Thursday, January 29, 2009

End of 19 and Start of 20

19.3 Viroids, viruses, and prions are formidable pathogens in animals and plants

Viral disease in Animals: Symptoms may be caused by direct harm to cells or by the body's immune response. Vaccines stimulate the immune system to defend the host against specific viruses.

Emerging viruses: Outbreaks of "new" viral diseases in humans are usually caused by existing viruses that expand their host territory . The H5N1 avian flu virus is being closely monitored for its potential to cause a serious flu pandemic.



Viral diseases in plants: Viruses enter plant cells through damaged cell walls (horizontal transmission) or are inherited from a parent (vertical transmission).



Viroids and prions: The simplest infectious agents. Viroids are naked RNA molecules that infect plants and disrupt their growth. Prions are slow-acting, virtually indestructable infectious proteins that cause the brain diseases in animals.

Prions are misfolded proteins that cause the misfolding of normal proteins when they come into contact with one another. Prions are infectious proteins.


CHAPTER 20: Biotechnology

DNA cloning yields multiple copies of a gene or other DNA segment.

Recombinant DNA is DNA that has been artificially made, using DNA from different sources anf often different species. An example is the introduction of a human gene into an E. coli bacterium.



Biotechnology is the process of manipulating organisms for the purpose of making products for the public.

Genetic engineering is the process of manipulating genes and genomes.

Gene cloning is the process by which scientists can create significant sample of specific segments of DNA that they can then manipulate in the lab.

link to gene cloning video: http://images.google.com/imgres?imgurl=http://www.upload.eg123.com/uploads/2f10bae678.jpg&imgrefurl=http://pharma2010.wordpress.com/2008/01/21/animation-to-genetic-1/%3Freferer%3Dsphere_related_content/&usg=__u8cXPen22F901Gj0--tkH8ZLlM8=&h=417&w=501&sz=27&hl=en&start=3&sig2=60IMxZQ9OYfvUIelSFOJRg&um=1&tbnid=Y8QQdCAjrU7_3M:&tbnh=108&tbnw=130&ei=oVWCSeIahpaxA83l9coN&prev=/images%3Fq%3Dvideo%2Bgene%2Bcloning%26um%3D1%26hl%3Den%26safe%3Doff%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DN


When a DNA molecule is cut by restriction enzymes the result will always be a set of
restriction fragments which will have at least one single-stranded end, called a sticky-end. Sticky ends can hydrogen bond with complementary single-stranded pieces of DNA, and these unions can be sealed with an enzyme called a DNA ligase.

The Cloning of genes generally occurs in five steps:

  1. First the vector and the gene mist both be isolated. The vecter and the gene must both be isolated. The vecter is the plasmid (usually bacterial) that will carry the DNA sequence to be cloned.

  2. The DNA in question must be inserted into the vector (plasmid).

  3. The vector must be inserted into the cell in order to be copied.

  4. The cells must be cloned.

  5. The cells carrying the clones myst be identified and isolated.

A genomic library is a collection of many bacterial or phage clones. Each clone carries copies of a particular DNA segment from a foreign genome, integrated into an appropriate DNA vector, such as a plasmid or a trimmed-down phage genome. In a complete genomic library, the foreign DNA segments cover the entire genome of an organism.

PCR require double-stranded DNA containing the target sequence, a heat-resistant DNA polymerase, all four nuclotides, and two 15 to 20 nucleotide DNA strands that serve as primers. One primer is complementary to one end of the target sequence on one strand, the second primer is complimentary to the other enf of the sequence on the other strand.

DNA technology allows is to study the sequence, expression, and function of a gene.

Gel eletrophoresis is a lab technique that is used to seperate macromolecules on the basis of their size and charge by using an electric current.

Southern blotting is a technique that is used to determine the presence of specific nucleotide sequences in DNA.
Cloning organisms may lead to production of stem cells for research and other applications.

Animal stem cells, which can be isolated from early embryos or adult tissues and grown in culture, are self-perptuating, relatively undifferentialted cells. Embryonic stem cells are easier to grow than adult stem cells and can theoretically give rise to all types of cells in an organism. The range of cell types that can arise from adult stem cells is not yet fully understood.

