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62 Cards in this Set
- Front
- Back
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Point mutations |
Changes in just one nucleotide pair of a gene This can lead to production of an abnormal protein ie: change in A and T in DNA can produce a U instead of an A in mRNA which codes for a different amino acid |
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Gene expression |
Process by which DNA directs protein synthesis In 2 stages: transcription and translation |
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Archibald garrod |
1902 said genes dictate phenotypes through enzymes that catalyze specific chemical reactions He thought symptoms of an inherited disease reflect an inability to synthesize a certain enzyme ie: black urine=lack of enzyme that breaks down alkapton |
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Metabolic pathway |
Cells synthesize and degrade molecules in a series of steps |
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Beadle and Tatum |
Exposed bread mold to X-rays (creating mutants) 3 classes of arginine-deficient mutants Each lacked a different enzyme needed for synthesizing arguine |
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Results of beadle and Tatum experiment provided support for... |
One gene-one enzyme hypothesis Which states that the function of a gene is to dictate production of a specific enzyme |
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Revised hypothesis is... |
One gene-one protein bc not all proteins are enzymes Many enzymes are composed of several polypeptides so new hyp: one gene-one polypeptide |
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Bridge between genes and the proteins for which they code.. |
RNA |
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Transcription |
Synthesis of RNA using DNA information Produces mRNA |
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Translation |
Synthesis of an polypeptide using information in the mRNA Ribosomes are the sites of translation |
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In prokaryotes, translation of mRNA can begin before... |
Transcription has finished In eukaryotic cells, the nuclear envelope separates transcription from translation |
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Primary transcript |
Initial RNA transcript from any gene prior to processing In eukaryotic RNA transcripts are modified through RNA to yield mRNA Cells are governed by a cellular chain: DNA to RNA to Protein |
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Triplet code |
Flow of information from gene to protein Transcribed into nonoverlapping three-nucleotide words of mRNA These words are then translated into a chain of amino acids (forming a polypeptide) |
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Template strand |
Provides a template for ordering the sequence of complementary nucleotides in an RNA transcript Always same strand for a given gene Determined by orientation of transcribing enzyme which is dependent of the DNA sequence at gene |
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Coding strand |
Nontemplate strand Nucleotides of this strand are identical to the RNA made |
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Codons |
mRNA base triplets Read in the 5’ to 3’ direction Specifies the amino acid to be placed at the corresponding position along a polypeptide |
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How many codons? |
64 deciphered in 1960s 61 are for amino acids, 3 triplets are stop signals to end translation |
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The genetic code is redundant but not.. |
Ambiguous More than one codon may specify a particular amino acid but no codon specifies more than one amino acid |
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Reading frame |
Correct groupings Codons must be read in the correct order for the polypeptide to be produced |
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Genetic code and evolution |
Genetic code is nearly universal Shared by simplest bacteria and most complex animals Genes can be transcribed and translated after being transplanted from one species to another |
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Transcription factors |
A collection of proteins in eukaryotes Mediate binding of RNA polymerase and initiation |
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Transcription initiation complex |
Complex of transcription factors and RNA polymerase II bonded ton promoter |
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TATA box |
Promoter Crucial in forming the initiation complex |
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Elongation of RNA strand in transcription process |
O |
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Transcription |
First stage of gene expression |
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RNA polymerase |
Catalyzes RNA synthesis Pries DNA strands apart and joins RNA nucleotides |
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RNA is complementary to the.. |
DNA strand RNA polymerase does not need a primer RNA follows same base pairing rules as DNA except uracil subs for thymine |
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Initiation of transcription |
Promoters signal start point and extend several dozen nucleotide pairs upstream of start point Transcription factors mediate binding of RNA polymerase and initiation of transcription All transcription factor and RNA polymerase create initiation complex TATA box promoter forms the initiation complex in eukaryotes |
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Start point |
The nucleotide where RNA polymerase actually begins synthesis of the mRNA Extends several dozen nucleotides pairs upstream from start pint |
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Transcription unit |
Stretch of DNA that is transcribed |
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3 stages of RNA transcription |
Initiation Elongation Termination |
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Initiation of transcription |
