Unit 6 AP BIO exam review

What are histones? What is the role of histones in regulating gene expression?

DNA wraps around Histone proteins in the nucleus. Sometimes DNA is wrapped so tightly that transcription can not happen, so the protein coded by that region can not be made.

What is the 'Central Dogma' of Biology? ______ >> ________ >> _____________

Dna ---> RNA --> protien

Percent of offspring that do not have Sickle Cell and are not susceptible to malaria _______

1/2

Come up with some way to remember (to link the facts together) that A and G are Purines and have a double ring, while C, T, and U are Pyrimidines and have just one ring. Then share your idea with someone and see what idea they came up with!

A and G got married and have 2 wedding rings C, T, and U build pyramids with one ring

What is the difference between a muscle cell and a nerve cell? Use the words Tissue Specific, Differentiation, Gene Expression, and Proteins in your answer.

Muscle cells and nerve cells each have a unique gene expression. Tissue specific genes in the muscle cell are turned on (ex - actin and myosin), whereas the gene expression of a nerve cell is different. The proteins being made by the cell lead it to be specialized, differentiated for its particular job in the body.

Draw a plasmid. Where are plasmids found in Prokaryotic cells? Where are they found in Eukaryotic cells (HINT consider the evolution of some Eukaryotic organelles!)?

Plasmids are small rings of DNA free floating inside Prokaryotes. They are also found in mitochondria and chloroplasts (consider the Endosymbiotic Theory that these organelles were once free-living prokaryotes)

Draw a simple diagram showing each way prokaryotes increase genetic variety. Then come up with a way to remember each one - somehow link the word with the process!

Drawing of Process ----------->Link the word to what it means In transformation, a bacterium takes up a piece of DNA floating in its environment. In transduction, DNA is accidentally moved from one bacterium to another by a virus. In conjugation, DNA is transferred between bacteria through a tube between cells.

The sickle cell gene is a result of a single base pair mutation. It is a recessive trait that can lead to a shortened life-span for people who are homozygous- however in some areas of Africa there is a very high incidence of Sickle Cell disease. Why is this? Use the words natural selection and heterozygote advantage in your explanation.

It is very high in Africa because being heterozygous for sickle cell is advantages that you have a resistance to malaria. This means that it helped increase the fitness of the individual meaning the allele frequency spread.

The lac operon is an INDUCIBLE operon. What does this mean? How does the operon turn on? (be specific to the lac operon).

This means it's default state is 'off', with the repressor bound to the operator. It can be INDUCED to turn on in the presence of an inducer - lactose. When lactose is present, it will bind to the repressor and cause its shape to change so that it falls off of the operator, allowing RNA Polymerase to translate the proteins in the operon.

Explain why transcription and translation can happen at the same time in Prokaryotes, but not in Eukaryotic cells.

Transcription and translation can happen at the same time because Prokaryotes do not have a nucleus, so the ribosomes for translation can come along and join up to a growing mRNA as it is being made by RNA Polymerase.

In the box, draw a punnett square showing the resulting offspring of two heterozygous individuals for the sickle cell trait.

but 2 would be heterozygous one would be dominate and one would be ressive

Cell Specialization is the process of stem cells becoming...

compartmentalized

Regulatory sequences of DNA do not code for a protein. What is their purpose?

turn on and off certain genes/ proteins being made

Describe an environment where this mutation would be neutral.

where it was a mixture of the 2 climates so it would be useful sometime but not always

Why is it beneficial for cells of a multicellular organism to be able to regulate their gene expression?

Cells are differentiated to do a particular job. Example: you would not want a cell in the brain to be making stomach acids! Each cell has its role in the health of the body, based on its gene expression.

How did Crick, Watson, Franklin and Wilkins contribute to our knowledge of DNA?

Combined, they revealed the double helix structure of the DNA molecule.

Then you must make many many copies of the DNA sample. What process will you use to do this?

You will use a Polymerase Chain Reaction machine, or PCR machine.

Name two reasons that a scientist might use an Electrophoresis machine.

dna analysis protien and antibody interactions

Here is a normal sequence of mRNA. Use a Codon Chart to transcribe and translate it into its amino acid sequence (this is the same sequence in 6.4) A - U - G - G - A - A - C - A - G - G - U - A - A - G - A

start, glu, gin, val, arg

What does the word 'transgenic' literally mean (its word parts) ____________ _____________

movement race

The promoter region of Gene A has a mutation such that the necessary transcription factor does not bind to it. This transcription factor turns on the gene. What does this mean for the production of Protein A? Explain.

