| A | B |
|---|
| What is does a nucleotide consist of? | a pentose sugar, phosphate and an organic (nitrogen) base |
| What are the names of the four nitrogen bases/organic bases in DNA.? | adenine, cytosine, thymine and guanine |
| What organic base/nitrogen base does adenine pair with? | thymine |
| What organic base or nitrogen base does cytosine pair with? | guanine |
| How many hydrogen bonds does cytosine and guanine have? | 3 |
| How many hydrogen bonds does adenine and thymine have? | 2 |
| What is the bond called that is a covalent bond that links the nucleotides together? | phosphodiester |
| Nucleic acids are long chain molecule (like protein but longer) and their building blocks are called? | nucleotides |
| What is the sugar called in DNA? | deoxyribose |
| What is the sugar called in RNA? | ribose |
| What are the nitrogen /organic bases called in RNA? | Adenine, uracil, cytosine and guanine |
| Explain how condensation synthesis occurs in building a nucleotide. | A nucleotide is made of a sugar, phosphate and an organic or nitrogen base. In order to join them two water molecules will be made. |
| Explain how condensation synthesis occurs when nucleotides are joined together. | When a phosphate joins a sugar a water molecule will drop out and be produced. |
| What is meant by DNA being antiparallel? | One strand of DNA is upside down due to the nitrogen bases or organic bases joining the sugar molecule at carbon 1. If one side is 5' then the other side must be 3'. |
| What is meant by 5'? | The 5th carbon on the sugar is shown. |
| What is meant by 3'? | The 3rd carbon on the sugar is shown. |
| Which of the nitrogen/ organic bases are purines? | adenine and guanine. They end in nine. |
| Which contains 2 carbon rings the pyrimidines or purines? | purines have 2 carbon rings and are larger |
| Which nitrogen/organic bases have a 1 carbon ring | pyrimidines |
| Name the pyrimidines. | cytosine, thymine and URACIL. OOPs Uracil does not end in Y. |
| In RNA which of the nitrogen/organic bases base pair together? | Adenine and uracil; Guanine and cytosine |
| In DNA which of the nitrogen/organic bases base pair together? | adenine and thymine; guanine and cytosine |
| What enzyme unwinds and unzips or breaks the hydrogen bonds to separate the DNA in DNA replication? | the enzyme helicase |
| What does DNA polymerase III do? | Adds complementary free floating nucleotides to the 3' end of the growing molecule. It also proofreads the molecule. By going back and correcting bases. |
| What does DNA polymerase I do? | It replaces RNA primers with DNA. |
| What does topoisomerase do? | It will nick the DNA strand and relieve the stress of DNA being highly wound. |
| What is the significance of complementary base pairing in the conservation of the base sequence of DNA? | Since every nitrogen/organic base will only base pair with its other one complementary base the new strand will be identical to the one from the old strand. So this process can continue forever without any change to the genetic material. |
| Compare DNA and RNA | DNA deoxyribonucleic acid, double helix, sugar deoxyribose, ATCG. RNA - ribonucleic acid, single stranded, ribose sugar, A,U,C,G. |
| What are 3 kinds of RNA that are commonly found in cells? | mRNA, tRNA, rRNA |
| What is ribosomal RNA? | the major component of ribosomes |
| What is transfer RNA? | folded upon itself, it carries the amino acids to mRNA. |
| Is tRNA associated with a codon or anti-codon? | anit-codon |
| What is mRNA? | it is a sequence of nucleotides that determine the primary sequence of a polypeptide or protein. |
| Define transcription. | Transcription is the process in which RNA is produced from a DNA template. |
| Define translation. | Translation is the assemby of a polypeptide in a sequence specified by the order of nucleotides in the mRNA. |
| Where does transcription occur in the cell? | nucleus |
| Where does translation occur in the cell? | on the ribosome in the cytoplasm |
| For each gene only one of the two strands of DNA is transcribed. Which strand is that? | The template strand or anti-sense strand. |
| The DNA molecule has 2 strands. mRNA strand has the identical sequence except T is replaced with U in mRNA. Which strand is this in DNA? | The coding strand has the identical sequence to mRNA except T is replaced to U in mRNA. |
| What is found in the promoter region in transcription in protein synthesis? | TATA box and a starting site |
| What is a codon? | A codon is associated with mRNA and is composed of 3 nucleotides. AUG is a start codon and codes for methionine. |
| What is an anti-codon? | An anti-codon is associated with tRNA and is three nucleotides that are complementary to the codon. |
| What is meant by the genetic code is degenerate? | More than one codon can code for a single amino acid |
| 3 nucleotides will create how different possibilities of codons? | 64 possibilities |
| The sequence of the codons in mRNA determines the sequence of the amino acids in the? | polypeptide or protein |
| Define the terms degenerate and universal as they relate to the genetic code. | The triplet code is degenerate because more than one codon codes for a single amino acid. The code is universal because the same codon codes for the same amino acid. UUU, UUC on mRNA both code for phenalanine. CUU, CUC, CUA and CUG all code for leucine regardless of the species. |
| Explain the relationship between one gene and one polypeptide. | One gene one polypeptide means that every polypeptide chain is coded for by one gene. It also meas that a gene will only code for one polypeptide chain. Hemoglobin contains 4 polypeptide chains, 2 alpha and 2 beta chains. To make a hemoglobin molecule it would need 2 genes one for alpha and one for beta. |
| DNA replication occurs in a __ to ___ direction. | 5' to 3' direction |
