Untitled Lesson

12.1 RNA

Engage: Mystery Code

Decrypt the code:
4 14 1 | 18 14 1 | 3 15 4 5!

● DNA is like a coded message that contains

instructions for the cell.

● RNA is the messenger that carries this code to the

ribosomes to make proteins.

● Just like you used the key to decode the message,

the cell follows base-pairing rules to transcribe DNA
into RNA.

DNA Vs RNA

●Key Difference: Uracil (U) replaces Thymine (T) in RNA

○A pairs with U in RNA instead of A pairing with T in DNA.

●Analogy: Master Plan vs. Blueprints

○DNA = Master Plan (stays safe in the nucleus)

○RNA = Blueprint Copy (used to assemble proteins at ribosomes)

Feature

DNA

RNA

Sugar

Deoxyribose

Ribose

Strands

Double-stranded

Single-stranded

Bases

A=T C=G

A=U C=G

Location

Nucleus

Made in nucleus but moves to cytoplasm

Why RNA?

Why RNA?

●DNA contains the instructions for making proteins, but it stays in the nucleus.

●RNA is the working copy that carries the instructions to the ribosomes.

The Role of RNA

●RNA helps put the genetic code into action by directing the production of proteins.

●Proteins determine the traits and functions of an organism.

Three Types of RNA (Each Has a Different Job)

1.

Messenger RNA (mRNA) – Carries genetic instructions from DNA to ribosomes.

2.

Ribosomal RNA (rRNA) – Helps build ribosomes, which assemble proteins.

3.

Transfer RNA (tRNA) – Brings amino acids to the ribosome to build proteins.

AB Partner Activity:

● Partner A: Explain why DNA cannot leave the

nucleus.

● Partner B: Explain why RNA is the better

molecule for transporting information.

Transcription: Making RNA from DNA

● Definition: The process of

copying a gene's DNA
sequence into an RNA strand.

● Purpose: To create mRNA that

carries the instructions to make
proteins.

● Location: In the Nucleus

Apicius: One of the oldest cookbooks in the

world.

●DNA is like the original Apicius cookbook, safely
stored in the library.

●RNA is like a handwritten copy of a recipe that a chef
takes to the kitchen.

Steps of Transcription

2. Elongation

○RNA polymerase moves along the DNA
template strand, adding complementary
RNA nucleotides.

○Base-pairing rules:

■A=U

■T=A

■G=C

3. Termination

○RNA polymerase reaches a stop signal,
ending transcription.

○The new mRNA strand detaches and
leaves the nucleus.

1.

Initiation

○RNA polymerase binds to a region on DNA called the promoter.

○DNA strands unzip, exposing one strand as a template.

RNA Editing (Pre-mRNA to mRNA)

●

Not all RNA is
immediately useful.

●

Introns (non-coding
regions) are removed.

●

Exons (coding regions)
are spliced together to
form the final mRNA.

●

The edited mRNA leaves
the nucleus and heads to
the ribosome.

Key Takeaways

● RNA is essential for carrying out DNA’s instructions.
● Three types of RNA work together to make proteins.
● Transcription converts DNA’s instructions into

mRNA.

● mRNA editing ensures the final message is

accurate before translation.

Practice Transcription

Using the pink DNA strands, write the complementary
RNA sequence that would be transcribed from the
DNA template.

If absent try this: GGCATTAGCAACGT

(answer in speaker notes