Multiple Choice

1. To cause a human pandemic, the H5N1 avian flu virus would have to

a. spread to primates
b. develop into a virus with a different host range
c. become capable of human-to-human transmission
d. arise independently in chickens
e. become much more pathogenic

2. Which of the following do both viruses and bacteria have in common?
a. metabolism
b. ribosomes
c. genetic material made of nucleic acid
d. cell division
e. independent existence

3. Which of the following are not emerging viruses?
a. AIDS
b. SARS
c. HIV
d. Ebola virus
e. Malaria

4. When an animal is cloned what is removed from the egg cell donor?
a. mRNA
b. rRNA
c. DNA
d. nucleus
e. mitochondria

5. True or False. Embryonic stem cells are easier to grow than adult stem cells

answers: 1. c, 2. c, 3. e, 4. d, 5. True

A great web link for a review of DNA replication

Here is a link from Emily B. to help everyone with DNA replication

http://www.wiley.com/college/pratt/0471393878/student/animations/dna_replication/index.html

It has some extra detail but is very helpful,
Enjoy

Wednesday, January 28, 2009

Chapter 19 Notes Continued

The basics of the lytic cycle:

(Youtube video: http://www.youtube.com/watch?v=wVkCyU5aeeU&feature=PlayList&p=B1AC4F7A9C99C847&playnext=1&index=33)

Attachment: The virus attaches to the host cell
Entry: The virus injects its DNA into the host cell
Replication: The virus directs the replication of its own DNA
Assembly: The new phages are assembled
Release: The host cell bursts, releasing the new viruses. These
new viruses then spread to other host cells. (Note:
the host cell is killed in the process)

The basics of the lysogenic cycle:

(YouTube video: http://www.youtube.com/watch?v=_J9-xKitsd0&feature=PlayList&p=B1AC4F7A9C99C847&index=34)

Attachment: The virus attaches to the host cell
Entry: The virus injects its DNA into the host cell
Replication: The virus' DNA combines with the host cell's DNA
and both are replicated together
Assembly: When the host cell reproduces, it also reproduces the
virus' DNA and is packaged into new host cells (The
host cell is not killed in the process)

Note: After the lysogenic cycle, the cell MAY undergo the lytic
cycle, but it doesn't have to.

Retroviruses are RNA viruses that use the enzyme reverse transcriptase to transcribe DNA from an RNA template. The new DNA then integrates into a chromosome in the nucleus of an animal cell, and the host transcribes the viral DNA into RNA. HIV is a retrovirus

Here is a website that has videos, pictures, and information on HIV/AIDS: http://www.boehringer-ingelheim.com/hiv/art/art_videos.htm

Multiple Choice:

1. What is the function of reverse transcriptase in retroviruses?
a. It uses viral RNA as a template for making complementary RNA
strands
b. It hydrolyzes the host cell's DNA
c. It uses viral RNA as a template for DNA synthesis
d. It converts host cell RNA into viral DNA
e. It translates viral RNA into proteins

2. HIV, the virus that causes AIDS, only infects certain cells within the immune system. This is because
a. the virus is not very mobile within the body and only comes into contact with a limited number of immune cells
b. other cells produce toxins that destroy the virus before infection can take place
c. the virus binds to specific receptors that are only present on certain immune cells
d. the virus gets into all cells, but the viral RNA is immediately destroyed in all but a small number of immune system cells
e.
infection requires the presence of a specific DNA sequence that is only present in the genome of certain immune system cells
3. When a virus infects an E. coli cell, what part of the virus enters the bacterial cytoplasm?
a. the entire virus
b. only nucleic acid
c. protein capsid and enclosed nucleic acid
d. tail fibers
e. only protein capsid






Answers: 1. b
2. c
3. b

from Kelli

Tuesday, January 27, 2009

Next Unit: Evolution


A very interesting article to get you thinking about Unit 8, our next unit on Evolution.
Click on it to enlarge

Monday, January 26, 2009

Hey guys, today in class I asked why we have introns if they are spliced out during RNA processing and I think I found the beginnings of an answer, here's the introduction to the article at http://www.pnas.org/content/96/18/10267.full:

