DNA Flashcards
What are the two types of nucleic acids?
DNA and RNA
What is a deoxyribose nucleotide?
DNA. Which consist of a phosphate, nitrogen base and a 5 carbon sugar
What is a ribose nucleotide?
RNA. It’s the same as DNA but it has an extra OH on the 2nd sugars carbon.
Nitrogen bases:
C and T
A and G
C and T are pyrimidines= single bonds
A and G are purines= double bonds
* base pairing is C///G
* complementary is A//T
What is DNA?
- Double helix that is formed from 2-anti-parrallel strands
- OH bonds link nitrogen bases
- Phosphodiester bonds join nucleotides through condensation rxn’s
What is RNA?
Single strand nucleotides
The 3 types are:
tRNA- (transfer RNA) carries amino acids
rRNA- found in ribosomes of the cytoplasm
mRNA- (messenger RNA) carries messages from DNA to ribosomes
Differences between RNA and DNA
- DNA has thymine while RNA has uracil
- DNA is double stranded while RNA is single stranded
- DNA contains deoxyribose while RNA contains ribose
Nucleoside vs nucleotide
Nucleoside- Nitrogen base + sugar
Nucleotide- Nitrogen base + sugar + phosphate
DNA REPLICATION: Step 1
-HELICASE unzips the double helix by breaking the OH bonds between the base pairs and GYRASE relieves the tension during the unzipping process
DNA REPLICATION: Step 2
-DNA POLYMERASE 3 starts attaching nucleotides together and SSB prevent the strands from rejoining
DNA REPLICATION: Step 4a
- PRIMASE adds RNA primer
- DNA POLYMERASE proof reads and fixes new strand
DNA REPLICATION: Step 4b
- LAGGING STRAND is synthesized
- DNA POLYMERASE 3 adds deoxyribonucleotides from primer to primer forming okazaki fragments
- DNA LIGASE joins fragments by creating phosphodister bonds
DNA REPLICATION: Step 5
2 new semi conservative strands are produced
Discovery of DNA (the scientists)
Griffith- Bacterial transformation
Chargraff- The base pair rule
Avery- DNA= hereditary material of viruses
Hammerling- Hereditary info is stored in the nucleus
Wilkins + Franklin- Shape of DNA is helix
Watson + Crick- Shape of DNA is double helix
Meselson + Stahl- Theory of semi- conservative replication
What makes up a chromosome?
DNA + protein
Thymine, adanine, cytosine and guanine %
T and A = 30% (60%)
C and G = 20% (40%)
———-
100%
Transcription
RNA POLYMERASE splits the 2 halves of the DNA strands then uses 1 half as a template to copy or “transcribe” the other half.
RNA = uracil instead of thymine
EXAMPLE
Template DNA-TTACG
Complementary DNA- AATGC
Messenger RNA- AAUCG
Translation
Transfer RNA (tRNA) anticodons that match messenger RNA codons. Each tRNA can hold an amino acid. The amino acids are then joined together to form a polypeptide
EXAMPLE
Anticodon- AUG (mRNA)
Codon- UAC
Gene control in prokaryotes- Lac operon
Lactose operon (lac operon) is the stretch of DNA that can be turned on or off to regulate production of lactose degrading enzymes
The operon has 3 important regions which are:
- The promoter/ TATA sequence (binding site of RNA polymerase) to begin transcription
- Operator (binding site for repressor protein)
- Cluster of 3 genes:
LacZ- codes for B-GS
LacY- codes for B- GSP
LacA- codes for B- GST
MUTATIONS: Deletion
Base is lost
- identical mutation= neutral
- different mutation= harmful
MUTATIONS: Insertion
Base is added
MUTATIONS: Substitution
3 types:
Missense- Amino acid is switched
Silent- no change
Nonsense- Changes amino sequence to a STOP
What are restriction enzymes?
“Molecular scissors”. These are enzymes that cut double strands into fragments or specific sequences
What is methylase?
Adds a methyl group and alters chemical composition.
What is the difference between sticky and blunt ends?
-Sticky ends: fragment end of a DNA molecule with short single strands that overhang.
Blunt ends: fragment ends of a DNA molecule that is perfectly base paired.
BIOTECHNOLOGY: PCR
Components Polymerase Chain Reaction required: DNA template DNA polymerase enzyme Primers Nucleotides Rxn bufffer
BIOTECHNOLOGY: RFLP
Everyone has different amounts of the genetic sequences called VNTRs or Variable Number Tandem Repeats. These VNTRs make different sized RFLP’s
BIOTECHNOLOGY: DNA fingerprinting
- After DNA is isolated it is amplified with PCR.
- The DNA is treated with restriction enzymes (DNA is cut a specific sequences) resulting in different sized fragments
- These fragments are called RFLP’s
- The DNA fragments can be observed when an experiment called Gel Electrophoresis is done
BIOTECHNOLOGY: Gel electrophoresis
Here, DNA frags are separated out of the gel using a nylon membrane
The nylon membrane is treated causing the OH bonds in the DNA to separate the strands
The single stranded DNA is cross linked to the nylon membrane
- Everyone has a different pattern of bands which make up ur DNA finger print
What are the 5 components of electrophoresis?
Driving force Sample (DNA, RNA, protein) The support (agarose etc) Buffer Detecting system (stain)
What is a plasmid?
Double stranded DNA molecules that lacks a protein coat and naturally exists in the cytoplasm in bacteria
Plasmid cloning
The multiple cloning site is the region in the plasmid that has been engineered to have recognition sites of a number of endonucleases
