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. DNAProtein

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 Synthesis DNA  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).