Mutations

Question 1

What is a mutation?

Answer 1

Change in the genetic code of an allele

Question 2

How can mutations happen?

Answer 2

As cells divide (for growth, repair, maintenance) and miss checkpoints during mitosis

Question 3

What can mutations be caused by?

Answer 3

• Environmental agents
• Chemicals
• Errors in the genetic code

Question 4

What can mutations be?

Answer 4

Negative, positive or neutral

Question 5

What are the two main types of mutations?

Answer 5

-Point Mutations
-Chromosomal Mutations

Question 6

What are Point Mutations?

Answer 6

Failure by the replicating cell to copy the genetic information accurately:
-Base pair substitutions
- Insertions
- Deletions

Question 7

What are the three types of Point Mutations? Describe them.

Answer 7

• Base-pair Substitutions
  One nitrogenous base is accidentally replaced with a different base
• Insertions
  One or more nitrogenous bases is inserted during the copying process
• Deletions
  One or more nitrogenous bases is deleted during the copying process

Question 8

What are chromosomal mutations?

Answer 8

Errors that involve an entire chromosome or large part of a chromosome

Question 9

What is an example of a chromosomal mutation? What are examples of those?

Answer 9

Non-disjunction
- Down Syndrome
- Short stature
- Heart defects
- Developmental delays

Question 10

What are other examples of Chromosomal Mutations?

Answer 10

• Large scale deletions, insertions, or inversion (flipping) of entire portions of a chromosome (contain thousands of bases).

Question 11

Where do most mutations occur?

Answer 11

In the parts of the DNA that do not code for genes

Question 12

What happens to many mutations that occur?

Answer 12

They are often quickly repaired, but as organisms age, mitosis occurs more frequently leading to higher chance of mutations (cancer)

Question 13

Where do the mutations occur that are not passed on to offspring?

Answer 13

In body cells (autosomes)

Question 14

Where do the mutations occur that can be passed on to offspring? Why does this happen? (3 points)

Answer 14

• In sex cells (gametes)
• DNA that mutates in the egg or sperm becomes part of the DNA in the zygote if fertilization takes place
• This means that the new individual will have a copy of the mutation in every cell of its body and will be able to pass the mutation on

Question 15

What happens if a mutation is dominant?

Answer 15

• Could be expressed phenotypically in the 1st generation
• i.e. Huntington’s disease

Question 16

What happens if a mutation is recessive?

Answer 16

• Likely will not be expressed for many generations until by chance, two individuals with same mutation produce a homozygous recessive mutation in the offspring
  -Cystic Fibrosis

Question 17

Describe the mutation of Sickle-Cell Anemia

Answer 17

• Both harmful and beneficial
• Inherited a mutated gene where adenine is substituted by thymine
• Red blood cells (usually round) become C-shaped (causes movement through blood vessels to be obstructed)
• Blood flow is impaired and cells must be removed and destroyed
• Can be painful, increased risk of infection
• SCA can also have a positive property as well
• Fighting malaria
• Malaria parasite enters the blood, but since the person is affected by SCA, the cells sickle when oxygen is low and cells are destroyed

Question 18

Describe the mutation of Lactose Intolerance and Tolerance

Answer 18

• Lactose tolerant individuals contain a mutation and will continue to produce the enzyme for digestion
• All individuals are born lactose intolerant

Question 19

What are spontaneous mutations?

Answer 19

• Happen by accident in nature
• Result of incorrect copying of DNA during mitosis and meiosis

Question 20

What are induced mutations?

Answer 20

• Result of exposure to a physical or chemical agent
• Cigarette smoke, radiation