Download DNA, RNA, and Proteins part 2 - Tri-City

5/12/15 13.3 Extended Response
Chapter 13
RNA and Gene
Expression
—  Chemical structures that are involved in
physiological processes, such as hemoglobin in
blood, insulin that regulates blood glucose levels,
and enzymes that regulate body functions, are all
made of proteins.
—  Name some parts of the human body that contain
Doerfler
Biology I
Decoding the Information in DNA
proteins (Be specific and discuss their function).
RNA vs. DNA
—  Traits are determined by proteins that are built from
instructions coded in DNA
—  Not built directly from DNA…
•  Ribonucleic acid (RNA) is involved
—  RNA is also a nucleic acid (like DNA)
—  Molecule made of nucleotides linked together
—  Differs from DNA in three ways
•  Single strand of nucleotides
•  Contain the five-carbon sugar ribose
•  In addition to A,G, and C nitrogen bases, also includes U (uracil)
•  NO thymine!
•  Uracil is complementary to adenine
Decoding Cont.
Gene Expression (Protein
Synthesis)
—  Instructions for making a protein are transferred
from a gene to an RNA molecule in a process
called transcription
—  Cells then use 2 different types of RNA to read the
instruction and put together the amino acids that
make up the protein in a process called
translation
—  Gene expression (or protein synthesis) is the
entire process by which proteins are made based
on the info encoded in DNA
1 5/12/15 Transfer of Information from DNA
to RNA
—  FYI – RNA polymerase – adds and links
complementary RNA nucleotides during transcription
(sound familiar?)
—  Step 1 – RNA polymerase binds to the gene’s promoter
– a sequence of DNA that acts as a “start” signal
—  Step 2 – RNA polymerase unwinds and separates the
strands of DNA, exposing the DNA nucleotides on
each strand
—  Step 3 – RNA polymerase adds and links
complementary RNA nucleotides
—  Follows base pairing rules for DNA, EXCEPT FOR?
—  Continues until the “stop” sequence
Transcription, cont.
—  RNA nucleotides are linked together by covalent
bonds
—  As RNA forms a single strand, the two strands of
DNA close up by forming hydrogen bonds between
them, re-forming the double helix
—  In DNA replication, DNA is the template and it
makes a new DNA. In transcription, DNA is the
template, but makes RNA.
—  Transcription occurs in the cytoplasm in
prokaryotes (why?), in the nucleus in eukaryotes
The Genetic Code: ThreeNucleotide “Words”
**Real Life…
—  Death cap mushrooms are
deadly if eaten…
—  Once the poison reaches the
liver cells, it binds to RNA
polymerase
—  The poison prevents liver cells
from making RNA and thus, from
making proteins
—  Liver failure – and death – can
result
RNA’s role in Translation
—  Different types of RNA are made during
—  Translation takes place in the cytoplasm
transcription
—  When a cell needs a particular protein, messenger
RNA (mRNA) is made
—  Transfer RNA (tRNA) - single strands of RNA that
—  It carries instructions for making a protein from a gene
and delivers it to the site of translation
—  RNA instructions are written as series of three-
nucleotide sequences on the mRNA called codons
—  Each codon corresponds to an amino acid or signifies a
start or stop signal for translation
temporarily carry a specific amino acid on end
—  Folded into a compact shape and has an anticodon
•  Anticodon – three-nucleotide sequence that is complementary to
mRNA
—  Ribosomal RNA (rRNA) – part of the structure of
ribosomes
—  Each ribosome temporarily holds one mRNA and
two tRNA molecules
•  64 total codons
2 5/12/15 Translation
Translation, cont.
Translation
Translation
—  STOP
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