Unit 12: Gene Function and the Genetic Code Flashcards
What was the Beadle and Tatum (1941) experiment?
They discovered what genes do by making them defective. They damaged a gene then observed the effect on the phenotype.
What did the Beadle and Tatum experiment involve using N. Crassa?
They exposed N. Crassa to X-rays to induce mutations in its DNA. Observed that some mutants couldn’t grow unless additional nutrients (like amino acids) were provided.
What did the results of the Beadle and Tatum experiment lead to?
Result led to one-gene, one-enzyme hypothesis- Each gene contains information to make an enzyme.
How did Beadle and Tatum test their one-gene, one-enzyme hypothesis?
They tested hypothesis by studying three-step metabolic pathway that produces arginine. Tested to see if mutated molds could still grow without arginine since normal mold can make its own arginine.
What are the enzymes involved in the metabolic pathway for arginine synthesis?
Precursor –> enzyme 1 –>Ornithine –> enzyme 2 —>Citrulline –> enzyme 3 –> Arginine
Genes have a _______ and a _____.
Genes have a regulatory region and a coding region.
What is the regulatory region of a gene?
The regulatory region contains the promoter, which is a sequence of DNA that relays information where to start transcription of DNA into mRNA.
What is the coding region of a gene?
The coding region contains the gene body that is actively transcribed. The coding region gets copied into mRNA.
What does the coding region consist of?
It consists of introns (not transcribed) and exons (transcribed, copied into mRNA).
Why is the one gene, one enzyme hypothesis incorrect?
Today we know that genes can code for more than one protein using alternative arrangements of the genetic code.
What is the central dogma?
Summarizes the flow of information in cells:
1. Genes are stretches of DNA that code for proteins.
2. DNA sequence codes for mRNA sequence.
3. mRNA sequence codes for sequence of amino acids in protein.
___ codes for ___, which codes for ______.
DNA codes for RNA, which codes for proteins.
What is transcription?
Process of using DNA template to make complementary mRNA.
What is translation?
Process of using information in mRNA to synthesize proteins.
What is the link between genotypes to phenotypes?
DNA (genotype) –> mRNA –> Proteins –> phenotype
What determines an organism’s genotype?
Determined by sequence of bases in DNA.
What determines an organism’s phenotype?
Product of proteins it produces.
What are the DNA bases?
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
What are the mRNA bases?
Adenine (A)
Uracil (U) instead of thymine
Cytosine (C)
Guanine (G)
What bases pair together when DNA is replicated?
In DNA, A pairs with T, and C pairs with G.
What bases pair together when transcribing DNA in mRNA?
- A (adenine) in DNA will pair with U (uracil)
- T (thymine) in DNA will pair with A.
- C (cytosine) in DNA will pair with G.
- G (guanine) in DNA will pair with C .
What occurs after bases are paired together in transcription?
Translation occurs. The mRNA codons are translated into a specific sequence of amino acids to form a protein.
What is a genetic code?
Genetic code specifies how a sequence of DNA codes for a sequence of amino acids.
What are codons?
Codons are sequences of three nucleotides in mRNA that specify a particular amino acid during the process of translation. (Ex. AUG, UCU, UAA)
What is redundant as it pertains to genetic code?
All but two amino acids are encoded by more than one codon. Multiple codons can code for the same amino acid.
What is unambiguous as it pertains to genetic code?
One codon never codes for more than one amino acid.
What is non-overlapping as it pertains to genetic code?
Codons are read one at a time.
What is nearly universal as it pertains to genetic code?
All codons specify the same amino acids in all organisms (with a few minor exceptions).
What is conservative as it pertains to genetic code?
If several codons specify the same amino acid, the first two bases are usually identical. Mutations are often less harmful due to the similarity in amino acid properties
