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BIO 1120 - Exam III
Chapter 17
| Term | Definition |
|---|---|
| Gene expression is the process by which _____ directs the synthesis of proteins. | DNA |
| What is the name of the British physician who first suggested that genes dictate phenotypes through enzymes? | Archibald Garrod |
| What may occur to a person who has the disease alkaptonuria? | Their urine will be black-colored. |
| A bread mold used by Beadle and Tatum were haploid or diploid species? | Haploid |
| What was the reason Beadle and Tatum used haploid species for their work? | Because the organism is haploid, phenotypes depend only on one allele. |
| True or false: All proteins are enzymes. | False |
| What is the difference between DNA and RNA? | DNA contains a deoxyribose sugar. RNA contains a ribose sugar. |
| A DNA molecule will contain what 4 bases? | A, T, C, G |
| An RNA molecule will contain what 4 bases? | A, U, C, G |
| Name the process: RNA is synthesized using information from DNA. | Transcription |
| What is the product of transcription? | mRNA |
| Name the process: A polypeptide is synthesized using the information of mRNA. | Translation |
| What is the site of translation? | Ribosomes |
| How does gene expression in bacteria differ from gene expression in eukaryotic cells? | In bacteria, translation of an mRNA begins while transcription is still in progress. |
| Where does pre-mRNA directly come from? | DNA |
| Pre-mRNA is also known as what? | Primary transcript |
| What is the central dogma? | DNA -> RNA -> Protein |
| What is a triplet code? | A specific three nucleotide sequence that accounts for a singular amino acid |
| What is the strand in which mRNA is synthesized on called? | Template strand |
| For any given gene, which strand is used as a template? | The same strand will always be used as a template. |
| What are codons? | Three nucleotide sequences of DNA or RNA that codes for a specific amino acid |
| The nontemplate strand is also called the _____ strand. | Coding |
| Codons are found where? | mRNA |
| What direction are codons read in? | 5' to 3' |
| 300 nucleotides along an mRNA strand codes for how many amino acids? | 100 |
| _____ of the 64 triplets code for amino acids. | 61 |
| What amino acid codes for "start" and an amino acid? | Met (methionine) |
| There can be multiple codons for one amino acid, but a codon cannot _____ _____ _____ _____ _____. | Code for another amino acid |
| What is the reading frame? | The correct grouping of triplet codons |
| Messenger RNA is transcribed from the _____ strand of a gene. | Template |
| What enzyme pries apart the two strands of DNA and joins RNA nucleotides together complementary to the DNA template strand? | RNA polymerase |
| RNA polymerases _____ need pre-existing primers. | Don't |
| What are the three stages of transcription? | Initiation, elongation, and termination |
| What is the DNA sequence where RNA polymerase attaches and initiates transcription called? | Promoter |
| Bacteria have a DNA sequence called _____ that signals the end of transcription. | Terminator |
| What is a transcription unit? | A region of DNA that is transcribed into an RNA molecule. |
| What does a eukaryotic promoter most commonly consist of? | TATA nucleotide sequence |
| What must first bind to the DNA before RNA polymerase II can bind in correct orientation (initiation of transcription)? | A transcription factor that recognizes the TATA box |
| Additional transcription factors bind to DNA along with RNA polymerase II, forming what? | Transcription initiation complex |
| How does RNA polymerase bind to DNA during initiation of transcription in bacteria? | Part of the RNA polymerase can recognize and bind to the promoter |
| What happens to the double helix of DNA as RNA polymerase moves along it? | The double helix untwists and retwists. |
| mRNA from what kind of cells (bacteria or eukaryotic) require no further modification following elongation? | Bacteria |
| What is the sequence in which eukaryotic cells use as a transcription "stop" signal (aka: polyadenylation signal sequence)? | AAUAAA |
| The promoter sequence in DNA is _____stream. | Up |
| RNA processing (modification of pre-mRNA) includes splicing out introns, joining of exons, and alteration of _____ and _____ ends. | 5' and 3' |
| Which end of pre-mRNA receives a 5' cap? | 5' end |
| What is 5' cap? | A modified from of guanine nucleotide added onto 5' end of pre-mRNA |
| Which end of pre-mRNA receives a poly-A tail? | 3' end |
| What is a poly-A tail? | A sequence of 50-250 adenine nucleotide sequences added onto 3' end of pre-mRNA |
| What are the three fictions of the 5' cap and poly-A tail? | Help facilitate the export of mature mRNA; protect mRNA from degradation by hydrolytic enzymes; help ribosomes attach to 5' end |
| What are UTRs (untranslated regions)? | parts of mRNA that will not be translated into a protein but have other functions |
| what occurs during RNA splicing? | Introns are removed and exons are joined together. |
| What are introns? | Portions of the primary mRNA that are removed. |
| What are exons? | Portions of the primary mRNA that are joined together following the removal of introns. |
| Tru or false: A majority of RNA sequences on a transcription unit are introns. | True |
| Introns are removed by a large complex of proteins and small RNAs called a _____. | Spliceosome |
| What are ribozymes? | RNA molecules that function as enzymes |
