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