What makes you look like your parents?

Your parents passed down their DNA to you.

What’s carried in your DNA that gives you your traits &

characteristics?

GENES!

What is a gene?

• A gene is a set of DNA instructions that control the production (synthesis) of proteins within the cell.

DNA Protein

DNA Protein

• So, to express our traits, our cells need to convert DNA into proteins.

How do we convert 1 macromolecule into another?

Nucleic Acid Protein

Converting DNA into Protein

• This process, protein synthesis, involves 2 steps:– Transcription– Translation

RNA is the link between DNA & protein!

• DNA is found in the nucleus of cells, but proteins are built in the cytoplasm.

• DNA cannot leave the nucleus, so a copy of the gene is made in the form of a similar nucleic acid called RNA (ribonucleic acid) during transcription.

• The RNA leaves the nucleus, attaches to a ribosome & then is used to make a protein during translation.

RNA & Protein Synthesis

The Central Dogma of Biology

DNA RNA Protein

What is RNA?

• RNA is very similar to DNA:– RNA is a nucleic acid macromolecule.– RNA is made of nucleotides.

• Do you remember the 3 parts of a nucleotide?– 1 5-carbon sugar– 1 phosphate group– 1 nitrogenous base

DNA vs. RNA

• RNA contains the sugar ribose, while DNA contains the sugar deoxyribose.

• RNA is single stranded, while DNA is double stranded.

DNA vs. RNA

• RNA contains uracil instead of thymine.

• Both DNA & RNA have adenine, cytosine, & guanine.

RNA – 3 Types

• Messenger RNA (mRNA): acts as a messenger & carries a copy of the information in DNA to the ribosome where proteins are made

RNA – 3 Types

• Ribosomal RNA (rRNA): found within ribosomes; ribosomes are made of both proteins & rRNA

RNA – 3 Types

• Transfer RNA (tRNA): brings amino acids to the ribosome to be added to the protein chain that is being made– There is 1 tRNA for each of

the 20 amino acids.

The 20 Amino Acids that Build Proteins

Why are proteins important?

& how do they give us our traits?

Each protein has a specific function within living cells.

• Can be enzymes, to speed up & regulate chemical reactions

• Making pigments that determine flower color in plants

• Determine your blood type

• Regulate cell growth & development

• Lactose is the sugar found in milk (disaccharide).

• When your body digests lactose, it gets broken down into glucose & galactose (monosaccharides).

• Lactase is the enzyme that breaks down lactose.– Enzymes are proteins!

Lactose Intolerance

• People who are lactose intolerant have a mutation in the gene that codes for lactase.

• Since they don’t produce lactase, they can’t digest lactose.

Protein SynthesisDNA RNA Protein

• Protein synthesis (making proteins from your genes) occurs in 2 steps:– Transcription– Translation

Protein Synthesis – Transcription

DNA RNA Protein

• Genes carry the instructions to build a protein.

• DNA is located in the nucleus, but proteins are built in the cytoplasm.

• We need to make a copy of the instructions in the form of RNA (transcription).– RNA can leave the nucleus & take the instructions to the

ribosomes.

Transcription

• The process in which the nucleotide sequence of DNA is copied into a complementary sequence of RNA– Occurs in the nucleus– DNA mRNA Protein

Transcription – Step 1

• The enzyme RNA Polymerase binds to the DNA in the nucleus & breaks the hydrogen bonds between the 2 strands.

Transcription – Step 2

• Using 1 strand of DNA as a template, RNA Polymerase adds nucleotides 1 by 1 & forms the new mRNA strand.

Transcription – Step 3

• When transcription is complete, the mRNA leaves the nucleus through the nuclear pores & enters the cytoplasm of the cell.

DNA is like the “master plan” & mRNA is like the “blueprint”.

• The master plan stays in the office (the nucleus) & the blueprint can be taken to the construction site (the ribosome).