Chapter 11DNA and Genes

Section 2

From DNA to Protein

Genes and Proteins

• The sequence of nucleotides in DNA are a code for building proteins.

• Proteins are important because they– make up some structures in organisms.

– make up enzymes that all chemical reactions in organisms

RNA

• RNA is an nucleic acid that helps the cell build proteins.

• www.biologycorner.com/bio1/DNA.html

RNA Structure

• RNA is made up of a single strand of nucleotides.

• RNA nucleotides differ from DNA nucleotides in 2 ways–Ribose sugar instead of

deoxyribose sugar

–Uracil instead of thymine

Difference Between DNA and RNA

• DNA–Deoxyribose

sugar

–Thymine

• RNA–Ribose sugar

–Uracil

Three Types of RNA

• Messenger RNA (m-RNA)

• Ribosomal RNA (r-RNA)

• Transfer RNA (t-RNA)

Messenger RNA

• Copies DNA’s instructions for making proteins and brings those instructions from the nucleus to the cytoplasm.

• www.accessexcellence.org/AB/GG/rna.html

Ribosomal RNA

• Makes up the ribosome. The ribosome binds to mRNA and uses the instructions to hook together amino acids into long chains that will become proteins.

Transfer RNA

• Brings amino acids to the ribosomes.

• ghs.gresham.k12.or.us/.../chpt15/chpt15.htm

Transcription

• Transcription is what happens when m-RNA makes a copy of DNA

Steps of Transcription• DNA molecule unzips.• RNA nucleotides form base pairs

with DNA nucleotides. RNA nucleotides bond together to form an m-RNA molecule

• m-RNA leaves the nucleus and enters the cytoplasm.

Science at a Distance

© 1997, 1998, 1999, 2000 Professor John Blamire

The Genetic Code

• When m-RNA enters the cytoplasm, it has instructions for how to build proteins. These instructions are written in a nitrogenous base language and must be translated into a language that proteins understand.

Genetic Code

• On m-RNA, a sequence of 3 nucleotides is called a codon.

• Each codon codes for a specific amino acid.

• www.answers.com/topic/genetic-code

http://www.biology.arizona.edu

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Translation

• Translation is when the message in the nitrogenous base sequence of m-RNA is changed into an amino acid sequence in proteins.

Proteins

• Proteins are made up of 20 different amino acids. The sequence of the amino acids determines the function of the protein.

Role of t-RNA

• Each t- RNA can bond to a specific amino acid on one side of the t-RNA molecule.

• The other side of the t-RNA molecule has 3 nitrogenous bases called anticodons.

• Anticodons base pair with codons during translation

Steps of Translation

• The codon AUG is a start codon. This codon is the first step in the building of proteins.

• staff.jccc.net/.../translation/steps.html

Steps of Translation

• m-RNA attaches to ribosome

• t-RNA brings an amino acid to the ribosome.

• t-RNA anticodons form base pairs with m-RNA codons.

• © 2006 The Board of Regents of the University of Wisconsin System.

Steps of Translation

• t-RNA anticodons form base pairs with m-RNA codons.

• Amino acids form peptide bonds to one another and break away from t-RNA.

Translation• Amino acids will

continue to bond together until a stop codon is encountered. At this point, the amino acid chain will enter the cytoplasm for further processing.

• Brooklyn College

City University of New York

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