Mutation

Question 1

Genetic Variation Is Due to Mutations

Answer 1

• Occurs between each of us as members of our species
• Occurs between different species
• Mutations are the source of genetic variation.
  Mutations occur during DNA replication or DNA damage.
• Mutation– any inheritable change in nucleotide sequence is a
  mutation.
  The genetic change must be replicated during DNA replication and passed on during cell division to be inherited.
  ⁻ Otherwise, there is still the opportunity for DNA repair to occur a mutation requires DNA replication of the change and cell division for inheritance by daughter cells.

Question 2

Point Mutations

Answer 2

Changes in a Single Nucleotide

Question 3

Single Base-Pair Changes can be
Synonymous = Silent Mutations

Answer 3

No Change in the amino acid sequence

Question 4

Single Base-Pair Changes can be
Nonsynonymous Mutation

Answer 4

Changes in one amino acid in the sequence

Question 5

Nonsense Mutations: create stop codons

Answer 5

Question 6

Insertions and Deletions (Indels)
* Insertions or deletions of one or
two base pairs change the
reading frame. Frameshift
* An in-frame insertion or deletion
of three base pairs can result in
the addition or deletion of an
amino acid.

Answer 6

Question 7

Cystic Fibrosis:
Example of an In-frame
Deletion

Answer 7

Question 8

Transposable Elements (TE)

Answer 8

Question 9

13.4 Chromosomal Level Mutations

Answer 9

Question 10

Example of chromosome breaks and translocation:
Philadelphia Chromosome results in leukemia

Answer 10

Question 11

13.5 DNA damage
How do mutations occur? Major types of DNA damage

Answer 11

Question 12

13.5 DNA Repair: Our cells have several mechanisms
to Repair and Restore to original DNA sequence

Answer 12

There are many different repair mechanisms that prevent mutations.
***Most important is the proof reading ability of DNA polymerase. (99%)
Some mechanisms restore DNA to its original sequence.
* Some will reverse the damage, which is TRUE repair.
* Some will remove the damaged or incorrect nucleotide and replace with
the correct one.

Question 13

DNA Repair: Our cells have several mechanisms
to Repair and Restore to original DNA sequence

Answer 13

Some will remove and replace.
1. Post-replication Mismatch Repair—2nd chance to
correct replication errors (segment of DNA is
removed). Mismatch will distort the DNA shape.
2. Base Excision Repair—corrects damaged bases (single
nucleotide is removed)

Question 14

Mismatch Repair versus Base Excision Repair

Answer 14

Question 15

Genotype versus Phenotype: Key Terms

Answer 15

• Genotype refers to the genetic makeup of a cell or an organism. ⁻ It is estimated that 1/1000 nucleotides differs between each of us.
• Polymorphism –any genetic difference among individuals in a population. (specific sites in specific genes)(common changes as occurs in multiple individuals)* Alleles are different versions of the same gene. They have differences in their nucleotide sequences. In general, you have two alleles per gene, one on each
  chromosome.
  ⁻ Homozygous means you have the same version in both alleles of a gene, so exactly two copies of the same nucleotide sequence.
  ⁻ Heterozygous means you have two different versions of a gene in your alleles, so two different
  nucleotide sequences.
• Phenotype is the observable trait. It is the expression of the genotype.
  ⁻ Due to genotype and influenced by environment. Example in b-globin (HBB)

Question 16

Polymorphisms and Alleles

Answer 16

Question 17

Genetic differences can be

Answer 17

• Neutral—Do not affect survival or reproduction ⁻ Example: Being able to taste specific things or not.
• Harmful—Has observable characteristics that decrease survival and/or reproduction.
  ⁻ Example Huntington’s Disease
• Beneficial—Helps us survive or be more successful in some way ⁻ Example of persistence of lactase expression
• Harmful and Beneficial
  Example: mutations in HBB that cause Sickle Cell Disease
  ⁻ Harmful: painful and life-threatening vaso-occlusive crises
  ⁻ Beneficial: protection from the malaria
• The impact of mutations can be dependent on the environment.
  ⁻ persistence of lactase expression
  ⁻ being an HBB A/S heterozygote in countries that have malaria.

Question 18

Germ-line versus Somatic mutations