Lesson 3: Protein synthesis

Question 1

Importance of protein synthesis

Answer 1

the info stored in genes can only be useful to a cell if it is read and turned into proteins.

Question 2

How can each cell in the human body perform its own specialized functions, if all cells have the same genetic information?

Answer 2

Not all genes in a cell are expressed and turned into proteins. Only those genes related to the cells specialized function are expressed, In this way, each cell uses a subset of the total genetic code to meet its specialized needs.

Question 3

Where is the DNA during the transcription process in eukaryotic cells?

Answer 3

nucleus

Question 4

What is the central dogma of genetics?

Answer 4

transcription from DNA to RNA and translation from RNA to protein

Question 5

What is the one gene-one polypeptide hypothesis?

Answer 5

it says that one gene is responsible for producing one polypeptide

Question 6

Explain why a codon that is 2 nucleotides long would be unable to code for all 20 amino acids?

Answer 6

because there are only four nucleotide bases, a codon that is two nucleotides long could only code for a maximum of 4 x 4= 16 amino acids, this is less than 20 needed.

Question 7

How do you translate mRNA codons into amino acids.

Answer 7

use genetic code chart.

Question 8

What are the stages and phases of protein synthesis?

Answer 8

Stage 1: Transcription - Making an RNA Copy of the gene
phase 1: initiation
phase 2:elongation (making the mRNA molecule)
phase 3: termination

Stage 2: Translation - reading the RNA Copy and assembling the polypeptide
phase 1: initiation
phase 2: elongation (making the polypeptide)
phase 3: termination

Question 9

What is transcription?

Answer 9

• The process by which DNA is copied (transcribed) to mRNA, which carries the information needed for protein synthesis.
• RNA polymerase is the main transcription enzyme.
• Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins).
• RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule.
• Transcription ends in a process called termination. Termination depends on sequences in the RNA, which signal that the transcript is finished.

Question 10

Explain the process of protein synthesis.

Answer 10

https://www.atdbio.com/content/14/Transcription-Translation-and-Replication

Question 11

Compare DNA and RNA by their shape, function and nucleotide types.

Answer 11

nucleotide types -
DNA: G,T,A,C
RNA: G,U,A,C

shape -
DNA: double stranded helix
RNA: single stranded helix

function -
DNA: stores all hereditary info
RNA: mRNA and tRNA

Question 12

For RNA what are the roles of mRNA and tRNA?

Answer 12

mRNA: carries transcripts of DNA

tRNA: transports amino acids

Question 13

Using one sentence for each, explain the roles of mRNA, rRNA, and tRNA during translation.

Answer 13

mRNA provides a temporary copy of the gene in the DNA blueprint and attach that copy to the ribosome, where the correct sequence of amino acids can be joined together.

Question 14

Using one sentence for each, explain the roles of mRNA, rRNA, and tRNA during translation.

Answer 14

• mRNA provides a temporary copy of the gene in the DNA blueprint and attach that copy to the ribosome, where the correct sequence of amino acids can be joined together.
• rRNA when combined with proteins forms the structure of the ribosome. Once formed, the ribosome then reads the mRNA and assembles the polypeptide.
• tRNA brings the amino acids to the ribosome in the correct sequence, using the anti-codons on the bottom of the tRNA to complement the mRNA codon.

Question 15

What is it that signals the termination of translation?

Answer 15

Aby one of the three STOP codons (UAA, UAG, and UGA) will signal the termonation of translation.

Question 16

What are transcription factors, and what is their role in protein synthesis in eukaryotes?

Answer 16

Before transcription can begin in eukaryotes, a protein called an initiation factor binds to the promoter region. This facilitates the binding of other transcription factors that stabilize the RNA polymerase to help it bind to the correct starting codon on the mRNA transcript. The transcription factors can either inhibit or stimulate the transcription process.

Question 17

What is an operon and why is it considered an efficient way to regulate genes?

Answer 17

An operon is a group of genes that are regulated by one regulatory protein. The genes in the operon are expressed together or not at all. This is an efficient way to regulate genes that are involved in the same biochemical pathway because only one regulatory protein is needed instead of several - one each, to control each gene.

Question 18

Describe one example of positive regulation in an operon.

Answer 18

When glucose levels are low in a cell, an activator protein will bind to a site close to the promoter (Plac) region on the lac operon. This makes it easier for the RNA polymerase to bind to the promoter so that the lac genes will be transcribed at a higher rate, which will ultimately result in more glucose for the cell.

Question 19

Gene level mutations

Answer 19

The DNA sequence of a gene can be altered in a number of ways. … This type of mutation is a change in one DNA base pair that results in the substitution of one amino acid for another in the protein made by a gene. Nonsense mutation. A nonsense mutation is also a change in one DNA base pair.

Question 20

What are point mutations and what are the three types.

Answer 20

A point mutation involves the substitution of one nucleotide but it only affect the codon in which it occurs. It has no effect on neighbouring codons in the gene.