IB Bio HL DNA

Explain the four levels of protein structure, indicating the significance of each level

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Explain the process of translation, including ribosomes, polysomes, start codons, and stop codons

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Outline a basic technique used for gene transfer involving plasmids, a host cell (bacterium, yeast or other cell), restriction enzymes (endonucleases) and DNA ligase

1. DNA Extraction A plasmid is removed from a bacterial cell, a gene of interest is removed from an organism's genome using a restriction endonuclease which cut at specific sequences of DNA, gene of interest and plasmid are both amplified using PCR technology 2. Digestion and Ligation Plasmid is cut with the same restriction enzyme that was used to excise the gene of interest, cutting with certain restriction enzymes may generate short sequence overhangs that allow the two DNA constructs to fit together, gene of interest and plasmid are spliced together by DNA ligase creating a recombinant plasmid 3. Transfection and Expression Recombinant plasmid is inserted into the desired host cells, the transgenic cells will hopefully produce the desired trait encoded by the gene of interest, the product may need to be isolated from the host and purified in order to generate sufficient yield

Draw and label a simple diagram of the molecular structure of DNA

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Discuss the relationship between one gene and one polypeptide

A gene is a sequence of DNA which encodes a polypeptide sequence A gene sequence is converted into a polypeptide sequence via the processes of transcription (making an mRNA sequence transcript) and translation (polypeptide synthesis) Translation uses tRNA molecules and ribosomes to join amino acids into a polypeptide chain according to mRNA sequence All organisms show the same relationship between genes and polypeptides (common ancestory) Some proteins may consist of a number of polypeptide chains and need multiple genes When a gene is mutated it may lead to the synthesis of a defective polypeptide, affecting protein function Genes encoding for tRNA and rRNA do not code for polypeptide sequences A single gene may code for multiple polypeptides if alternative splicing occurs

Explain the process of transciption in prokaryotes, including the role of the promoter region, RNA polymerase, nuceloside triphosphate and the terminator

A gene is sequence of DNA which transcribed into RNA and contain three main parts Promoter: Responsible for the initiation of transcription (in prokaryotes, a number of genes may be regulated by a single promoter -- this is an operon) Coding Sequence: The sequence of DNA that is actually transcribed (may contain introns in eukaryotes) Terminator: Sequence that serves to terminate transcription (mechanism of termination differs between prokaryotes and eukaryotes)

Elongation

A second tRNA molecule pairs with the next codon in the ribosomal A-site The amino acid in the P-site is covalently attached

State that DNA replication is semi-conservative

A semi-conservative process because when a new double-stranded DNA molecule is formed One strand will be from the original molecule, one strand will be newly synthesized

State the names of the four bases in DNA

Adenine, guanine, thymine, cytosine

Translocation

Amino acids are transloacted to a growing polypeptide chain

Termination

At certain "stop" codons, translation is ended and the polypeptide is released

Analyze DNA profiles to draw conclusions about paternity or forensic investigations. The outcomes of this analysis could include knowledge of the number of human genes, the location of specific genes, discovery of proteins and their functions, and evolutionary relationships

Paternity Testing: Children inherit half of their alleles from each parent and thus should possess a combination of their parent alleles Forensic Investigation: Suspect DNA should be a complete match with the sample taken from a crime scene if a conviction is to occur

Transcription is the process by which a DNA sequence (gene) is copied into a complementary RNA sequence and involves a number of steps:

RNA polymerase binds to the promoter and causes the unwinding and separation of the DNA strands Nucleoside triphosphates (NTPs) bind to their complementary bases on the antisense strand RNA polymerase covalently binds the NTPs together in a reaction that involves the release of two phosphates to gain the required energy RNA polymerase synthesizes an RNA strand in a 5' - 3' direction until reaches the terminator At the terminator, RNA polymerase and the newly formed RNA strand both detach from the antisense template, and the DNA rewinds Many RNA polymerase enzymes can transcribe a DNA sequence sequentially, producing a large number of transcripts Post-transcriptional modification is necessary in eukaryotes

