14.1: Genes specify proteins via transcription and translation

Question 1

Gene expression

Answer 1

the process by which DNA directs the synthesis of proteins ( sometimes RNA)

Question 2

3 types of RNA to know

Answer 2

• mRNA
• tRNA
• rRNA

Question 3

Archibald Garrod

Answer 3

1st to say genes dictate phenotypes through enzymes, biochemists later found that it is a metabolic pathway of multiple enzymes

Question 4

George Beadle and Boris Eupharsi:

Answer 4

speculated that the Drosophila mutation affecting eye color had to do with the lack of a specific enzyme

Question 5

Neurospora Crassa

Answer 5

Used by Beadle and Edward Tatum, by causing a mutation in one allele in a cell, it was easy to deduce the wild-type gene. They had modest food requirements and were able to grow off of the minimal medium

Question 6

Nutritonal Mutants

Answer 6

unable to synthesize a particular essential nutrient, could only grow on the complete medium. It was hypothesized that in each of these, a specific gene for an enzyme that synthesizes a nutrient had been disabled

Question 7

One-gene one polypeptide hypothesis

Answer 7

Each gene codes for a polypeptide (protein or part of a protein)(Proved by Beadle and Edward Tatum using Neurospora)

Question 8

4 critiques of the hypothesis

Answer 8

1. Researchers later found that not all enzymes are proteins so it was then stated as the one gene-one protein
2. Then it was realized that each polypeptide is specified by its own gene, so it was then revised to the one gene-one polypeptide
3. Eukaryotic gene can code for a set of closely related polypeptides via a process called alternative splicing
4. few genes code for RNA molecules that have important functions in cells even though they are never translated into proteins

Question 9

Transcription

Answer 9

the synthesis of RNA using the information in DNA

Question 10

mRNA

Answer 10

produced by transcription, if moving towards translation, can be destroyed to stop protein synthesis

Question 11

Translation

Answer 11

synthesis of a polypeptide, using the info in the mRNA

Question 12

Ribosomes

Answer 12

sites of translation, the kitchen of proteins

Question 13

differences in eu and pro

Answer 13

• In prokaryotes, translation of mRNA can begin before transcription has finished
• In a eukaryotic cell, the nuclear envelope separates transcription from translation
• Eukaryotic RNA transcripts are modified through RNA processing to yield the finished mRNA

Question 14

primary transcript

Answer 14

the initial RNA transcript from any gene prior to processing

Question 15

central dogma

Answer 15

the concept that cells are governed by a cellular chain of command: DNA → RNA → protein

Question 16

triplet code

Answer 16

the genetic instructions for a polypeptide chain are written in the DNA as a series of nonoverlapping, 3 nucleotide words, found in mRNA(codons) and is translated into a chain of amino acids

Question 17

template strand

Answer 17

the DNA strand that is transcribed(can change based on the enzyme)

Question 18

coding strand

Answer 18

the nontemplate strand and also is identical to the codons of the mRNA, the sequence is used in a gene’s sequence is reported

Question 19

Codons

Answer 19

3 nucleotide segments (triplet code), codons are read in the 5’→3’ direction and they are turned into amino acids, 3:1 ratio

Question 20

Marshal Nirenberg

Answer 20

deciphered the first codon(UUU), he placed this into a test tube containing all 20 amino acids and more, it was then translated into a polyphenylalanine chain. He then deduced the function of the UUU codon, this was also done with AAA, GGG, and CCC

Question 21

How many codons actually code for amino acids?

What is the start codon??

Answer 21

61/64 codons code for amino acids, the other 3 are stop codons which mark the end of translation

AUG is the start codon and is stands for methionine and is usually the thing polypeptide chains begin on, can be removed by an enzyme