Unit 1: human cells- Gene expression

Question 1

Transcription?

Answer 1

The first stage of protein synthesis
happens in the nucleus
involves the formation of mRNA from a single strand of DNA
begins at the start of a DNA strand called the promoter region
RNA polymerase attaches to the DNA strand unwinding/unzipping it to separate the two strands
as it does this RNA nucleotides base pair with the exposed bases on the DNA strand
does this by joining Adenine to Uracil and Cytosine to Guanine
Any Thymine’s on DNA strand pair with Adenine
transcription ends when the RNA polymerase reaches a terminator region
The mRNA strand which has now been formed is called the PRIMARY TRANSCRIPT

Question 2

What does the primary transcript of mRNA undergo?

Answer 2

The primary transcript will now undergo splicing to remove non-coding regions called introns from the strand. This forms a MATURE TRANSCRIPT.

Question 3

What does the mature transcript formed do?

Answer 3

The mature transcript formed of coding regions called exons will now leave the nucleus and head out into the cytoplasm towards the ribosome. The second stage called Translation will then occur at the ribosome.

Question 4

What are the 3 types of RNA involved in gene expression?

Answer 4

mRNA
tRNA and
rRNA

Question 5

Translation?

Answer 5

Translation is the 2nd stage of gene expression
occurs at the ribosome
involves he synthesis of a polypeptide chain which will later become a finalised protein.

Question 6

process of translation?

Answer 6

The mRNA attaches to binding site on the ribosome.
Every three bases on a messenger RNA is known as a codon. A second type of RNA (tRNA) is found in the cytoplasm and has a triplet of bases exposed at one end of the strand. This triplet is known as an anticodon. A the other end of the tRNA strand is an attachment site for an amino acid. Each anticodon acts as a code word for a particular amino acid. The tRNA will pick up the relevant amino acid and attach at the attachment site for transfer to the mRNA strand

Question 7

What is the function of transfer RNA?

Answer 7

Picks up a SPECIFIC amino acid from the cytoplasm and brings it to the ribosome.

Question 8

What is the function of messenger RNA?

Answer 8

Carries the genetic code from the nucleus to the ribosome.

Question 9

What is the function of ribosomal RNA?

Answer 9

Along with protein it gives structure to the ribosome.

Question 10

Where is mRNA made?

Answer 10

in the nucleus.

Question 11

When is mRNA’s function used?

Answer 11

The first stage of protein synthesis.

Question 12

When is tRNA’s function used?

Answer 12

The second stage of protein synthesis.

Question 13

What does RNA consist of?

Answer 13

Units called nucleotides.

Question 14

What are nucleotides made of in RNA?

Answer 14

A phosphate, a base and a ribose sugar.

Question 15

In RNA what are the four types of bases?

Answer 15

Adenine, Cytosine, Guanine and Uracil.

Question 16

What is the complementary base pair for Adenine in RNA?

Answer 16

Uracil.

Question 17

What is the complementary base pair for Cytosine in RNA?

Answer 17

Guanine.

Question 18

How are proteins made?

Answer 18

Proteins are made by joining together amino acids in a specific sequence.

Question 19

What does the protein produced by the protein synthesis rely on?

Answer 19

The order of amino acids which is dictated by the order/ sequence of the bases on the DNA.

Question 20

What are the two main stages of Protein synthesis?

Answer 20

Transcription and Translation.

Question 21

What are the stages of transcription?

Answer 21

1) The section of DNA which codes for the desired protein (gene) UNWINDS and UNZIPS.
2) This is carried out by an enzyme called RNA PLYMERASE.
3) Free nucleotides enter the nucleus and RNA POLYMERASE joins them with their complementary DNA base starting at the 3’ en.
4) Only one strand is copied.

Question 22

What is the strand of mRNA produced by transcription called?

Answer 22

The PRIMARY TRANSCRIPT.

Question 23

Why is only one gene transcribed to form mRNA?

Answer 23

So the PRIMARY TRANSCRIPT ONLY CODES FOR ONE PROTEIN.

Question 24

What does the primary transcript contain?

Answer 24

It contains regions which CODE for the production of the protein called EXONS and regions which are NON CODING which are called INTRONS.

Question 25

What are introns of the primary transcript?

Answer 25

INTRONS are NON CODING REGIONS which have to be REOMVED.

Question 26

What are exons of the primary transcript?

Answer 26

EXONS are CODING REGIONS and are joined together to form a MATURE TRANSCRIPT.

Question 27

What is DNA splicing?

Answer 27

DNA splicing is where INTRONS are REMOVED and the EXONS are joined together to form a MATURE TRANSCRIPT of mRNA.

Question 28

What happens once the mature transcript is produced?

Answer 28

The MATURE mRNA leaves the nucleus and enters the cytoplasm.

Question 29

What us the function of tRNA?

Answer 29

To pick up a specific amino acid and bring them to the ribosome.