Translocation

Ribosome moves along one codon position, the deacylated tRNA moves into the E-site and is released, while the tRNA bearing the dipeptide moves into the P-site Another tRNA molecules attaches to the next codon in the newly emptied A-site and the process is repeated Ribosome moves along the mRNA sequence in a 5' to 3' direction, synthesizing a polypeptide chain Multiple ribosomes can translate a single mRNA sequence simultaneously (forming polysomes)

Outline the structure of ribosomes, including protein and RNA composition, large and small subunits, three tRNA binding sites and mRNA binding sites

Ribosomes are made of protein (for stability) and ribosomal RNA Consist of a small subunit containing an mRNA binding site, large subunit contains three tRNA BINDING SITES Ribosomes can be either found freely in the cytosol or bound to the rough ER Ribosomes differ in size in eukaryotes and prokaryotes

State that free ribosomes synthesize proteins for use primarily within the cell, and that bound ribosomes synthesize proteins primarily for secretion or for lysosome

Ribosomes floating freely in the cytosol produce proteins for use within the cell Ribosomes attached to the rough ER are primarily involved in producing proteins to be exported from the cell or used in the lysosome These proteins contain a signal recognition peptide on their nascent polypeptide chains which direct the associated ribosome to the rough ER

State that, in gel electrophoresis, fragmens of DNA move in an electric field and are separated according to their size

Samples of fragmented DNA are placed in the wells of an agarose gel Gel is placed in a buffering solution and an electrical current is passed across the gel DNA is negatively charge due to its phosphate, and moves to the positive end (anode) Smaller fragments are less impeded by the gel matrix and move faster through the gel Fragments are thus separated according to size

Pre-Initiation

Specific tRNA-activating enzymes catalyze the attachment of amino acids to tRNA molecules, using ATP for energy

Explain how a DNA double helix is formed using complementary base pairing and hydrogen bonds

Two polynucleotide chains of DNA are held together by hydrogen bonds between complementary base pairs. Adenine pairs with thymine via two hydrogen bonds. Guanine pairs with cytosine via three hydrogen bonds In order for bases to be facing each other and be able to pair, the two strands must run in opposite directions (anti-parallel) As the chain lengthens, the atoms that make up the molecule will arrange themselves in an optimal energy configuration

Most of the DNA of a human cell is contained in the nucleus. Distinguish between unique and highly repetitive sequences in nuclear DNA.

U: occur once in genome; H: occur many times; U: long base sequences; H: short sequences/5-300 bases; U: (may be) genes; H: not genes; U: (may be) translated/coding sequences; H: never translated; U: small differences between individuals; H: can vary greatly; U: exons (are unique sequences); H: introns (may be repetitive); U: smaller proportion of genome; H: higher proportion of genome; satellite DNA is repetitive; repetitive sequences are used for profiling; prokaryotes do not (usually) contain repetitive sequences;

Distinguish between unique or single-copy genes and highly repetitive sequences in nuclear DNA

Unique - small proportion of genone, occurs once in the genome, long base sequences, usually genes, may be translated, low rate of mutation, very similar between individuals, not used for DNA profiling, exons are examples of unique sequences Repetitive Sequences: higher proportion of genome, occurs many times, short base sequences, not genes, never translated, higher rate of mutation, varies greatly between individuals, used for DNA profiling, introns are examples of repetitive sequences

Secondary Structure

Way the chains of amino acids fold or turn upon themselves Held together by hydrogen bonds between amine and carboxylic groups may form an alpha helix, a beta-pleated sheet or a random coil provides a level of structural stability

Codons

are a triplet of bases which encodes a particular amino acid As there are four bases, there are 64 different codon combinations The order of the codons determines the amino acid sequence for a protein The coding region always starts with a START codon and terminates with a STOP codon

