gene expression 1.3

Question 1

gene expression

Answer 1

involves transcription and translation of DNA sequences

Question 2

what’s the first step of protein synthesis

Answer 2

transcription which is when the gene on the DNA strand that codes for the protein is copied into a molecule of mRNA

Question 3

what is the second step of protein synthesis

Answer 3

translation which takes place at the ribosome when mRNA code is used to make the protein

Question 4

which structures are involved in transcription

Answer 4

mRNA

Question 5

which structures are involved in translation

Answer 5

tRNA and rRNA

Question 6

how many strands does RNA have

Answer 6

RNA is a single stranded molecule

Question 7

what is RNA composed of

Answer 7

RNA nucleotides

Question 8

what does each RNA nucleotide consist of

Answer 8

a ribose sugar, a phosphate group and a base

Question 9

what are the RNA nucleotide bases

Answer 9

adenine, uracil, guanine and cytosine

Question 10

messenger RNA function

Answer 10

carry a copy of the DNA code from the nucleus to the ribosome

Question 11

what is each triplet in mRNA called

Answer 11

a codon which codes for a specific amino acid

Question 12

transfer RNA structure

Answer 12

tRNA folds due to the complementary base pairings A-U and G-C

Question 13

transfer RNA function

Answer 13

carries a specific amino acid to the ribosome during translation

Question 14

what does tRNA molecules contain

Answer 14

they contain an anticodon (an exposed triplet of bases) at one end and an attachment site for a specific amino acid at the other end

Question 15

ribosomal RNA function

Answer 15

to bring tRNA molecules bearings amino acids into contact with the mRNA molecule during translation

Question 16

ribosome structure

Answer 16

made up of rRNA and protein

Question 17

transcription function

Answer 17

the synthesis of a molecule of mRNA from a section of DNA (a gene) by the enzyme RNA polymerase

Question 18

process of transcription

Answer 18

-RNA polymerase moves along the DNA strand unwinding the double helix and breaking the hydrogen bond between base pairs and separating the two DNA strands

-RNA polymerase synthesises the primary transcript of mRNA using RNA nucleotides by complementary base pairings

Question 19

RNA splicing function

Answer 19

to form the mature mRNA transcript

Question 20

process of RNA splicing

Answer 20

-the introns of the primary transcript are non coding regions and are removed from the strand

-the exons are coding regions and are joined together to form the mature transcript of mRNA

-the order of exons is unchanged during splicing

Question 21

translation function

Answer 21

to translate mRNA into a polypeptide at a ribosome

Question 22

process of translation

Answer 22

-translation begins at a start codon and ends at a stop codon

-tRNA anticodons bond to mRNA codons by complementary base pairings

-this translates the mRNA genetic code into a sequence of amino acids

-the amino acids are held together by peptide bonds

-each tRNA then leaves the ribosome as the polypeptide is formed and is free to pick up another amino acid

Question 23

protein structure

Answer 23

proteins are made up of chains of amino acids of which there are 20 different types

Question 24

the length of a protein

Answer 24

can vary from a thousand to just a few

Question 25

how are the amino acids linked together

Answer 25

by peptide bonds which forms a polypeptide chains

Question 26

what do polypeptide chains fold into

Answer 26

they fold to form the 3D shape of a protein and are held together by hydrogen bonds and other interactions between individual amino acids

Question 27

what does the shape of a protein determine

Answer 27

their function