Term
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Definition
| refers to the process of copying the nucleotide sequence in DNA by synthesis of RNA |
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Term
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Definition
| refers to converting the genetic code in RNa to an amino acid sequence of a protein. |
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Term
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Definition
| is a heritable change in DNA that leads to an altered protein or gene product. |
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Term
| how is transcription initiated? |
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Definition
| RNA polymerase has to bind to a promoter sequence on the DNA and begins to make an RNA transcript that is complementary to the template strand of the DNA. |
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Term
| In what direction is RNA synthesis? |
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Definition
| 5' to 3', where the RNA polymerase adds nucleotides to the 3' hydroxyl end of the elongating polynucleotide strand. |
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Term
| What is released when nucleotides are being added to the elongating RNA transcript? |
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Definition
| pyrophosphate = two phosphate |
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Term
| When is transcription done? |
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Definition
| When RNA polymerase reaches a terminal sequence. |
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Term
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Definition
| Messenger RNA contains the information that specifies the amino acid sequence of polypeptides. |
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Term
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Definition
| Ribosomal RNA does not encode amino acid sequences, rather it is part of the structure of ribosomes which function in translation of mRNA to sythesize a polypeptide. |
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Term
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Definition
| Transfer RNA shuttles amino acids to ribosomes adn lines the amino acids up in teh order specified by mRNA. |
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Term
| Start codons and stop codons |
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Definition
start: aug (methionine)
stop:uaa, uga, uag |
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Term
| how many amino acids are there? |
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Definition
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Term
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Definition
| three nucleotides that represents an amino acid |
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Term
| Why is a genetic code redundant? |
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Definition
| because a give amino acid may be specified by more than one codon, but it is not ambiguous. |
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Term
| When is tRNA consider to be charged? |
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Definition
| When there is an amino acid attached to it. |
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Term
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Definition
| An anti codon. Anti codon corresponds to the codon on the amino acid. |
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Term
| What is aminoacyl-tRNA synthetase? |
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Definition
| an enzyme that specifically attaches the amino acid that corresponds to its anti codon. |
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Term
| Where does translation occur? adn what is required? |
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Definition
| on ribosomes and requires mRNA and tRNA charged with their amino acids. |
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Term
| ribosomes consist of what? |
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Definition
| small and large subunits. |
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Term
| where do the subunits assemble? |
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Definition
| on the 5' end of the mRNA. |
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Term
| WHat is initiation of translation? in other words what is an initiation complex? |
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Definition
| initiation complex consist of a charged tRNA bound to the start codon at the 5' end of mRNA and the small ribosomal subunit. Next the large subunit joins the complex with energry provided from GTP. tRNA first occupies the P site. |
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Term
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Definition
| This is where the polypeptide chain is elongated. E, P A slots are on teh ribosome. The next complementary charged tRNA goes to the A site on the complex. The tRNA on the p site is now unchaged becuase it shifts over to the E site and the amino acid on that one moved over to the one on the A site which is now on the P site. The uncharged tRNA is on teh E site where it leaves. |
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Term
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Definition
| the process keeps repeating until it hits a stop codon. UAG UGA UAA |
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Term
| WHat is hte energy provided for elongation? |
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Definition
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Term
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Definition
| Elongation ends when a stop codon hits the A site. Teh stop codon binds a release factor, which hydrolyzes the bonds between the chain adn the tRNA in the p site. this separates the polypeptide chain with the ribosome complex. Once the polypeptide chain leaves the whole ribosome complex falls apart adn is ready to be used again. |
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Term
| What are polyribosomes or polysomes? |
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Definition
| Several ribosomes can translate the same mRNA producing multiple polypeptides at the same time. This beaded structure is referred to as polyribosomes/polysomes. |
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Term
| What does polysome formation do? |
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Definition
| it increases the rate of protein synthesis |
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Term
| What is a signal or localization sequence or address label? |
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Definition
| this indicated where the destination of the polypeptide, whether inside or outside the cell. |
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Term
| Where does translation of mRNA occur? |
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Definition
| it alwyas occurs on a free ribosome in the cytoplasm. |
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Term
| As the polypeptide is made the amino acid sequence determines what...? |
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Definition
It determiens whether
*translation should continue to completion and directed to an organelle
*OR translation should be paused until the translation complex is direct to the rough endoplasmic reticulum. |
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Term
| When is the translation complex directed to the ER? |
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Definition
| When the signal sequence of a poly peptide is hydrophobic. |
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Term
| Describe the process of the translation complex being directed to the ER. |
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Definition
*mRNA is translated,if the polypeptide is hydrophobic, the polypeptide begins with a unique sequence that may bind to a signal receptor protein, which will dock with a receptor protein in the ER.
