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Chapter 15: Genes and Genetic Basis of Metabolism and Development…
Chapter 15: Genes and Genetic Basis of Metabolism and Development
Concepts
plants composed of numerous type of cells
differential activation of genes
differentiates and develops unique of proteins
underly developmental process
DNA
deoxyribonucleic acid
cell contain a source info hold sequence info for all proteins
genes
each DNA responsible for coding amino acid in particular protein
DNA sequence analysis
powerful process is extremely repaid
recombinant DNA techniques
genetic engineering
helping us understand process occur
between perception of stimulus& plant's response stimulus
Storing Genetic Information
Protecting the Genes
messenger RNA
mRNA
carries info from DNA to protein synthesis
nucleosome
histones form aggregates & DNA wraps around
forming spherical structure
chromatin
dense enzymes cannot penetrate
DNA relatively inert
DNases
DNAases
exposed directly to DNA-digesting enzymes
The Genetic Code
codons
necessary for nucleotides to be read
used in group of three
64 possible triplets
can be made using four mucleotides
stop codons
three codons
UAA
UAG
UGA
start codon
AUG
signals point in mRNA
degenerate
multiple codons exit for most amino acids
genetic code
The Structure of Genes
The Structure of Genes
TATA box
#
regions particularly important
one
RNA polymerase ll
TATA box is damaged by either mutation
or experimental treatment
structure region
promoter
controlling region involved in regulate synthesis mRNA from structural region
genes composed
codes for amino acid sequence
enhancer elements
most eukaryotic genes have other promoter sequences
located even father upstream
as many as several hundred base pair
from structural region of gene
promoter region
hormone alters cell metabolism
produce intracellular chemical messengers activate genes by binding directly
exons
nucleotides whose codons eventually expressed as a amino acid in proteins
introns
nucleotides are not expressed
but instead intervene between exons
Transcription of Genes
transcription
after RNA polymerase binds
encounters start signal
begins actually creating RNA
hairpin loop
small kink
believed affect RNA polymerase
hnRNA
heterogeneous nuclear RNA
rapidly modified by nuclear enzymes
poly(A) tail
approximately 200 bases long
only exception being mRNAs for histone proteins
Protein Synthesis
Ribosomes
small particles"read" genetic message in mRNA
construct proteins guided by information
ribosomal RNA
rRNA
two subunits
one larger than the other
each made up both proteins
80S
found in cytoplasm of eukaryotes
relatively large and dense
70S ribosomes
plastids
mitochondria
prokaryotes are smaller
tRNA
transfer RNA
tRNA
protein synthesis
amino acid are carried to ribosomes by ribonucleic acids
anticodon
tRNA are necessary
b/c codon cannot interact directly with amino acid
genetic code can be read only by ribonucleic acid
has three nucleotide sequence
amino acid attachment site
all tRNAs have small part
an anticodon
amino acid activation
special class of enzymes recognizes each tRNA
attaches correct amino acid
mRNA Translation
translation
synthesis of protein molecule by ribosomes under guidance of mRNA
eukaryotic initiation factors
elFs
several initiation factors
bind to small subunit
frameshift error
reading nucleotides in the wrong set of three
virtually all codons are misread
typically result in completely useless proteins
Control of Protein Levels
trans-acting factors
transcription factors come form somewhere bind to DNA
cis-acting fctors
promoters
enhancers
TATA box
micro RNAs
gene expression controlled by family of short RNA
Analysis of Genes and Recombinant DNA Techniques
Nucleic Acid Hybridization
DNA melting
and DNA denaturation
separation
produces solution of single-stranded DNA molecules
DNA hybridization
and reannealing
reformation of double-stranded DNA by cooling solution of single-stranded DNAs
Restriction Endonucleases
class of bacterial enzymes
palindromes
recognized by restriction endonuclease present
in both strands
running in opposite directions
DNA ligase
DNA repair enzyme
added to mixture to repair the cuts two fragments join together
recombinant DNA
DNA prepared
Identifying DNA Fragments
restriction map
separated by gel electrophoresis
made visible by staining
restriction fragment length polymorphism
RFLP
two species not closely related
fragment profiles differ
DNA Cloning
placing of DNA fragments into bacteria
just described
extremely useful technique
plasmid
short
circular piece of DNA occurs in bacteria
vectors
several plasmids
such as pBR322
genetically engineered to be ideal DNA fragment
yeast artificial chromosomes
YACs
used insted
DNA Sequencing
chain termination method
first cloned obtain a large sample
divided into four batches
pyrosequencing method
DNA added solution with all enzymes for replication
open-reading frame
ORF
regions found appears have three gene-like features
Sequencing Entire Genomes
above only effective for fragment
less than several hundred bases long
Genetic Engineering of Plants
ti plasmid
after gene and promoter have been prepared
attached to insertion vector
form bacterium
Agrobacterium tumefasciens
recombinant DNA techniques have made it possible for botanist to
identify
isolate
study the structure&activity of many genes
Viruses
Virus Structure
retroviruses
diversity of nucleic acids in plant viruses
single-stranded RNA
split genome viruses
not all of nucleic acid is packaged as one particle
Virus Metabolism
bacteriophages
viruses attack bacteria
invade a living cell in order to reproduce
type of organisms attacked
plants
animals
fungi
protozoans
algae
prokaryotes
Formation of New Virus Particles
viral components assemble into new particles
Origin of Viruses
portions of genes of the host species
species closely related to host
Plant Diseases Cause by Viruses
at least thousand different virus-caused diseases
