Ch.8 Flashcards
Genetics
study of what gene are, how they carry information, how info is expressed and how genes are replicated
Gene
a segment of DNA that encodes a functional product, usually a protein
Chromosome
structure containing DNA and the genes
Genome
all the genetic information in a cell
Genomics
molecular study of genomes
Genotype
the genes of an organism
Phenotype
expression of genes
Expression
genetic info is used within a cell to produced proteins needed
Recombination
genetic information can be transferred horizontally between cells of the same generation
Replication
genetic information can be transferred vertically to the next generation of cells
Adenine
combines with Thymine
Guanine
combines with Cytosine
Cytosine
combines with Guanin
Thymine
combines with Adenine
Dna Synthesis Occurs
At the 5 prime to 3 prime direction , started by RNA primers that make chunks of 5-10 strands, then DNA polymerase takes that and builds for it , the leading strand is made continuously because it can only add at the 3 prime end and it needs to maintain the structure because of this the lagging strand is made in pieces (okazaki fragments) because it is being made from the 3 to 5 . It has to keep the antiparallel structure A hydroxyl group is needed at te 3 prime position in order to build .
It is built in the 5 to 3 prime direction, and read in the 3 to 5 prime direction (template) in order to keep the anit parallel nature of the duplex
Called the trombone model
Dna replication process consists of
Replication enzymes break weak hydrogen bonds between nucleotides and the double helix separates
Hydrogen bonds form between new complementary nucleotides
Enzymes then catalyze the formation of sugar-phosphate bonds between sequential nucleotides on each resulting daughter strand
nucleotide
A nucleoside triphosphate bonds to sugar and loses two phosphate, the hydrolysis of the phosphate bonds gives energy to the reaction
DNA Gyrase
enzyme that relaxes tension ahead of the replication fork
DNA Ligase
makes covalent bonds to DNA strands, joins Okazaki fragments and new segments in excision repair
DNA polymerase
Synthesizes DNA, proofreads and repairs DNA , copies DNA
Helicase
unwinds double stranded DNA , opens up the structure to begin with
RNA Primase
an RNA polymerase that makes RNA primers from a DNA template , the helpers of dna polymerase
Topoisomerase
also Relaxes supercoiling ahead the replication for, separates DNA circles at the end of the DNA replication
So how does the trombone model work with all these enzymes
So essentially Helicase and other enzymes unwind the double helix while proteins stabilize the unwound dna, the leading strand is synthesized by DNA Polymerase with the help of RNA primers, DNA ligase joins the okazaki fragments in the lagging strand. DNA gyrase and topoisomerase ease tension ahead of the replication fork before it unwinds.
Dna replication is circular and happens in two directions , what is this called?
bidirectional replication
Codon
a set of 3 nucleotides in mRNA that codes for an amino acid or stop signal
Starts at the start codon AUG (codes for amino acids) and ends at nonsense codons, UAA, UAG, UGA
How many codons in mRNA and how many amino acids
61 sense codons, 20 amino acids , 3 codons are nonsense codons (stop signals)
What does it mean to say that the genetic code is degerate?
because some amino acids have more than one codon
polyribosome
Rna+ ribosome
Constitutive genes
are expressed at a fixed rate, like the genes involved in Glycolysis
Other genes are expressed only as needed
Inducible genes
are off and must be on
Repressible genes
on and must be turned off
Catabolite repression aka Glucose effect
inhibition of alt carbon sources by glucose , no glucose? Lag time for genes to turn off for lactose to be used instead
Graph showing e coli grows fast on glucose, but will use lactose if needed at the cost of longer spawn time
Mutation
alteration of nucleotide sequences, can happen spontaneously or in the presence of mutages, base changes additions, or deletions are different types
Mutagen
is an agent that causes mutations increases rate to 10^-5 or 10^-2 per replicated gene ie 10 to 1000x
Spontaneous mutation
occurs in the absence of a mutagen 1 in 10^9 for replicated base pairs or 1 in 10^6 for replicated genes
Point mutation/base substitution
change in one base
Missense mutation
consequence of a point mutation result in change of an amino acid
Nonsense Mutation
consequence of a point mutation where it results in a nonsense codon (stop codon)
Frame mutation
insertion or deletion of one or more nucleotides pairs causing a shift in the reading frame, bigger chance of something serious happening
Radiation
causes formation of ions that can mess with nucleotides and deoxyribose phosphate backbone
Uv radiation
causes thymine dimers (lesoins in the DNA)
So repair comes in, photolysis separate thymine dimers caused by UV radiation
There is also nucleotide excision repair
Vertical gene transfer
occurs during reproduction between generation of cells
Horizontal gene transfer
the transfer of genes between cells of same gen
Genetic recombination
Exchange of genes between two DNA molecules occurs when two chromosomes break and rejoin Donor DNA → Receipts
Species that can do this are competent Naked dna
conjugation
A plasmid is sent from a donor F+ to recipient F-, the F- is converted to an F+ cell,, through the mating bridge or sex pilus
plasmid
a small circular piece of DNA found in bacterial cells
bacterialphage
Another way that it can be done is via bacterial viruses called bacterialphage
Phage DNA can combine to the host cell DNA this is transduction
specific transduction
Viruses can specify which gene they want to change
Transposons
segments of DNA that can move from one region to another , contain insertion sequences for cutting and resealing DNA
