Lecture 8 Flashcards
what is genetic material?
Information contained in genes that gets passed onto new generation; Source of variability among organisms
what are the 4 characteristics needed for a molecule to be genetic material?
replication, store information, express information, and allow variation by mutation
what is the central dogma of genetics?
DNA > RNA > protein
What are the characteristics of retroviruses?
-They convert their RNA to DNA before taking over the host cell
=Replicate unusually
RNA serves as a template for DNA synthesis
-Complementary synthesis of DNA by RNA-dependent DNA polymerase reverse transcriptase
what was the Hershey-Chase experiment?
- foundation experiment responsible for finding DNA was the source of genetic material
- P32 found DNA and S35 found proteins
- There is then radioactivity in the dna but the others inject their genome but leave their radioactive “ghost” on the outside
- The ghosts are labeled and cells are not and the opposite was true for the dna infected phages
what do nucleotides consist of?
- a nitrogenous base
- a pentose sugar
- a phosphate group
what are the two kinds of nitrogenous bases?
- purines
- pyrimidines
Purines
- nine membered ring
- adenine
- guanine
pyrimidines
- six membered rings
- cytosine
- thymine
- uracil (RNA)
What nitrogenous bases do DNA have?
A, T, G, and C
what nitrogenous bases do RNA have?
A, C, U, and G
what is the difference between deoxyribose and ribose sugar?
deoxy means without oxygen, the difference is that there is not an oxygen on the 2’ hydrogen
what is the 5’ group attached to?
a phosphate group
what is the 3’ group attached to?
a nucleotide
what is a nucleoside?
a nitrogenous base with a pentose sugar
what is a nucleotide?
the same thing as a nucleoside, but it has a phosphate group attached to it
what are the three types of nucleosides?
nucleoside monophosphate, nucleoside diphosphate, and nucleoside triphosphate
how are nucleotides linked?
through phosphodiester bonds, they are connected from the 5’ group to the 3’ group
what is adenine complementary to?
thymine and uracil
what is guanine complementary to?
cytosine
what are the three classes of RNA?
messenger RNA, ribosomal RNA, and transfer RNA
ribosomal RNA (rRNA)
- structural components of ribosomes for protein synthesis
- catalytic ribosomes that start the process of making proteins
messenger RNA (mRNA)
- template for protein synthesis
- carry genetic information from the gene to the ribosome
- piece of RNA that encodes proteins and the process of making proteins
- leaves the nucleus and goes into the cytoplasm
transfer RNA (tRNA)
- carries amino acids for protein synthesis
- is an adapter molecule that can read the mRNA and bring the right amino acid to make a protein
are there other forms of RNA?
- Telomerase RNA and RNA primers: used to replicate DNA at the ends of chromosomes
- SnRNA: small nuclear RNA that processes mRNA
- RNA, micro RNA, and siRNA: gene regulation
what does semiconservative mean?
each replicated DNA molecule consists of an old strand and a new strand
how does the semiconservative model work?
- the two strands of the parent DNA is then split apart, then one new strand of DNA is made
- it consists of one old strand and one new strand
what direction does DNA polymerase go into?
5’ to 3’ direction
what are the 7 issues that need to be resolved in DNA replication?
- Unwinding of helix
- Reduce increased coiling generated during unwinding
- Synthesis of primer for initiation
- Discontinuous synthesis of second strand
- Removal of the R N A primers
- Joining of gap-filling D N A to adjacent strand
- Proofreading
how do you know the difference between genes and proteins?
genes are lower case and have italics while proteins are upper case and have no italics
dnaA
- unwinding of the helix
- initiator protein encoded by dnaA gene
- binds to ORI causing conformation change
- exposes ssDNA for DNA helicase to bind
DNA helicase
- made of dnaB polypeptides
- recruits holoenzyme to bind to replication fork and initiate replication
- unwinds DNA
reducing the supercoiling
- DNA gyrase
- snips to allow tension to unravel
- relieves coiled tension from sunwinding helix
Where does DNA replication begin?
at the origin of replication (ORI)
what does the ORI do?
- where new synthesis of DNA begins
- unwinding occurs
replication fork
- is at the site of replication
- where the helix is unwound
what is the termination sequence for DNA synthesis?
TER
what way is replication?
bidirectional
-there are two replication forks
replicon
length of DNA being replicated
how many ORIs do bacteria have?
1
DNA polymerase 1
- directs DNA synthesis
- requires a DNA template
- chain elongation
chain elongation
- occurs in the 5’ to 3’ direction, adding one nucleotide at a time to the 3’ end
- once a nucleotide is added, two terminal phosphates cleaved off, providing a newly exposed 3’ OH
DNA Polymerase 1,2,3
-can elongate existing DNA strand by adding a monomer to the 3’ end, but cannot initiate DNA synthesis
DNA Polymerase 1, 2, 4, 5
- involved in DNA repair
- repair DNA damaged by external forces like UV light
DNA Polymerase 3
acts as a holoenzyme (has multiple functioning parts as a single structure)
alpha
- polymerase 3 subunit
- 5’ - 3’ polymerization
epsilon
- polymerase 3 subunit
- 3’ - 5’ exonuclease
theta
- polymerase 3 subunit
- core assembly
tau
- polymerase 3 subunit
- connects core to rest of the holoenzyme
synthesis of primer for initiation
- made from RNA
- recruited to replicate from helicase
- provides the 3’ OH required by DNA pol 3 for elongation
- DNA pol 1 removes primer to replace with DNA
discontinuous synthesis of second strand
-there are two strands of a double helix that run antiparallel to each other
continuous strand
- continuous DNA synthesis
- leading strand that only have one RNA primer
discontinuous strand
- discontinous DNA synthesis
- lagging strand with many RNA primers
removal of RNA primers
- Okazaki fragments
- lagging strand synthesized as Okazaki fragments
- DNA pol 1 removes primers
- DNA is then filled in the gaps
joining of gap filling DNA
- DNA ligase
- catalyzes phosphodiester bonds
- seals nicks and joins fragments
proofreading
- DNA polymerase is not perfect
- relies on exonuclease activity 3’ - 5’ to remove nucleotide mistakes and fic them
