Unit 3 - Gene Expression

Question 1

in a cell, how many genes are expressed

Answer 1

a fraction of the genes in a cell are expressed

Question 2

what does gene expression involve

Answer 2

gene expression involves the transcription and translation of DNA sequences

Question 3

what is an RNA composed of

Answer 3

RNA is single stranded and is composed of nucleotides containing ribose sugar, phosphate and one of four bases: Cytosine, Guanine, Adenine and Uracil.

Question 4

what three types of RNA are involved in gene translation and gene transcription

Answer 4

mRNA - messenger RNA
tRNA - transfer RNA
rRNA - ribosomal RNA

Question 5

what is the function of mRNA

Answer 5

mRNA carries a copy of the DNA code from the nucleus to the ribosome, mRNA is transcribed from DNA in the nucleus and translated into proteins by ribosomes in the cytoplasm. lastly every three bases (triplet of bases) on the mRNA molecule is called a codon and codes for a specific amino acid.

Question 6

what is the function of tRNA

Answer 6

tRNA folds due to complementary base pairings, each tRNA molecule carries its specific amino acid to the ribosome. A tRNA molecule has an anti-codon (an exposed triplet of bases) at one end and an attachment site for a specific amino acid at the other.

Question 7

what is the function of rRNA

Answer 7

rRNA and proteins form the ribosome

Question 8

what is the function of RNA polymerase

Answer 8

RNA polymerase moves along the DNA unwinding the double stranded helix and breaking the weak hydrogen bonds between the bases. RNA polymerase synthesises a primary transcript of mRNA from RNA nucleotides by complementary base pairings.

Question 9

in RNA what is the complementary base pairing to Adenine

Answer 9

Uracil

Question 10

what is formed in RNA splicing

Answer 10

RNA splicing forms mature mRNA transcript

Question 11

What are Introns

Answer 11

Introns are noncoding regions of the primary transcript which are removed

Question 12

what are Exons

Answer 12

Exons are coding regions and are joined together to make the mature transcript

Question 13

In RNA splicing what remains unchanged

Answer 13

the order of Exons

Question 14

where does translation begin and end

Answer 14

it begins at a start codon and ends at a stop codon

Question 15

how do anticodons bond to codons

Answer 15

they bond via complementary base pairings translating the genetic code into a sequence of amino acids

Question 16

what join amino acids together

Answer 16

peptide bonds

Question 17

what happens to each tRNA in the ribosome

Answer 17

the tRNA leaves the ribosome as the polypeptide is formed

Question 18

how are different mature mRNA transcripts produced

Answer 18

different mature mRNA transcripts are produced from the same primary transcript depending on which exons have been retained

Question 19

how are different proteins expressed from one gene

Answer 19

different proteins can be expressed from one gene as a result of alternative RNA splicing

Question 20

how are proteins formed

Answer 20

proteins are formed by polypeptide chains which fold and form a three-dimensional shape of a protein which is held together by hydrogen bonds and other interactions between individual amino acids

Question 21

what determines a proteins function

Answer 21

proteins have a large variety of shapes which determine their function.

Question 22

what is determined by by proteins as a result of gene expression.

Answer 22

phenotypes are determined by proteins produced as the result of gene expression

Question 23

what also has an influence on phenotype

Answer 23

environmental factors also have an influence of phenotype