Compare DNA transcription with translation.

both in 5` to 3` direction both require ATP DNA is transcribed and mRNA is translated transcription produces RNA and translation produces polypeptides/ protein RNA polymerase for transcription and ribosomes for translation/ ribosomes in translation only transcription in the nucleus (of eukaryotes) and translation in the cytoplasm/ at ER tRNA needed for translation but not transcription

Compare the processes of DNA replication and transcription.

both involve unwinding the helix both involve spearating the two strands both involve breaking hydrogen bonds between bases both involve complementary base pairing both involve C pairing with G both work in a 5` --> 3` direction both involve linking/ polymerization of nucleotides replication with DNA nucleotides and transcritpion with RNA nucleotides details of ribose/ deoxyribose difference adenine pairing with uracil instead of thymine only one strand copied not both no ligase/ no Okazaki fragments with transcription DNA or RNA polymerase both require a start signal but this signal is different for each transcripiton has only one starting point but replication has multiple starting points replication gives two DNA molecules whilst transcription gives mRNA

Transfer RNA

clover leaf shaped sequence that carries an amino acid

Describe the genetic code

composed of mRNA base triplets called codons 64 different codons each codes for the addition of an amino acid to a growing polypeptide chain the genetic code is degenerate meaning more than one codon can code for a partiuclar amino acid the genetic code is universal meaning it is the same in almost all organisms (AUG is the) start codon some (nonsense) codons code for the end of translation

Outline the structure of the nucleosomes in eukaryotic chromosomes.

contain histones eight histone molecules form a cluster in a nucleosome DNA strand is wound around the histones wound around twice in each nucleosome (another) histone molecule holds the nucleosome(s) together

Draw a labelled diagram to show four DNA nucleotides, each with a different base, linked together in two strands.

four nucleotides shown in diagram with one nucleotide clearly labelled; base, phosphate and deoxyribose (shown as pentagon) connected between the correct carbons and labelled at least once; backbone labelled as covalent bond between nucleotides correctly shown as 3 to 5 bond; two base pairs linked by hydrogen bonds drawn as dotted lines and labelled; two H bonds between A and T and three H bonds between C and G; adenine to thymine and cytosine to guanine; do not accept initials of bases antiparallel orientation shown;

Explain briefly the advantages and disadvantages of the universality of the genetic code to humans

genetic material can be transferred between species/ between humans one species could use a useful gene from another species transgenic crop plants/ livestock can be produced bacteria/ yeasts can be genetically engineered to make a useful product viruses can invade cells and take over their genetic apparatus viruses cause disease

State a role for each of four different named enzymes in DNA replication.

helicase splits/ breaks hydrogen bonds/ uncoils DNA/ unwinds DNA (DNA) polymerase III adds nucleotides (in 5' to 3' direction) extending existing strand (RNA) primase synthesizes a short RNA primer (which is later removed) on DNA (DNA) polymerase I replaces RNA primer with DNA (DNA) ligase joins Okazaki fragments/ fragments on lagging strand/ makes sugar-phosphate bonds between fragments

Quaternary Structure

interaction between multiple polypeptides or prosthetic groups that results in a single, larger, biologically active protein held together by a variety of bonds

Describe the roles of mRNA, tRNA and ribosomes in translation.

mRNA with genetic code/ codons tRNA with anticodon tRNA with amino acid attached ribosome with two sub-units mRNA held by ribosome start codon two tRNA molecules attached with mRNA on ribosome peptide bond between amino acids on tRNA polypeptide forms continues until a stop codon is reached polypeptide is released

Compare the structure of RNA and DNA

names of sugars, bases, and number of strands DNA: has the sugar deoxyribose, has the base thymine, is double-stranded, forms a double helix RNA: has the sugar ribose, has the base uracil, is usually single-stranded, does not form a double helix

Explain the process of DNA replication.

