RNA

We know that DNA is the genetic material and its sequence of nucleotide bases carry some sort of code. This code holds instructions that tell a cell how to build proteins, which in turn help to determine an organism’s characteristics.

But how does a cell understand and read this code to make proteins?

RNA Chapter 13

What is RNA? Ribonucleic acid Can be thought of as a disposable copy

of a piece of DNA

What is RNA’s job? To make proteins (Protein Synthesis)

Recall that…

Segments of genes in our DNA contain a code for proteins that determine our traits

DNA is confined to the nucleus

Protein synthesis takes place in the ribosomes

Proteins are made up of amino acids

Why RNA? RNA can travel outside of the nucleus (via the

nuclear membrane’s pores) and carry DNA’s code to the ribosomes

Ribosomes piece together amino acids based on the RNA code to build the proteins

The DNA stays safe inside the nucleus and the RNA can travel to do the rest of the work!

DNA- Contains the “master plan” with all information needed to build a protein.

RNA- The “builder”, who works from a blueprint, or disposable copy, of the master plan.

The cell uses the DNA’s “master plan” to prepare RNA “blueprints”.

Structure of RNA Single stranded Ribose Sugar Phosphate group Adenine, Uracil, Cytosine, Guanine

Types of RNA Three main types Messenger RNA (mRNA) – Carries DNA

code to ribosomes for translation. Ribosomal RNA (rRNA) – Ribosomes are

made of rRNA and protein. Transfer RNA (tRNA) – brings amino

acids to ribosomes for protein synthesis.

rRNA- Structure of ribosomes

tRNA- Carries amino acids to ribosomes

mRNA-Carries message to ribosomes- Made during transcription

Transcription (RNA Synthesis) Segments of DNA serve as templates to

produce complementary RNA molecules

1. RNA Polymerase binds to DNA at the promoter site Promotor: Region of DNA that shows

enzymes where to attach.

2. RNA polymerase separates DNA strands by breaking hydrogen bonds

3. One strand of DNA is used as a template to form a strand of RNA

DNA’s Adenine pairs with RNA’s Uracil DNA’s Thymine pairs with RNA’s Adenine Guanine and Cytosine pair normally

4. RNA polymerase eventually reaches a terminator signaling it to stop transcription

5. mRNA strand un-attaches, and travels through nuclear membrane’s pores to the ribosome

The ribosome will read this code and make proteins from it- a process known as translation (which we will get to later on)

RNA strands are edited before they’re translated Some parts are removed and others are

expressed Introns- Portions cut out and discarded Exons- Expressed genes

Why? Makes it possible for a single gene to produce

many different forms of RNA Evolution- Small changes in sequences cause

dramatic effects on the cellular functioning of genes

Transcription Video

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