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Ch 15 Genes and the Genetic Basis of Metabolism and Development (Analysis…
Ch 15 Genes and the Genetic Basis of Metabolism and Development
Storing Genetic Information
Protecting the Genes
messenger RNA (mRNA)
carries information from DNA to site of protein synthesis
Several Ways that DNA is Stored Safely
DNA does not participate directly in protein synthesis
Most DNA is stored in the nucleus, protected from the cytoplasm by the nuclear envelope
Histone proteins hold most nuclear DNA in an inert, resistant form
Nucleosome
histones form aggregates and DNA wraps around them
The Genetic Code
Codon
in mRNA
set of three nucleotides that specifies an amino acid to be made into a protein
Stop Codons
signal that ribosomes should stop protein synthesis
UAA
UAG
UGA
Start Codon
signals the point in mRNA where protein synthesis should begin
AUG
Degenerate code
amino acids are coded by several codons, not just one
The Structure of Genes
Structural Regions
codes for amino acid sequence
Promoter
controlling region involved in regulating the synthesis of mRNA from structural region
TATA Box
short sequence about 6-8 base pairs long rich in A & T
Exons
sequences of nucleotides whose codons are eventually expressed as sequences of amino acids in proteins
Introns
sequences of nucleotides that are not expressed but intervene between exons.
Transcription of Genes
transcription
reading of DNA by RNA polymerase with the simultaneous production of RNA
Hairpin Loop
believed to affect RNA polymerase
hnRNA
heterogeneous nuclear RNA
modified by nuclear enzyme
Protein Synthesis
Ribosomes
small particles that read the genetic info in mRNA
construct proteins guided by that ^ information
80S
found I cytoplasm of eukaryotes
relatively large and dense
70S
plastids, mitochondria, and prokaryotes
smaller and lighter
tRNA
Transfer RNA
amino acids are carried to ribosomes by ribonucleic acids
anticodon
complementary to and hydrogen bonds to the codon
mRNA
translation
synthesis of a protein molecule by ribosomes under mRNA
Frameshift Error
Reading nucleotides in the wrong sets of 3
P channel
groove of ribosome small subunit in which the nascent protein-carrying tRNA occurs
A channel
adjacent to p channel
groove in ribosome small subunit where free amino acid-carrying tRNA occurs
Control of Protein Levels
transcription factors
proteins that bind to promoter or enhancer regions and activate genes
trans-acting
transcription factors come from somewhere else and bind to DNA
cis-acting
promoters, enhancers, and TATA boxes are apart of gene itself
Analysis of Genes and Recombinant DNA Techniques
Nucleic Acid Hybridization
DNA melting/DNA denaturation
separate of which produces a solution of single-stranded DNA
DNA hybridization/reannealing
reformation of double-stranded DNA by cooling a solution of single stranded DNA
Restriction Endonucleases
enzymes that recognize specific sites in DNA double helices
then cut two strands in complementary sites
palindromes
sequences recognized by restriction endonuclease is present in both strands running in opposite directions
can be forward or backward
Identifying DNA Fragments
restriction map
map of a DNA molecule made by exposing it to restriction endonucleases, showing the number of cleavage sites and number of bases between sites
restriction fragment length polymorphism (RFLP)
if two species are not closely related, their fragmented profiles differ
reverse transcriptase
virus enzyme that synthesizes DNA using RNA as a template
complementary DNA
cDNA
complementary to exons of a gene
Expression Profiling
uses cDNA to examine gene expression during development
or to compare development in one species with that in another
DNA microarray
orderly matrix
DNA Cloning
producing large numbers of identical copies of DNA
usually by inserting into bacteria and allowing bacteria to multiply
plasmid
short, circular piece of DNA that occurs in bacteria and acts as tiny bacterial chromosome
vector
carrier
Yeast Artificial Chromosomes
YACs
has essential of yeast chromosome for plant
Polymerase Chain Reaction
PCR
method of copying minute quantities of DNA using bacterial enzymes
DNA Sequencing
chain termination method
DNA to be sequenced is first cloned to obtain a large sample and is then divided into four batches
pyrosequencing method
DNA is added to solution with all enzymes for replication
open reading frame (ORF)
sequence of DNA that has many components of a gene but is not known to act like a gene
Sequencing Entire Genomes
organelles are extracted from a cell
chromosome is isolated from others and sequenced individually
Genetic Engineering of Plants
GMOs
genetically modified organisms
some people like, some do not
obtaining genes is easy
but inserting them properly into DNA so that they can be transcribed and translated is not easy
ti plasmid
commonly used vector for recombinant DNA studies
Viruses
Virus Structure
only protein and nucleic acid
retrovirus
contain single stranded RNA
may act as mRNA
split genome virus
not all of their nucleic acid is packaged as one particle
Virus Metabolism
bacteriophage
viruses that attack bacteria
can only attack a specific bacteria
virulent
virus multiple quickly and dominates cell
temperate
replicated in S phase
don't attack yet
Formation of New Virus Particles
most are self assembly process
viruses remain in cell until broken
Origin of Viruses
highly evolved parasites
also can self assemble
Plant Diseases Caused by Viruses
detection is difficult
try not to safe entire crop
just a breeding stock
heat treatments help
virus free plants come from shoot apical meristem propagation
