4.4 Cells use DNA and RNA to make proteins

DNA is the information molecule DNA provides the recipes for proteins to carry out their jobs. Proteins are made of amino acids and the DNA stores the information needed to make a particular protein. The information is in a form of a code Part of a cookbook The entire book Chromosomes The letters and words DNA Recipes make the food Proteins Recipe for one dish Gene Different versions of the same dish alleles

DNA and the Genetic Code DNA take the shape of a double-stranded spiral. DNA is made up of nucleic acids (DNA and RNA). Nucleic acids are made up of nucleotides. There are four different nucleotides and they are identified by their bases: Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Adenine always pairs with thymine (A-T) Cytosine always pairs with guanine (C-G) The bases fit together like a jigsaw puzzle “All Tigers Can Growl”

Replication Replication is a process where DNA is copied before it condenses into chromosomes. This takes place at the end of interphase. Steps of replication: The double helix unzips at various points and in both directions and the parent strands become templates for building the complimentary daughter strands. Free floating nucleotides bond to the exposed strand There are now two identical strands of DNA, each with one original parent strand and one new daughter strand

RNA is needed to make proteins RNA (ribonucleic acid) is a molecule that carries genetic information for DNA to a ribosome, where the genetic information is used to bring together amino acids to form a protein. In order for DNA to make proteins, it needs RNA to connect three bases to an amino acid. The three bases (triplet code), indicates what amino acid is made. There are 20 different types of amino acids. RNA’s job is to copy the DNA info, carry and match amino acids and connect amino acids to form a protein. 3 types of RNA: Messenger RNA (mRNA)—forms a copy of DNA recipe Transfer RNA (tRNA)—picks up amino acids and transfers them to where the chain is being made Ribosomal RNA (rRNA)—brings together the other two type of RNA to from the chain of amino acids

Transcription Transcription is the process of transferring information from DNA to mRNA. During transcription, DNA is used as a template. Only one side is use to make a complementary strand of mRNA and only individual genes are transcribed. Transcription is different from replication, in that only one strand is transcribed, which means that mRNA is made of one strand. When complete, the mRNA is released and does not stay with the DNA. Adenine pairs with uracil instead of thymine

Translation Replication and transcription is completed and passes along information that is coded in the language of nucleotide bases (ATCG). To make the protein, it must be translated into the language of amino acids. Translation occurs in the cytoplasm and involves all three types of RNA.

How a cell makes proteins First, mRNA is produced using a strand of DNA as a code. The mRNA moves to the cytoplasm and attaches to a ribosome. There, the three nucleotides of the bases for mRNA match up with the tRNA carrying a specific amino acid. The ribosome brings together mRNA and tRNA, linking together the amino acid. The ribosome assembles the amino acids into their proper sequence to form a protein.