y)
The human genome is split into how many chromosomes
24
22 automsomes + 2 different allosomes (X,Y)