Effects and causes of mutations

Question 1

When do mutations have no effect?

Answer 1

there is no effect on the phenotype of an organism because normally functioning proteins are still synthesis

Question 2

When are mutations damaging?

Answer 2

• the phenotype of an organsim is affected in a negative way
• protein are:
  
  • no longer synthesis
  • non-functional
• can interefere with one or more essential processes

Question 3

Whne are mutations beneficial?

Answer 3

• very rarely a protein is snythesised that results in new and useful characteristic in the phenotype

Question 4

How do mutations occur?WHat increases the risk of them?

Answer 4

• can occur spontaneously, often during DNA replications
• rate of mutation is increased by mutagens
  
  • mutagens is a chemical, physical, or biological agent which causes mutations

Question 5

What occurs spontatenously?

Answer 5

depurination or depyrimidation

loss of base

can lead to insertion of an incorrect base through complementary base pairing during DNA replication

Question 6

How do free radicals cause mutations?

Answer 6

• free radicals, which are oxidising agents, can affect the structure of nucleotides
• also disrupt base pairing during DNA replications

Question 7

How is the risk of mutations from free radicals reduced?

Answer 7

• antioxidants
  
  • vitamin A, C and E
  • anticarcinogens becuase of their ability to negate the effects of free radicals

Question 8

What are some physical mutagen? What effect do they have?

Answer 8

ionising radiations such as X-rays

break one or both DNA strands - some breaks can be repaired but mutations can occur in the process

Question 9

What are some chemical mutagens and how do they work?

Answer 9

deaminating agents

chemically alter bases in DNA such as converting cystosine to uyracil in DNA, changing the base sequence

Question 10

What are some biological agents?

Answer 10

• alkylating agents
  
  • methyl or ethyl groups are attached to bases
  • resulting in the incorrect pairing of bases during replication
• base analogs
  
  • incorporated into DNA in place of the usual base during replication
  • changing the base sequence
• viruses
  
  • viral DNA may insert itself into a genome
  • changing the base sequence

Question 11

WHere do silent mutation occur>

Answer 11

• occur in the non-coding regions of DNA (introns)
• or code for the same amino acid due to the degenerate nature of the genetic code
• may also result in changes to the primary strucutre but do not change the ovarall structure of the functions of the proteins synthesised