The shape of the transcription factor is specific to bind to a particular sequence on the DNA. If the sequence is wrong, it will not recognize the site, and will not bind. In this case, the gene will be permanently turned off, unable to make protein A.

Around 90% of the processed food sold in the United States contains Genetically Modified ingredients. Name two types of plants that have been genetically modified, what new trait they now have, and why it was developed (what is the benefit).

1. corn --> made to have bigger sweeter juicer, more bright yellow kernels = more food 2. apples--> larger, harder, less prone to bruising, sweeter, thicker skin --> more food and more appealing to consumer

Percent of offspring have Sickle Cell disease _________ Percent of offspring susceptible to malaria _________

1: 4 1: 4

Now re-write the mRNA sequence with one point mutation that would be neutral to the organism with this sequence (recognize this point mutation is a reflection of a point mutation that would be in the DNA, transcribed here into mRNA). Translate your mutated sequence. Why is this mutation neutral?

A - U - G - G - A - A - C - A - G - G - U - ((C)) - A - G - A yep = start, glu, gin, val, arg

Now re-write the mRNA sequence with a point mutation that COULD be positive to the organism with this sequence. Translate the mutated sequence into amino acids. Why might this be a positive mutation?

A - U - G - G - A - A - C - A - G - G - U - A - ((A)) - G - A yep = start, glu, gin, stop

Re-write the mRNA sequence with one point mutation that would still lead to the same amino acid sequence. Put a line between the codons. Underline your point mutation.

A - U - G // - G - A - A //- C - A - G -// G - U - A -// A - G - ((G)) start, Glu, Gin, Val, arg

Draw a line between each codon. Then use the Codon Chart on the next page to translate this mRNA sequence into amino acids. A - U - G - G - A - A - C - A - G - G - U - A - A - G - A

A - U - G // - G - A - A //- C - A - G -// G - U - A -// A - G - A start, Glu, Gin, Val, arg

You will first cut the DNA sample into small pieces. What tool will you use to do this? (type of enzyme)

A restriction enzyme.

A scientist has noted the gene expression of a group of cells. Read the unique gene that is expressed and determine what type of cell it must be. Achedocholine Hemoglobin Actin and myosin Antibodies Insulin

Achedocholine: neurotransmitter released by nerve cells to send signals to other types of cells Hemoglobin: is the iron-containing protein compound within red blood cells that carries oxygen throughout the body Actin and myosin: two types of proteins that form contractile filaments in muscle cells Antibodies: immunity and globulin describes protein. Insulin: Hormone

Explain: What causes the DNA molecules to move through the gel? How does the gel separate the pieces by size?

DNA is a negatively charged molecule. When the Gel Electrophoresis machine is turned on, an electric charge moves though the gel, with a negative charge at the top, and a positive charge at the bottom. DNA is repelled by the like charge near the top, and drawn to the opposite charge near the bottom. Smaller size pieces (like 80 bp) more easily move though the gel, and get further down the gel, while large pieces (like 300 bp) move much slower, and are kept closer to the top.

You have roughly 20,000 genes in your genome - but the ability to produce over 2 million different proteins! How is this possible? (HINT read standard IST-1N6d)

Different sections of mRNA can be removed in order to make different RNA sequences and therefore different proteins. The immune system takes advantage of alternative splicing to generate different shaped protein antibodies from a single string of DNA code.

What leads to cell differentiation during development? Use the word transcription factors in your answer.

Different transcription factors are expressed in different cell types, which turn onor off particular genes that lead to the differentiation of the cell. Some genes,like HOX genes, are master switches that control major portions of the bodyplan, and turn on sequentially in development.