occurs during (S phase of ) interphase/in preparation for mitosis/cell division; DNA replication is semi-conservative; unwinding of double helix / separation of strands by helicase (at replication origin); hydrogen bonds between two strands are broken; each strand of parent DNA used as template for synthesis; synthesis continuous on leading strand but not continuous on lagging strand; leading to formation of Okazaki fragments (on lagging strand); synthesis occurs in 5 3direction; RNA primer synthesized on parent DNA using RNA primase; DNA polymerase III adds the nucleotides (to the 3 end) added according to complementary base pairing; adenine pairs with thymine and cytosine pairs with guanine; (Both pairings required. Do not accept letters alone.) DNA polymerase I removes the RNA primers and replaces them with DNA; DNA ligase joins Okazaki fragments; as deoxynucleoside triphosphate joins with growing DNA chain, two phosphates broken off releasing energy to form bond;

Discuss the relationship between genes and polypeptides.

originally assumed one gene codes for one polypeptide (one) gene is transcribed into (one) mRNA mRNA is translated by a ribosome to synthesize a polypeptide many exceptions to one gene --> one polypeptide found many more proteins made than there are genes some genes do not code for polypeptides some genes code for tRNA/rRNA some genes regulate gene expression genetic information transcribed by eukaryotes is edited before it is translated polypeptides may be altered before they become fully functional proteins

Draw and label a diagram showing the structure of a peptide bond between two amio aciids

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Outline DNA nucelotide structure in terms of sugar, base and phosphate

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Ribosomal RNA

primary component of ribosomes

Outline the structure of a ribosome.

small subunit and large subunit; mRNA binding site on small subunit; three tRNA binding sites / A, P and E tRNA binding sites; protein and RNA composition (in both subunits);

Explain the structure of the DNA double helix, including its subunits and the way in which they are bonded together.

subunits are nucleotides one base, one deoxyribose and one phosphate in each nucleotide description/ diagram showing base linked to deoxyribose C1 and phosphate to C5 four different bases - adenine, cytosine, guanine and thymine nucleotides linked up with sugar-phosphate bonds covalent/ phosphodiester bonds two strands (of nucleotides) linked together base to base A to T and G to C hydrogen bonds between bases antiparallel strands double helix drawn or described

Outline the structure of tRNA.

tRNA is composed of one chain of (RNA) nucleotides tRNA has a position/end/site attaching an amino acid (reject tRNA contains an amino acid) at the 3' terminal / consisting of CCA/ACC tRNA has an anticodon anticodon of three bases which are not base paired / single stranded / forming part of a loop tRNA has double stranded sections formed by base pairing double stranded sections can be helical tRNA has (three) loops (somethimes with an extra small loop) tRNA has a distinctive three dimensional / clover leaf shape

Messenger RNA

transcript copy of a gene used to encode a polypeptide

Explain the process of translation.

translation involves initiation, elongation/translocation and termination; mRNA binds to the small sub-unit of the ribosome; ribosome slides along mRNA to the start codon; anticodon of tRNA pairs with codon on mRNA: complementary base pairing (between codon and anticodon); (anticodon of) tRNA with methionine pairs with start codon / AUG is the start codon; second tRNA pairs with next codon; peptide bond forms between amino acids; ribosome moves along the mRNA by one codon; movement in 5 to 3 direction; tRNA that has lost its amino acid detaches; another tRNA pairs with the next codon/moves into A site; tRNA activating enzymes; link amino acids to specific tRNA; stop codon (eventually) reached;

Tertiary Structure

way a polypeptide folds and coils to form a complex molecular shape interactions between R groups, hydrogen bonds, disulphide bridges, ionic bonds, and hydrophilic/hydrophobic interactions may be important for the function of the enzyme

Distinguish between the sense and antisense strands of DNA

DNA consists of two polynucleotide strands, only one of which is transcribed into RNA The antisense strand is transcribed into RNA. Its sequence will be complementary to the RNA sequence and will be the "DNA version" of the tRNA anticodon sequence The sense strand is not transcribed into RNA Its sequence will be the DNA version of the RNA sequence (identical except for T instead of U)

Distinguish between RNA and DNA

DNA is double-stranded while RNA is single-stranded; DNA contains deoxyribose while RNA contains ribose; the base thymine found in DNA is replaced by uracil in RNA; one form of DNA (double helix) but several forms of RNA (tRNA, mRNA and rRNA);

Explain how the process of DNA replication depends on the structure of DNA.

