Chapter 10: HOW GENES WORK

The ribosomes then:

"Read" the mRNA codons Starting at the start codon AUG Ending at the stop codons UAA, UAG, UGA Facilitate complementary base pairing of the anticodons of tRNAs carrying the correct amino acids to the codons of the mRNAs Link them together with covalent bonds

Medicago can produce needed vaccines using plants:

6 times faster and 12 times more cheaply than eggs

What does gene regulation allow a cell to do? a.It enables the cell to change which gene and how much a gene is expressed. b.It allows a cell to compensate for mutations or deficiencies in its DNA. c.It allows a cell to reproduce more rapidly and effectively. d.It allows a cell to change how fast it replicates its DNA.

A

Mutations can cause:

A DNA sequence not to be translated or transcribed The amino acid chain to end prematurely The final protein to fold incorrectly

Frameshift:

A point mutation insertion or deletion in an mRNA codon Changes every codon after it Creates a completely different protein

DNA to RNA:

A to U G to C C to G T to A

Transcription requires:

An RNA polymerase enzyme A promoter: a sequence of DNA near the beginning of a gene

Mature tobacco leaves:

Are stripped from the plant Then digested by enzymes The solution is filtered to isolate the hemagglutinin flu vaccine protein.

Which amino acid always begins an amino acid chain? Which codon and anticodon are associated with that amino acid?

At the start of the initiation phase of translation, the ribosome attaches to the mRNA strand and finds the beginning of the genetic message, called the start codon. This codon is almost always AUG, which corresponds to the amino acid methionine.

At what step during gene expression are introns removed from RNA molecules? a.transcription of RNA b.RNA splicing c.translation of RNA d.degradation of RNA

B

Which of the following is the best and most basic description of what gene expression is? a. the process in which you inherit characteristics like hair and eye color from your parents b. the process in which the protein coded for by a gene in the DNA is converted to that specific protein c. the process that determines which of two or more possible alleles in a genotype is made visible in the

B

DO cause frameshift mutations.

Base insertions and deletions

DNA to RNA Base Pairing

Base pairing between a DNA template and an mRNA is different than a DNA template to new DNA molecule.

Do not cause frameshift mutations.

Base substitutions

Gene expression can be controlled at several points:

Before transcription Transcription mRNA Translation After translation Protein

Many amino acids have several codons specific for them in the genetic code. This property is called a.universality. b.unambiguity. c.redundancy. d.conservation.

C

RNA Processing: These steps include:

Chemical modification of both ends of the mRNA RNA splicing

Starting at the start codon AUG

Codes for the amino acid methionine

How is RNA different from DNA? a.RNA has only one strand instead of two. b.RNA has uracil instead of thymine. c.RNA uses the information held in the DNA. d.all of the above.

D

Gene Regulation: Can down-regulate gene expression

Decrease or slow expression down

The genetic code is unambiguous:

Each codon codes for only ONE specific amino acid.

Unambiguous:

Each codon codes for only ONE specific amino acid.

Gene regulation:

Enables organisms to change which genes they express in response to internal signals or external cues in the environment Allows production of different proteins as needed by different cell types Can up-regulate gene expression Can down-regulate gene expression

The genetic code is universal:

Every organism on earth uses the same set of codons to code for the same amino acids.

What do you predict would happen if the introns were not removed from RNA before translation? Why would it be a problem if the introns were not removed?

If introns were not edited out of the RNA strand, the RNA strand would probably have many problems. Errors would most likely occur in the instruction code for amino acids and proteins and the cell therefore would not get the amount of proteins needed.

RNA Processing

In eukaryotic cells, but not prokaryotic cells, mRNAs undergo modifications before they can leave the nucleus.

Gene Regulation: Can up-regulate gene expression

Increase or speed expression up

Why is only one strand of DNA used as a template?

It seems reasonable that only one strand is used, because transcription of RNA from both strands would produce two complementary RNA strands from the same stretch of DNA, and these strands presumably would produce two different kinds of protein (with different amino acid sequences).

Ribosomes

Makes proteins Read the mRNA information in sets of three bases at a time, called a codon

Biopharming:

Manufacturing vaccine proteins in plants Usually faster than using chicken eggs, which is how influenza vaccines are normally grown can also produce human enzymes for treatment of diseases. -Example: carrot cell cultures producing protein treatment for Gaucher disease

Redundant:

Many amino acids are coded for by two or more codons.

Mike Wanner is VP of Operations at Medicago and oversees the growing of tobacco

Not to smoke, chew, or dip Rather, to make the flu vaccine Growing Tobacco to Treat the Flu

Swine Flu: H1N1

One of the first vaccines that Medicago produced was a vaccine for influenza virus H1N1. It had taken months for vaccines grown in chicken eggs to reach the market. Medicago produced its vaccine, ready for testing, in just 19 days.

Tobacco or Egg? Large amounts of pathogen proteins are needed to make vaccines.

Plants can grow much faster and more cheaply than using the traditional method of eggs.

The mRNA is transported out of the nucleus into the cytoplasm to the

Ribosomes

Translation requires:

Ribosomes Template mRNA tRNA

Why do vaccine producers not simply replicate the entire viral genome, instead isolating the gene for one protein and replicating only that gene?

The anti bodies will attack the proteins. The virus will inject The virus will spread the viral DNA, Must find the protein coat of the virus

Transcription:

The first step of gene expression, when information in DNA is converted to information in RNA.

RNA Processing: RNA splicing completes the mRNA:

The noncoding introns are cut out. The protein coding exons are pasted back together.

Gene expression:

The process by which genes are transcribed into RNA and then translated to make proteins

Translation:

The second step of gene expression, when information in RNA is converted into the order of amino acids in a protein. The process by which ribosomes convert the information in mRNA into proteins

Two-Step Dance, Transcription: DNA to RNA

The synthesis of RNA based on a DNA template

What role do the bacteria play in this process? Why are they needed?

The viral DNA goes into the bacteria. The bacteria will replicate the viral DNA. It will go through the process of transcription The synthesized hemagglutinin gene is inserted into the Agrobacterium genome, and the bacteria replicate. More viral DNA and more protein

The genetic code is redundant:

There are 61 amino-acid-coding codons. There are only 20 amino acids found in proteins. Many amino acids are coded for by two or more codons.

Transcription Termination

Transcription stops when the RNA polymerase reads through a special sequence of bases called a terminator

RNA polymerase:

Unzips the DNA double helix at the start of the gene Reads the sequence of DNA template nucleotides As, Ts, Gs, and Cs Inserts complementary RNA nucleotides As, Us, Gs, and Cs Constructs the messenger RNA (mRNA) molecule

RNA has...

Uracil (U) instead of Thymine (T)

If a mutation occurred within the promoter or terminator region, do you think it would affect the mRNA transcribed? Why or why not?

Yes, If there's a mutation that does not stop it will give a longer prtotin strand

Where is the mRNA destined to go once it has been transported out of the nucleus?

mRNA formed in the nucleus is transported out of the nucleus and into the cytoplasm where it attaches to the ribosomes. Proteins are assembled on the ribosomes using the mRNA nucleotide sequence as a guide. mRNA carries a "message" from the nucleus to the cytoplasm.