Promoters signal start point and extend several dozen nucleotide pairs upstream of start point Transcription factors mediate binding of RNA polymerase and initiation of transcription All transcription factor and RNA polymerase create initiation complex TATA box promoter forms the initiation complex in eukaryotes |
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Elongation of RNA strand in transcription process |
RNA polymerase moves along the DNA, it untwist the double helix (10-20 bases at a time) Nucleotides are added to the 3’ end of the growing RNA molecule |
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Transcription progresses at a rate of.... |
40 nucleotides per second in eukaryotes A gene can be transcribed simultaneously by several RNA polymerases |
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Termination of transcription |
In eukaryotes-RNA polymerase II transcribes the polyadenylation signal (AAUAAA) sequence RNA transcript is released 10-35 nucleotides past this polyadenylation sequence Different in bacteria |
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Termination in bacteria |
The polymerase stops transcription at the end of the terminator Detaches from DNA and releases transcript Requires no further modification |
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Eukaryotic cells modify RNA after... |
Transcription |
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Alternative RNA splicing |
Some introns contain sequences that may regulate gene expression Some genes can encode more than one kind of polypeptide (depending on which segments are treated as exons during splicing) Consequently, number of different proteins produced is greater than its number of genes |
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Domains |
discrete regions in proteins, modular architecture Different Exons code for different domains in a protein Exon shuffling may result in new evolution of new proteins |
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RNA processing |
Enzymes in the eukaryotic nucleus modify pre-mRNA before the genetic messages are released into cytoplasm |
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During RNA processing, both ends of the primary transcript are |
Altered In most cases, certain middle sections of molecule are cut out and remaining parts spliced together also |
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Each end of a pre-mRNA molecule is modified in a particular way |
5’ end receives a modified nucleotide 5’cap 3’ end gets a poly-A tail |
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End modifications share several functions |
Facilitate the export of mRNA to the cytoplasm Protect mRNA from hydro lyric enzymes Help ribosomes attach to 5’ end |
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Long noncoding stretches of nucleotides that lie between coding regions... |
Introns and Exons |
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Introns |
No coding regions Intervening sequences |
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Exons |
Other regions Eventually expressed (translated into amino acid sequences) |
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RNA splicing |
Removes introns and joins Exons Creates an mRNA molecule with a continuous coding sequence |
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Spliceosomes |
Consist of different proteins and several small RNAs that recognize the splice site Carries out RNA splicing in some cases RNAs of the spliceosome also catalyze the splicing reaction |
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Eukaryotic cells modify RNA after... |
Transcription |
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Alternative RNA splicing |
Some introns contain sequences that may regulate gene expression Some genes can encode more than one kind of polypeptide (depending on which segments are treated as exons during splicing) Consequently, number of different proteins produced is greater than its number of genes |
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Domains |
discrete regions in proteins, modular architecture Different Exons code for different domains in a protein Exon shuffling may result in new evolution of new proteins |
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Ribozymes |
Catalytic RNA molecules that function as enzymes and can splice RNA |
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End modifications share several functions |
Facilitate the export of mRNA to the cytoplasm Protect mRNA from hydro lyric enzymes Help ribosomes attach to 5’ end |
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During RNA processing, both ends of the primary transcript are |
Altered In most cases, certain middle sections of molecule are cut out and remaining parts spliced together also |
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Each end of a pre-mRNA molecule is modified in a particular way |
5’ end receives a modified nucleotide 5’cap 3’ end gets a poly-A tail |
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End modifications share several functions |
Facilitate the export of mRNA to the cytoplasm Protect mRNA from hydro lyric enzymes Help ribosomes attach to 5’ end |
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RNA splicing |
Removes introns and joins Exons Creates an mRNA molecule with a continuous coding sequence |
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Spliceosomes |
Consist of different proteins and several small RNAs that recognize the splice site Carries out RNA splicing in some cases RNAs of the spliceosome also catalyze the splicing reaction |
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Exons |
Other regions Eventually expressed (translated into amino acid sequences) |
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Domains |
discrete regions in proteins, modular architecture Different Exons code for different domains in a protein Exon shuffling may result in new evolution of new proteins |
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Spliceosomes |
Consist of different proteins and several small RNAs that recognize the splice site Carries out RNA splicing in some cases RNAs of the spliceosome also catalyze the splicing reaction |
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Small scale mutations |
Point mutations within a gene can be divided into two categories |
