Genetics Flashcards
Structure and function of DNA
Structure: long, double stranded helix
- “rungs” of DNA consist of nitrogen bases (A,T,G,C)
- “side rails” of DNA consist of alternating patterns of sugar and phosphate held together by phosphodiester bonds
- antiparallel arrangement (5’ to 3’- 3’ to 5’)
- made of deoxyribonucleotides(sugar deoxyribose)
Function:
-directs and regulates the construction of proteins necessary for a cell to perform its functions
Structure and function of RNA
Structure:
- single stranded
- like DNA, RNA has 5’ to 3’ directionality
- Uracil replaces Thymine
- made of ribonucleotides (sugar ribose)
Function:
- can fold on itself to form helical and loop structures
- coding, decoding, regulation and expression of genes
What are nucleotides composed of? (* Be able to diagram a nucleotide)
- Phosphate group
- 5 carbon sugar
- Nitrogenous base
Central Dogma of Gene Expression
-the general flow of genetic information from DNA to RNA to protein
* remember to include reverse transcription, transcription and translation (where those occur)
How is DNA replicated in prokaryotes?
- DNA replication starts when factors called the primosome are recruited to the origin of replication in the chromosome
- The primosome includes helicase to unwind the DNA and primase to lay down RNA primers to jump-start replication
- Helicase unwinds the DNA and a bubble of single stranded DNA forms.
- DNA polymerase III binds DNA with this bubble region and replication starts
- At the replication fork (point where unwinding occurs) Helicase unwinds the DNA helix
- Single-strand DNA-binding proteins bind to DNA to keep them seperated until they are copied
- specialized enzymes gyrase and topoisomerases relieve coiling tension
What is protein synthesis?
- genetic information within a cell is read and used to create gene products (proteins)
Where and how does proteins synthesis occur in a prokaryotes and eukaryotes?
Where?: the cytoplasm
How?: Transcription and Translation
What is transcription?
-The first stage of protein synthesis where genes in DNA are copied into a new format, RNA
Process of Transcription
- RNA polymerase performs transcription
- RNA polymerase binds to the promoter- beginning region of a gene in DNA
- it unwinds the DNA to reveal single-stranded template DNA
- lays down complementary ribonucleotides (U pairs wih A, G pairs with C)
- continues until it reaches the termination sequence
- RNA polymerase falls off the DNA
- Newly made RNA transcript released
What is Translation?
- reading mRNA to build proteins
Process of Translation
Initiation
- Ribosome attaches to mRNA and scans it until it reaches a start codon
- Initiator tRNA carrying amin acid methionine enters the ribosomes P site
- Multiple ribosomes latch onto a single mRNA molecule forming polysomes
Elongation
- Incoming tRNA enters “A” site
- Peptide bond forms between amin acids transferring growing protein to tRNA “A” site
- Ribosome shifts down mRNA; tRNA in “P” site shifts to “E” site to exit ribosome; tRNA in the “A” site shifts to the “P” site
- cycle repeats until stop codon is encountered
Termination
- Ribosome encounters stop codon
- Termination factor enters the ribosome
- Ribosome releases the protein and detaches from mRNA
What is Reverse Transcription?
- RNA is used as a template to build copy DNA
- requires reverse transcriptase
What is mRNA?
-carries genetic message in triplet codons and is translated to build a protein
What is tRNA?
-adaptor molecule that ushers amino acids into the ribosome during translation
What is rRNA?
-takes on complex stem and loop structures and combines with proteins to build ribosomes
What is a codon? Where is it located?
-a triplet of nucleotides found in mRNA
What is an anticodon? Where is it found?
-sequence of three nucleotides forming a unit of genetic code in tRNA
What are Introns?
- interveining sequences of mRNA that are not decoded to build the protein (these are cut and removed)
- part of RNA splicing
- allows one gene to actually code for more than one protein in a eukaryote
What are Inducible Operons?
- OFF by default
- certain conditions activate transcription
ex. ) (lac) operon
What are Repressible Operons?
- ON by default
- Actively transcribed until they are switched off (repressed)
Ex.) (arg) operon
What are silent, missense, and nonsense mutations?
silent: mutations that do not change the amino acid sequence of a protein
missense: the meaning of a codon is changed in a way that the wrong amino acid is added to the growing protein
nonsense: a mutation that causes a codon to go from encoding an amino acid to encoding a stop signal
What is a frameshift mutation?
-inserting or deleting bases from the coding region of a genetic sequence
What is an Ames Test?
-identifies if a chemical is a mutagen of bacterial DNA
Process of horizontal gene transfer-transfer of DNA from a donor cell to a recipient cell (*conjugation)
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- high frequency strains arise when the fertility plasmid merges with the bacterial cells chromosome
Process of horizontal gene transfer (*transformation)- ability to pick up, incorporate and express DNA from the environment
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Process of horizontal gene transfer (*transduction)- the passing of new genetic material into a bacterial cell from a virus
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Positive screening techniques to identify mutants
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Negative screening techniques to identify mutants
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