"The evolutionary origin of spliceosomal introns has been the subject of much controversy. Introns are proposed to have been both lost and gained during evolution. If the gain or loss of introns are unique events in evolution, they can serve as markers for phylogenetic analysis. We have made an extensive survey of the phylogenetic distribution of seven spliceosomal introns that are present in Fugu genes, but not in their mammalian homologues; we show that these introns were acquired by actinopterygian (ray-finned) fishes at various stages of evolution. We have also investigated the intron pattern of the rhodopsin gene in fishes, and show that the four introns found in the ancestral chordate rhodopsin gene were simultaneously lost in a common ancestor of ray-finned fishes. These changes in introns serve as excellent markers for phylogenetic analysis because they reliably define clades. Our intron-based cladogram establishes the difficult-to-ascertain phylogenetic relationships of some ray-finned fishes. For example, it shows that bichirs (Polypterus) are the sister group of all other extant ray-finned fishes.
Two competing theories have been proposed to explain the origin of spliceosomal introns, which are widespread in eukaryote genomes but absent from prokaryotes. The “introns early theory” states that the introns are ancient and have been lost in different lineages (1, 2). On the other hand, the “introns late theory” maintains that the spliceosomal introns were inserted into the eukaryote genes later in evolution (36). Although the distribution of intron phases and the correlation between intron positions and protein module boundaries have been proposed as evidence for the ancient origin of introns (2), the restricted phylogenetic distribution of some introns suggests that they arose late in evolution (710).
We and others have identified extra spliceosomal introns in the pufferfish (Fugu) and some other teleosts that are absent from mammals (refs. 1118; B. Peixoto and S.B., unpublished work). Likewise, extra introns were also found in some mammalian genes (16, 19, 20). These discordant introns could be the result of either loss of ancestral introns or gain of novel introns in different lineages. Because the spliceosomal introns are not self-splicing and are not known to be mobile, the loss or the gain of spliceosomal introns in a lineage is likely to be a unique event, occurring at a specific point in its evolution; hence it might serve as a decisive marker for evolutionary studies. To evaluate and confirm whether the extra vertebrate introns are the result of a loss or gain of introns, we made an extensive survey of the phylogenetic distribution of seven of these introns, including one each from the growth hormone gene (15), the major histocompatibility class II B-chain (MhcII) gene (13) and the mixed lineage leukemia-like (Mll) gene (16), and two each from the dystrophin gene (14) and the RAG1 gene (21). We also analyzed the distribution of introns in the rhodopsin gene, which has been shown to contain introns in mammals (22) and in primitive chordates such as lampreys (23) and skates (24), but not in some teleosts (25). "

End of Chapter 18 and the beginning of Chapter 19


Transcription initiation is another important control point in gene expression. At this stage, DNA control elements that bind transcription factors (needed to initiate transcription) are involved in regulation.

Gene control also occurs after transcriptionm and during RNA processing, in alternative RNA splicing
Some things to consider:
1.Why do so many inherited diseases involve splicing errors and why to they show up as human cancers?

Splicing errors are associated with 15% of inherited diseases. Many of these genetic mutations cause inappropriate exon skipping, which ultimately cause defects in protein expression. The unerlying mechanisms responsible are poorly sliced genes.
2. What types of problems or questions drive our current research efforts? Why are there far fewer protein coding genes than can account for the size of the human proteasomes?

The control of gene expression also oc
curs both prior to translation and just after translation, when proteins are processed. "blocking translation"
Protein processing and degradation by proteasomes are subject to regulation.

mRNA degradation: Each mRNA has a characteristic life span, determined in part by sequences in the 5' and 3' UTR's (prime ends) mRNA may last anywhere from hours to weeks.

(18.3) Genes make up only a small group of the genomes of most eukaryotes; only about 97% of the DNA does not code for proteins, These noncoding regions of DNA are made up of introns, repetitive sequences, and sequences whose function is not yet understood. Repetitive DNA is responsible for anumer of genetic disorders.

The molecular biology of cancer:
Oncogens are caner-causing genes; proto-oncogenes are genes that code for proteins that are responsible for normal cell growth. Protooncogenes become oncogens when a mutation occurs that causes an increase in the product of the protoonogene or that increases the activity of the protooncogene itself.
p53 gene "guardian angel of the genome":
  1. activates gene 21 whose product halts the cell cycle by binging to cyclin-dependent
  2. When DNA demage is irreversible p53 will activate suicide
  3. p53 can also turn on genes dirctly involved in DNA repair
  4. (*also see: http://en.wikipedia.org/wiki/P53)
Cancer can also be caused by amutation a gene whose products normally inhibit all divison. these genseaare called tumor-suppressor genes. The incidence of cancer inceases with age because multiple somatic mutations are required to produce a cancerous cell.

Chapter 19: Viruses
Researchers disovered viruses int he late 1800's by studying a plant disease, tobacco mosaic disease.