DNA molecule is double (stranded) hydrogen bonds linking the two strands are weak/ can be broken DNA can split into two strands split by helicase helicase moves progressively down the molecules backbones are linked by covalent/ strong bonds strands do not therefore break/ base sequence conserved reference to semi-conservative replication base pairing/ sequences are complementary A=T and C=G the two original strands therefore carry the same information the two new strands have the same base sequence as the two original ones the strands have polarity base/ nucleotides added in 5` to 3` direction the two strands have opposite polarity discontinuous segments/ Okazaki fragments added to one strand DNA ligase needed to connect the segments

Explain that each tRNA molecule is recognized by a tRNA-activating enzyme that binds a specific amino acid to the tRNA, using ATP for energy

Each different tRNA molecule has a unique shape and chemical composition that is recognized by a specific tRNA-activating enzyme The enzyme first binds the amino acid to a molecule of ATP The amino acid is then transferred to the 3' end of the appropriate tRBA, attaching to a terminal CCA sequence on the acceptor stem and releasing the AMP molecule tRNA molecules with an amino acid attached is thus said to be 'charged' and is now capable of participating in translation Energy in the bond linking the tRNA molecule to the amino acid will be used in translation to form a peptide bond between adjacent amino acids

Explain the significance of complementary base pairing in the conservation of the base sequence of DNA

Each of the nitrogenous bases can only pair with its complementary partner. DNA is replicated by the combined action of helicase and DNA polymerase. The new strands formed will be identical to the original strands separated from the template. The two DNA molecules formed will be identical to the original molecule

Termination

Elongation and translocation continue until the ribosome reaches a stop codon Codons do not code for any amino acids and instead signal for translation to stop Polypeptide is released and the ribosome disassembles back into subunits Polypeptide may undergo post-translational modification prior to becoming a functional protein

State that eukaryotic RNA needs the removal of introns to form mature MRNA

Eukaryotic genes may contain non-coding sequence called introns that need to be removed before mature mRNA is formed The process by which introns are removed is called splicing The removal of exons (alternative splicing) can generate different mRNA transcripts (and different polypeptides) from a single gene

State that DNA replication is initiated at many points in eukaryotic chromosomes

Eukaryotic genomes are much larger than prokaryotic genomes, DNA replication is initiated at many points simultaneously in order to limit the time required for DNA replication to occur The specific sites at which DNA unwinding and initiation of replication occurs are called origins of replication and form replication bubbles As replication bubbles expand in both directions, they eventually fuse together, two generate separate semi-conservative double strands of DNA

State that, when genes are transferred between species, the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal

Genetic code is universal, meaning that for every living organism the same codons code for the same amino acids (rare exceptions) Genetic information from one organism could be translated by another

Explain the process of DNA replication in prokayrotes, including the role of enzymes (helicase, DNA polymerase, RNA primase, and DNA ligase), Okazaki fragments and deoxynucleoside triphosphates

Helicase unwinds and separates the double stranded DNA by breaking the hydrogen bonds between the base pairs. Occurs at specific regions (replication origins), creating a replication fork of two polynucleotide strands in antiparallel directions RNA primase synthesizes a short RNA primer on each template strand to provide an attachment and initiation point for DNA polymerase III DNA polymerase III adds deoxynucloside triphosphates to the 3' end of the polynucleotide chain, synthesizing in a 5' to 3' direction. dNTP's pair up opposite their complementary ase partner, and as they join with their DNA chain, the two phosphates are broken off, releasing the energy needed to form a phosphodiester bond. Synthesis is continuous on the strand moving towards the replication fork (leading strand). Synthesis is discontinous on the strand moving away from the replication fork (lagging strand) leading to the formation of Okazaki fragments DNA polymerase I removes the RNA primers and replaces them with DNA DNA ligase joins the Okazaki fragments together to create a continuous strand