TOPIC 6.6 Gene Expression and Cell Specialization

ENDURING UNDERSTANDING IST-2 Differences in the expression of genes account for some of the phenotypic differences between organisms. LEARNING OBJECTIVE IST-2.C Explain how the binding of transcription factors to promoter regions affects gene expression and/or the phenotype of the organism. ESSENTIAL KNOWLEDGE IST-2.C.1 Promoters are DNA sequences upstream of the transcription start site where RNA polymerase and transcription factors bind to initiate transcription. IST-2.C.2 Negative regulatory molecules inhibit gene expression by binding to DNA and blocking transcription. LEARNING OBJECTIVE IST-2.D Explain the connection between the regulation of gene expression and phenotypic differences in cells and organisms. ESSENTIAL KNOWLEDGE IST-2.D.1 Gene regulation results in differential gene expression and influences cell products and function. IST-2.D.2 Certain small RNA molecules have roles in regulating gene expression

TOPIC 6.7 Mutations

ENDURING UNDERSTANDING IST-2 Differences in the expression of genes account for some of the phenotypic differences between organisms. LEARNING OBJECTIVE IST-2.E Describe the various types of mutation. ESSENTIAL KNOWLEDGE IST-2.E.1 Changes in genotype can result in changes in phenotype— a. The function and amount of gene products determine the phenotype of organisms. The normal function of the genes and gene products collectively comprises the normal function of organisms. Disruptions in genes and gene products cause new phenotypes. IST-2.E.2 Alterations in a DNA sequence can lead to changes in the type or amount of the protein produced and the consequent phenotype. DNA mutations can be positive, negative, or neutral based on the effect or the lack of effect they have on the resulting nucleic acid or protein and the phenotypes that are conferred by the protein ILLUSTRATIVE EXAMPLES § Mutations in the CFTR gene disrupt ion transport and result in cystic fibrosis. § Mutations in the MC1R gene give adaptive melanism in pocket mice. ENDURING UNDERSTANDING IST-4 The processing of genetic information is imperfect and is a source of genetic variation LEARNING OBJECTIVE IST-4.A Explain how changes in genotype may result in changes in phenotype. ESSENTIAL KNOWLEDGE IST-4.A.1 Errors in DNA replication or DNA repair mechanisms, and external factors, including radiation and reactive chemicals, can cause random mutations in the DNA— a. Whether a mutation is detrimental, beneficial, or neutral depends on the environmental context. b. Mutations are the primary source of genetic variation. IST-4.A.2 Errors in mitosis or meiosis can result in changes in phenotype— a. Changes in chromosome number often result in new phenotypes, including sterility caused by triploidy, and increased vigor of other polyploids. b. Changes in chromosome number often result in human disorders with developmental limitations, including Down syndrome/ Trisomy 21 and Turner syndrome. ILLUSTRATIVE EXAMPLES § Antibiotic resistance mutations § Pesticide resistance mutations § Sickle cell disorder and heterozygote advantage LEARNING OBJECTIVE IST-4.B Explain how alterations in DNA sequences contribute to variation that can be subject to natural selection. ESSENTIAL KNOWLEDGE IST-4.B.1 Changes in genotype may affect phenotypes that are subject to natural selection. Genetic changes that enhance survival and reproduction can be selected for by environmental conditions— a. The horizontal acquisitions of genetic information primarily in prokaryotes via transformation (uptake of naked DNA), transduction (viral transmission of genetic information), conjugation (cell-to-cell transfer of DNA) and transposition (movement of DNA segments within and between DNA molecules) increase variation. b. Related viruses can combine/recombine genetic information if they infect the same host cell. c. Reproduction processes that increase genetic variation are evolutionarily conserved and are shared by various organisms.

TOPIC 6.5 Regulation of Gene Expression

ENDURING UNDERSTANDING: Differences in the expression of genes account for some of the phenotypic differences between organisms. LEARNING OBJECTIVE IST-2.A Describe the types of interactions that regulate gene expression. ESSENTIAL KNOWLEDGE IST-2.A.1 Regulatory sequences are stretches of DNA that interact with regulatory proteins to control transcription. IST-2.A.2 Epigenetic changes can affect gene expression through reversible modifications of DNA or histones. IST-2.A.3 The phenotype of a cell or organism is determined by the combination of genes that are expressed and the levels at which they are expressed— a. Observable cell differentiation results from the expression of genes for tissue specific proteins. b. Induction of transcription factors during development results in sequential gene expression LEARNING OBJECTIVE IST-2.B Explain how the location of regulatory sequences relates to their function. ESSENTIAL KNOWLEDGE IST-2.B.1 Both prokaryotes and eukaryotes have groups of genes that are coordinately regulated— a. In prokaryotes, groups of genes called operons are transcribed in a single mRNA molecule. The lac operon is an example of an inducible system b. In eukaryotes, groups of genes may be influenced by the same transcription factors to coordinately regulate expression.