Chapter 19 Vocab:

Capsid: The protein shell that encloses a viral genome. It may be rod-shaped, polyhedral, or more complex in shape.

Viral envelopes: A membrane that cloaks the capsid that in turn encloses a viral genome.
Bacteriophages:
A virus that infects bacteria

Host range: The limited range of host cells that each type of virus can infect.

Virulent phage: A phage that reproduces only by a lytic cycle.

Restriction enzymes: An endonuclease that recognizes and cuts DNA molecules foreign to a bacterium. The enzyme cuts at specific nucleotide sequences.

Lysogenic cycle: A type of phage reproductive cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage and does not kill the host.

Temperate phages: A phage that is capable of reproducing by either a lytic or lysogenic cycle.

Prophage: A phage genome that has been inserted into a specific site on a bacterial chromosome.

Retrovirus: An RNA virus that reproduces by transcribing its RNA into DA and then inserting the DNA into a cellular chromosome; an important class of cancer-causing viruses.

Reverse transcriptase: An enzyme encoded by certain viruses that uses RNA as a template for DNA synthesis.

Viroid: A plant pathogen consisting of a molecule of naked, circular RNA a few hundred nucleotides long.

Prion: An infectious agent that is a misfolded version of a normal cellular protein. Prions appear to increase in number by converting correctly folded versions of the protein to more prions.


Pretest for misconceptions:

Unlike viruses, viroids do not encode proteins: False
Unlike viruses, the genetic material for vioids is RNA: False
Unlike viruses, prions are infectious proteins: True
Unlike viruses, prions do not include nucleic acids: True


Classify as true or false:
Viruses are 2D rather than 3D: false
The viral genome can be single stranded or double stranded: true
Viruses are intracellular parasites: true
An isolated virus is unable to reproduce: true


The genetics of viruses and bacteria:

(19.1) Viruses: Smaller than ribosomes, viruses are about 20nm across. The genetic material of viruses can be double or single-stranded DNA, or single or double RNA. The viral genome is enclosed by a proteins shell called a capsid. Some viruses also have viral envelops tat surround the capsid and aid the viruses in infecting their hosts.
(19.2) Bacteriophages, which are also called phages are viruses that infect bacteria. Viruses use enzymes, ribosomes, and small molecules of host cells to synthesizing progeny viruses each type of virus has a chracteristic host range.
Pages (viruses that infect bacteria) can reproduce by two alternative mechaisms: the lytic cycle or lysogenic cyle
(http://www.youtube.com/watch?v=wVkCyU5aeeU&feature=related)


Viruses are energy parasites; they can only reproduce within a host, and each virus can only reproduce within a particular group of hosts.
Some viruses (called virulent phages) have a reproductive cycle that ends in the death of the host cell, and this is called the lytic cycle. In this course of the lytic cycle, the phage attaches to receptors on the cell surface, injects its DNA into the host, and directs the replication of its own DNA. New phages are assembled and then produce lysozyme, which disintegrates the cell wall so that the cell dies and new phages are released.

Multiple Choice:

1) The simplest infectious biological systems are
A) viroids. B) viruses. C) bacteria. D) A and B. E) B and C.

2) Which of the following is a true statement about viruses?
A) A single virus particle contains both DNA and RNA.
B) Viruses are classified below the cellular level of biological organization.
C) Even small virus particles are visible with light microscopes.
D) A and B only are true.
E) A, B, and C are true.

3) A researcher lyses a cell that contains nucleic acid molecules and capsid units of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur?
A) The plants would develop some but not all of the symptoms of the TMV infection.
B) The plants would develop symptoms typically produced by viroids.
C) The plants would become infected, but the sap from these plants would be unable to infect other plants.
D) The plants would develop the typical symptoms of TMV infection.
E) The plants would not show any disease symptoms.

4) Which of the following is a characteristic of all viruses?
A) nucleic acid genome
B) a protein capsid
C) glycoprotein cell wall
D) A and B only
E) A, B, and C



1) Answer: A 2) Answer: B 3) Answer: D 4) Answer: D




The rest of chapter 18

sorry I was supposed to do the blog on friday but I was busy that night and got home late and totally forgot about it but here are the notes we took on friday:
*Inducible Operon:
*An inducible operon is usually OFF but can be stimulated (induced) when a specific molecule interacts with the regulatory protein.
*Inducible operons usually function in catabolic pathways, which break down a nutrient to simpler molecules. By producing the appropriate enzymes only when the nutrient is available, the cell avoids wasting energy and precursors making proteins that are not needed.
*18.2--> Eukaryotic gene expression can be regulated at any stage
*Chromosome modification:
  • Genes in highly compacted chromatin is generally not transcribed
  • Histone acetylation seems to loosen chromatin structure, enhancing transcription
  • DNA methylation generally reduces transcription.

