Unit 4 (Part 2). Nucleus Flashcards
DNA replication is describe as
SEMICONSERVATIVE
Replication always starts at
specific locations on the
DNA, which are
called
origins of replication
DNA double helix acts as a
_______ for the synthesis of
a new, complementary
strand.
template
In E.coli, origin is
about ____ base pairs long.
245
Two Y-shaped structures
called _______ forming ________
replication
forks
replication
bubble
THeSis PDOLLi [DNA replication process (analysis)]
- Topoisomerase - relieves unwinding strain ahead of replication forks by breaking, swiveling and rejoining DNA strands
- Helicase - unwind parental double helix at replication fork
- Single-strand binding protein - binds to and stabilizes single-stranded DNA until it is used as a template
- Primase - synthesizes RNA primer from 5’ end of leading strand and 5’ end of each Okazaki fragments of lagging strand
- DNA POLYMERASE (1) DNA pol III - synthesizes new DNA strand by adding nucleotides to an RNA primer or pre-existing DNA nucleotides
(2) DNA pol I - removes RNA nucleotides of primer and replaces them with DNA nucleotides - DNA Ligase - joins Okazaki fragments of lagging strand
Relieves unwinding strain ahead of replication forks by breaking, swiveling and rejoining DNA strands
Topoisomerase
Unwind parental double helix at replication fork
Helicase
binds to and stabilizes single-stranded DNA until it is used as a template
Single-strand binding protein -
synthesizes RNA primer from 5’ end of leading strand and 5’ end of each Okazaki fragments of lagging strand
Primase
synthesizes new DNA strand by adding nucleotides to an RNA primer or pre-existing DNA nucleotides
DNA polymerase III
removes RNA nucleotides of primer and replaces them with DNA nucleotides
DNA polymerase I
joins Okazaki fragments of lagging strand
DNA Ligase
Which statement is INCORRECT about the importance of DNA replication
A. DNA replication makes an exact copy.
B. DNA must be replicated everytime a cell
divides.
C. Replication ensures that the correct genetic
information is passed on from cell to cell and
generation to generation.
D. Errors in replication can cause mutation, thus
replication is low fidelity.
E. It is essential for the continuation of life.
D
low fidelity —-> high fidelity
Stages of RNA Synthesis / Transcription (3)
Initiation Stage
Elongation Stage
Termination Stage
RNA is Composed of:
➢Sugar (ribose)
➢Phosphate
➢Phosphodiester linkage
➢Nitrogenous bases:
A,G,U,C
- protein coding regions?
- protein non-coding regions?
Exons
Introns
In transcription, the addition _______ of _________ and
5’ cap
3’ poly A tail
Intron Splicing
occurs by using
spliceosome
mRNA nitrogenous bases are grouped into three called
codons
How many codons in the genetic code?
64
Start codon?
Stop codons?
AUG (methionine)
UGA, UAG, UAA
Which statement is not true about initiation stage of protein synthesis/translation?
A. Small ribosomal unit attached to the start codon of mRNA.
B. Amino acid brought by specific rRNA
C. tRNA anticodon will complement with the mRNA codon.
D. Attachment of the large ribosomal unit
(with A, P, and E sites) completing the translation complex.
B.
Amino acid brought by specific [tRNA]
exit site of uncharged tRNA
E site
where the peptide bond between amino acid
formed
P site (Peptidyl tRNA binding site)
receiving the incoming amino acid
A site (Aminoacyl tRNA binding site)
elongation stops when it reaches the stop codons (UGA, UAG, UAA).
Termination Stage
Gene rapair fix the following problems: (3)
• Base mismatches and mismatch repairs
• Base Excision Repair
• Nucleotide Excision Repair
Mechanism for Double strand Break (2)
• Homologous recombination
• Non-homologous end joining
A mechanism of gene rrpair that can cause
mixed up
Non-homologous end joining
