Lecture 8 and 9: DNA and RNA Flashcards
Aneuploidy
- presence of one or more extra chromosomes or the absence of one or more chromosomes.
- can occur by mitosis or meiosis or crossover during metaphase
Karyotypes
-is a test to identify and evaluate the size, shape, and number of chromosomes in a sample of body cells. Extra or missing chromosomes, or abnormal positions of chromosome pieces, can cause problems with a person’s growth, development, and body functions
DNA Ligase
seals DNA (okazaki) fragments on lagging strand -repairs and joins together two DNA strands
DNA polymerase
repairs gaps between Okazaki fragments
- responsible for DNA replication
- needed so the cells DNA can duplicate
- Deoxynucleotide polymerization
DNA primase
Initiates synthesis of RNA primers
Topoisomerases
relieves torsional strain that results from helicase
Helicase
unwinds dna strands which forms replication fork( two DNA strands ripped apart)
-ATP driven
Synthesis of a new DNA strand is written in which of the following direction
B. 5’ to 3’
Types of DNA Damage
Replication-Natural
Trisomy 21
- Extra chromosome on 21
- Down syndrome
Diploid
Two sets of genetic info
- one maternal, one paternal
23 sets-> 46 chromosomes
RNA
- ribose sugar
- has uracil
- single stranded
- is a complementary copy of DNA
- made in shorter units than DNA
Cyclic nucleotides
play an important role in cell signaling
ATP
Adenosine 5 Triphosphate
Purines
- Have two rings
- A and G
Pyrimidine
- Have one ring
- C, G and U
Nucleoside
Base+Sugar
Nucleotide
Base+Sugar+Phosphate
Which of the following statement is correct? Ribose and deoxyribose are present in mammals in a:
A. D‐beta configuration?
B. L‐beta configuration?C. D‐alpha configuration?
D. L‐alpha configuratio
A. D‐beta configuration?
D-sugars are in the body
Transcription
DNA -> RNA
-carried out by RNA polymerase
tRNA
Transfer RNA
Links mRNA to amino acid
miRNA
inhibit/modulates translation
–Transcribed from DNA
snRNA
intron removal
RNA Polymerase
- Starts copying template strand
- no proofreading
- DOES NOT participate in mRNA splicing
Translation
mRNA to protein
Splicing
Introns are removed and exons are spliced together
Rifamycin group
inhibit RNA synthesis by targeting RNA polymerase
Coding Strand
5’ to 3’
Template Strand
3’ to 5’
IncRNA
regulate mRNA and gene
transcription via RNA Pol II
DMD
Exon is deleted which is a mutation that abolishes expression of dystrophin which is an essential protein that maintains muscle fiber integrity
Ribose
ribonucleic acid
Deoxyribose
deoxyribonucleic acid
- lacks oxygen on the 2’ carbon
In DNA A pairs with____
and G pairs with ____
T
C
How many copys of genetic info do we have?
two
Is all DNA in one linear strand?
No we have chromosomes
How do we go
from meters of
DNA to microns?
Histones → nucleosomes
DNA replication – S phase
- Requires several origins of replication
-Occurs from ssDNA template - Requires RNA primer to initiate replication
- is directional
- Requires ligation of individually copies and
re-condensation into chromatin structure
Okazaki fragments
- Lagging ( 3’ to 5’)
- Leading strands ( 5’ to 3’)
Polymerase can only make new DNA
in the 5’-3’ direction from a 3’-5’ template
DNA replication in eukaryotic cells
- Binding of initiator proteins
- Binding of DNA Helicase
- Loading DNA Helicase onto DNA strand
- DNA helicase unwinds the DNA double strand
- RNA primer syntheis enables DNA polymerase to start first DNA chain
6 Formation of replication forks
Single-strand binding proteins (SSBs)
- Prevent premature reannealing of daDNA
Spontaneous/endogenous DNA damage
– Deamination
– Oxidation (ROS)
– Methylation
Exogenous DNA damage
– UV radiation
– Ionizing radiation
– Drugs and environmental exposure
In RNA
no primer is needed compare to in DNA replication
- no proofreading
Coding strand ATGATCTCGTAA -> mRNA
AUGAUCUCGUAA
Coding strand ATGATCTCGTAA -> template strand
TACTAGAGCATT
Endogenous
having internal cause or origin
Endogenous RNA
miRNA
snRNA
IncRNA
Rifamycin group: Rifampin, Rifabutin, Rifapentine
Inhibit RNA synthesis by targeting RNA polymerase.
Transcription begins when
RNA polymerase binds to a so-called promoter sequence on the DNA molecule
- They express genes at different times -> development, differentiation, adaptation
Mechanisms regulating gene expression
- Gene amplification
- Gene rearrangment
- RNA processing
- Alternate mRNA splicing
- Transport of mRNA from nucleus to cytoplasm
- Regulation of mRNA stability
- Compartmentalization
- ncRNA silencing and activation
mRNA processing and splicing – Intron removal
- Primary transcript
- Nucleophilic attack at 5’ end of intron
- Lariat formation
- Cut at 3’ end of intron
- Ligation of 3’ end of exon 1 to 5’ end of exon 2
Which of the following statement about RNA polymerase complex
is false? RNA polymerase
A. binds to the promotor region on the DNA strand
B. participates in mRNA transcription
C. participates in mRNA elongation
D.participates in mRNA splicing
D.participates in mRNA splicing
From a gene to a protein
• mRNA → proteins through
- Initation
- Elongation
- Termination
Requires:
• mRNA
• tRNA
• rRNA
What would be the anticodon for the start codon AUG?
UAC
Codon is read
Anti-codon is read
5’ to 3’ AUG mRNA
3’ to 5’. UAC
Translation initiation
- mRNA must associate with rRNA • Location “start” codon (AUG) = codon • Matched to AUC on tRNA = anticodon • Attached to methionine • Amino acid chain begins
Elongation
- “Read” mRNA in sets of 3 NA = codon
- Growing chain in P-site; amino acid added in A site, then shift down
- Repeat until reach codon with “empty” anti-codon/tRNA
Termination
• Chain elongation will
stop when tRNA
associating lacks an
amino acid
miRNA are also transcribed from
DNA (specific genes encoding for miRNA)
Transcription takes place in ____ where translation takes place in ____
Nucleus
RIbosome
Which of the following statements about miRNA is correct?
A. miRNAs are transcribed from RNA
B. miRNAs are transcribed from DNA
C. miRNAs are involved in mRNA splicing
D. miRNAs are involved in DNA transcription
B. miRNAs are transcribed from DNA
Duchenne Muscular Dystrophy (DMD)
an X-linked genetic disease and one of the most severe form of
muscular dystrophy
- 1 in 5,000 male births
- is due to missense mutations in the dystrophin gene abolishing
expression of the dystrophin, an essential protein that maintains muscle fiber integrity
Phosphorodiamidate Morpholino Oligomer (PMO)
A Promising Drug to Treat DMD
exon skipping therapy
- In frame – mRNA translated,
Truncated protein product