TOPIC 6.2 Replication

ENDURING UNDERSTANDING: Heritable information provides for continuity of life LEARNING OBJECTIVE IST-1.M Describe the mechanisms by which genetic information is copied for transmission between generations. ESSENTIAL KNOWLEDGE IST-1.M.1 DNA replication ensures continuity of hereditary information— a. DNA is synthesized in the 5' to 3' direction. b. Replication is a semiconservative process—that is, one strand of DNA serves as the template for a new strand of complementary DNA. c. Helicase unwinds the DNA strands. d. Topoisomerase relaxes supercoiling in front of the replication fork. e. DNA polymerase requires RNA primers to initiate DNA synthesis. f. DNA polymerase synthesizes new strands of DNA continuously on the leading strand and discontinuously on the lagging strand. g. Ligase joins the fragments on the lagging strand. X The names of the steps and particular enzymes involved - beyond DNA polymerase, ligase, RNA polymerase, helicase, and topoisomerase - are beyond the scope of the AP Exam

TOPIC 6.8 Biotechnology

ENDURING UNDERSTANDING: Heritable information provides for continuity of life LEARNING OBJECTIVE IST-1.P Explain the use of genetic engineering techniques in analyzing or manipulating DNA. ESSENTIAL KNOWLEDGE IST-1.P.1 Genetic engineering techniques can be used to analyze and manipulate DNA and RNA— a. Electrophoresis separates molecules according to size and charge. b. During polymerase chain reaction (PCR), DNA fragments are amplified c. Bacterial transformation introduces DNA into bacterial cells. d. DNA sequencing determines the order of nucleotides in a DNA molecule. X The details of these processes are beyond the scope of this course. The focus should be on the conceptual understanding of the application of these techniques ILLUSTRATIVE EXAMPLES § Amplified DNA fragments can be used to identify organisms and perform phylogenetic analyses. § Analysis of DNA can be used for forensic identification. § Genetically modified organisms include transgenic animals. § Gene cloning allows propagation of DNA fragments

TOPIC 6.1 DNA and RNA Structure

ENDURING UNDERSTANDING: Heritable information provides for continuity of life. LEARNING OBJECTIVE IST-1.K Describe the structures involved in passing hereditary information from one generation to the next. ESSENTIAL KNOWLEDGE IST-1.K.1 DNA, and in some cases RNA, is the primary source of heritable information. IST-1.K.2 Genetic information is transmitted from one generation to the next through DNA or RNA— a. Genetic information is stored in and passed to subsequent generations through DNA molecules and, in some cases, RNA molecules. b. Prokaryotic organisms typically have circular chromosomes, while eukaryotic organisms typically have multiple linear chromosomes. IST-1.K.3 Prokaryotes and eukaryotes can contain plasmids, which are small extra-chromosomal, double-stranded, circular DNA molecules. LEARNING OBJECTIVE IST-1.L Describe the characteristics of DNA that allow it to be used as the hereditary material. ESSENTIAL KNOWLEDGE IST-1.L.1 DNA, and sometimes RNA, exhibits specific nucleotide base pairing that is conserved through evolution: adenine pairs with thymine or uracil (A-T or A-U) and cytosine pairs with guanine (C-G)— a. Purines (G and A) have a double ring structure. b. Pyrimidines (C, T, and U) have a single ring structure.

TOPIC 6.3 Transcription and RNA Processing

ENDURING UNDERSTANDING: Heritable information provides for continuity of life. LEARNING OBJECTIVE IST-1.N Describe the mechanisms by which genetic information flows from DNA to RNA to protein. ESSENTIAL KNOWLEDGE IST-1.N.1 The sequence of the RNA bases, together with the structure of the RNA molecule, determines RNA function— a. mRNA molecules carry information from DNA to the ribosome. b. Distinct tRNA molecules bind specific amino acids and have anti-codon sequences that base pair with the mRNA. tRNA is recruited to the ribosome during translation to generate the primary peptide sequence based on the mRNA sequence. c. rRNA molecules are functional building blocks of ribosomes. IST-1.N.2 Genetic information flows from a sequence of nucleotides in DNA to a sequence of bases in an mRNA molecule to a sequence of amino acids in a protein. IST-1.N.3 RNA polymerases use a single template strand of DNA to direct the inclusion of bases in the newly formed RNA molecule. This process is known as transcription. ST-1.N.4 The DNA strand acting as the template strand is also referred to as the noncoding strand, minus strand, or antisense strand. Selection of which DNA strand serves as the template strand depends on the gene being transcribed. IST-1.N.5 The enzyme RNA polymerase synthesizes mRNA molecules in the 5' to 3' direction by reading the template DNA strand in the 3' to 5' direction. IST-1.N.6 In eukaryotic cells the mRNA transcript undergoes a series of enzyme-regulated modifications— a. Addition of a poly-A tail. b. Addition of a GTP cap. c. Excision of introns and splicing and retention of exons. d. Excision of introns and splicing and retention of exons can generate different versions of the resulting mRNA molecule; this is known as alternative splicing.

