chapter 16 Flashcards
What did T.H Morgan’s group show
That genes exist as parts of chromosomes
What are the two chemical components of chromosomes
dna and proteins
who was frederick griffith
british officer who tried to develop a vaccine against pneumonia
what bacteria did griffith study
streptococcus pneumonia
what is streptococcus pneumonia
bacteria that causes pneumonia in mammals
what strains did griffith have
two strains (varieties of bacterium) one pathogenic and one nonpathogenic
what does pathogenic mean
disease causing
what does nonpathogenic mean
harmless
why was the frederick griffith experiment important
it first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation.
what two strains does streptococcus have
smooth and rough strain
what are some characteristics of the smooth strain
capsule that protects it from the immune system
highly pathogenic
what are some characteristics of the rough strain
lacks capsule and easily killed
nonpathogenic or harmless
what happens when the smooth strain is injected into the mice
it dies
what happens when the rough strain is injected into the mice
it survives
what happened when the smooth strain was heated and injected into the mice
the mice survived
what happened when the heat killed smooth strain and the rough stain were injected to the mice and what did it indicate
the mouse died; transformation
what is transformation
rocesses by which genetic material in the form of “naked” deoxyribonucleic acid (DNA) is transferred between microbial cells
Who later identified the transforming change as DNA
□ Oswald avery, Maclyn McCarty, Colin MacLeod
why are avery, mccarty and macleod important
showed that DNA (not proteins) can transform the properties of cells
what was the avery,mccarty, macleod experiment
took lysate of heat killed s strain and treated it with different enzymes and dnase did not convert the s train to r strain
what are bacteria phages
virus that infects bacteria
what is a virus
small collection of genetic code, either DNA or RNA, surrounded by a protein coat. A virus cannot replicate alone.
How can a virus produce more viruses
□ Must infect a cell and take over the cell’s metabolic machinery
what did scientists believe in the early 20th century
that proteins was the genetic material
what are the order of the experiments
griffith, avery macleod mccarty, hershey and chase
in the Hershey chase experiment what were the two bacteriophages labeled with
bacteriophage coat was labeled with (Protein) S35 and the bacteriophage dna was labeled with P32 (DNA)
what organism was used in the hershey chase experiment
bacteriophage
what were hershey and chase trying to prove
if dna is the genetic material or protein
what two things do viruses contain
dna core with a protein coat
what did they use to label the dna
radioactive tags
where is phosphate found
in dna and not in proteins
where is sulfur found
in proteins
what did they figure out with the sulfur labeled tag
most of the radioactivity remained with the virus and did not enter the bacteria
what bacteriophage did hershey and chase use
e.coli
what is the polymer of nucleotides
dna
what are the components of dna
nitrogenous base, deoxyribose pentose sugar, phosphate group
what are the dna bases
adenine, guanine, thymine, cytosine
a =?
t
g =?
c
what were chargaffs rules
dna base composition varies between species
the percentages of a and t bases are roughly equal and the percentages of g and c bases are roughly equal
what is rosalind franklin famous for
x ray crystallography which provided clues to the structure of dna
what does a double helix mean
the dna has two strands
what was franklins arrangement of the dna
sugar phosphate backbones were outside of the dna molecule
negatively charged phosphate groups facing aqeuous solutions
who were watson and crick and what did they do
scientists that discovered the shape of dna was a helix
what did watson construct
□ An antiparallel structure
what does antiparallel mean
Subunits run in opposite directions
what type of bond links the nucleotides together
covalent sugar phosphate bonds
the phosphate group is attatched to what ed
5 end of sugar
the bases are attatched to what end
1 end of the sugar
what is the bond that keeps the bases together
hydrogen bond
what interaction happens between stacked base pairs
van der waals
what is dna replication
the copying of dna
what is the semiconservative model
after one round of replication, every new DNA double helix would be a hybrid that consisted of one strand of old DNA bound to one strand of newly synthesized DNA
what is the conservative model
the entire original DNA double helix serves as a template for a new double helix
what is the dispersive model
each strand of both daughter molecules contains a mixture of old and newly synthesized dna
what was the importance of the meselson and stahl experiment
supported the semiconservative model of dna replication
what is the origins of replication
where replication of chromosomal dna begins and they are short stretches of dna that have specific nucleotides
what are some characteristics of the e coli chromosome
circulur and has a single origin
what is the replication fork
y shaped region where the parental strands are being unwound
what is helicase
enzyme that untwist the double helix at the replication forks and make them available as template strands
what are single-strand binding proteins
bind to the unpairaed dna strands and keep them from re-pairing
what is topoisomerase
breaks and rejoins dna strands and it relives the dna
what direction is dna read
5 to 3
what end is dna added
3 end
what can the enzymes not do in dna replication
initiate synthesis of dna they can only add nucleotides to an already existing chain
what is a primer
pre existing chain of rna that is produced during dna synthesis
what is primase
starts a complementary rna chain with a single rna nucleotide ands rna nucleotides one at a time
what does dna polymerase do
catalyze the syntehsis of new dna by adding nucleotides to the 3 end
proof read the dna
what does dna poly 3 do in ecoli
adds dna nucleotide to the rna primer
what do most polymerases require
a primer and a dna template strand
what is the leading strand
a single DNA strand that, during DNA replication, is replicated in the 3’ – 5’ direction
what is the lagging strand
a single DNA strand that, during DNA replication, is replicated in the 5’ - 3’ direction
synthesized disontinuously
what are okazaki fragments
segments of the lagging strand
what happens in a mismatch pair
other enzymes remove and replace incorrectly paired nucleotides
what is a nuclease
dna cutting enzyme
what is a nucleotide excision repair
dna repair system
what is a telomere
the repetitive DNA repeat sequences at the end of linear eukaryotic chromosomes protecting chromosome ends from degradation and illegitimate recombination
what are the functions of telomeres
- ) prevent the stagered ends of the daughter molecule from activating the cells systems
- ) buffer zone that protects against organisms genes shortening
what is a nucleosome
the basic unit of dna packing
what are histones
proteins that help pack the dna in interphase
what is euchromatin
less compacted and more dispersed dna
what is heterochromatin
more compact and denser chromatin