Explain DNA replication in terms of unwinding the double helix and separation of the strands by helicase, followed by formation of the new complementary strands of DNA polymerase

Helicase~ unwinds the DNA and separates the two polynucleotide strands by breaking the hydrogen bonds between complementary base pairs. The two separated polynuclotide strands act as templates for the synthesis of new polynucleotide strands DNA Polymerase: synthesizes new strands from the two parental template strands. Free deoxynucleoside triphosphates are aligned opposite their complementary base partner and are covalently bonded together by DNA polymerase to form a complementary nucleotide chain. The energy for this reaction comes from the cleavage of the two extra phosphate groups

Explain the process of translation, leading to polypeptide formation

Include the roles of messenger RNA, transfer RNA, codons, anticodons, ribosomes. and amino acids Translation is the process of protein synthesis in which the genetic information encoded in mRNA is translated into a sequence of amino acids in a polypeptide chain Ribosomes bind to mRNA in the cell's cytoplasm and move along the mRNA molecule in a 5' to 3' direction until it reaches a start codon Anticodons on tRNA molecules align opposite appropriate codons according to complementary base pairing Each tRNA molecule carries a specific amino acid RIbosomes catalyze the formation of peptide bonds between adjacent amino acids (via a condensation reaction) Ribosome moves along the mRNA molecule synthesizing a polypeptide chain until it reaches a stop codon, at this point translation stops and the polypeptide chain is released

State that eukaryotic genes contain introns and exons

Intron: a non-coding sequence of DNA within a gene (intervening sequence) that is cut out by enzymes when RNA is made into mature mRNA Exon: the pat of the gene which codes for a protein (expressing sequence). Eukaryotic DNA contains introns but prok. DNA does not

Initiation

Involves the assembly of an active ribosomal complex

State that DNA replication occurs in a 5' to 3' direction

Is semi-conservtive, meaning a new strand is synthesized from an original template strand Occurs in a 5' - 3' direction, in that new nucelotides are added to the C3 hydroxyl group such that the strand grows from the 3' end DNA polymerase enzyme responsible for adding new nucelotides moves along the original template strand in a 3'-5' direction

The genetic code. . .

Is universal: every living thing uses the same code (there are only a few and minor exceptions) is degenerate: there are only 20 amino acids but 64 codons, so mmore than one codon may code for the same amino acid (this allows for silent mutations whereby a change in the DNA sequence does not affect the polypeptide sequence)

Elongation

New amino acids are brought to the ribosome according to the codon sequence

State that nucleosomes help to supercoil chromosomes and help to regulate transcription

Nucleosomes protect DNA from damage, and allow long lengths of DNA to be packaged (supercoiled) for mobility during mitosis/meiosis When supercoiled, DNA is not accessible for transcription Cells will have some segments of DNA permanently supercoiled and these segments will differ between different cell types

Outline how DNA nucleotides are linked together by covalent bonds into a single strand

Nucleotides are linked into a single strand via a condensation reaction Phosphate group joins with the hydroxyl group attached to the 3' C of the sugar Results in a phosphodiester bond between the two nucleotides and the formation of a water molecule Successive condensation reactions between nucleotides results in the formation of a long single strand

Primary Structure

Order/sequence of the amino acids of which the protein is composed Formed by covalent peptide bonds b/w adjacent amino acids Controls all subsequent levels of structure b/c it determines the nature of the interactions b/w R groups of different amino acids

Initiation

The small ribosomal subunit bind to the 5' end of mRNA and moves along it until it reaches the start codon Next, the appropriate tRNA molecule binds to the codon via its anticodon (according to complementary base pairing) The large ribosomal subunit aligns itself to the tRNA molecule at its P-site and forms a complex with the small ribosomal subunit

State that translation occurs in a 5' to 3' direction

The start codon is located at the 5' end of the mRNA sequence and the ribosome moves along it in the 3' direction. Hence translation occurs in a 5'-3' direction.

