Download Chapter 13- RNA and Protein Synthesis

Chapter 13- RNA and
Protein Synthesis
BIG IDEA: How does info. flow from
DNA to RNA to direct the synthesis
of proteins.
13.1 RNA
How is RNA different from DNA?
-Ribonucleic acid, RNA is a nucleic acid consisting of a
large chain of nucleotides
3 Important diff. between DNA and RNA:
1. sugar is ribose, NOT deoxyribose
2. RNA is generally single-stranded instead of
double-stranded
3. RNA contains uracil in place of thymine
Functions of RNA:
Messenger RNA (mRNA)- carry info. from DNA to
other parts of cell
Ribosomal RNA (rRNA)- subunits that make up
proteins
Transfer RNA (tRNA)- transfers each amino acid to
the ribosome as specified by the messages in mRNA
How does the cell make RNA?
- In transcription, segments of DNA serve as
templates to produce complementary RNA
molecules.
- RNA complements base sequences of DNA
- RNA polymerase binds DNA to complementary
strand
Promoter- a specific base sequence that tells RNA polymerase
where to start and stop RNA synthesis
RNA Editing
Introns- pieces of RNA that are cut out and discarded
Exons- The remaining pieces of RNA that are spliced (put) back
together to form the final RNA
13.2 Ribosomes and Protein
Synthesis
What is the genetic code and how is it read?
Bases (in the case of RNA)- A,U, C, and G form
the genetic code.
Code is read 3 letters @ a time. Each “word” is 3
bases long, and corresponds to an amino acid
Each 3 letter “word”= codon
4 different bases in RNA= 64 different possible 3base codons
Most amino acids can be specified by more than 1
codon.
Can be read using genetic code table
GAC AAG TCC ACA ATC
1. From left to right, write the sequence of mRNA transcribed.
2. Use codon table to translate into amino acids
3. Repeat step 1 using complementary strand as new base
What role does the ribosome play in assembling
proteins?
- Ribosomes use the sequence of codons in
mRNA to assemble amino acids into
polypeptide chains
Translation is the decoding of mRNA→ protein
Steps in Translation
1. Begins @ start codon (AUG). Ribosome
attaches to mRNA
1. “EPA” assembly line
1. Continues until ribosome reaches “stop” codon.
Central Dogma of Molecular Biolgy
Information is transferred from DNA → RNA →
protein
Gene expression= the in which DNA, RNA, and
proteins put genetic info. into action in living cells.
13.3 Mutations
Mutations are heritable changes in the
genetic information
Point mutations
-Changes in 1 or a few nucleotides that occur @ a single
point
*Substitution- 1 base (A/U/C/G) is changed into a different
base. Usually affect 1 amino acid and may have no affect
*Insertion/Deletion (frameshift mutation)- 1 base is
inserted or deleted from DNA sequence. Can change every
amino acid following the mutation.
Chromosomal mutations:
1) deletion: loss of part or all of chromosome
2) duplication: extra copy of all or parts of
chromosome
3) inversion: reversing the direction of parts
4) translocation: part of chromosome breaks off and
reattaches to diff. chromosome
What type of mutation?
milk → mile
fast → fats
beast → best
lot → lost
Some mutations are caused by physical agents
in the environment, called mutagens
The effects of mutations can have little/no
effect, or can negatively disrupt gene
function
Harmful mutations
mutations
Change protein
structure or gene
activity
● Some cancers
● Diseases
vs. Helpful
New or altered
functions in proteins
that can be useful to
organisms in changing
environments.
● Genetic diversity
● Disease resistance
13.4 Gene Regulation and
Expression
To conserve energy prokaryotes transcribe certain
genes @ a time.
-Regulated by DNA-binding proteins
Operon= group of genes that are regulated together
lac (lactose) operon is on when lactose is present ,
bacteria knows when it needs nutrients
Promoter=where RNA-polymerase binds to start
transcription
Operator= region that controls rate of transcription
Eukaryotic gene regulation: transcription factors control the
expression of genes
● Some open up chromatin to start transcription, some attract
RNA polymerase, etc.
● Cell specialization (nerve cells, epithelial,cardiac, etc.)
● RNA interface (RNAi) turns genes on and off, plays a role in
growth/development
Cell differentiation = cells become specialization in
structure and function
Master control genes (homeotic genes) regulate
where specific organs grow in the body
Homeotic genes are like switches that trigger
certain patterns of development and
differentiation in cells and tissues.