Human Cells: Gene Expression

Question 1

What is gene expression?

Answer 1

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

Question 2

What does gene expression involve?

Answer 2

The transcription and translation of DNA sequences

Question 3

Genes are expressed to produce what?

Answer 3

Proteins

Question 4

Only a fraction of the genes in a cell are what?

Answer 4

Expressed

Question 5

Transcription and translation involves three types of RNA what are they?

Answer 5

mRNA, tRNA and rRNA

Question 6

What is RNA?

Answer 6

It is single stranded and is composed of nucleotides containing ribose sugar, phosphate and one of four bases: Adenine, Cytosine, Guanine and Uracill

Question 7

Messenger RNA (mRNA) does what?

Answer 7

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

Question 8

mRNA is transcribed from DNA where? And then translated where?

Answer 8

Transcribed from DNA in the nucleus.

Translated into proteins by ribosomes in the cytoplasm

Question 9

What is the name and function of each triplet of bases on the mRNA molecule?

Answer 9

A codon.

It codes for a specific amino acid

Question 10

Why does transfer RNA (tRNA) fold?

Answer 10

Due to complementary base pairing

Question 11

What does a tRNA molecule have?

Answer 11

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

Question 12

What does each tRNA molecule carry?

Answer 12

Its specific amino acid to the ribosome

Question 13

What forms the ribosome?

Answer 13

Ribosomal RNA (rRNA) and proteins

Question 14

DNA is transcribed to produce what?

Answer 14

Messenger RNA (mRNA), which carries a copy of the genetic code

Question 15

What happens in transcription?

Answer 15

The enzyme RNA polymerase moves along DNA unwinding the double helix and breaking the hydrogen bonds between the bases

Question 16

RNA polymerase synthesises what?

Answer 16

A primary transcript of mRNA from RNA nucleotides by complementary base pairing

Question 17

Uracil in RNA is complementary to what?

Answer 17

Adenine

Question 18

Eukaryotic genes have what?

Answer 18

Introns and exons

Question 19

The introns of the primary transcript are what?

Answer 19

Non-coding regions and are removed

Question 20

The exons of the primary transcript are what?

Answer 20

Coding regions and are joined together to form the mature transcript

Question 21

What happens to the order of exons during RNA splicing?

Answer 21

It is unchanged

Question 22

RNA splicing forms what?

Answer 22

A mature mRNA transcript

Question 23

What does the mature mRNA transcript do?

Answer 23

Carries a copy of the DNA code from the nucleus to the ribosomes, where it is translated

Question 24

What is tRNA involved in?

Answer 24

The translation of mRNA into a polypeptide at a ribosome

Question 25

Most codons code for specific amino acids but what other types of codons are there?

Answer 25

Start codons and stop codons

Question 26

Where does translation begin and end?

Answer 26

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

Question 27

Amino acids are carried by what?

Answer 27

Specific tRNA molecules

Question 28

tRNA anticodons align and bond to mRNA codons by complementary base pairing, doing what?

Answer 28

Translating the genetic code into a sequence of amino acids

Question 29

Peptide bonds join the amino acids together to form what?

Answer 29

A polypeptide

Question 30

Following polypeptide formation, what happens to tRNA?

Answer 30

It exits the ribosome to collect further amino acids

Question 31

Different proteins can be expressed from one gene, as a result of what?

Answer 31

Alternative RNA splicing

Question 32

Different mature mRNA transcripts are produced from the same primary transcript depending on what?

Answer 32

Which exons are retained

Question 33

Polypeptide chains fold to form what?

Answer 33

The three-dimensional shape of a protein, held together by hydrogen bonds and other molecular interactions between individual amino acids

Question 34

Proteins have a large variety of shapes which determines what?

Answer 34

Their functions

Question 35

Gene expression results in what?

Answer 35

Proteins which determine the phenotype of an individual organism

Question 36

What also influences phenotype?

Answer 36

Environmental factors