16 How Genes Work Flashcards
What two scientist proposed: the one gene, one enzyme hypothesis?
George beadle and Edward tatum
What is gene expression?
-the process of translating the information in DNA into functioning molecules within the cell
What are nonfunctioning alleles called?
Knock-out, null, or loss of function alleles
How did two scientist test one gene, one enzyme hypothesis?
- damage a gene by creating a mutant,
- then observe the resulting effect on the mutants phenotype
Results: inspired hypothesis and proposed that each gene contains information needed to make an enzyme
What two scientist further tested the one gene, one enzyme hypothesis through the cells production of arginine?
Srb and Horowitz
What did Srb and Horowitz hypothesized?
Different genes lead to the synthesis of each of the three enzymes required to make arginine
How did Srb and Horowitz test their hypothesis?
- used radiation to create thousands of mutant cells
- performed genetic screening
- allowing them to select those mutants incapable of producing arginine
What were the results of Srb and Horowitz experiment?
Results support the one-gene, one-enzyme hypothesis
- three distinct mutants were produced
- each was deficient in one of the three enzymes in the arginine metabolic pathway
Scientist then understood genes code instruction for making proteins
What is the central dogma of molecular biology?
Francis crick proposed:
1) DNA is an information storage molecule
2) the sequence of bases in DNA is a kind of code
3) different combinations of bases specify the 20amino acids
- a particular stretch of DNA (gene) contains the information to specify the amino acid sequence of one protein.
- the information encoded in the base sequence of DNA is not directly translated into amino acid sequence of protein.
What two scientist proposed RNA molecules act as a link between genes found in the nucleus and protein-manufacturing centers in cytoplasm?
François Jacob and Jacques Monod
What is transcription?
The process by which the hereditary information in DNA is copied to RNA
What is translation?
The process where the order of nucleotide bases is converted to the order of amino acids.
Central dogma
- organism’s genotype: determined by sequence of bases in DNA
- organism’s phenotype: determined by the product of the proteins it produces
- alleles of the same gene differ in their DNA sequence
- proteins produced by different alleles of the same gene frequently differ in amino acid sequence
DNA —> mRNA —> protein
Exceptions to central dogma
- many genes code for RNA molecules that do not function as mRNA and are not translated into protein. (perform other important functions in the cell)
- sometimes information flows backwards
- viral genes maybe composed of RNA and use reverse transcriptase, a viral polymerase, to synthesize as DNA version
Who predicted each word in the genetic code contains three bases?
George Gamow
What is a codon?
- The group of three bases
- specifies a particular amino acid
What two scientist proved the three base codon?
Marshall Nirenberg and Philip Leder
What is the code of the start codon?
AUG
What are the codes for the three stop codons?
UGA, UAA, UAG
What is a mutation?
- Any permanent change in an organism’s DNA
- A modification in a cells information archive
- A change in its genotype
- Able to create new alleles
What are the different types of mutations?
- point mutations: results from a single base change
- chromosome-level mutations: larger scale, often result from the addition or deletion of chromosomes from the individual’s karyotype
When does point mutation occur?
- occur when the DNA polymerase inserts the wrong base into the newly synthesized strand of DNA
- result in change of the DNA base sequence
- if the DNA polymerase proof reading and mismatch repair system fails
What are missense or replacement mutations?
Results in changes in the amino acid sequence of the encoded protein
Silent mutations
Do not change the amino acids sequence of the gene product
