Exam 3: Cell Bio: RNA and Protein Synthesis
Terms in this set (38)
Life cannot exist without...
enzymes and other proteins
The path leading from genes to proteins involves...
two steps, called transcription and
assembly of an RNA molecule
a certain type of RNA directs the linkage of amino acids to produce a polypeptide chain
The genetic "code words"
by which DNA's instructions are translated into proteins are the same in all species of organisms
A mutation is...
a permanent change in a gene's base sequence
Mutations give rise to...
alterations in protein structure and protein function
theory that states that, in cells, information only flows from DNA to RNA to proteins,
DNA -> RNA -> Protein
Replication Transcription Translation
(Nucleus) (Nucleus) (Cytoplasm)
RNA (Ribonucleic Acid)
2. Four nucleotides, one is different
DNA - Thymine RNA - Uracil
DNA - A, C, G, T. RNA - A, C, G, U.
3. Ribose instead of deoxyribose
1. Messenger RNA (mRNA)
a. Complementary copies of DNA sequences
b. Formed from only one strand of the DNA
c. Carries the code from genes to ribosomes
2. Ribosomal RNA (rRNA)
combines with protein to form ribosomes, on
which protein synthesis occurs (with two
3. Transfer RNA (tRNA)
carries amino acids to ribosome (with
Structure of an RNA Nucleotide
Uracil instead of
Base Pairing of RNA with DNA
Codon and Protein Synthesis Step One
Protein synthesis is a two-step process:
1. Transcription-nucleotide message sent from nucleus to cytoplasm
a. DNA nucleotide sequence "copied" (using complementary base pairing) as a "messenger" nucleotide sequence of RNA (mRNA)
b. The synthesis of mRNA; similar to DNA
c. The entire DNA molecule in a chromosome is not transcribed, only a specific gene or family of genes is transcribed
is the process of making proteins from DNA nucleotide message
Codon and Protein Synthesis Step Two
2. Translation- Nucleotide sequence of mRNA used to synthesize a sequence of amino acids
a. occurs on the endoplasmic reticulum (Rough ER)
b. mRNA codons are used to specify amino acids
c. Ribosomes "read" mRNA codes to synthesize a specific amino acid sequence
d. each of the 20 amino acids has a specific "carrier" transfer RNA that brings the AAs to the ribosome
e. Complementary base pairing between the mRNA and tRNAs determines the amino acid sequence
f. Ribosomes need to recognize the beginning and end:
1) Initiation (start) codon: AUG (methionine)
2) Stop codons: UAA, UAG, UGA
the genetic code words are a sequence
of nucleotides of mRNA that are read in
blocks of three (read in triplets).
one gene - one protein
one codon - one amino acid
4 nucleotides, if read 2 at a time, 16 possible
combination; if read in triplets, 64 possible
combinations. (Only 20 AAs)
coding sequences of DNA.
one type of non-coding sequences of
DNA (in eukaryotes, more than 90% of
DNA sequences are non-coding sequence)
The genetic code is
nearly universal. All
living things share
1. Common ancestors
2. Genetic engineering
A tobacco plant expressing a firefly gene ( a gene codes for the firefly enzyme that catalyzes the chemical reaction that release energy in the form of light)
The process of copying information from DNA into new strands of messenger RNA (mRNA). The mRNA then carries this information to the cytoplasm, where it serves as the blueprint for the manufacture of a specific protein
RNA polymerase binds with promoter and transcription begins
Assembly or RNA transcript and the transcript is released from the DNA
Finishing touches on mRNA transcripts
The Genetic Code
64 kinds of codons
Only 20 amino acids
The structure of RNA is very similar to the DNA structure, although there are three main differences between these two nucleic acids. RNA nucleotides have ribose as a sugar, and contain uracil base instead of thymine in one of the nucleotide types. RNA is usually a one strand nucleic acid but it can form RNA-RNA duplexes in all cells during the RNA processing and gene expression. The four nucleotide substrates for synthesis of RNA are: adenosine 5′-triphosphate (ATP), cytidine 5′-triphosphate (CTP), guanosine 5′-triphosphate (GTP) and uridine 5′-triphosphate (UTP), which are abbreviated to A, C, G and U, respectively structure
short-chain RNA molecules present in the cell (in at least 20 varieties, each variety capable of combining with a specific amino acid) that attach the correct amino acid to the protein chain that is being synthesized at the ribosome of the cell
Attachment site for amino acid
A sequence of three bases of a tRNA molecule that pairs with the complementary three-nucleotide codon of an mRNA molecule during protein synthesis.
The most abundant type of RNA, which together with proteins froms the structure of ribosomes. Ribosomes coordinate the sequential coupling of tRNA molecules to mRNA codons; also called ribosomal RNA.
Components of ribosomes
tRNA and mRNA are loaded onto a ribosome
Polypeptide chain forms as mRNA passes
between ribosome subunits
Stop codon and detachment of mRNA and
mRNA transcript leaves nucleus
Peptide bond formation
Additional amino acid forms a peptide bond
between amino acids 2 and 3
Stop codon moves in
Polypeptide chain is released from the ribosome
the formation of proteins by using information contained in DNA and carried by mRNA
Affect Protein Synthesis?
Sequences can change
Mutations and Gene
Point Mutation- A Mutation limited to about one or a few base pairs in a single gene. ( two types: 1. substitutions 2. insertions or deletion)
a. silent substituition
b. conservative substitution
c. significant change in protein (rare occasion ->enhence success of its descendants)
d. missense and nonsense
Insertions and deletions: Frameshift mutation produces nonfunctional protein
Cells cannot stay alive without...
without enzymes and other proteins
The amino acid sequence of a polypeptide chain corresponds to...
to a gene region in a double-stranded DNA molecule
The path from genes to proteins is...
In transcription, double-stranded DNA is...
unwound at a gene region
In translation, the three classes of RNA's
interact in the synthesis of polypeptide
Translation proceeds through three stages:
Initiation, elongation, and termination
Gene mutations are ...
heritable small-scale changes in DNA's base sequence