Term
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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 w/absence of specific enzyme |
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Term
| Beadle-Tatum Expericments |
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Definition
Exposed Neurospora spores
-to X-rays or UV rays
-induced mutations prevented metabolic production of essential molecules
Each mutant strain
-had mutation in only one gene
-each gene affected only 1 enzyme |
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Term
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Definition
information encoded in DNA
-codes sequences of amino acids in proteins
2-step process:
1. transcription
2. translation |
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Term
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Definition
Synthesizes messenger RNA (mRNA)
-complementary to template DNA
-specifies amino acid sequences of polypeptide chains |
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Term
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Definition
Synthesized polypeptide chain
-specified by mRNA
-also requires tRNA and ribosomes
Codon
-sequence of 3 mRNA nucleotide bases
-specifies one amino acid
-or a start or stop signal |
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Term
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Definition
RNA nucleotides
-ribose (sugar)
-bases (uracil, adenine, guanine. cytosine)
-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
| How is the genetic code redundant & virtually universal? |
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Definition
redundant
-some amino acids have more than one codon
virtually universal
-suggesting all organisms have a common ancestor
-few minor exceptions to standard code found in all organisms |
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Term
| How are DNA replication and RNA transcription similar? |
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Definition
Similar enzymes
-RNA polymerase for RNA synthesis
-DNA polymerase for DNA replication
Carry out synthesis in 5'-3' direction
Use nucleotides w/3 phosphate groups
Antiparallel synthesis
-strands of DNA are antiparallel
-template DNA strand and complementary RNA strand are antiparallel (DNA template read in 3'-5' direction & RNA synthesized in 5'-3' direction)
Transcription in same except uracil base used in RNA synthesis instead of thymine in DNA replication |
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Term
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Definition
located in cytosol
decoding molecule in translation
anticodon (in loop 2)
-complementary to mRNA codon
-specific for 1 amino acid
has shape, coiled and twisted over itself |
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Term
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Definition
| enzymes that covalently bind tRNA to specific amino acid |
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Term
| How do ribosomes function in polypeptide synthesis? |
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Definition
Ribosomes bring together all machinery for translation
-couple tRNAs to mRNA codons
-catalyze peptide bonds b/w amino acids
-translocate mRNA to read next codon |
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Term
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Definition
| each ribosome is made of 1 large ribosomal subunit & 1 small ribosomal subunit |
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Term
| What do each subunit of ribosomes contain? |
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Definition
| ribosomal RNA (rRNA) & many proteins |
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Term
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Definition
1st stage of translation
Initiation factors bind to small ribosomal subunit
Ribosomal subunit then binds to mRNA at start codon (AUG)
Initiator tRNA binds to start codon and then binds large ribosomal subunit |
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Term
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Definition
a cyclic process
-adds amino acids to polypeptide chains
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
-which triggers the release of polypeptide chain
-translation complex dissociates |
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Term
| Main difference b/w Eukaryotic mRNA and Bacterial mRNA |
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Definition
| Genes and mRNA molecules are more complicated than those of bacteria |
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Term
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Definition
after transcription, 5' cap (modified guanosine triphosphate) is added to the 5' end of mRNA molecule
Poly-A tail (adenine-containing nucleotides) may be added at 3' end of mRNA molecules |
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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 sequences |
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Term
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Definition
synthesize DNA from an RNA template
-HIV-1 (virus that causes AIDS)
enzyme reverse transcriptase
-reverses flow of genetic information |
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Term
| Effects of base substitution |
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Definition
may alter or destroy protein function
-missense mutation (codon change specifies a different amino acid)
-nonsense mutation (codon become a stop codon)
or may have minimal effects
-if amino acid is not altered
-if codon change specifies a similar amino acid |
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Term
| Results of missense mutation |
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Definition
| results in a polypeptide of normal length, but with an amino acid substitution |
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Term
| Results of nonsense mutations |
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Definition
| results in production of truncated (shortened) polypeptide, which is usually not functional |
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Term
| Frameshift mutations (definition & effects) |
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Definition
insertion or deletion of 1 or 2 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 the gene |
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