Gene Expression and Protein Synthesis Part 2 - (Week 4)

Question 1

Why was the one gene-one polypeptide hypothesis revised?

Answer 1

• some proteins are not enzymes

Question 2

More details on proteins:

Answer 2

• polymers consisting of amino acids linked by peptide bonds

- composed of several polypeptides, having their own gene

Question 3

What happens in the flow of gentic infromation from genes to proteins?

Answer 3

• info from genes is located in the specific sequences of nucleotides
• DNA inherited by an organism leads to specific traits by ditacting the synthesis of proteins
• proteins are links between genotype & phenotype

Question 4

What is gene expression?

Answer 4

• process by which DNA directs protein synthesis (transcription & translation)

Question 5

Genetic information can be provided by DNA or RNA. True of False?

Answer 5

True - the translation of RNA into protein = unidirectional

Question 6

What happens in the central dogma?

Answer 6

• info cannot be transferred from protein to protein to nucleic acid
• can be transferred between nucleic acid to nuclei acid and from nucleic acid to protein
• info in nucleic acid can be perpetuated or transferred
• transfer of info into a polypeptide = irreversible

Question 7

What is a genome?

Answer 7

• complete set of genetic instructions for any organism (RNA/DNA)
• copied during the process of replication
• coding system for genetic info = same in all living organsims

Question 8

What are the basic principles of transcription and translation?

Answer 8

• RNA = bridge between genes & proteins for which they code

- ribosomes are the sites of translation

Question 9

What is transcription?

Answer 9

• synthesis of RNA using info in DNA

mRNA for protein coding genes

Question 10

What is translation?

Answer 10

• synthesis of a polypeptide using info in the mRNA (in ribosomes)

Question 11

What happens to mRNA produced by transcription in proakaryotes?

Answer 11

• it is immediately transferred without more processing (coupled)

Question 12

What happens to mRNA produced by transcription in eukaryotes?

Answer 12

• nuclear envelope separates transcription site from translation
• mRNA = modified through RNA processing to yield mature mRNA that can be used for protein synthesis

Question 13

How many nucleotides bases are there in DNA?

Answer 13

Four

Question 14

How many nucleotides correspond to an amino acid?

Answer 14

Five

Question 15

What is the flow of information from gene to protein based on?

Answer 15

A triple code - series of 3-nucleotides

Question 16

What is the code of a gene transcribed into?

Answer 16

• a complementary three-nucleotide code of mRNA - a codon

- then translated into a chain of amino acids - froming a polypeptide

Question 17

What is a codon?

Answer 17

A triplet RNA code

Question 18

Out of the 64 possible codons, how many are stop/termination codons?

Answer 18

• 3, which are universally the same in almost all living organisms
• also 61 sense codons

Question 19

What does it mean when the genetic code is “degenerate”?

Answer 19

• more than 1 codon may specify a particular amino acid (but not ambiguous)

Question 20

Why do codons need to be read in the correct reading frame? (correct groupings)

Answer 20

• in order for the specified polypeptide to be produced

Question 21

The amino acids are specified by each codon in their 3-letter abbreviation. True or False?

Answer 21

True - written in 5’ to 3’

Question 22

How has the genetic code evolved?

Answer 22

• shared by the simplest bacteria to the most complex animals (universal)
• they can be transcribed & translated after being transplanted from one species to another
• the same codons are assigned to the same amino acids and START & STOP signals in the vast majority of genes in animals, plants & microorganisms (with some exceptions)