Key Area 3

Question 1

What are genes made of?

Answer 1

DNA

Question 2

Where are genes found?

Answer 2

On chromosomes inside the nucleus

Question 3

What does a gene carry the code for?

Answer 3

A protein

Question 4

What happens if a gene is expressed?

Answer 4

The protein that is coded for by that gene will be produced by the cell at a ribosome

Question 5

What 2 processes are involved in gene expression?

Answer 5

Transcription and Translation

Question 6

What 3 types of RNA are involved in transcription and translation?

Answer 6

mRNA (messenger)
rRNA (ribosomal)
tRNA (transfer)

Question 7

What does RNA stand for?

Answer 7

Ribonucleic Acid

Question 8

What is RNA?

Answer 8

A single stranded molecule composed of nucleotides

Question 9

What is an RNA nucleotide composed of?

Answer 9

Ribose Sugar
Phosphate
Base

Question 10

What are the 4 possible bases in RNA?

Answer 10

Adenine
Guanine
Cytosine
Uracil

Question 11

How are RNA nucleotides joined?

Answer 11

In the same way as DNA nucleotides - sugar phosphate backbone etc.

Question 12

What does mRNA do?

Answer 12

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

Question 13

How does mRNA carry the code from the nucleus to ribosome?

Answer 13

It is transcribed from DNA in the nucleus and translated into proteins by ribosomes in the cytoplasm

Question 14

What is a codon?

Answer 14

A triplet of bases

Question 15

What does each codon do?

Answer 15

Codes for a specific amino acid

Question 16

What does rRNA do?

Answer 16

Forms the ribosome along with proteins

Question 17

What is tRNA involved in?

Answer 17

The translation of mRNA into a polypeptide at a ribosome

Question 18

What do tRNA molecules do?

Answer 18

Carry specific amino acids to the ribosome where they are joined together to produce a polypeptide

Question 19

What is different about tRNA structurally?

Answer 19

It folds due to complementary base pairing

Question 20

What is an anti codon?

Answer 20

An exposed triplet of bases

Question 21

Describe the structure of tRNA

Answer 21

4 bits that stick out - amino attachment site at one end and anti codon at the other

Question 22

Describe Transcription

Answer 22

RNA polymerase moves to the area of the chromosome that contains the gene which is to be expressed

RNA polymerase unwinds the double helix and breaks hydrogen bonds between bases

RNA polymerase synthesizes a primary transcript of mRNA nucleotides by complementary base pairs

The process continues along the gene and the nucleotides are joined together

The mRNA primary transcript detaches from the DNA and is ready to undergo splicing

Question 23

What 2 regions do genes contain?

Answer 23

Coding and non coding

Question 24

What are coding regions called?

Answer 24

Exons

Question 25

What are non coding regions called?

Answer 25

Introns

Question 26

What process do exons and introns undergo to give the primary transcript?

Answer 26

Transcription

Question 27

What happens to introns during transcription?

Answer 27

They are removed

Question 28

What happens to exons during transcription?

Answer 28

They remain and will be expressed

Question 29

How are exons joined together?

Answer 29

Splicing

Question 30

What happens to the order of the exons during splicing?

Answer 30

It remains unchanged

Question 31

What happens to the mature transcript?

Answer 31

It leaves the nucleus and moves towards a ribosome for the process of translation

Question 32

What will be at the beginning of the mature transcript?

Answer 32

A specific sequence known as the start codon

Question 33

What will be at the end of the mature transcript?

Answer 33

A stop codon

Question 34

Where does translation begin?

Answer 34

The start codon

Question 35

Where does translation end?

Answer 35

The stop codon

Question 36

How is the genetic code translated into a sequence of amino acids?

Answer 36

Anti codons bond to codons by complementary base pairing

Question 37

How are amino acids joined together?

Answer 37

peptide bonds forming a polypeptide

Question 38

What happens to tRNA as the polypeptide is formed?

Answer 38

It leaves the ribosome

Question 39

What happens structurally to the polypeptide?

Answer 39

It will fold to create the 3D shape of a protein

Question 40

How is the polypeptide structure maintained?

Answer 40

Hydrogen bonding and other interactions between individual amino acids

Question 41

What does a protein's shape determine?

Answer 41

It's function

Question 42

What do proteins produced by a cell as a result of gene expression determine?

Answer 42

Our phenotype

Question 43

What is a phenotype?

Answer 43

Physical characteristics

Question 44

What other factors can influence phenotype?

Answer 44

Environmental factors such as diet, chemicals, and radiation

Question 45

How many genes are in the human genome?

Answer 45

25000

Question 46

how many types of protein can a human cell produce?

Answer 46

Over 1 million

Question 47

How is it possible for 1 gene to produce more than 1 protein?

Answer 47

Alternative Splicing

Question 48

What happens in Alternative splicing?

Answer 48

different combinations of exons can be included in the mature transcript, meaning different proteins are produced after translation