Unit 1.3 Gene expression

Question 1

What is RNA

Answer 1

A single stranded molecule, compromised of nucleotides

Question 2

What do the nucleotides in RNA contain

Answer 2

ribose sugar, phosphate & base (cytosine, guanine, adenine & uracil)

Question 3

What does gene expression involve

Answer 3

The transcription & translation of DNA sequences

Question 4

How much of the genes in a cell are expressed

Answer 4

Only a fraction

Question 5

The differences between DNA & RNA

Answer 5

DNA- 2 strands
RNA- 1 strand

DNA- adenine pairs with thymine
RNA- adenine pairs with uracil

DNA- nucleotide contains deoxyribose sugar
RNA- nucleotide contains ribose sugar

DNA- found in the nucleus
RNA- found in the nucleus & cytoplasm

Question 6

3 types of RNA

Answer 6

messenger RNA
transfer RNA
ribosomal RNA

Question 7

Function of mRNA

Answer 7

copies a section of the DNA code & carries it to the ribosome in the cytoplasm

Question 8

Function of tRNA

Answer 8

carries specific amino acids into position at the ribosome

Question 9

Function of rRNA

Answer 9

along with proteins make up the ribosome which is involved in protein synthesis

Question 10

What is a triplet of bases on a mRNA molecule called

Answer 10

a codon

Question 11

What does one codon code for

Answer 11

a specific amino acid

Question 12

What causes tRNA to fold

Answer 12

Complementary base pairing

Question 13

What type of codon do tRNA molecules contain

Answer 13

Anti-codon (an exposed triplet of bases)

Question 14

What site is at the other end of a tRNA molecule, to help carry the specific amino acids to the ribosome

Answer 14

The attachment site

Question 15

What does DNA carry the code for

Answer 15

Making proteins

Question 16

What are the 3 stages of protein synthesis called

Answer 16

Transcription (of gene), RNA splicing, Translation

Question 17

What happens in the transcription stage

Answer 17

The section of the DNA code required (gene) is copied into mRNA. This is known as the primary transcript.

Question 18

What happens in the RNA splicing stage

Answer 18

The non-coding information (introns) in the primary transcript must be removed by splicing. The coding regions (exons) are joined together after the introns are removed, creating a mature mRNA strand.

Question 19

What happens in the translation stage

Answer 19

The spliced mature mRNA strand is used to assemble amino acids in the correct order to make the protein

Question 20

Where does transcription occur

Answer 20

The nucleus

Question 21

Where does RNA splicing occur

Answer 21

The nucleus

Question 22

Where does translation occur

Answer 22

The ribosome (in the cytoplasm)

Question 23

Explain the steps in the process of transcription

Answer 23

1- RNA polymerase moves along the DNA, unwinding the double helix.
2- weak hydrogen bonds between bases break, so DNA strands separate
3- RNA polymerase adds free moving RNA nucleotides to the growing mRNA strand, by complementary base pairing
4- weak hydrogen bonds form between the new base pairs (of the DNA template & mRNA strand)
5- strong chemical bonds form between the new RNA nucleotides (opposite the DNA), allowing a new strand to be formed
6- weak hydrogen bonds break between DNA & RNA, allowing mRNA to break from the DNA template
7- a primary mRNA transcript is formed & ready to undergo splicing
8- weak hydrogen bonds reunite the 2 original DNA strands into a double helix again

Question 24

What are long sections of DNA that do not code for a polypeptide called

Answer 24

Introns

Question 25

Where are introns found

Answer 25

In between sections of DNA that do code for the proteins (polypeptides)

Question 26

What are the coding regions on DNA called

Answer 26

Exons

Question 27

What makes up the mature mRNA

Answer 27

Only exons (order is unchanged)

Question 28

What happens once the mature mRNA is created

Answer 28

It leaves the nucleus & enters the cytoplasm for the next stage

Question 29

What enzyme directs transcription

Answer 29

RNA polymerase

Question 30

What is translation

Answer 30

The process which translates the code found on mRNA into a polypeptide

Question 31

What molecule is involved in the translation of mRNA

Answer 31

tRNA

Question 32

Describe the steps in process of translation

Answer 32

1- translation is initiated by the start codon (AUG) on the mRNA strand 2- tRNA molecules become attached to their specific amino acid molecules 3- these tRNA molecules then accumulate at the ribosome 4- the first tRNA molecule moves in & its anticodon forms a complementary base pair with the codon on the mRNA 5- another tRNA molecule carries an amino acid to the ribosome. more complementary base pairings occur, bringing the amino acids inline with each other. A peptide bond forms between the amino acids 6- the first tRNA molecule detaches from the mRNA & is free to collect another amino acid from the cytoplasm 7- this process is repeated all along the mRNA transcript until a stop codon is reached at the 3’ end & the newly formed polypeptide chain is complete

Question 33

What is always the start codon

Answer 33

AUG

Question 34

Function of a ribosome

Answer 34

Site of protein synthesis

Question 35

What type of bond forms between amino acids & what does this create

Answer 35

Peptide bonds & a polypeptide

Question 36

How can different proteins be expressed from one gene

Answer 36

As a result from alternative RNA splicing

Question 37

How does alternative RNA splicing work

Answer 37

Different mature mRNA transcripts are produced from the same primary transcript depending on which exons are retained

Question 38

What do polypeptide chains fold to form & what holds this together

Answer 38

A 3D shape of a protein, held together by hydrogen bonds & other interactions between amino acids

Question 39

What is a phenotype

Answer 39

The physical appearance of an organism

Question 40

What can determine the phenotype

Answer 40

The proteins produced from gene expression or environmental factors

Question 41

What is a cells function determined by

Answer 41

The sequence of the DNA bases in its genes

Question 42

What is a cells structure determined by

Answer 42

The proteins that are synthesised when the genes are expressed

Question 43

What is gene expression influenced by

Answer 43

Environmental factors, inside & outside of the cell