TOPIC 6.4 Translation

ENDURING UNDERSTANDING: Heritable information provides for continuity of life. LEARNING OBJECTIVE IST-1.O Describe how the phenotype of an organism is determined by its genotype. ESSENTIAL KNOWLEDGE IST-1.O.1 Translation of the mRNA to generate a polypeptide occurs on ribosomes that are present in the cytoplasm of both prokaryotic and eukaryotic cells and on the rough endoplasmic reticulum of eukaryotic cells. IST-1.O.2 In prokaryotic organisms, translation of the mRNA molecule occurs while it is being transcribed. IST-1.O.3 Translation involves energy and many sequential steps, including initiation, elongation, and termination X The details and names of the enzymes and factors involved in each of these steps are beyond the scope of the AP Exam IST-1.O.4 The salient features of translation include— a. Translation is initiated when the rRNA in the ribosome interacts with the mRNA at the start codon. b. The sequence of nucleotides on the mRNA is read in triplets called codons. c. Each codon encodes a specific amino acid, which can be deduced by using a genetic code chart. Many amino acids are encoded by more than one codon. d. Nearly all living organisms use the same genetic code, which is evidence for the common ancestry of all living organisms. e. tRNA brings the correct amino acid to the correct place specified by the codon on the mRNA. f. The amino acid is transferred to the growing polypeptide chain. g. The process continues along the mRNA until a stop codon is reached. h. The process terminates by release of the newly synthesized polypeptide/protein. X Memorization of the genetic code is beyond the scope of the AP Exam IST-1.O.5 Genetic information in retroviruses is a special case and has an alternate flow of information: from RNA to DNA, made possible by reverse transcriptase, an enzyme that copies the viral RNA genome into DNA. This DNA integrates into the host genome and becomes transcribed and translated for the assembly of new viral progeny. X The names of the steps and particular enzymes involved—beyond DNA polymerase, ligase, RNA polymerase, helicase, and topoisomerase—are beyond the scope of the course and the AP Exam.

Genotype is: Phenotype is:

Genotype: organism's full hereditary information. Phenotype: is an organism's actual observed properties, such as morphology, development, or behavior

There is a mutation in the regulatory gene that turns off Gene B, such that the regulatory protein does not bind to the DNA. What does this mean for the production of Protein B? Explain.

If the transcription factor is the wrong shape, it will not recognize he specific sequence on the DNA it is supposed to bind to. In this case, if the regulatory protein can not bind to the regulatory sequence, it will be permanently turned on, continually making protein B.

Based on their structure (shape) explain why purines must always match with pyrimidines. In your explanation, include how a proofreading enzyme would identify a location where two purines are accidentally matched up, and a location where two pyrimidines are matched up.

Purines pair with pyrimidines because their size and shape make them a perfect fit for hydrogen bonding

What does each of these numbers represent in the diagram of the lac operon?

RNA polymerase Repressor Promoter Operator Inducer (lactose sugar) proteins needed to break down lactose

You can get the polio vaccine one time and be immune for life, but you must take a flu vaccine each year to be immune for just that season. This is because the flu (and HIV as well) are retroviruses. How are retroviruses different from other viruses? How does this difference lead to the need to get a flu shot every year?

Retroviruses are a group of viruses, so retroviruses carry special characteristics, which are not seen in viruses. • Virus contains genetic material as DNA or RNA but retrovirus contains only RNA. You need a new flu short every year because it can change its genetic coding so that the previous vaccine is not effective

Why is it beneficial for single cellular organisms to be able to regulate their gene expression?

