2.3/4 REVIEW LEC

Question 1

Important enzyme in translation

Answer 1

aminoacyl tRNA synthetases

Question 1

Factors pertaining to translation

Answer 1

initiation, elongation, and release factors

Question 2

What does aminoacyl tRNA synthetase do?

Answer 2

Hooks up amino acid to proper tRNA to prepare the tRNA for translation

Question 3

What components make up the site of translation

Answer 3

mainly: large and small ribosomal subunits
also: tRNA with corresponding amino acid

Question 4

describe codon-anticodon pairing in translation

Answer 4

The tRNA has a codon sequence opposite (Anticodon) to the codon sequence of mRNA being translated.

first base in codon (5’ end) matches with last base in anticodon (3’ end)

Question 5

Real world example: why is translation important?

Answer 5

Antibiotics work by disrupting translation process at ribosomal site.

Question 6

what factors contribute to assembly in translation?

Answer 6

initiation factors

Question 7

What factors contribute to delivery of charged tRNA (with attached aa)?

Answer 7

elongation factors

Question 8

Is translation a process requiring energy?

Answer 8

Yes, GTP hydrolysis drives translation

Question 9

what contributes to over a million protein types?

Answer 9

genome: 20-25,000 genes > (alternative promoters, alt splicing, mRNA editing)> transcriptome: 100,000 transcripts > (post translational modifications)> over a million proteins

Question 10

What is an example of cells detecting changes in environment?

Answer 10

eat cookie> stimulus: sensory cells in pancreas detect glucose levels increased> insulin released > effector cells: body cells (liver and muscle cells) take up glucose and store it as glycogen> decreased glucose levels in blood

Question 11

If insulin polypeptide sequence is 110 aa long, why is the functional insulin protein 51 aa’s?

Answer 11

alpha chain- 21 aa
beta chain- 30 aa
preproinsulin > signal sequence detaches, disulphid bonds form > proinsulin > C chain falls of > insulin alpha and beta chain liked by disulphide bonds.

Question 12

What are some other post translational modifications?

Answer 12

Methylation, phosphorylation, acetylation

Question 13

how are methylation, phosphorylation and acetylation effective?

Answer 13

Addition of one of these function groups to the polypeptide chain changes the structure and function of the polypeptide.

Question 14

what is alternative splicing?

Answer 14

a primary transcript from the same gene can be spliced in different ways resulting in different mRNAs and eventually different proteins.

Question 15

What is meant by alternate receptors?

Answer 15

receptors with a different affinity to a product.

Question 16

What is an example of alternate receptors and their significance.

Answer 16

• receptors of insulin can have different affinities to insulin due to alternate splicing:
  exon 11 is present in the mRNA coding for insulin receptors:
• the receptors will have a low affinity to insulin
• these receptors are found in the liver
  If exon 11 is absent:
• the insulin receptors will have a higher affinity to insulin
• these receptors are found in skeletal muscle.

Question 17

What is insulins purpose?

Answer 17

Insulin binds to insulin receptors which triggers cytoplasmic signaling proteins to induce glucose transport proteins to uptake glucose in the cell.

Question 18

intracellular signals can be amplified: T or F

Answer 18

true, intracellular signals associated with a specific receptor can transduce messages and amplify them. This increases efficiency.

Question 19

What is neurospora crassa?

Answer 19

red bread mold

Question 20

Who preformed an experiment with neurospora crassa studying the relationship between genes and enzymes?

Answer 20

Beadle and Tatum, Srb and Horowitz

asked: what do genes do?

Question 21

How many mutants of the neurospora crassa were used in the experiment and how were they mutated?

Answer 21

3 mutations were made, by UV and x-ray treatments which created errors in dna and influenced production of enzyme 1,2, and 3

Question 22

define wild type characteristics

Answer 22

a species that is able to live on minimal medium and create all necessary amino acids and substances it needs to survive.

Question 23

What is minimal medium

Answer 23

a support medium containing molecules needed by wild types for growth

Question 24

What did Srb and Horowitz hypothesize

Answer 24

each genes has info required to make different enzyme (e.g. one gene one enzyme)

Question 25

Metabolic pathway for arginine synthesis

Answer 25

precurser> enzyme 1> ornithine> enzyme 2> citrulline> enzyme 3> Arginine

Question 26

Results of Srb, Horowitz, Beadle, and Tatum's experiment

Answer 26

Wild type grew on all mediums Arg 1 mutants grew on media with ornithine, citrulline, or arginine Arg 2 mutants only grew on media with citrulline or arginine added Arg 3 mutants only grew on media with arginine added

Question 27

What are the conclusions of the Srb, Horowitz, Beadle, and Tatum experiment

Answer 27

mutant growing on ornithine must be able to synthesize arginine from ornithine mutant growing on citrulline must be able to synthesize arginine from citrulline Mediums not growing with citrulline or ornithine, a defect must be present in Arg 3 enzyme.

Question 28

Summarize the Srb, Horowitz, Beadle, Tatum neurospora crassa experiment

Answer 28

Different mutants had different defects in different genes Metabolic pathway leading to the synthesis of arginine can be determined by examining mutants. ornithine is the precursor to citrulline which is the precursor to arginine

Question 29

Overall significance of neurospora crassa experiment

Answer 29

One gene one enzyme hypothesis ... later... one gene one polypeptide hypothesis .... later... One gene one... hypothesis (due to post translational mods)