DNA and Polypeptide Synthesis

Question 1

What is Polypeptide Synthesis?

Answer 1

Sequence read by the cell to produce a chain with specific sequence of amino acids. Amino acids are called a polypeptide and combine to form functional proteins. Has two important steps: transcription and translation.

Question 2

Where is the genetic code stored to produce polypeptides?

Answer 2

Stored in DNA to produce polypeptides, translated by DNA.
Note: order of nucleotides determines which polypeptide is synthesised. Three nucleotides read at a time and transcribed into mRNA, called a codon.

Question 3

What are the three types of RNA?

Answer 3

Messenger RNA (mRNA)
Ribosomal RNA (rRNA)
Transfer RNA (tRNA)

Question 4

What does mRNA do?

Answer 4

Formed by nucleus during transcription and carries the code from nucleus to ribosomes

Question 5

What does rRNA do?

Answer 5

Made in the nucleolus of the cell. Based on the nucleotide sequence of DNA. rRNA binds with proteins to form the ribosomes.

Question 6

What does tRNA do?

Answer 6

Transfer amino acids from the cytoplasm to ribosomes to form a polypeptide chain. There are 64 total codons with 3 stop codons (61 specifying amino acids)

Question 7

Common features of genetic code in eukaryotes?

Answer 7

• Stop and start triplet sequences - regions where encoding begins and ends for specific genes
• Promoter - section of gene found on the DNA before the start of the triplet at the 5’ end where transcription begins.
• Exons - regions of DNA that are the coding segments
• Introns (space DNA)

Question 7

Common features of genetic code in eukaryotes?

Answer 7

• Stop and start triplet sequences -
• Promoter - section of gene found on the DNA before the start of the triplet
• Exons - regions of DNA that are the coding segments
• Introns (space DNA)

Question 8

What is Gene Expression?

Answer 8

A process in which the information stored in a gene synthesises a functional gene product (protein or RNA). This process is highly regulated so proteins or ENA are only produced if needed.

Question 9

What is transcription?

Answer 9

Production of a single-stranded mRNA from DNA.

Question 10

What are the three steps of transcription?

Answer 10

Initiation
Elongation
Termination

Question 11

What happens in the initiation process of Transcription?

Answer 11

• RNA polymerase binds to promoter DNA sequence found near the start of each gene
• RNA polymerase then separates the strands of DNA to provide a single stranded template

Question 12

What happens in the elongation process of Transcription?

Answer 12

• The template strand of DNA is read by RNA polymerase, building an mRNA molecule according to the base-pair rule (grows from 5’ to 3’)
• RNA transcript is equivalent to an RNA strand of the non-template strand of DNA

Question 13

What happens in termination in transcription?

Answer 13

Terminator sequence is reached and it causes the RNA transcript to be released by the RNA polymerase

Question 14

What is RNA processing?

Answer 14

Step after transcription but before translation

It forms mature mRNA from pre-RNA.

Question 15

Describe the process of RNA processing

Answer 15

Forms mature mRNA, by removing the introns so that only exons are carried to the ribosomes for translation.

Question 16

What are the steps for RNA processing?

Answer 16

Includes:

• The addition of a 5’ cap and a poly(A) tail
• Splicing the introns from the transcript

Question 17

Function of mRNA

Answer 17

Carries DNA code to ribosomes

Question 18

Function of tRNA

Answer 18

Carries amino acids to ribosomes

Question 19

Function of tRNA

Answer 19

Forms part of the ribosome structure

Question 20

Function of DNA

Answer 20

Carries inherited genetic code

Question 21

Function of RNA polymerase

Answer 21

Catalyses the transcription of RNA from DNA

Question 22

Function of triplet

Answer 22

three-base code on DNA

Question 23

Function of a codon

Answer 23

Three-base code on mRNA

Question 24

Function of anti-codon

Answer 24

Three-base code on tRNA