RNA

DNA’s equally important cousin

Quick Check-Up

• What does DNA do?• Is DNA important?• Summarize the big

concepts we learned about DNA

DNA

• SUPER IMPORTANT!!• Codes for everything-

traits, diseases, proteins • Way too important to

leave the nucleus• How does it tell the cell

what to do then?

A cheap and disposable copy

• DNA needs to send a cheaper, less valuable copy of itself out of the nucleus.

• DNA= master plan• RNA= copy

(disposable)

RNA• Ribonucleic Acid• RNA is used to

directly make proteins

• What are some differences you notice?

Some Differences

DNA• Sugar: Deoxyribose• Double stranded• Thymine• Stays in the nucleus

RNA• Sugar: Ribose• Single stranded• Uracil• Can leave the

nucleus

When RNA is made, it is the same as the complementary DNA (made during replication),

except Thymine is replaced with Uracil

What are the 4 main differences between DNA and RNA?

1.

2.

3.

4.

• These differences make it easy for the cell to tell DNA and RNA apart.

THE BIG PICTURERNA is the working copy of DNA. It helps with different jobs outside the nucleus.

RNA helps with Protein Synthesis

• RNA is used to help make proteins by coding for different amino acids (the building blocks of proteins).

There are multiple RNAs

Each RNA has a specific job.• Messenger RNA (mRNA)• Ribosome RNA (rRNA)• Transfer RNA (tRNA)

RNA vs. DNA

Click on the picture for a clip reviewing the differences. There is a worksheet to go along with it.

Let’s make some RNA

• Come up with a strand of RNA using 15 base pairs.

The 3 Types of RNA

Messenger RNA

• Messenger RNA is shortened to “mRNA”.

• Carries a copy of the DNA message to the ribosome to make proteins

• Made by a process known as Transcription

• Linear

Ribosomal RNA

• This is simply RNA that makes up part of the ribosome (rRNA)

• Globular• What does a ribosome

do?

Transfer RNA

• tRNA codes for and carries a specific amino acid

• T-shaped• It brings this amino acid

to the ribosome to be used to make a protein

• This process is known as Translation.

Back to mRNA

• What does it stand for, again?

• It is made in a process known as transcription.

Transcription• The process in

which mRNA is made

• Complementary to the strands of DNA- except for one big difference!

• Only one gene (a specific section of the DNA strand) gets transcribed

• RNA polymerase

RNA Polymerase

• Just like DNA polymerase RNA polymerase creates a complementary strand of RNA nucleotides.

• Thousands of strands of RNA can be made from a single gene

Promoters

• These are signals in the DNA that show RNA polymerase where to begin making RNA

• It is a specific base sequence

Big Picture and Preview

Click on the picture for a clip reviewing transcription and previewing translation. There is a worksheet to go along with it.

Let’s recap real quick

• DNA codes for proteins, which are responsible for different functions and traits of cells and organisms.

• DNA is too valuable to leave the nucleus.

• So what needs to happen…?

RNA

• RNA is used to as a travelling and disposable copy of DNA.

• mRNA copies the message DNA has and takes it to the ribosome.

To the Ribosome!

• mRNA takes the message to the ribosome, but now the message needs to be translated…

tRNA!!!

• Transfer RNA (tRNA) translates the message mRNA has.

• Carries amino acids to the ribosome

• Why do we need amino acids?

What do amino acids have to do with proteins?

• Proteins are made up of long chains of amino acids called polypeptides.

• The shape and function of a protein are determined by the types of amino acids and their order.

How do they know what amino acid to use?

• tRNA carries the amino acids needed to make proteins to the ribosome.

• tRNA reads the mRNA bases and pairs up with complementary bases.

Bases

• What are the bases of RNA?

• These bases are like the letters of a language (the genetic code).

• Words of the genetic code are made up of 3 “letters” or bases.

• These “words” are called codons.

Recap

• The language= the genetic code• Words of this language are called codons• Codons are three letter “words” that match

with a specific amino acid• The “letters” are the bases

How to read this language?

Start and Stop Codons

• AUG is a start codon- this tells where the ribosome should start reading the bases on the mRNA.

• mRNA is then read 3 bases at a time.

• Continues until a stop codon is read.

BINGO!!

Let’s practice, then we will use these different codes to play

What does translation mean?

That’s exactly what is happening!

• tRNA is translating the words (codons) of mRNA into amino acids.

• tRNA =Google translator

A quick map…

In the Ribosome….

• The mRNA gets read 3 bases (1 codon)at a time

• Codons go with a particular amino acid

• tRNA brings the amino acid to pair up with the codon.

• How??

tRNA

• On tRNA there are 3 unmatched base pairs.

• These pair up with the codons on mRNA so there can be a match

• These 3 unmatched bases are known as Anti-codons

Back in the Ribosome…

• After the ribosome reads one codon (and matches it with the correct anti-codon), it moves on to the next one.

• It begins creating a chain of amino acids joined together by peptide bonds

• What is a chain of amino acids called?

Finally, a protein• After several

polypeptides are complete, they twist and fold together to create a protein.

Remember what can happen when DNA doesn’t come out exactly as it should?

• When DNA gets copied wrong it can disrupt the very important sequence of bases.

• The changes to the bases are called mutations.

Mutations

Gene Mutation• Affects the genes• Can affect a single base

(point mutation) or multiple bases (frameshift mutation)

• Frameshift mutations can disrupt the coding of all the amino acids following the mutation

• Protein wouldn’t work

Chromosome Mutation• Affects chromosomes• Changes location of genes

on chromosomes

Effects of Mutations

• Mutations can occur naturally or by artificial means. (about 1 in every 10 million bases)

• Mutagens- agents that cause mutations

• Can be harmful (obviously)

• Can be helpful?? Say what?

Teenage Mutant Ninja Turtles!