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

• Answers1. 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 Vocabulary1. gene2. chromosome3. chromosomal mutation4. codon5. double helix6. frameshift mutation7. messenger RNA mRNA8. monosomy9. mutation10. nitrogen base11. nondisjunction12. point mutation13. replication14. ribosomal RNA rRNA15. transcription16. transfer RNA tRNA17. translation18. trisomy19. anticodon20. protein

Chapter 10 Vocabulary• Section 11. ribonucleic acid (RNA) (208)2. uracil (208)3. transcription (208)4. translation (208)5. gene expression (208)6. RNA polymerase (209)7. messenger RNA (211)8. codon (211)9. genetic code (211)10. transfer RNA (212)11.anticodon (212)12. ribosomal RNA (212)• Section 21. operator (216)2. operon (216)3. lac operon (216)4. repressor (216)5. intron (218)6. exon (218)7. 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

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.

Each codon specifies an amino acid.

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.

Review

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.

• First the DNA “unzips” down the center

• Nucleotides floating free in the cell bond in the open spaces.

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….

Frame shift Mutation

• A single base is added or deleted

• This causes the entire line to be read differently!!!

• CCG AAU GGU

• ADD ONE C AND

• CCCGAAUGGU READS

• CCC GAA UGG U

CHROMOSOMAL MUTATIONS

• Parts of chromosomes break off

• Join to the wrong chromosome

• Chromosomes do not separate correctly during meiosis: non disjunction

Trisomy monosomy

• Three where there should be two

• Or

• One where there should be two.

Essay

• Explain the process of making a protein from start to finish.

1. Make sure your steps are in the correct sequence.

2. Add as many details as possible.

3. Name the processes and the enzymes.

4. The more items listed, the more points.

5. Do not contradict yourself.

Exchange papers

• Check to see if all of the parts are there and they are in order.

• Give a point for each of the items included in the paper.

• Count up the points.

• Give the paper back to the owner…

• How did you do?

Things that should be in the answer:1. Starts in the nucleus with the DNA gene.2. DNA to RNA is called transcription3. RNA polymerase is the enzyme that unzips and transcribes

DNA to RNA.4. Complimentary bases A-U, T-A, C-G, G-C ( no Thymine in RNA)

5. mRNA goes out of nucleus to the cytoplasm to find a ribosome.6. Ribosome matches mRNA to tRNA7. mRNA has the codon8. codon is a set of 3 nitrogen bases that codes for an amino

acid.9. tRNA has the anti codon on one end10. tRNA has the amino acid on the other end11. ribosome has an A and a P site 12. amino acids bond together with peptide bonds to form proteins13. The part of the process that occurs on the ribosome is called

translation

Incomplete dominance

• A mixture of the two phenotypes

• Produces a new

• Phenotype.

• Red X White = Pink

Co dominance

• Both are expressed

• Like a dog with several colors fir

Multiple alleles

• More then two alleles for a trait.

• Like eye color or skin color

• A range of colors result not just two.