DNA Flashcards
Genome
Is the cells genetic information: mainly composed of DNA
Chromosomes
Are thread like structures within cells
- contains DNA and associated proteins
Gene
Is a segment of DNA that codes for a specific functional product; unit of genome
Transcription
Cells do not transfer the information coded in DNA directly but first make an RNA copy of the gene. This is called transcription
Central Dogma
The information is copied as RNA nucleotide sequences; RNA molecules in ribosomes then synthesize polypeptides in a process called translation.
These processes make up the CENTRAL DOGMA of genetics: DNA is transcribed to RNA, which is translated to form polypeptides.
DNA->RNA->protein
Nucleotides
Nucleus acids are polymers of basic building blocks called nucleotides.
Any of various compounds consisting of a nucleoside combined with a phosphate group and forming the basic constitution of DNA.
Deoxyribonucleotides
Are linked through their sugars and phosphates to form the two backbones of a helical, double stranded DNA(dsDNA) molecule.
Together make DNA?
Anti-parallel
The two strands are oriented in the opposite direction to each other; one strand runs in 3’ to 5’ direction,while the other runs in a 5’ to 3’ direction.
Scientists say the two strands are antipatallel.
The base pairs extend into the middle of the molecule in a way reminiscent of steps of a spiral staircase.
DNA replication
Is an anabolic polymerization process that allows a cell to pass copies of its genome to its decendants.
DNA begins
Helipads unzips the DNA molecule by breaking hydrogen bonds between complementary nucleotide bases, which exposes the bases of the replication fork.
Replication is semi- conservative
One strand serves as a template for the new strand
Each of the two new DNA molecules generated one of the original parental strand.
Two original strands are antipatallel, cells synthesize new strands in different ways.
One new strand, called the leading strand, is synthesized continuously-5’ to 3’- as a single long chain of nucleotides.
The other is called the lagging strand, is also synthesized 5’ to 3’ but in short segments that are later joined.
Helix stairs
A, G,T,C
A to G
T to C
- Primace
Comes in and lays the foundation for the replication process.
Complementary base pairs
The bases of nucleotides hydrogen bond to one another in specific ways called complementary base pairs. In DNA, the complementary bases thymine and Adenine bond together with two hydrogen bonds with Adenine.
Codon
Triplet of nucleotide which coded for a specific amino acid.
64 possible codons
For 22 possible amino acids
61 sense codons ; remaining are on sense codons
Genetic code
Universal code used by all living organisms
-ribosomes decipher m- RNA information using the code.
Inhibitors of translation
Aminoglycosides:
-binds irreversibly to the 30s subunit of ribosomes
Distorts shape, leads to misreading of m-RNA condon
-transported into bacterial cells that had respitory metabolism
Ex: streptomycin, neomycin, amikscin,gentamicin
Tetracyclines
Causes interference in t- RNA attachment to m- RNA: ribosome complex
Prevents protein sythesis continuation
Selective toxicity: due to higher sensitivity and greater accumulation inside bacterial cell over animal cell
Doxycycline, oxytetrscyline, chloroyetracycine
Macrolides
Complex structure
Binds to 50s subunit of Ribosome
Specifically stops translocation, prevents continuation of protein sythesis
Resistance: due to modification of ribosome target site of these antibiotics
Ex: enthromycin, clarithromycin
Steps in protein sythesis
Step 1; copy of one side of DNA strand is made mRNA
2: mRNA moves to cytoplasm then ribosome
3: mRNA goes through ribosome 3 bases at a time
4: transfer RNA(tRNA) matches up with the open DNA bases
5: tRNA releases the amino acid at the top which joins the chain of amino acids being produced.
Translation
Involves decoding the sequence of mRNA to amino acid sequence of proteins.
Ribosomes
Provide platform where codons of mRNA are transformed to amino acids sequence of proteins
Has small subunit P,A,and E site present on large sub unit. To
3steps of translation
- Imitation
- Elongation
- termination
Initiation process
30s
T-RNA with formul methionine
Initiation factors
MRNA- codons
GTP
50s subunit
DNA methylation
Daughter strands in which a cell adds a methyl group
Plays a role in a variety of cellular processes including the following;
Control of genetic expression
Initiation of DNA replication
Protection against viral infection
Repair of DNA
Horizontal gene transfer
Occurs in bacteria by several ways:
Transformation
Conjugation
Transduction
R plasmid
R genes.
Resistance factor
Coded for resistance charteristics
R plasmid
Codes for plasmid transfer to other cells by conjugation
Transformation
DNA transfer by competence factor
Possible only when cell is competent
Is efficient when donor and recipient are closely related
Artificially: high voltage electric currant
Conjugation
Pili and occurs when bacteria are in close contact
Contact required
Opposite
Larger quantity
Transduction
Mediated by a virus
Generalized transduction
Specialized - specific portions