| What are the three properties that allow RNA to act as a catalyst? | RNA has a specific 3-D shape; RNA contains functional groups; RNA can create hydrogen bonds with other nucleic acids |
| Why can a single gene encode for more than one kind of polypeptide? | Introns |
| Name the process: different mRNA molecules are produced from the same primary transcript due to the removal of certain introns and joining of other exons. | Alternative RNA splicing |
| What are domains (of proteins)? | Discrete structural and functional regions on proteins |
| True or false: Introns increase the probability of crossing over between the exons of alleles of genes. | True |
| How do introns increase the probability of crossing over? | Introns provide more terrain for crossovers without interruptions coding sequences. |
| What is the function of tRNA? | To transfer an amino acid from the cytoplasmic pool of amino acids to a growing polypeptide chain |
| What is are the two things at the end of a tRNA molecule? | An amino acid and a nucleotide triplet |
| A tRNA molecule consists on how many RNA molecules? | One |
| What is the cause for tRNA's 3-D structure? | Hydrogen bonding between nucleotide pairs |
| What end of the tRNA molecule is the binding site for amino acids? | 3' end |
| Where is tRNA made in the cell? | Nucleus |
| What role does aminoacyl-tRNA synthetases play in translation? | They correctly match up a tRNA with amino acid. |
| What type of bond is formed between an amino acid and tRNA? | Covalent bonding |
| What is wobble? | The 5' end of a tRNA anticodon can form a hydrogen bond with more than one kind of base in the third position of the 3' end of a codon |
| Are eukaryotic ribosomes larger or smaller than bacterial ribosomes? | Larger |
| What are tRNAs made up of (2 things)? | Proteins and rRNA |
| Where are ribosomal subunits synthesized (created)? | Nucleolus |
| How many RNA molecules are bacterial ribosomes made up of? | 3 |
| How many RNA molecules are eukaryotic ribosomes made up of? | 4 |
| What are the four binding sites on ribosomes? | mRNA binding site; E site; P site; A site |
| What is the role of the P site? | Holds the tRNA carrying the growing polypeptide chain |
| What is the role of A site? | Holds the tRNAc carrying the next amino acid |
| Where do discharged tRNAs leave the ribosome? | E site |
| What end (amino or carboxyl) are amino acids added to? | Carboxyl end |
| Ribosomal RNA also acts as a _____ for the translation reaction. | Catalyst |
| When does initiation begin in translation? | When an mRNA strand and MET tRNA are bought together along with the two ribosomal subunits |
| What molecule is used as energy in translation? | GTP |
| What three things are first attached during initiation of translation? | mRNA; tRNA; small ribosomal subunit |
| The three steps of elongation of translation are codon recognition, _____ bond formation, and translocation. | Peptide |
| What steps in elongation of translation require energy (GTP)? | Codon recognition and translocation |
| How many base triplets code for a stop? | 3 |
| What is added to a terminated polypeptide instead of an amino acid? | A water molecule |
| What are some examples of amino acid modifications post-translation? | Chemical additions such as sugars, lipids, or phosphate groups |
| Free ribosomes mostly synthesize proteins that go where? | Stay inside the cell |
| Bound ribosomes mostly synthesize proteins that go where? | Secreted outside the cell |
| Protein synthesis always begins where? | Free ribosomes in the cytoplasm |
| What signals that a free ribosome changes to a bound ribosome? | A signal peptide |
| Where is the signal peptide found? | Amino end of the growing polypeptide |
| What is the name of the particle that leads free ribosomes to the ER when signaled? | Signal-recognition particle |
| What is a polyribosomes? | A string of ribosomes translating the same mRNA molecule |
| What is the main difference between gene expression in bacteria and eukaryotic cells? | Gene expression occurs simultaneously in bacteria. |
| What is the ultimate source of new genes? | Mutations |
| What is a point mutation? | A change in a single nucleotide pair |
| A _____ disorder or hereditary disease is a mutation that has an adverse effect on the phenotype of a person. | Genetic |
| What kind of mutation causes sickle-cell anemia? | Point mutation |
| What two types of mutations involve one or more nucleotide pairs? | Insertions and deletions |
| What is a nucleotide-pair substitution? | A type of point mutation in which one nucleotide in DNA is replaced by another |
| Name the mutation: This mutation has no observable effect on the phenotype. | Silent mutation |
| What is a missense mutation? | A substitution mutation that changes one amino acid to another |
| Name the mutation: This mutation causes a change in a codon for an amino acid into a stop codon. | Nonsense mutation |
| What type of mutation occurs due to insertions and deletions? | Frameshift mutations |
| True or false: Insertions and deletions occurring outside of coding regions are frameshift mutations. | False |
| Can nucleotide-pair substitutions occur outside gene expression? | Yes: DNA replication & recombination |
| What are spontaneous mutations? | Mutations that occurs when a base is mismatched during replication and later transcribed incorrectly |
| What are the physical and chemical agents that cause mutations in DNA called? | Mutagens |
| Mutagen radiation can disrupt what part in DNA? | Thymine dimers |
| What type of enzyme is Cas 9? | Nuclease |
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