*The signal sequence after passing through a channel in the receptor protein is removed by an enzyme in the ER.
*Translation continues with the newly synthesized polypeptide being extruded into the lumen of the ER.
*In this way the polypeptide is isolated from the cytoplasm while being modified in the ER and Golgi before reaching its final destination in or out of the cell. |
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Term
| what happens after translation? |
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Definition
| Some proteins are modified in order to achieve their final functional form. |
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Term
| What is posttranslational modifications? |
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Definition
| Before polypeptides become active proteins, they may need additional modifications before they become active proteins. |
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Term
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Definition
| cutting off a portion of the polypeptide. |
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Term
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Definition
| adding sugar residue to the polypeptide. |
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Term
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Definition
| adding one or more phosphate groups. |
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Term
| Translation summary-converting a sequence of RNA nucleotides to a protein amino acid sequence. |
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Definition
*each codon in mRNA binds the anitcodon of a specific molecule of tRNA, which carries a certain amino acid.
*As the amino aicd are brought together in sequence they are bonded together to form a poly peptide(protein)
*a change in the DNa nucleotide sequence of a gene leads to a corresponding change in the mRNA which may lead to an alteration in the amino acid sequence of a protein.
*changes in protein structure an result in an alteration of phenotype.
*changes in DNa (mutations) occur naturally adn represent the source of genetic variation needed for the process of natural selection which drives evolution. |
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Term
| What are Somatic mutations |
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Definition
*mutations in the cell.
*not passed on to offsprings |
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Term
| What is germ line mutation? |
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Definition
*mutations in cell that give rise to gametes.
*Source of new alleles in offsprings, including numerous recessive traits in humans. |
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Term
| What is Induced or Spontaneous mutations. |
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Definition
spontaneous for example is when DNA polymerase makes errors.
Induced is when DNa is damaged from toxic chemicals or external enviornmental damage. |
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Term
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Definition
| are changes in a single base pair in the DNA molecule adn may change a dominant allele to a recessive allele. |
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Term
| What are Chromosomal mutations |
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Definition
| represent more extensive alterations in chromosomes which will likely affect the action of many genes. |
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Term
| What is a silent mutation. |
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Definition
| Since some genetic code is redundant and more then one codon can code for the same amino acid, a single nucleotide altercation can jus lead to a silent mutation. |
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Term
| What is a missense mutation? |
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Definition
| occurs when a change in a single nucleotide in a gene alters the amino acid sequence in the polypeptide product of the gene in some cases the function of the protein is not affected in other case it makes a dominant trait to a recessive trait. |
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Term
| What is a nonsense mutation? |
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Definition
| change in the nucleotide base produces a stop codon leading to a shorten polypeptide adn a complete loss of function. |
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Term
| What is a Frame shift mutation. |
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Definition
| Some poitn mutation results from an addition or deletion of a base pair, which, in either case, alters the reading frame of mRNA transcribed from the gene. |
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Term
| What is (PKU) phenylketonuria |
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Definition
* a single gene recessive trait casued by a point mutation.
*Homozygous recessive individuals (1 out 12000 births in U.S) have a non-functional enzyme, phenylalanine hydroxylase) in the liver to convert phenylalanine to tyrosine.
*excess of phenylalanine in the blood leads to accumulation of toxic phenylpyruvic acid.
*if not treated with a low phenylalnine diet, individual suffer emntal retardation.
*decected amino acid change (tryptophan instead of arginine) at the possition 408 in the 451 amino acid polypeptide chain.
*Heterozygous individuals show no symptoms becase they produced enough normal enzyme. |
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Term
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Definition
| deletion,duplication,inversion,translocation |
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Term
| Chromosomal mutation:What is deletion? |
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Definition
| an entire segment of DNA molecule is lost fro mteh chromosome. |
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Term
| Chromosomal mutation: duplication |
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Definition
| Deletion of a segment from one homologous chromosome with insertion into the other member of the pair may lead to a duplication. |
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Term
| Chromosomal mutation:inversion |
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Definition
If a fragment of chromosome is reattached, but in a wrong orientation
ex like attahced upside down or side ways. |
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Term
| Chromosomal mutation: translocation |
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Definition
| reattaching a segment to a different chromosome. |
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Term
| Chromosomal mutation: why does it happen? |
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Definition
*natural ex errors in replication or during cross over.
*unnatural ex chemical mutagens |
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Term
| the central dogma of molecular biology! |
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Definition
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