1.3 Gene Expression

Question 1

What 3 types of RNA does transcription and translation inolve?

Answer 1

• mRNA (messenger RNA)
• tRNA (Transfer RNA)
• rRNA (Ribosomal RNA)

Question 2

What is gene expression?

Answer 2

the process by which specific genes are activated to produce a required protein

Question 3

What are the differences between DNA and RNA?

Answer 3

• DNA is double stranded RNA is single stranded
• DNA nucleotides have a deoxyribose sugar whereas RNA nucleotides have a ribose sugar
• Bases in DNA are A,C,T and G whereas bases in RNA are A, U, C and G (uracil replaces thymine)

Question 4

What is the role of RNA?

Answer 4

transcription and translation of DNA sequences

Question 5

What is mRNA and what is its role?

Answer 5

• transcribed from DNA in the nucleus and translated into proteins by ribosomes in the cytoplasm
• mRNA carries a copy of the DNA code from the nucleus to the ribosome.

Question 6

What is the role of tRNA?

Answer 6

carry its specific amino acid to the ribosome

Question 7

What is the structure of tRNA?

Answer 7

• folds due to complementary base paining
• anti codon (an exposed triplet of bases) at one end
• specific amino acid attachment site at the other

Question 8

What is the role of rRNA?

Answer 8

combine with proteins to from the ribosome

Question 9

What is transcription?

Answer 9

transcription is the synthesis of mRNA from a section of DNA.

Question 10

What is the role of RNA polymerase? and therefore what is the process of transcription

Answer 10

• the enzyme responsible for transcription
• moves along the DNA molecule unwinding the double helix and breaking the hydrogen bonds between bases
• synthesises a primary mRNA transcript from RNA nucleotides by complementary bas paring

Question 11

What is the primary transcript?

Answer 11

The molecule produced when RNA polymerase transcribes a gene

Question 12

What is an intron?

Answer 12

a non-coding region of a gene

Question 13

What is an exon?

Answer 13

a coding region of a gene

Question 14

What is RNA splicing?

Answer 14

• The removal of the introns from the primary transcript.

- The remaining exons are spliced together to form the mature transcript.

Question 15

where does RNA splicing happen?

Answer 15

the nucleus

Question 16

What is translation?

Answer 16

the synthesis of a polypeptide following the code within the mature mRNA transcript.

Question 17

What is a codon and where is it found?

Answer 17

• The code for one amino acid.
• It is a sequence of 3 nucleotides (triplet of bases)
• it is a triplet of bases on the mature mRNA transcript

Question 18

What is the structure of ribosomes and what is its function?

Answer 18

• small, roughly spherical structures found in all cells
• they contain the enzymes essential for protein synthesis
• they bring tRNA molecules bearing amino acids into contact with the mRNA

Question 19

What is the translation process?

Answer 19

• begins at a start codon and ends at a stop codon
• anticodons bond to codons by complementary base pairing
• translating the genetic code into a sequence of amino acids
• peptide bonds join the amino acids together
• tRNA leaves the ribosome and a polypeptide is formed

Question 20

what is alternative RNA splicing?

Answer 20

• the same gene can make several different proteins depending on which exons are used
• exons must stay in the same order
• some exons are treated as introns
• different mature mRNA transcripts are produced from the same primary transcript

Question 21

What are the two stages of gene expression and where do they happen in a cell?

Answer 21

1. transcription - nucleus

2. translation - ribosome

Question 22

What is an anticodon and where is it found?

Answer 22

• an anticodon is an exposed triplet of bases on tRNA that is complementary to codons on the mRNA strand
• it is found at the opposite end of the tRNA from the amino acid attachment site

Question 23

How are amino acids joined to make a protein?

Answer 23

peptide bonds

Question 24

What are the chemical bonds that form to make proteins different shapes?

Answer 24

• hydrogen bonds

- other interactions between individual amino acids

Question 25

Describe the structure of a protein

Answer 25

• amino acids are linked by peptide bonds to form polypeptides
• fold to form 3D protein
• held together by hydrogen bonds and other interactions between individual amino acids
• shape determines their function

Question 26

What is phenotype determined by?

Answer 26

the proteins produced as a result of gene expression

-and environmental factors also influence