Chapter 13-Gene Expression Flashcards
What are the differences between DNA and RNA?
1) Sugars: deoxyribose vs. ribose (2H vs 2OH), 2) nitrogenous bases: T vs U, 3) single stranded vs double stranded
What is gene expression?
gene expression involves a series of steps in which the information in the sequence of bases in DNA specifies the makeup of the cell’s proteins which then affect the phenotype in some way; the first major step of gene expression is transcription and the second major step is translation
What did biochemist James Sumner discover?
he showed the enzyme urease to be a protein in his experiment which was the first clear identification of an enzyme as a protein
What did Archibald Garrod discover?
Garrod’s work on inborn errors of metabolism provided evidence that genes specify proteins. Garrod studied a rar genetic disease called alkaptonuria and hypothesized that people with alkaptonuria lack the enzyme that normally oxidizeds homogentisic acid.
Describe Beadle and Tatum’s experiments with Neurospora.
Beadle and Tatum exposed Neurospora spores to X-rays or UV rays to induce mutant strains, and then identified strains that carried a mutation preventing the fungus from producing a chemical essential for growth. Their work revealed that each mutant strain had a mutation in only one gene and that each gene affected only one enzyme.
What did Linus Pauling discover?
Pauling showed that a mutation of a single gene alters the structure of the protein hemoglobin.
What is the one gene-one enzyme hypothesis?
when there is a mutation, the mutation is only in one gene and each gene only affects one enzyme
What are the differences between DNA and RNA?
DNA: has deoxyribose sugar, is two stranded, contains thymine as a nucleic base; RNA: constains ribsose, uracil as a nucleic base, and is usually one stranded
Outline the flow of genetic information in cless, from DNA to RNA to polypeptide.
The process by which information encoded in DNA specifies the sequences of amino acids in proteins involves transcription and translation. During transcription, an RNA molecule complementary to the template DNA strand is synthesized. Messenger RNA (mRNA) molecules contain information that specifies the amino acid sequences of polypeptide chains. During translation, a polypeptide chain specified by the mRNA is sythesized. Each sequence of three nucleotide bases in the mRNA constitutes a codon, which specifies one amino acid in the polypeptide chain, or a start or stop signal. Translation requires tRNAs and cell machinery, including ribosomes.
What is mRNA, tRNA, and rRNA?
mRNA is messenger RNA, it is a single strand of RNA that carries the information for making a protein, it can also be thought of as a complementary copy of the template DNA strand; tRNA is transfer RNA, it is a single strand of RNA that folds back onto itself to form a specific shape, each kind of tRNA bonds with only one kind of amino acid and carries it to the ribosome; rRNA is ribosomal RNA, which is in globular form, it is an important part of the structure of ribosomes and has catalytic functions needed during protein synthesis
What is an anticodon?
a sequence of three nucleotides in transfer RNA that is complementary to, and combines with, the three-nucleotide codon; it hydrogen bonds with the mRNA codon by complementary base pairing
Where does transcription occur in eukaryotic and prokaryotic cells? Translation?
transcription occurs in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells; translation occurs in the cytoplasm of both eukaryotic and prokaryotic cells