*Eukaryotic Chromatin Structure:

*In eukaryotic cells, DNA and proteins are packed together as chromatin. the first level of packing in chromosomes involves DNA and proteins called histones, in nearly equal amount, folded together to resemble beads on a string. Nucleasomes are the basic unit fo DNA packing- the are the complex of DNA and histones.

*In interphase, the chromosome are extended in the nucleus (and at this point are called euchromatin), but as the cell prepares for mitosis, the chromosomes become packed into a form referred to as heterochromatin.

*In histone acetylation, acetyl groups are added to amino acids of histone proteins; this makes the chromatin less tightly packed and encourages transcription.

*The Control of Gene Expression: DNA methylation

*The expression of gened can be turned off and on at any point along the pathway from gene to functional protein.

*Genes in heterochromatin (which is highly packed) usually are not transcribed; this is one form of gene control.DNA methylation (the addition of methyl groups) is one way in which the transcription of genes is controlled. Apparently methylation of DNA is responsible for the long-term inactivation of genes.

*Transcription initiation is another important control point in gene expression. At this stage, DNA control elements that bind transcription factors (needed to initiate transcription) are involved in regulation.

*Questions!!:

1. Is an inducible operon usually...

a) turned ON and could be turned OFF.

b) turned OFF and could be turned ON.

c) turned OFF and can NOT be turned ON.

d) turned ON and can NOT be turned OFF.

2. TRUE or FALSE. Histone is wrapped by chromatin.

3. When can expression genes be turned on and off along the pathway from gene to functional protein?

a) at ANY point

b) not possible

c) only at one specific point


Review for Mock AP Exam

I thought that I would never recommend this, but to view great animations that help clarify understanding of all the processes: mitosis, meiosis, DNA replication, photosynthesis, protein synthesis, ect. it would be a great idea to visit dnatube.com or youtube.com to view animations. DNA tube has some complex ones, but some that will refocus your attention back to some of these complicated processes.

On youtube, you can be specific, like type in dna replication or trp operon or lytic cycle and it will usually point you in the right direction.

Please offer me feedback if you find something great or if this helps you.
Remember "big picture"

Friday, January 23, 2009

Prokaryotic Operons



The Lac Operon animation


Remember that the operons are a way for prokaryotic organisms to express or not express their genes. This is natural to them. It is how they conserve energy when their internal or external environment changes. We learn about these operons so that we can understand how we might manipulate the eukaryotic cell. The eukaryotic cell has its own mechanisms for gene expression, but we are learning if we can control expression through methylation, acetylation, transcription, cytoplasmic factors, etc.

Thursday, January 22, 2009

Chapter 17 Mutations Start Chapter 18

Mutations



Mutations are alternations in the genetic material of the cell; point mutations are alternations of just one base pair of a gene. Point mutations are the most common. They come in 2 basic types:






1. Base pair substitutions refer to the replacement of one nucleotide and its complementary base pair in DNA with another pair of nucleotides.

  • Missense Mutations are those substitutions that enable the codon to still code for an amino acid, although it might not be the correct one

  • Nonsense Mutations are those substitutions that change a regular amino acid codon into a stop codon, ceasing translation

  • Silent Mutations (another example of base pair substitution from the book) are substitutions that have no effect on the new proten due to the redundancy of the genetic code.

2. Insertions and Deletions refer to the additions and losses of nucleotide pairs in a gene. They can cause a frameshift mutation which causes the mRNA to be read incorrectly.




Mutagens are substances or forces that interact with DNA to cause mutations. X-rays and some other forms of radiations are known mutagens, as are certain chemicals.





Chapter 18: Regulation of Gene Expression

The control of gene expression enables individual bacteria to adjust their metabolism to enviornmental change. Cells control metabolism by regulating enzyme activity or by regulating enzyme synthesis through activating or inactivating genes.