| Explain the process of DNA replication in eukaryotes. | 1. The DNA is a helix and is unwound by helicase. 2. Helicase will then break the hydrogen bonds. 3. Topoisomerase nicks one of the DNA strands to relieve the stress of the highly twisted molecule. 4. Deoxyribonucleoside triphosphates are present in the nucleus to be added by DNA polymerase III to the 3' end of the growing strand. 5. The enzyme primase lays down a RNA primer to start the leading strand. 6. The leading strand will grow in a 5' to 3' direction by DNA polymerase III adding deoxyribonucleosides to the 3' end of the primer. 7. When DNA polymerase III adds the deoxyribonuclueosides to the growing DNA strand the second and third phosphate is removed making it a deoxyribonucleotide. The lagging strand is produced by primase laying down a RNA primer in a 5' to 3' direction. Okazaki fragments are small segments of DNA which are attached to the primer at the 3' end. 8. Primase back stitches and lays a primer down and DNA polymerase III lays down the okazaki fragment at the 3' end of the primer. 9. Another primase lays a primer down and DNA polymerase III lays the okazaki fragment down at the 3' end of the primer. DNA polymerase I replaces the RNA with DNA. 10. DNa ligase then forms the bonds attaching the DNA segments. |
| In eukaryotic chromosomes DNA replication occurs at _______ ________ allowing DNA to be replicated very rapidly.. | In eukaryotic cells, DNA replication is initiated at many points |
| Distinguish between the sense and the antisense strands of DNA. | DNA is a double helix. One strand that is the coding strand or sense strand is not transcribed. The template strand or antisense strand is transcribed by mRNA. The sense strand or coding strand and mRNA have the exact same sequence except that mRNA has uracil instead of thymine. |
| What occurs in RNA processing during protein synthesis? | mRNA needs to take a long journey to the ribosome in the cytoplasm and needs to be protected from hydrolytic enzymes. Therefore RNA processing will place a 5' cap or guanine triphosphate which will also function as an attach here sign for ribosomes. At the 3' end of mRNA a poly A tail (30-200 A's), inhibits the degradation of mRNA and helps the ribosome attach to it. Spliceosomes will cut out the introns or noncoding segments of mRNA and splice together the exons (coding segments) of the mRNA. |
| A small group of viruses known as retroviruses cause their host to produce an enzyme called _______ ________ that produces DNA from RNA. | reverse transcriptase |
| Explain transcription in protein synthesis. | Transcription involves a promoter region which consists of a startpoint and a TATA box 25 nucleotides upstream from the startpoint. Transcription factors are necessary to help RNA polymerase recognize the promoter site. The RNA polymerase will move down the molecule adding ribonucleotides to the growing mRNA strand until it hits the teminator site. Pre-mRNA is then released. This occurs in the nucleus. Now pre-mRNA is ready for RNA processing. |
| Explain translation in protein synthesis. | Translation is the synthesis of polypeptide chains. It involves all 3 kinds of RNA. mRNA, tRNA and rRNA. mRNA attaches to the small subunit of the ribosome with the 5' cap assisting. tRNA with its amino acid methionine come in and attaches to the codon on the mRNA and the anti codon on tRNA. This is initiation because the initiator tRNA has the amino acid met which initiates translation. The large ribosomal subunit attaches so that the initiator tRNA is in P site. There are 3 sites on the large ribosome EPA. Codon AUG hooks up with anticodon UAC. Elongation occurs by codon recognition where an incoming aminocyl tRNA brings a new amino acid into the A site. Peptide bond formation occurs by the growing polypeptide chain attaches to the tRNA in A site and forms a peptide bond. Translocation occurs when the tRNA in the A site moves to the P site taking the mRNA with it. The tRNA in P site moves to the E site and is release from the ribosome. Termination or the last step in translation is when the ribosome reaches a termination codon or stop codon. A release factor (protein) will move into the A site instead of tRNA. The release factor hydrolyzes the bond between the tRNA in the P site and the last amino acid of the polypeptide chain. The polypeptide is then freed from the ribosome. The 2 ribosomal subunits and other components dissociate. A protein is made! |
| State 6 functions of proteins, giving a named example of each. | enzymes- globular proteins- amylase. 2. hormones- insulin 3. antibodies- globular proteins assisting in defense against foreign particles 4. structural proteins- collagen- fibroous structural proteins that build tendons and is important in your skin. 5. Cell membrane proteins- passage of substances in and out of cell 6. hemoglobin- binds to oxygen due to the heme group attached to it. |
| Name the four levels of protein | primary, secondary, tertiary and quarternary |
| Explain the secondary structure of a protein? | This involves hydrogen bonding of carboxyl and amino groups. The alpha helix is due to the polypeptide forming a helix which is made from hydrogen bonding in a helical form between carboxyl and amino groups. The beta pleated sheets are formed by hydrogen bonding two polypeptide chains together creating a pleated sheet. Both can be found in the secondary structure. |
| Explain the tertiary structure of protein. | This is where the R groups which are different in every amino acid. They react and cause the protein to fold accordingly. The cysteines form disulfide bridges between the -SH or sulfhydryl groups causing it to fold. There are weak interactions going on such as van der Waals, and hydrophobic interactions between the R groups. Hydrogen bonding is occuring. |
| Explain the quarternary structure of protein. | This is when 2 or more polypeptide chains come together and fold. THe different polypeptide chains are kept together by hydrogen bonds, attraction between positive and negative charges, hydrophobic forces and disulfide bridges or any of these combinations. |
