chap 8 Flashcards
*genetics
study of what genes are,
how they carry information,
how infomation is expressed,
how genes are replicated
*gene
a segment of DNA encodes a functional product = protein
*chromosome
containing DNA that physically carries hereditary information; contain the genes
*genome
every DNA in cell. all the genetic information in the cell
plasmid
extra piece of chromosomal self-replicating structure in bacterial cells that carries genes; not essential for cell growth
*genomics
molecular study of genomes
*genotype
genes of an organism
*phenotype
expression of the genes
horizontal transfer
transfer genes from parent cell to daughter cell
DNA structure:
Polymer of nucleotides
adenine, thymine, cytosine, guanine
DNA structure:
double helix
associated with proteins
DNA structure:
backbone is
deoxyribose-phosphate
DNA structure:
- strands are held together by
- stands are:
- hydrogen bonds
between A=T and C=G - antiparallel
DNA replicates
semiconservative
half
DNTP=Deoxy Nucleotide Tri Phosphate serves as;
DNTP serves as energy source and building blocks for DNA replication
DNA is copied by;
DNA polymerase = make polymers, cannot start a new strand
DNA polymerase (many issues) copies RNA from DNA template
- 5’ to 3’ direction
- initiated by RNA primer
- leading strand is synthesized continuously
- lagging strand is synthesized discontinuously
- Okazaki fragments
- RNA primers are removed and Okazaki fragments joined by a DNA polymerase and DNA ligase(=tie pieces together)
DNA Ligase
= glue bottle = makes covalent bonds to join DNA strands; joins Okazaki fragments and new segments in expression repair
DNA Gyrase
relaxes supercoiling ahead of the replication fork
Helicase
“un-zip” unwinds double stranded DNA
RNA Primase
RNA polymerase that makes RNA primers from a DNA template
Enzyme adds…“un-zip”
bacterial DNA replication:
bidirectional
Topoisomerase remove supercoils in DNA molecule
flattens, uncoils, keep off making knots
bacterial DNA replication:
DNA is methylated = functional maturation
- bacteria methylate Adenine
- methylation plays ole in variety of processes;
control of genetic expression,
initiation of DNA replication
protection against viral infection
repair of DNA
DNA replication: Eukaryotes
bacteria start top, goes around
similar to bacterial replication difference: - use 4 DNA polymerases - thousands of replication origins - shorter Okazaki fragments - plant and animal cells methylate only cytosine bases
relationship between Genotype and Phenotype
- Genotype = set of genes in genome. you carry
- Phenotype = physical expression, future, function
gene function = protein synthesis
2 steps
- transcription (DNA to mRNA=copy)
- translation (mRNA to protein=ribosome)
Transcription;
- DNA is transcribed to make 3 types of RNA : mRNA, tRNA, rRNA (ribosome RNA)
- begins when RNA polymerase binds to the Promoter sequence(transcribe only one side)
- proceeds 5’ to 3’ direction
- stops when reaches the Terminator sequence
Transcription (1, 2, 3)
- initiation - promoters fit well to RNA polymase. not so fit, then may have lower binding rate.
- elongation
- termination
Transcriptional differences in Eukaryotes
- RNA transcription occurs in the nucleus
- transcrition also occurs in mitochondria & chloroplasts
- 3 types of RNA polymerases
- numerous transcription factors
mRNA processed before translation:
+ capping
+ polyadenylation
+ splicing
Only Eukaryotes have 2 section:
Exon =expressed segments
Intron =interrupting segments
Translation;
- mRNA is translated in codons (3 nucleotides)
- translation of mRNA begins at the start codon AUG
- translation stops at stop codons: UAA, UAG, or UGA
Bacteria can transcription & translation at the same time! =
= faster!
*genetic code
- 64 sense codons on mRNA encode the 20 amino acids
- redundant: not perfect. potential negative
tRNA carries the complementary
anticodon
control of transcription
75% of genes are expressed all time
Ionizing radiation effect:
The formation of free radicals=highly reactive ions
Transformation is the transfer of DNA from a donor to a recipient cell
As naked DNA in solution
Operandi model:
Synthesis of inducible enzyme to occur, the substrate must:
Bind to to the repressor
Protein synthesis, both eukaryotes and prokaryotes use:
Codons to determine polypeptide sequences
promoter
A site where RNA polymerase binds to DNA
terminator
A site when RNA polymerase ends binding to DNA=RNA synthesis ends
mRNA
carries coded information for making specific proteins from DNA to ribosomes.
operon:
only in bacteria
= a set of operator (O) and promotor (P) sites and the structural genes they control. Regulated by regulatory gene.
inducible operons
- active repressor binds with operator, prevents transcription from operon. 2. when inducer Allolactose binds to repressor protein, inactivated repressor cannot block transcription. production of enzymes needed (and can digest lactose).
repressible operons
- the repressor is inactive, transcription and translation proceed, leads synthesis of tryptophan. 2. when tryptophan (corepressor) bids to the repressor protein, repressor activates and binds with the operator - preventing transcription from the operon.
point mutation (base substitution)
1 point in the DNA sequence is replaced with a different base.
Frameshift mutation
insertion or deletion of 1 or more nucleotide pairs.
Deletion frame-shift mutations
chemical
repair of mutations:
photolyases (light repair) :bacteria only
photolyases (light repair) :bacteria only
repair of mutations:
nucleotide excision repair
= all organisms have
repair of mutations:
mismatch repair
= proof reading mechanism
mutagens
mutagens increase to -10x10x10x10x10 or -10x10x10per replicated gene.
chemical increase mutation (disinfected procedure) = anti HIV, anti virus.
radiation= ionized(Xray) and nonionized(UV light)
Ames test= reverse gene mutation (70’s Bruce Ames)
= to creare reversible mutation.
suspected mutagen was added one of two samples of rat liver extract in the culture of histidine-dependent salmonella. Increased numbers of histidine synthesizing revertants, if the test chemical is a mutagen and potential carcinogen (cancer causing substance)
- silent mutation
= genotype changes but phenotype remains the same = no effect on amino acid sequence.
- missense mutation
= base substitution results in change in amino acid = sickle cell anemia.
- nonsense mutation
= base substitution results in a nonsense (stop) codon.
- insertion
The eca tra n
- deletion
Thc atr an
operon=
set of genes that on bacterial chromosomes that allow them to regulate amount of products made