Repressible vs. Inducible Operons

The Repressible Operon : The trp operon is said to be a repressible operon because its transcription is usually ON but can be inhibited (repressed) when a specific molecule (ex. tryptophon) binds allosterically to a regulatory protein.

This "binding" makes the repressor active not the operon.





The enzymes for tryptophan synthesis are said to be repressible. Repressible enzymes generally function in anabolic pathways (building up), which synthesize essential end products from raw materials (precursors). By suspending production of an end product when it is already present in sufficient amounts, the cell can allocate its organic precursors and energy for other uses.




Here is a little preview of Chapter 18!






Review Questions!
1. This kind of mutation will occur whenever the number of nucleotides inserted or deleted is not a multiple of three. This causes improperly grouped codons and a nonfunctional protein.
A. Frameshift mutation
B. Nonsense Mutation
C. Missense Mutation
2. What is an example of a mutagen?
A. Visible light
B. UV light
C. Radio waves
3. The trp operon is what kind of operon?
A. Repressible
B. Corepressor
C. Inducible
4. Repressible Operons are usually turned off
A. True
B. False
5. Repressible enzymes function in catabolic pathways
A. True
B. False
Answers: A, B, A, B, B
So don't forget tomorrow is Chapter 18 vocab quiz and you Chapter 17 essay is due!












Wednesday, January 21, 2009

Chapter 17: Translation and Mutations

Sorry this is so late...

The Synthesis of Protein Translation

Translation is the synthesis of a polypeptide, under the direction of a ribosome.

tRNA is a type of RNA that functions in transferring particular amino acids from a pool of amino acids in the cell’s cytoplasm to a ribosome. The ribosome takes an amino acid and incorporates it into a growing polypeptide.

Each type of tRNA is specific for a particular amino acid; at one end it loosely binds the amino acid, and at the other end it has a nucleotide triplet called an anticodon, which allows it to pair specifically with a complementary codon on the mRNA.

The mRNA is read codon by codon, and one amino acid is added to the chain for each codon read.

In translation, wobble refers to the fact that the third nucleotide of a tRNA can form hydrogen bonds with more than one kind of base in the third position of a codon.

Mutations

Mutations are alterations in the genetic material of the cell; point mutations are alterations of just one base pair of a gene.

Types of point mutations include:

Base- Pair Substitutions

  • missense mutations: the altered codon still codes for an amino acid that makes sense, although not necessarily the right sense
  • nonsense mutations: changes a codon for an amino acid to a stop codon; the resulting polypeptide will be shorter and probably nonfunctional
Base-Pair Insertions or Deletions
  • Frameshift Mutation: occurs whenever the number of nucleotides inserted or deleted is not a multiple of three
Here's a real basic overview, big picture type of video on translation. Keep in mind that they omitted the E site.
http://www.youtube.com/watch?v=D5vH4Q_tAkY

Here's an overview of protein synthesis:
  1. TRANSCRIPTION: RNA is transcribed from a DNA template.
  2. RNA PROCESSING: In eukaryotes, the RNA transcript (pre-mRNA) is spliced and modified to produce mRNA, which moves from the nucleus to the cytoplasm
  3. FORMATION OF INITIATION COMPLEX: After leaving the nucleus, mRNA attaches to the ribosome.
  4. AMINO ACID ACTIVATION: Each amino acid attaches to its proper tRNA with the help of a specific enzyme (aminoacyl-tRNA synthetase) and ATP.
  5. TRANSLATION: A succession of tRNAs add their amino acids to the polypeptide chain as the mRNA is moved through the ribosomoe one codon at a time. (When completed, the polypeptide is released from the ribosome--its a protein in primary structure!)

Multiple Choice:

1. How many ribosomal subunits are there?
a. 1
b. 2
c. 3
d. 4
2. What is added to the mRNA before it leaves the nucleus?
a. Promoter and Terminator
b. 5' cap and 3' Poly-A tail
c. Initiation Complex and End Sequence
d. Codon and Anticodon
3. In which direction does the mRNA get built?
a. 3' to 5'
b. 5' to 3'
4. What does the growing polypeptide chain become after translation?
a. a nucleic acid
b. lipid
c. carbohydrate
d. protein




Answers: b, b, b, d

Good night and good luck...
Remember, tomorrow: Ch 17 Essay, and Ch 18 Vocab Check. The take home packet isn't due til Jan 30th, the day after the talent show. And since I know you're all coming to that, you will be getting it done before that night! :D

Jen M.