Term
| What did Garrod's Work show |
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Definition
Inborn errors of metabolism:
-evidence that genes specify proteins
Alkaptonuria:
-rare genetic disease
-lacks enzyme to oxidize homogentisic acid
Gene mutation:
-associated with absence of specific enzyme |
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Term
| Describe Beadle and Tatum's Experiments with Neurospora |
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Definition
Exposed neurospora spores to X-Ray or UV radiation
-induced mutations prevented metabolic production of essential molecules
Each mutant strain had mutation only in one gene, each gene affected only one enzyme |
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Term
| What did Beadle and Tatum demonstrate? |
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Definition
| Relationship between genes and proteins in the 1940's. |
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Term
| How does genetic info in cells flow from DNA to RNA to Polypeptide? |
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Definition
| Transcription and translation |
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Term
| What does info encoded in DNA do? |
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Definition
-Codes sequences of amino acids in proteins
-2 step process:
Transcription
Translation |
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Term
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Definition
Synthesizes messenger RNA(mRNA):
-Complementary to template DNA strand
-Specifies amino acid sequences of polypeptide chains |
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Term
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Definition
Synthesizes polypeptide chain:
-specified by mRNA
-also requires tRNA and ribosomes
Codon:
-sequence of 3 mRNA bases
-specifies one amino acid, or a start or stop signal |
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Term
| What is the difference between the structures of DNA and RNA? |
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Definition
RNA nucleotides:
-ribose(sugar)
-bases(UGAC)
-3 phosphates
RNA subunits:
-covalently joined by 5'-3' linkages
-form alternating sugar-phosphate backbone |
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Term
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Definition
-mRNA codons specify a sequence of amino acids
64 codons
-61 code for amino acids
-3 codons are stop signals |
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Term
| Why is the genetic code said to be redundant? |
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Definition
| Some amino acids have more than one codon |
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Term
| How is the genetic code virtually universal? |
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Definition
Few minor exceptions to standard code found in all organisms:
-suggests that all organisms have a common ancestor |
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Term
| A sequence of DNA base triplets is... |
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Definition
| -transcribed into RNA codons |
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Term
| What are the similarities and differences between the processes of transcription and DNA replication? |
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Definition
-Enzymes
-Antiparallel Synthesis
-Transcription |
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Term
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Definition
-RNA polymerases
-DNA polymerases
-Carry out synthesis in 5'-3' direction
-Use nucleotides with 3 phosphate groups |
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Term
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Definition
Strands of DNA are antiparallel
Template DNA strand and complementary RNA strand are antiparallel:
-DNA template reads 3'-5' direction
-RNA template reads 5'-3' direction |
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Term
| Transcription in RNA synthesis and DNA replication |
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Definition
| are the same except uracil is submitted for thymine. |
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Term
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Definition
-Located in the Cytosol
-"Decoding" molecule in translation
-Anticodon: complementary to mRNA codon, specific for 1 amino acid |
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Term
| What is different between mRNA and tRNA? |
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Definition
| tRNA has a shape caused by H bonds, while mRNA is more linear. |
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Term
| How does tRNA help convert the DNA to an amino acid? |
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Definition
| tRNA attaches to specific amino acid and is covalently bound by aminoacyl-tRNA synthetase enzymes |
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Term
| How do ribosomes function in polypeptide synthesis? |
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Definition
They bring together all machinery for translations
-Couple tRNAs to mRNA codons
-Catalyze peptide bonds between amino acids
-Translocate mRNA to read next codon |
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Term
| Describe the structure of ribosomes |
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Definition
Each ribosome is made of
-1 large subunit
-1 small subunit
Each subunit contains:
-rRNA
-many proteins |
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Term
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Definition
1st stage of translation
Initiation factors:
-Bind to small subunit which binds to mRNA at start codon
Initiator tRNA:
-binds to start codon then binds large subunit |
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Term
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Definition
A cyclic process:
-adds amino acids to polypeptide chain
Proceeds in 5'-3' direction along mRNA
Polypeptide chain grows
-from amino end to carboxyl end |
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Term
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Definition
Final stage of translation:
-when ribosome reaches stop codon
A site binds to release factor:
-triggers release of polypeptide chain
-dissociation of translation complex |
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Term
| What are the three stages of translation? |
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Definition
-Initiation
-Elongation
-Termination |
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Term
| How do bacterial and eukaryotic mRNA differ? |
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Definition
| Genes and mRNA molecules of eukaryotes are more complicated than those of bacteria. |
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Term
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Definition
After transcription:
-5' cap is added to 5' end of mRNA molecule
Poly-A-Tail:
-may be added at 3' end of mRNA molecule |
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Term
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Definition
-noncoding regions (interrupt exons)
-removed from original pre-mRNA |
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Term
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Definition
-coding regions in eukaryotic genes
-spliced to produce continuous polypeptide coding sequence |
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Term
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Definition
Synthesize DNA from an RNA template
-Ex: HIV-1(VIrus that causes AIDS) |
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Term
| Enzyme Reverse Transcriptase |
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Definition
| Reverses flow of genetic information |
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Term
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Definition
May alter or destroy protein function
-missense mutation: codon change specifies a different amino acid
-nonsense mutation: codon becomes a stop codon
May have minimal effects
-if amino acid is not altered
-if codon change specifies similar amino acid |
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Term
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Definition
Insertion or deletion of one or two base pairs in a gene.
-Destroys protein function
-Changes codon sequences downstream from the mutation |
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Term
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Definition
| -Movable DNA sequences "jump" into the middle of a gene |
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Term
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Definition
-replicate by forming RNA intermediate
-reverse transcriptase converts to original DNA sequence before jumping into gene |
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Term
| Mutations can cause change in the |
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Definition
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