Single celled organisms can only utilize the resources in its environment. If it is making proteins that are not useful at the time, it is a waste of resources. Ex: bacteria will only make lactase when lactose sugar is in the environment.

Briefly describe what happens in each stage of translation. Include the roles of rRNA, mRNA, tRNA, codons, anticodons, and amino acids. initiation elongation termination

Step 1: Initiation The point at which the replication begins is known as the Origin of Replication (oriC). Helicase brings about the procedure of strand separation, which leads to the formation of the replication fork. Step 2: Elongation The enzyme DNA Polymerase III makes the new strand by reading the nucleotides on the template strand and specifically adding one nucleotide after the other. If it reads an Adenine (A) on the template, it will only add a Thymine (T). Step 3: Termination When Polymerase III is adding nucleotides to the lagging strand and creating Okazaki fragments, it at times leaves a gap or two between the fragments. These gaps are filled by ligase. It also closes nicks in double-stranded DNA.

Put a star beside the antisense strand. Why would this strand (that is used as a template for RNA Polymerase) be called the antisense, or noncoding strand? Explain.

Template strand or "Antisense strand" runs in 3'- 5' direction, opposite to the coding strand. It contains complementary nucleotide sequences to the transcribed mRNA. After transcription, the mRNA before converted into mature mRNA, it undergoes certain post-transcriptional modifications. The template strand also contains "Anticodons" that carry triplet codes or triplet nucleotide sequences complementary to the anticodon sequence of the t-RNA.

What is the purpose of the poly-A tail and the GTP cap?

The 5' Cap and the Poly A Tail The cap is added by the enzyme guanyl transferase. This enzyme catalyzes the reaction between the 5' end of the RNA transcript and a guanine triphosphate (GTP) molecule. Once in place, the cap plays a role in the ribosomal recognition of messenger RNA during translation into a protein.

Briefly explain in your own words how the base pairing rules of DNA lead to its ability to be used as the hereditary material of life (aka, to be copied and passed to a resulting daughter cell).

The base pairing rules for DNA are governed by the complementary base pairs: adenine (A) with thymine (T) in an A-T pairing and cytosine (C) with guanine (G) in a C-G pairing. Conversely, thymine only binds with adenine in a T-A pairing and guanine only binds with cytosine in a G-C pairing.

Okay, but why can't T (a pyrimidine) match with G (a purine)? Based on the number of hydrogen bonds that are available in adenine, thymine, guanine and cytosine, explain why A always matches with T, and C with G. In your explanation, include how a proofreading enzyme would identify a location where G and T are accidentally matched up, and a location where A and C are matched up.

The best explanation for why adenine bonding with thymine only and guanine with cytosine only is through the base pairing rule in DNA where the bases only have a set of available bonds to allow complementary base pairing, where each base can only bond with a specific base partner. These hydrogen-bonded nitrogenous bases are called base pairs. In complementary base pairing, cytosine can make three hydrogen bonds with guanine, and adenine can form two hydrogen bonds with thymine. The structures complement each other like a lock and a key system. It can be observed in the structure of these nitrogenous bases that purines have an imidazole ring attached to the pyrimidine ring in their structure. A purine has to make a hydrogen bond with another pyrimidine because there is only enough space between the two strands to accommodate a purine and a pyrimidine. Therefore, two purines will not fit between the strands while two pyrimidines will be too far to bond.

What would happen if there was a mutation in the regulatory gene for the lac operon so that the regulatory protein did not bind to lactose sugar?

The binding of lactose sugar causes the regulatory protein (the repressor) to come off of the promoter, allowing transcription to occur. If lactose could not bind to the protein, the operon would stay 'off' even in the presence of lactose - the bacteria would not be able to make the enzymes needed to digest lactose.

On diagram, label the leading strand and the lagging strand - briefly explain why Replication works a bit differently on the leading vs. lagging strand. Use the word antiparallel

The main difference between leading and lagging strand is that the leading strand is the DNA strand, which grows continuously during DNA replication whereas lagging strand is the DNA strand, which grows discontinuously by forming short segments known as Okazaki fragments. Therefore, to form a continuous strand, the leading strand does not require ligase while the lagging strand requires ligase to ligate Okazaki fragments together. Furthermore, the leading strand opens in the 3' to 5' direction while the lagging strand opens in the 5' to 3' direction and runs anti-parallel.

