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Chpt. 16 & 17 (Chapter 17: (mutations (nucleotide-pair substitutions…
Chpt. 16 & 17
Chapter 17:
Gene Expression
DNA directs the synthesis of proteins
2 stages
transcription
DNA- directed synthesis of RNA
information is "rewritten"
mRNA
carries a genetic message from the DNA
complementary to DNA template
Uracil instead of Thymine
nontemplate DNA strand
coding strand
for each gene, only 1 of the 2 strands of DNA is transcribed
template strand
provides the template
RNA polymerase
pries 2 strands of DNA apart and joins together RNA nucleotides
polymerase attaches
promoter
end of transcription
teminator
3 stages
initiation
DNA strands unwind
polymerase initiates RNA synthesis
elongation
polymerase moves downstream
unwind DNA
elongating RNA transcript 5'>3'
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termination
RNA transcript released
polymerase detach from DNA
translation
RNA-directed synthesis of a polypeptide
change in language
translate mRNA into polypeptide
nucleotide triplets
codons
complementary to template strand
identical to mRNA
read in the 5'>3' direction
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tRNA
transfers an amino acid to polypeptide in ribosome
consist of single RNA strand
anticodon
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site of translation
ribosomes
similar for bacteria&eukaryote
difference in flow of genetic info
Bacteria
no nuclei
nuclear membranes don't separate bacterial DNA&mRNA from ribosomes
allow translation to begin while transcription still in process
Eukaryotes
have nuclei
nuclear envelope separates transcription from translation
transcription
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translation
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triplets of nucleotides
smallest units of uniform length
can code for all the amino acids
flow of information from gene to protein
based on triplet code
polypeptide chain written in DNA as 3 nucleotide words
mutations
point mutations
lead to production of nonfunctional proteins
nucleotide-pair substitutions
missense
nonsense mutations
insertions/ deletions
frameshift mutations
spontaneous
chemical and physical mutagens cause DNA damage that can alter genes
Chapter 16:Molecular Basis of Inheritance
DNA = Genetic Material
Genes exist as parts of chromosomes
2 components of chromosomes
DNA
transforms bacteria
transformation
change in
genotype
phenotype
can program cells
bacteriophages
viruses that infect bacteria
used as tools
viruses
DNA enclosed by protein
simpler than cells
polymer of nucleotides
nitrogenous base
Pyridmidines
single ring
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Purines
two rings
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Chargaff's rules
varies b/w species
% of bases equal
deoxyribose
phosphate group
structure of DNA
3-D
X-ray crystallography
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DNA replication
template strand
chains unwind then acts as a template
exact replica of parental
conservative
parentals acts as templates
restore parental double helix
semiconservative
parentals seperate
function as template for new strand
all tests support this model
dispersive
contain mixture of old and new DNA
origins of replication
short stretches of DNA that have specific nucleotides
proteins attach and open replication "bubble"
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Proteins
macromolecule
great heterogeneity
specificity of function
chromatin
composed of DNA & histones
histones bind to each other
formation of nucleosomes
most basic units of DNA packing