Thursday, March 31st

Objective: Explain and apply laws of heredity and their relationship to the structure and function of DNA

Agenda:1. Introduction to RNA2. Transcription modeling activity

1. What is base pairing?2. How did it help Watson and Crick model DNA?

Warm-up

Why do we care?

From genes to proteins

• DNA RNA amino acid protein

TranslationPolymerization

Transcription

RiboNucleic Acid

Three main differences:• The sugar in RNA is ribose instead of deoxyribose. • RNA is generally single-stranded.• RNA contains uracil in place of thymine.

DNA RNA

Is the model below DNA or RNA? How do you know?

Three Main Types of RNA

• Messenger RNA (mRNA)• Ribosomal RNA (rRNA)• Transfer RNA (tRNA)

mRNA

• Carries copies of instructions for assembling proteins from the nucleus to ribosome.

Transcription

• RNA polymerase separates the DNA. It adds nucleotides to make a complementary strand of RNA.

Transcription

• RNA polymerase binds only to regions of DNA known as promoters.

• Promoters are signals in DNA that indicate to the enzyme where to bind to make RNA.

Transcription

Sketch this picture and label the RNA polymerase, DNA, and mRNA

RNA Editing• DNA contains large sequences

that are not involved in coding for proteins called introns. The sequences that do code are called exons.

• During "editing" the introns are cut out and the exons are spliced together. This new version is called mRNA and is ready to leave the nucleus.

rRNA

• Ribosomes are made up two parts: protein and rRNA. These are outside the nucleus.

tRNA

• During protein construction, tRNA brings amino acids to the growing protein.

Sketch this picture and label the tRNA, rRNA, and mRNA

Modeling questionsWhat is produced in transcription?

If the DNA strand is AUTGGGTCAG, what is the complementary DNA strand?

If the DNA strand is TGACCTGCCT What is the complementary RNA strand?

If the DNA analysis of a gene shows 20% adenine bases (A), what would be the percentage of thymine (T)?

Cytosine (C)?Guanine (G)?Uracil (U)?

Exit Ticket

What is the purpose of transcription?

Our DNA contains instructions to build what?

The shape of DNA is a(n) ________.

What does tRNA do?