C1 Gene expression

Question 1

What is DNA?

Answer 1

A double stranded polynucleotide that coils together to form a helix, which is joined together by It is the genetic material of al living organisms

Question 2

How are DNA nucleotides joined together?

Answer 2

By a condensation reaction to form a phosphodiester bond, making a long polymer chain

Question 3

Describe the transcription of DNA to RNA

Answer 3

1) The DNA helix unwinds and unzips as the hydrogen bonds between nitrogenous bonds break to expose the bases of the DNA nucleotides that make up a gene to act as a template strand
2) Only one chain of the DNA acts as a template
3) This unwinding and unzipping is catalysed by DNA helicase
4) Free mRNA nucleotides in the nucleus align opposite the template DNA strand and make temporary hydrogen bonds with their complementary bases, this is catalysed by RNA polymerase
(RNA uracil base pairs with adenine on DNA)
5) RNA polymerase bonds with RNA nucleotides by phosphodiester bonds
7) Pre-mRNA is spliced to form mRNA, splicing allows it to be small enough to leave the nucleus

Question 4

Describe splicing

Answer 4

Splicing is a process when introns are removed and exons are joined together by spliceosomes, this makes the mRNA small enough to leave the nucleus

Question 5

What are the four different nitrogenous bases in DNA?

Answer 5

Adenine, cytosie, guanine and thymine

Question 6

What are the complementary base pairs?

Answer 6

A binds to T, T to A, C to G and G to C

Question 7

What is a codon?

Answer 7

A series of 3 mRNA nucleotides that codes for an amino acid

Question 8

Describe the translation of RNA

Answer 8

1) mRNA attaches to the ribosome and the ribsome reads it until it finds start codon AUG
2) tRNA binds to the mRNA codon with the corresponding anticodon, UAC, forming temporary hydrogen bonds
3) A second tRNA molecule complementary to second codon, brings the next amino acid for it and binds to the second codon
4) Now two amino acids are held together, a peptide bond forms between them
5) Eventually a chain of a amino acids form the protein (polypeptide)
6) The chain of amino acids leaves the ribosome and can be modified into its functioning form

Question 9

What is a gene mutation and when does it happen?

Answer 9

A change in base sequence of a gene, it happens during DNA replication

Question 10

What is gene expression?

Answer 10

A process by which a gene produces its product and the product carries out its function

Question 11

What is transcription?

Answer 11

The process of making a copy of the genetic information stored in a DNA strand into a complementary strand of mRNA

Question 12

What is a gene?

Answer 12

A section of DNA on a chromosome that codes for a polypeptide

Question 13

What is an anticodon?

Answer 13

A group of three bases on a tRNA molecule that are complementary to an mRNA codon

Question 14

What is tRNA (transfer RNA)?

Answer 14

A type of RNA molecule that transfers amino acids to the ribosomes during protein synthesis

Question 15

What is translation?

Answer 15

A process by which mRNA is decoded and a polypeptide is produced

Question 16

What are the three types of mutations?

Answer 16

Deletion, substitution, insertion

Question 17

What is deletion mutation?

Answer 17

A mutation in which one or more pairs of nucleotides are removed from a gene

Question 18

What happens during substitution mutation?

Answer 18

A single base is replaced, potentially altering the gene product

Question 19

What happens during insertion mutation?

Answer 19

One or more nucleotides are added to a gene

Question 20

How mutation results in a non-functional protein?

Answer 20

Primary structure of the protein would alter which would change how the protein folds in the tertiary structure

Question 21

What would happen as result of mutation in a stop codon?

Answer 21

It results in a shorter polypeptide chain

Question 22

What are germline mutations?

Answer 22

DNA alterations occurring in gametes that can be transmitted to offspring

Question 23

What is a somatic mutation?

Answer 23

A mutation that occurs in the body cells. Cannot be inherited.