State that transcription is carried out in a 5' to 3' direction

Transcription is carried out in a 5' - 3' direction (of the new RNA strand)

Outline DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase

Transcription is the process by which an RNA sequence is produced from a DNA template RNA polymerase separates the DNA strands and synthesizes a complementary RNA copy from one of the DNA strans Covalently bonding ribonucleoside triphosphates that align opposite their exposed complementary partner (using the enegy from he cleavage of the additional phosphate groups to join them together) Once the RNA sequence has been synthesized, RNA polymerase will detach from the DNA molecules and the double helix will reform The sequence of DNA that is transcribed into RNA is called a gene Transcription occurs in the nucleus (where DNA is) and, once made, the mRNA moves to the cytoplasm (where translation can occur)

Outline the use of polymerase chain reaction to copy and amplify minute quantities of DNA. Details of methods are not required

PCR is a way of producing large quantities of a specific target sequence of DNA Occurs in a thermal cycler Denaturation: DNA sample is heated to separate it into two strands Annealing: DNA primers attach to opposite ends of the target sequence Elongation: Heat-tolerant DNA polymerase copies the strands

Describe the application of DNA profiling to determine paternity and also in forensic investigation

DNA sample is collected and amplified using PCR Satellite DNA is cut with specific restriction enzymes to generate fragments Individuals will have unique fragment lengths due to the variable length of their short tandem repeats Fragments are separated with gel electrophoresis DNA profile can be analyzed Paternity testing and forensic investigations

Describe the genetic code in terms of codons composed of triplets of bases

The genetic code is the set of rules by which informaion encoded in mRNA sequences is converted into proteins (amino acid sequences) by living cells.

Outline the structure of nucleosomes

Consists of DNA wrapped around eight histone proteins Contains major and minor grooves on its outer diameter, which expse chemical groups that can form hydrogen bonds DNA of eukaryotes associates with proteins called histones DNA is wound around an octamer of histones Octamer and DNA combination is secured to a H1 histone, forming a nucleosome

State that gel electrophoresis of DNA is used in DNA profiling

Technique by which individuals are identified on the basis of their respective DNA profiles Within the non-coding region of an individual's genome, there exists satellite DNA -- long stretches of repeating elements called short tandem repeats Sequences can be excised to form fragments, by cutting with a variety of restriction endonucleases

Outline three outcomes of the sequencing of the complete human genome

The Human Genone Project was an international cooperative venture established to sequence the 3 billion base pair in the human genome Mapping: We now know the number, location, and basic sequence of human genes Screening: This has allowed for the production of specific gene probes to detect sufferers and carriers of genetic disease conditions Medicine: With the discovery of new proteins and their functions, we can develop improved treatments Ancestry: It will give us improved insight into the origins, evolution, and historical migratory patterns of humans

Describe the structure of DNA, including the antiparallel strands, 3'5-5' linkages and hydrogen bonding between purines and pyrimidines

The carbon atoms in deoxyribose are numbered, with the nitrogenous bases attach to carbon one and the phosphate group is attached to carbon five Nucelotides are joined by a covalent phosphodiester bond between the carbon five phosphate group and the carbon three hydroxyl group. Why one nucelotide strand runs five prime to three prime Nitrogenous bases interact via hydrogen bonding In order for the bases to associate, one strand must run antiparallel to the other Double strannded DNA forms a double helix, with 10 nucleotides per turn and the structure containing both major and minor grooves