How Proteins Are Made CHAPTER 10
DNA, genes, chromosomes How does a chemical control so much?
DNA • Deoxyribo • Nucleic • Acid
Sugar: deoxy ribosePhosphate: H2PO4 • Nitrogen base: • Adenine • Guanine • Thymine • Cytosine
Answers 1. Proteins are chains of linked amino acids that have been folded into compact shapes. Some proteins play important roles as enzymes. Other proteins are structural components of cells and tissues. 2. Ribosomes are structures built of proteins and RNA that serve as assembly sites for protein synthesis. 3. DNA is an extremely long, linear molecule containing many genes; genes are relatively short segments of DNA that code for protein or RNA. 4. DNA is made of two strands of complementary nucleotides and contains the four bases adenine, thymine, cytosine, and guanine. DNA contains the sugar deoxyribose and serves to store the complete set of an organism’s genetic material. 5. In DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C).
General Vocabulary 1. gene 2. chromosome 3. chromosomal mutation 4. codon 5. double helix 6. frameshift mutation 7. messenger RNA mRNA 8. monosomy 9. mutation 10. nitrogen base 11. nondisjunction 12. point mutation 13. replication 14. ribosomal RNA rRNA 15. transcription 16. transfer RNA tRNA 17. translation 18. trisomy 19. anticodon 20. protein
Chapter 10 Vocabulary • Section 1 • ribonucleic acid (RNA) (208) • uracil (208) • transcription (208) • translation (208) • gene expression (208) • RNA polymerase (209) • messenger RNA (211) • codon (211) • genetic code (211) • transfer RNA (212) • anticodon (212) • ribosomal RNA (212) • Section 2 • operator (216) • operon (216) • lac operon (216) • repressor (216) • intron (218) • exon (218) • point mutation (219)
The instructions for building a protein are found in a gene and are “rewritten”to a molecule of RNA during transcription. The RNA is then “deciphered” during translation
The instructions needed to make proteins are coded in the nucleotides that make up a gene. The instructions are transferred to an mRNA molecule during transcription
From Genes to Proteins . The RNA is complementary to the gene, and the RNA nucleotides are put together with the help of RNA polymerase.
During translation, the mRNA molecule binds to a ribosome, and tRNAs carry amino acids to the ribosome according to the codons on the mRNA.
The amino acids are joined to form a protein. The genetic code (codons) used by most organisms to translate mRNA is nearly universal.
Gene Regulation and Structure Prokaryotic and eukaryotic cells are able to control which genes are expressed and which are not, depending on the cell’s needs. In prokaryotes, gene expression is regulated by operons. Gene expression is switched off when repressor proteins block RNA polymerase from transcribing a gene.
Lac operon: the operon that controls the production of lactose metabolism enzymes.
In eukaryotes, an enhancer must be activated for a eukaryotic gene to be expressed. Transcription factors initiate transcription by binding to enhancers and to RNA polymerases. Repressors are proteins that bind to the operon and physically block RNA polymerase from producing mRNA
Many eukaryotic genes are interrupted by segments of DNA that do not code for proteins; these segments are called introns. The segments of DNA that are expressed are called exons.
After transcription, the introns are cut out, and the exons are joined. The exons are then translated.
Mutations are changes in DNA. Gene alterations are mutations that change a gene. These mutations can involve a change in a single nucleotide or an entire gene.
What does DNA do? • It contains all of the instructions to make the proteins living things need for life!
How can all of that information fit into a single cell? • DNA is a long chemical molecule with only 4 different nucleotides. • It is the sequence of these nucleotides that makes each organism different.
A-T-C-C-G-G-G-A-G • This little piece of DNA had three codes: • ATC • CGG • GAC
The alphabet of life • A • T • C • G
In triplets or codons • The order of the bases makes all of the difference!!! • Change one letter and it is totally different. • Just like EAT is not the same as TEA • Same letters, different order= new meaning!!
DNA Replication • When new cells are made, DNA must make a copy of it self. • This process is called DNA replication.
The original molecule serves as a pattern for the new • The new strand is called complementary to the old one.
Translation • How to “translate” the code into proteins
DNA is in the nucleus • Messenger RNA comes into the nucleus and makes a copy of the section of DNA needed. • DNA unzips the section and RNA nucleotides copy the DNA • The mRNA takes the message out to the cytoplasm • RNA polymerase is the enzyme that does this!
Ribosomal RNA Reads the code by matching up with the messenger RNA and connecting the correct transfer RNA to the mRNA
Transfer RNA has the anticodon • mRNA has the codon • These match up like the strands of DNA.
tRNA • Each tRNA has an amino acid attached to it
rRNA • Ribosomal RNA “reads” the codon and attaches the correct anticodon. • The amino acids attached to the tRNA get bonded together to form a protein.
There are start and stop codes. • There are even enzymes that look for mistakes and make corrections. • Bu sometimes mistakes happen…
MUTATIONS • A change in DNA
Point mutations • A single base pair is changed. • THE DOG BIT THE CAT • THE DOG BIT THE CAR • Only one letter is different yet….