Genetics PPT 1 Flashcards
what do chromosomes consist of
nucleic acid and protein
what are the two forms that Streptococcus pneumoniae exist in
• Encapsulated, virulent form
Smooth in colony appearance
• Nonencapsulated, avirulent form
Rough in colony appearance
who did an experiment in 1928 with Streptococcus S and R Cells
Fred Griffith
who conducted a 14 year study to identify the
transforming agent identified by Griffith.
Oswald Avery (1944)
examined the nitrogenous bases found in DNA He found that the composition of the nitrogenous bases varies from species to species
Erwin Chargaff (1947)
The experiments by them provided additional evidence for DNA as the carrier of information
Hershey and Chase (1952)
what did Hershey and Chase do
used radioactive labels to identify the protein and DNA components of the T2phage
Complete set of genetic information is referred to as
a
genome
Genome of all cells is composed of
DNA
Functional unit of genome is the
gene
Gene codes for
gene product
Gene product is most commonly
protein
Study of transfer of genes
genetics
Study of sequence of DNA
genomics
Living cells must accomplish what two general tasks to multiply
DNA replication and DNA expression (gene expression)
Expression involves what
transcription and translation
this copies information in DNA to RNA
transcription
this interprets RNA to synthesize protein
translation
what is DNA made up of
deoxyribonucleotides
what do the nucleotides include
Phosphate group, 5 carbon sugar (Deoxyribose), and Nitrogenous base
what does the joining of nucleotides create
an alternating sugarphosphate backbone
DNA occurs as what
double-stranded molecule
strands are held together by what
hydrogen bonds
what are the complementary pairs
A is bound to T by two hydrogen bonds
G is bound to C by three hydrogen bonds
what causes strands to differ at the
ends
Chemical structure and
joining of nucleotide subunits
DNA molecule is
anti parallel
One strand has a phosphate attached at the number 5
carbon of the sugar
5 prime end
The other strand has a hydroxyl group attached to the number 3 carbon of the sugar
3 prime end
how does prokaryotic DNA usually exist
closed circular, double stranded DNA molecule
Looped and coiled extensively is what
supercoiled
Portion of the genome that contains an origin and is replicated as a unit
replicon
replication in prokaryotes is
bidirectional
why is DNA replicated
to create a second copy of the molecule
This is a complex process involving numerous enzymes
and proteins
DNA replication
two parental strands separate and serve as templates for synthesis of new strands
semiconservative
The two new molecules each contain
a parental and new strand
As the strands of DNA unwind, an area of replication called the ________ ______ is created
replication fork
As nucleotides are added, the replication fork moves along the
parental strand
how is DNA synthesized
one nucleotide at a time
enzymes, in regards to DNA replication, …
read DNA template in 3’ to 5’ direction
DNA polymerase, in regards to DNA replication, …
replicates in 5’ to 3’ direction
Is synthesized continuously as the DNA polymerase
moves towards the replication fork
leading strand
Is synthesized discontinuously, in pieces, as DNA
polymerase moves away from the replication fork
lagging strand
DNA polymerase must bind to ___ ____ to begin
synthesis
an RNA primer
what joins the fragments of the lagging strand
DNA ligase
complete sequence of events extending from formation of a new cell through next division
cell cycle
what are the two separate control pathways in E coli
sensitive to cell mass
sensitive to cell length
DNA replicated then septation begins
slow growth rate
DNA replicated and new round of DNA replication begins before septation begins
rapid growth rate
what does gene expression in bacteria involve
transcription and translation
Carries the coded information from DNA to the
ribosome, which is the site of protein synthesis
Plays an important role in translation
mRNA
transcription in prokaryotes…
catalyzed by a single RNA polymerase
• large multi-subunit enzyme
RNA polymerase can only add nucleotides…
to the 3’ end of a chain
RNA polymerase binds to a region of the DNA called the
promoter
one strand of DNA acts as a template
sense strand
strand not transcribed
nonsense strand
subunit that recognizes the promoter before initiation of transcription.
sigma factor
during this, RNA polymerase binds to the promoter and melts (unwinds) a short piece of DNA
initiation
The single-stranded mRNA transcript is synthesized in
the 5’ to 3’ direction
RNA polymerase advances along DNA, melting a
section at a time and allowing the previous section to
close
elongation
When polymerase encounters the termination code it
dissociates from DNA and releases mRNA
termination
A transcript for one gene
monocistronic
transcript for multiple genes
polycistronic
what are the RNA molecules involved in translation
- Ribosomal RNA (rRNA)
* Transfer RNA (tRNA)
what are the two general mechanisms of metabolic pathways
Allosteric inhibition of enzymes
Controlling synthesis of enzymes
Many genes are not regulated, their products being
produced all the time
constitutive enzymes
Regulation of gene expression… (3)
conserves energy and raw materials • maintains balance between the amounts of various cell proteins • allows organism to adapt to long-term environmental change