This is the lac operon of prokaryotic cells. What does it code for?

The proteins needed to breakdown the sugar lactose.

What would happen if there was a mutation in the regulatory gene for the lac operon so that the regulatory protein did not bind to the operator?

The regulatory gene codes for the regulatory protein (the repressor). If the Repressor did not bind to the operon, the operon would stay 'on' and make the lac proteins even when lactose is not present.

Do you think GMO foods should be labeled in the store? Why or why not?

Yes because although they have been tested and regulated they still should be up front that they are not organic and have had some chemical temeraring for though that would want to avoid it.

In your own words, what does it mean that DNA replication is a 'semiconservative' process?

as one of the two strands of the double-stranded DNA is an original DNA strand, which served as the template for the synthesis of the new strand. Since one of the two strands is always conserved, DNA replication is considered as a semiconservative process.

A always matches with T, and G always matches with C.....but why? Proofreading enzymes run along the DNA molecule to be sure there are no mis-pairings between bases, but how do they know when a mistake has happened?

complementary bases Consistent pairings of complementary bases allow cells to make double-stranded DNA from a single strand template, create messenger RNA from DNA and synthesize proteins from individual amino acids by matching nucleotides bases on messenger RNA with their complementary bases on transfer RNA. DNA proofreading is an essential phenomenon during the synthesis of new DNA strands because if there is a misincorporation of any nucleotide, it will cause mutation and ultimately damage the cell's cellular processes. Thereby, the cell keeps track of any misincorporation of nucleotide with the help of the enzyme DNA polymerase.

In general, most species on the planet have some way of increasing genetic variation, and all species are susceptible to random mutation. Why is genetic variation shared across all species? What is the advantage to genetic variation?

environments do not remain the same forever. A favorable trait today may be a disadvantage when the environment changes. Genetic variety helps to ensure that natural selection has something to work with. If (when) the environment changes, if there is no genetic variety, a species can not adapt, and it will likely die out. But, if there is variety in the population, there is a chance that some variations in some individuals will be favorable, will survive, and will pass those traits on to the next generation.

How can you remember that it is the exons that stay and the introns that must be removed during mRNA processing? Come up with a creative way to remember and share it with someone else.

exons are expressed introns are in the trash

Explain or draw the steps showing how pharmaceutical companies can use bacterial transformation to make human proteins (like insulin).

human DNA and bacterial DNA are combined to produce insulin. Human DNA is inserted into the plasmid of bacteria.

Describe an environment where this mutation would be positive (beneficial).

in the artic or snowy environment where the rabbit would blend into its surroundings

A wild rabbit is born with a mutation that causes his fur to be white. Describe an environment where this mutation would be negative (detrimental).

in the forest where it would be more advantageous to blend into the dark colors of the forest floor

To the right is a gel plate for an Electrophoresis machine. You have a sample of DNA that you want to run through the gel.

just read

In your own words, describe the job of each type of RNA, using the given word... mRNA use the word 'message' tRNA use the word 'transfer' rRNA use the word 'ribosome'

mRNA transcribes the genetic code from DNA into a form that can be read and used to make proteins. mRNA carries genetic information from the nucleus to the cytoplasm of a cell. rRNA is located in the cytoplasm of a cell, where ribosomes are found. rRNA directs the translation of mRNA into proteins. tRNA is located in the cellular cytoplasm and is involved in protein synthesis. Transfer RNA brings or transfers amino acids to the ribosome that corresponds to each three-nucleotide codon of rRNA. The amino acids then can be joined together and processed to make polypeptides and proteins.

Define microRNA: What does microRNA do?

microRNA are small pieces of RNA that bind to mRNA and preventtranslation - another form of gene expression regulation.

What is the significance of this famous experiment (what does it demonstrate)?

the Hershey-Chase experiments were a series of experiments conducted in 1952 by Alfred Hershey and Martha Chase that helped to confirm that DNA is genetic material. While DNA had been known to biologists since 1869, many scientists still assumed at the time that proteins carried the information for inheritance because DNA appeared to be an inert molecule, and, since it is located in the nucleus, its role was considered to be phosphorus storage. In their experiments, Hershey and Chase showed that when bacteriophages, which are composed of DNA and protein, infect bacteria, their DNA enters the host bacterial cell, but most of their protein does not. Hershey and Chase and subsequent discoveries all served to prove that DNA is the hereditary material.