35 - DNA Organization, Replication, Repair Flashcards
What is the substance within a chromosome? - condenses during cell division to form chromosomes
chromatin
Chromatin is consisted of
1.) dsDNA
2.) histones (basic)
3.) nonhistone proteins (acidic)
4.) RNA - in small quantity
Spherical particles that are composed of DNA would around an octameric complex of histone proteins
nucleosome
Histone protein characteristics
- basic
- hydrophobic
Organizational unit of chromatin
Nucleosome
Nucleosome composition
- octamer of histones
- 150 bp of DNA wrapped twice around the proteins
Nucleosome size
10 nm
Types of Histones
Covalent modification of core histone
DNA packing sequence
DNA > nucleosome (10nm fibril) > chromatin (30nm fibril) > chromosome
DNA in transcriptionally active regions is sensitive to nuclease attack of what enzyme
DNAse 1
Parts of a chromosome
(1) Chromatid
(2) Centromere
(3) Telomere
- Transcriptionally inactive chromatin
- Densely staining
- Chromatin is high in meC content
*Histones contain relatively lower levels of certain “activating” covalent modifications - high er levels of “repressing” histone PTMs
Heterochromatin
Two types of heterochromatin
Transcriptionally active chromatin - would stain less densely
Euchromatin
Chromatid are connected at a (1) in (2) region
(1) centromere
(2) A-T rich region
Essential for segregation during mitosis; anchors the mitotic spindle
Kinetochore
Short T-G rich repeats
Telomeres
Enzyme responsible for telomere synthesis and maintaining its length
Telomerase
Telomere shortening is associated with
cancer and aging
Nucleotide sequences in a gene
Target for recombination studies
Introns
In transcription, the introns are eliminated via
splicing
(True/False)
Most of the part of the DNA are non protein coding
False
DNA sequence class
- nonrepetitive DNA
- Unique-sequence DNA
- Repetitive-sequence DNA
Repetitive sequences
LINEs
long interspersed repeat sequences
SINEs
Short interspersed repeat solution
Microsatellite repeat sequences application
- polymerase chain reaction
- reverse transcripted PCR
Portion of the gene copied by RNA polymerase
Transcription unit
RNA processing
- removal of introns
- ligate extrons
- RNA splicing of mature mRNA that appears at the cytoplasm
Enzyme that unwinds the DNA in both directions from the origin
DNA Helicase
Two requirements for DNA replication
1.) DNA template
2.) Free 3’-OH group
(1) RNA primers that bind to the DNA are produced by
(2) removes RNA primers by
(1) primase
(2) 5’-3’ exonuclease activity of DNA polymerase 1
DNA replication enzymes
Enzyme that covalently closes the DNA
Ligase
5’ - 3’ strand that has continuous replication
Leading strand
3’ to 5’ strand with discontinuous replication
Lagging strand
DNA chain is covalently proposed, etc.
DNA ligase
What is released when the new base forms a phosphodiester
Pyrophosphate
3 Important properties
- chain elongation
- processivity
- proofreading
Dangerous radioactive chemicals
Genotoxin
What is the smallest unit of genetic expression?
A. operon
B. locus
C. cistron
D. inducer
C. cistron
What are the major products of RNA polymerase III?
A. snRNA
B. mRNA
C. rRNA
D. tRNA
D. tRNA
What enzymes cut DNA at specific DNA sequences within the molecule?
A. Endonucleases
B. Ligases
C. Exonucleases
D. Polymerases
A. endonucleases
In transcription
A. once the enhancer is located, DNA unwinds to expose transcriptions site
B. pyrophosphate is released following each cycle of polymerization
C. the nascent trinucleotide retains the 5- triphosphate of the initiating nucleotide
D. pyrophosphatases degrade the inorganic phosphate providing reversibility of the overall reaction
B
To initiate transcription, the DNA-dependent RNA polymerase binds to
A. RNA transcript
B. promoter
C. beta subunits
D. methyl cap
B
What comprises complementary DNA copies of the population of mRNAs in a tissue?
A. clones
B. sectors
C. library
D. chimera
A
What enzymes catalyze bonds between DNA molecules, joining them?
A. endonucleases
B. ligases
C. exonucleases
D. polymerases
B
Variations of DNA are called
A. mutations
B. polymorphisms
C. variants
D. recombinants
B
What determines the peptide sequence?
A. orders of the codons in the mRNA
B. exons
C. anticodons in the rRNA
D. charged enzymes
C
True of histone code EXCEPT
A. It is an important determinant of gene
activity.
B. Histones are subjected to specific post translational modifications.
C. Histone acetylation and deacetylation are best understood.
D. Posttranslational modifications histones are subjected to are irreversible. No. RATIONALIZATIO
D
