Chapter 16 - The Molecular Basis of Inheritance Flashcards
thomas hunt morgan
(1910)
genes are on the chromosome (chromosome = DNA + protein)
frederick griffith
(1928)
he discovered that it is a heritable factor that can “transform” bacteria (he did the mouse and S/R cells experiment)
oswald avery, colin macleod, & maclyn mccarty
(1944)
discovered that the “transforming” agent is DNA
what is a bacteriophage? what is it made of?
also known as “phage” is a duplodnaviria virus that is made of protein and DNA
a virus that parasitizes a bacterium by infecting it and reproducing inside it
a virus that infects bacteria
alfred hershey & martha chase
(1952)
DNA, not protein, is the genetic material of bacteriophages
erwin chargaff
(1952)
base composition varies between species
(base composition = proportions of the 4 nucleotides/bases, could be percentages)
found that in DNA, the ratios of adenine (A) to thymine (T) and guanine (G) to cytosine (C) are equal
rosalind franklin & maurice wilkins
(1952)
they found out from an X-ray diffraction photo of DNA that the DNA is a double helix (2 strands rather than 1)
DNA => uniform diameter, base-spacing
=> phosphates are on the outer part of the DNA while bases are on the inner part
james watson & francis crick
based on rosalind franklin and wilkin’s data they concurred that A is attached to T and G is attached to C
Adenine = Thymine
Guanine = Cytosine
what are the 3 key features of DNA?
1.) anti-parallel strands
(strand C: 3’ => 5’)
(strand W: 5’ => 3’)
2.) sugar phosphate “backbones”
3.) bases “glue” strands together with H-bonds
does DNA start at 3’ or 5’ end?
starts at 5’ end, 5’ end to 3’ end
what are the 3 possible models for DNA replication?
(look in notes for a picture)
1.) conservative = parents re-associate
2.) semi-conservative model (most accurate model of what actually happens) = parents serve as templates
=> produces hybrids; 1 parent, 1 new
3.) dispersive = each product strand is a mix of parent & new hybrid
matthew meselson & franklin stahl
(1958)
determined that the semiconservative model was most accurate
parent molecule
2 strands
new strand synthesis
nucleotides line up along the template according to base-pairing rule
DNA polymerase
type of enzyme that is responsible for forming new copies of DNA, in the form of nucleic acid molecules
adds nucleotides to a strand based on a template
what are the limitations of DNA polymerase?
1.) cannot open double-stranded DNA (needs helicase to open it)
2.) cannot keep single-stranded DNA (needs single-stranded binding protein to stabilize the single-strand DNA)
3.) requires existing strand to extend (needs primase to attach onto template so it can attach onto primase and continue its job)
true or false: several proteins help prepare template strands for replication
true
helicase
(enzyme, protein)
unwinds parental double helix at replication fork
single-stranded binding proteins
stabilize parental strands, preventing re-annealing (renaturation of a DNA sample that has been dissociated by heating)
binds to and stabilizes single-stranded DNA until it is used as a template
re-annealing
renaturation of a DNA sample that has been dissociated by heating
topoisomerase
relieves strain caused by strand unwinding by breaking, swiveling, & rejoining DNA strands
primase
synthesizes RNA primer at 5’ end of leading strand and at 5’ end of Okazaki fragment of lagging strand
leading strand of DNA
continuous strand
lagging strand of DNA
discontinuous strand (in fragments) and literally lagging behind the leading strand
synthesized away from the replication fork (DNA polymerase III)
series of segments called Okazaki fragments
DNA pol I
replaces RNA primers with DNA essentially
takes out RNA primers, reads DNA, and adds in complementary DNA sequence
removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides
lagging strand of DNA
discontinuous strand (in fragments) and literally lagging behind the leading strand
Okazaki fragments
(during replication of DNA)
short sections of DNA formed at the time of discontinuous synthesis of the lagging strand
DNA pol III
using parental DNA as a template
synthesizes new DNA strand by adding nucleotides to an RNA primer or a pre-existing DNA strand
DNA pol I
removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides
DNA ligase
seals gaps
joins Okazaki fragments of lagging strand
joins 3’ end of DNA that replaces primer to the rest of leading strand DNA
telomeres
non-protein coding repetitive sequence found at the ends of the chromosome
it acts as a buffer to protect protein coding genes
shortens with each replication
linear DNA starts shortening during replication
true
telomerase
protein-RNA complex, DNA synthesis (RNA-directed)
serves as a template for extending the 3’ end of the telomere
central dogma
a theory stating that genetic information flows only in one direction, from DNA to RNA to protein or RNA directly to protein
DNA => RNA => protein
RNA => protein
what are the main differences between DNA and RNA?
DNA
function: contains genetic information/instructions needed for organisms to develop, survive, and reproduce
location: nucleus
sugar: deoxyribose
length: several million base pairs (ATGC)
replication: self-replicating
strand: double-stranded
RNA
function: creates proteins via translation
location: nucleolus => cytoplasm
sugar: ribose
length: several thousand base pairs (AUGC)
replication: synthesized by transcription
strand: single-stranded
what is the relation between DNA and RNA?
RNA carries the information from the DNA and transforms that information into proteins that perform most cellular functions
DNA => RNA = makes proteins
