V. RNA Ribonucleic acid - PowerPoint Presentation

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V. RNA

Ribonucleic acid

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IntroThe genes in DNA code for instructions that control the production of proteins within the cellsThe first step in decoding these genetic messages is to copy DNA into

RNA (transcription)

These RNA molecules contain coded information for making proteins.

(translation)

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A. The Structure of RNARNA consists of a long chain of nucleotides.Each nucleotide is made up of

5-Carbon sugar

A phosphate group

A nitrogenous base

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B. DNA vs. RNAThere are three main differences between RNA and DNA:

The sugar in RNA is ribose (instead of deoxyribose)

RNA is single-stranded

RNA contains uracil instead of thymine

So A pairs with U in RNA

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C. Types of RNAMain function of RNA molecules is

protein synthesis.

The assembly of amino acids into proteins is controlled by RNA.

 

T

hree

main types of RNA:

messenger RNA

ribosomal RNA

transfer RNA.

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1. Messenger RNA (mRNA)

Disposable complementary copy of a gene

Contains instructions for assembly of a protein

Transfers code from nucleus to ribosomes in the cytoplasm

Exits through

nucleopores

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2. Ribosomal RNA (rRNA

)

Makes up part of the ribosome

Reminder: Ribosomes are where proteins are made

Ribosomes are made up of several dozen

proteins and RNA

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3. Transfer RNA (tRNA

)

Transfers amino acids

to the

ribosome.

One end- holds amino acid

Opposite end- Called the

anticodon

- can attach

tRNA

to mRNA

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HWWrite out questions!Make a Venn diagram to compare/contrast RNA and DNA.

Answer in complete sentences:

D

escribe how each type of RNA

will contribute to protein synthesis.

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VI. Protein SynthesisA. Overview

Transcription

In Nucleus

DNA

RNA

Translation

In cytoplasm on ribosome

RNA

 protein

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B. TranscriptionRNA molecules are produced by copying part of a sequence of DNA into a sequence in RNA

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Steps to Transcription:

RNA

polymerase binds to a beginning of a gene on a region of DNA called a

promoter

.

A

promoter is a sequence of DNA that acts as a start site

.

Enzymes (helicase) start

to unwind the DNA double

helix, separating th

e base pairs

Using one of the strands as a template, RNA

polymerase reads the bases and makes

a complementary strand

Continues until

a stop signal is reached-

Terminator

RNA breaks free and can leave the nucleus

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A single gene can produce several different forms of RNA.Very

small changes

in DNA or RNA sequences have dramatic effects in gene expression.

Called

mutations

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PracticeTranscribe the following sequences of DNAAAA GGG TTT CCC

TAC CGA AAT CAT

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C. TRANSLATIONThe decoding of an mRNA message into a polypeptide chain (protein) is known as translation

. (RNA

 Protein)

Translation takes place on ribosomes.

 

Protein Synthesis

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1. CODONS

A sequence of 3 nucleotides on mRNA is called a

codon

.

Codons can code for:

The start of a polypeptide chain

Start codon= AUG (Methionine)

One of 20 Amino acids (See chart)

The end of a polypeptide chain

Stop codons= UAA, UAG, UGA

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DNA CodeAGCGTGCCA

mRNA code

UCGCACGGU

mRNA

codon

UCG-CAC-GGU

write the amino acids that correspond to the codons on page 194

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AnswerSerineHistine

Glycine

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2. Anti-codon 3 nucleotides on tRNA that are

complementary

to a codon on mRNA

tRNA

is carrying the amino acid that the mRNA codon codes for

(this is how the correct amino acid is put into place in the polypeptide chain)

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3. Process of Translation

Messenger RNA is t

ranscribed

from DNA in the nucleus and released into the cytoplasm

Translation

:

Initiation-

mRNA

molecule attaches to a ribosome

Elongation-

A

mino

acids are transferred to the growing polypeptide chain

Termination- A stop codon is reached, and the protein is released from the ribosome.

http

://www.youtube.com/watch?v=5bLEDd-

PSTQ

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VII. The Roles of RNA and DNA The cell uses the vital DNA master plan to prepare RNA blueprintsThe DNA molecule remains within the safety of the nucleus, while RNA molecules go to the protein-building sites in the cytoplasm of the ribosomes.

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A. Genes and proteins Genes contain nothing more than instructions for assembling proteins.Ex: A gene that codes for an enzyme to produce pigment can control the color of a flower.

Ex: Another gene produces an enzyme specialized for the production of red blood cell surface antigen (determines blood type).

Proteins are microscopic tools, each specifically designed to build or operate a component of a living cell.

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Exit SlipTranscribe and translate the following DNA sequence: TAC TTA GGG CAT ATT

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HW1. 

During transcription, in what direction do you expect the mRNA to be made? (think about 5’ and 3’ ends)

2.

During translation, what would you expect to happen if a stop codon:

a: is reached early?

b: is never reached?

3. Transcribe and translate the following DNA sequence:

TAC TTA GGG CAT ATT

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StarterUse the following strand of DNA to make a protein:CGTAGTACCTCCATAAAACT***Remember: AA chain/codons do not begin until a start codon