BELLRINGER 10-24-11 Put this in the second box of your Bellringer

Page

1.What does “replicate” mean?

2.What is the end result of DNA replication?

3.Why does this process occur?

The other type of

NUCLEIC ACID

DNA holds the instructions to make proteins, but can NOT leave the nucleus.

Proteins are made outside of the nucleus on the tiny organelles called ribosomes.

The DNA needs a messenger to take a copy of the instructions to the

ribosomes so the proteins can be made.

What’s the problem?

• Other than DNA, what is another type of nucleic acid?

• There are 3 types of RNA, but today we will

only focus on one- mRNA.

Messenger RNA (mRNA) delivers a copy of DNA’s instructions from the

nucleus to the ribosomes.

• mRNA structure differs from DNA structure in three ways.

# 1 RNA is single stranded—it looks like one-half of a zipper

—whereas DNA is double stranded.

• The sugar in RNA is ribose;

• REMEMBER:DNA’s sugar is deoxyribose.

Ribose

# 2

• Finally, both DNA and RNA can contain four nitrogenous bases, BUT RNA does not have

Thymine.• Thymine is replaced by a similar base called

uracil (U).

Uracil forms a base pair with adenine in

RNA.

# 3

What do you notice

instead?

This picture is on the back of your notes.

Talk to your neighbor about the differences?

I will call on people at random.

• DNA provides mRNA with the instructions for making the proteins.

• mRNA takes the copy of instructions to the ribosome• The instructions are a code for how the protein should

be assembled (amino acid by amino acid)

What is the Role of mRNA in a cell?DNA - boss with instructions

mRNA - workers that take the instructions from the boss to the site to carry out the job.

The process of:

TRANSCRIPTION

mRNA is made in a process called transcription.

This occurs IN THE NUCLEUS

Transcribe means “to copy”

Steps of Transcription1. DNA uncoils and unzips, just as it does in DNA replication.

Steps of Transcription2.Free RNA nucleotides, containing A,U, C, and G

float up and attach to one side of the DNA strand.Unzipped DNANewly constructed mRNA

Steps of Transcription3.Once the mRNA strand is made, it’s hydrogen

bonds break.

4. Then it leaves the nucleus and goes to a ribosome in the cytoplasm.

Once the mRNA is detached, the DNA strand goes back

together.

TRANSCRIPTION

Transcription results in the formation of one single-stranded RNA molecule

DNA replication results in two double-stranded DNA molecules

What is the difference between DNA Replication and Transcription?

Talk to your neighbor!

What do DNA Replication and Transcription have IN COMMON?

Talk to your neighbor!

They both take place in the nucleus (if it involves DNA in a eukaryotic cell-

it’s happening in the nucleus)

They both have to do with making a copy of DNA (except DNA replication is

making a full EXACT copy)

Below is a nitrogenous base sequence on one side of a DNA strand.

1. What is the sequence on the mRNA strand after Transcription?

T A C C C G T A T T C G A A G G C TA U G G G C A U A A G C U U C C G A