RNARNA

Ribonucleic AcidRibonucleic Acid

Ribonucleic Acid (RNA)Ribonucleic Acid (RNA)

RNA is much more abundant than DNARNA is much more abundant than DNA

There are several important differences between There are several important differences between RNA and DNA:RNA and DNA:

- the pentose sugar in RNA is ribose, in DNA it’s - the pentose sugar in RNA is ribose, in DNA it’s deoxyribosedeoxyribose

- in RNA, uracil replaces the base thymine (U pairs - in RNA, uracil replaces the base thymine (U pairs with A)with A)

- RNA is single stranded while DNA is double - RNA is single stranded while DNA is double strandedstranded

- RNA molecules are much smaller than DNA - RNA molecules are much smaller than DNA molecules)molecules)

Structure of RNAStructure of RNA

Single strandedSingle stranded Ribose SugarRibose Sugar 5 carbon sugar5 carbon sugar Phosphate groupPhosphate group Adenine, Uracil, Cytosine, GuanineAdenine, Uracil, Cytosine, Guanine

Types of RNATypes of RNA

Three main typesThree main types Messenger RNAMessenger RNA (mRNA) – transfers (mRNA) – transfers

DNA code to ribosomes for translation.DNA code to ribosomes for translation. Transfer RNATransfer RNA (tRNA) – brings amino (tRNA) – brings amino

acids to ribosomes for protein synthesis.acids to ribosomes for protein synthesis. Ribosomal RNARibosomal RNA (rRNA) – Ribosomes are (rRNA) – Ribosomes are

made of rRNA and protein.made of rRNA and protein.

TranscriptionTranscription

RNA molecules are produced by copying part RNA molecules are produced by copying part of the nucleotide sequence of DNA into of the nucleotide sequence of DNA into complementary sequence in RNA, a process complementary sequence in RNA, a process called called transcriptiontranscription..

During transcription, RNA polymerase binds to During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a polymerase then uses one strand of DNA as a template from which nucleotides are template from which nucleotides are assembled into a strand of mRNA.assembled into a strand of mRNA.

mRNAmRNA

How Does it Work?How Does it Work?

RNA Polymerase looks for a region on RNA Polymerase looks for a region on the DNA known as a promoter, where it the DNA known as a promoter, where it binds and begins transcription.binds and begins transcription.

RNA strands are then edited. Some RNA strands are then edited. Some parts are removed (parts are removed (intronsintrons) - which are ) - which are not expressed – and other that are left not expressed – and other that are left are called exons or expressed genes.are called exons or expressed genes.

The Genetic CodeThe Genetic Code

This is the language of mRNA.This is the language of mRNA. Based on the 4 bases of mRNA.Based on the 4 bases of mRNA. ““Words” are 3 RNA sequences called Words” are 3 RNA sequences called

codonscodons.. The strand aaacguucgccc would be The strand aaacguucgccc would be

separated as aaa-cgu-ucg-ccc the amino separated as aaa-cgu-ucg-ccc the amino acids would then be Lysine – Arginine – acids would then be Lysine – Arginine – Serine - ProlineSerine - Proline

Genetic CodesGenetic Codes

TranslationTranslation

During translation, the cell uses information During translation, the cell uses information from messenger RNA to produce proteins.from messenger RNA to produce proteins.

A – Transcription occurs in nucleus.A – Transcription occurs in nucleus. B – mRNA moves to the cytoplasm then to the B – mRNA moves to the cytoplasm then to the

ribosomes. tRNA “read” the mRNA and obtain ribosomes. tRNA “read” the mRNA and obtain the amino acid coded for.the amino acid coded for.

C – Ribosomes attach amino acids together C – Ribosomes attach amino acids together forming a polypeptide chain.forming a polypeptide chain.

D – Polypeptide chain keeps growing until a D – Polypeptide chain keeps growing until a stop codon is reached.stop codon is reached.

Protein SynthesisProtein Synthesis The two main processes involved in The two main processes involved in protein synthesisprotein synthesis are are

- the formation of mRNA from DNA - the formation of mRNA from DNA (transcription(transcription))- the conversion by tRNA to protein at the ribosome - the conversion by tRNA to protein at the ribosome ((translationtranslation))

Transcription takes place in the nucleus, while translation takes Transcription takes place in the nucleus, while translation takes place in the cytoplasmplace in the cytoplasm

Genetic information is transcribed to form mRNA much the Genetic information is transcribed to form mRNA much the same way it is replicated during cell divisionsame way it is replicated during cell division

Translation to ProteinTranslation to Protein

MutationsMutations

Gene mutations result from changes in a Gene mutations result from changes in a single gene. Chromosomal mutations single gene. Chromosomal mutations involve changes whole chromosomes.involve changes whole chromosomes.

Gene MutationGene Mutation

Point MutationPoint Mutation – Affect one nucleotide – Affect one nucleotide thus occurring at a single point on the thus occurring at a single point on the gene. Usually one nucleotide is gene. Usually one nucleotide is substitutedsubstituted for another nucleotide. for another nucleotide.

Frameshift MutationFrameshift Mutation – – InsertingInserting an extra an extra nucleotide or nucleotide or deletingdeleting a nucleotide a nucleotide causes the entire code to “shift”. causes the entire code to “shift”.

Gene MutationGene Mutation

Chromosomal MutationsChromosomal Mutations

DeletionDeletion – Part of a chromosome is deleted – Part of a chromosome is deleted DuplicationDuplication – part of a chromosome is – part of a chromosome is

duplicatedduplicated InversionInversion – chromosome twists and inverts the – chromosome twists and inverts the

code.code. TranslocationTranslocation – Genetic information is traded – Genetic information is traded

between nonhomologous chromosomes.between nonhomologous chromosomes.

Chromosomal MutationsChromosomal Mutations

MutationsMutations

More MutationsMore Mutations

Gene RegulationGene Regulation

In simple cells (prokaryotic) lac genes In simple cells (prokaryotic) lac genes which are controlled by stimuli, turn which are controlled by stimuli, turn genes on and off.genes on and off.

In complex cells (eukaryotic) this process In complex cells (eukaryotic) this process is not as simple. Promoter sequences is not as simple. Promoter sequences regulate gene operation. regulate gene operation.

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