RNA and Protein Synthesis
Objectives
be able to use a codon chart
describe the three ways RNA differs from DNA in terms of structure
understand the steps involved in protein synthesis
Recall: DNAlocated in the nucleus of the cell (cannot leave)
polynucleotide - chains of nucleotides
each nucleotide consists of 3 things:
a nitrogen base
adenine, thymine, guanine, or cytosine
a sugar (deoxyribose)
a phosphate group
GenesGenes direct your body
contain the blueprint for:
what you look like
how you age
what diseases you are susceptible to
your strength and weaknesses
Amino Acids and Proteins
genes control the production of amino acids that join together to form proteins
proteins are found in everything:
cell membranes; tissues of the skin, bones, muscles, organs, hormones, and enzymes
Proteins direct growth and development, and many daily functions (homeostasis)
genes on the DNA (segment) serve as the instructions for what amino acids form what proteins, where the proteins are produced, and when they are produced
DNA codes for proteins - composed of amino acids
Proteins control the structure and function of organisms
ex) transport proteins and enzymes
Ribosomes create proteins in the cell (located in the cytoplasm)
DNA uses RNA to get the genetic information to the ribosome
Ribosomes
mRNA
RNA Functiondirectly involved in protein synthesis (proteins produce particular traits in individuals)
a gene does not directly control protein synthesis, instead it passes its genetic information on to RNA
DNA cannot work directly because it does not leave the nucleus, RNA can leave the nucleus
RNA Structure
RNA - ribonucleic acid
uses ribose sugar, not deoxyribose.
RNA bases are A, G, C and U (Uracil)
Uracil pairs with Adenine
Cytosine still pairs with Guanine
single-stranded nucleic acid
https://www.youtube.com/watch?v=JQByjprj_mA
Types of RNAThere are three main types of RNA
Messenger RNA (mRNA) - transfers DNA code to ribosomes for translation
Transfer RNA (tRNA) - brings amino acids to ribosomes for protein synthesis
Ribosomal RNA (rRNA) - Ribosomes are made in rRNA and protein
*RNA interference (RNAi) - interfere with ribosome production
ex) natural antibodies, defense mechanism (immune system)
mRNA: carries the message from the DNA out of the nucleus to the ribosome where protein synthesis occurs
tRNA: transfers the appropriate amino acid from the cytoplasm to the ribosome, the site of protein production (anticodon)
rRNA: translates the DNA message three nucleotides at a time (codon)
Codon: a sequence of three nucleotides (amino acid base pairs) at a time
each codon specifies “codes for” an amino acid
The genetic code - is the language that bridges the gap between genes and amino acids
Types of RNA
CodonTo crack the genetic code found in DNA we need to look at the sequence of bases
The bases are arranged in triplets called codons
A codon is: a specific sequence of three consecutive nucleotides that specifies a particular acid in a protein or starts/stops protein synthesis
it is a codon chart - not an anticodon chart
therefore you must use the mRNA codon to find the amino acid
Protein SynthesisTwo processes are required to synthesize protein
transcription and translation
RNA plays a critical role in the entire process
The same two steps produce all proteins
DNA RNA Proteintranscription translation
nucleus ribosome
Transcriptionmakes an RNA molecule complementary to a portion of DNA
copies the DNA using RNA polymerase
occurs in the nucleus where DNA unravels and the RNA binds to it creating mRNA (the chain of nucleotides) and rRNA (the codon triplets)
Transcription
Translation
occurs when the sequence of bases of mRNA directs the sequence of amino acids in a polypeptide
turns the DNA blueprint (now in the form of mRNA into a chain of amino acids (protein) with the help of rRNA and tRNA
https://www.youtube.com/watch?v=oefAI2x2CQM
Translation
Transcription and Translation
DNATranscript
mRNATranslate
tRNAAmino Acid
AGA
TGC
ACT
GCT
Summary
Both DNA and its mRNA transcription are linear sequences of nucleotides carrying the hereditary code
Every three bases (codon) specifies an amino acid to be included into a growing polypeptide chain that will make a protein
The genetic code is the same for all living things
Twenty amino acids exist in nature, and the genetic code contains 64 different codons
SummaryMost amino acids can be specified by more than one codon
For example, six codons specify leucine (UUA, UUG, CUU, CUC, CUA, CUG).
With few exceptions, the genetic code is universal for all forms of life
DNA ACG CCT AGT TGG ATC
Transcript mRNA
Translate tRNA
Amino Acid
Additional Resources
Why RNA is just as cool as DNA: https://www.youtube.com/watch?v=0Elo-zX1k8M
DNA: Crash Course Biology: https://www.youtube.com/watch?v=itsb2SqR-R0
How to read a codon chart: https://www.youtube.com/watch?v=LsEYgwuP6ko
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