Mutations 1 Base Mutations 2 Chromosomal Mutations What

Mutations 1) Base Mutations 2) Chromosomal Mutations

What Are Mutations? l Changes in the nucleotide sequence of DNA l May occur in somatic cells (aren’t passed to offspring) l May occur in gametes (eggs & sperm) and be passed to offspring

Are Mutations Helpful or Harmful? l Mutations happen regularly l Almost all mutations are neutral l Chemicals & UV radiation cause mutations l Many mutations are repaired by enzymes

Are Mutations Helpful or Harmful? l Some type of skin cancers and leukemia result from somatic mutations l Some mutations may improve an organism’s survival (better adapted to environment, therefore beneficial)

Types of Mutations

1) Base (Gene) Mutations -A base mutation is a change in DNA sequence (order of nucleotides). -Mutations are important because they increase genetic variation.

Mutations in Body Cells -Mutations in body (somatic) cells cannot be passed on to your children, however, they can cause cancer or other problems in your body. A cancer cell.

Cancer as a result of mutations in body cells: A person with skin cancer-This is why it’s important to always wear sunscreen!

Cancer as a result of mutations in body cells: Tongue cancer and lung cancer are often caused by changes in body cells as a result of smoking, so don’t smoke!!!

Mutations in Reproductive (Germ) Cells -Mutations in germ (sex) cells can lead to changes in the DNA sequence which will can be passed down to a person’s children.

Good vs. Bad Mutations can be good as well as bad. A good mutation could lead to a change in a protein that allows an animal to run faster or see better. A bad mutation could lead to a change in a protein that causes a genetic disease such as Sickle Cell Anemia or Hemophilia.

Mutagens l A mutagen is something that causes a mutation. Ex: radiation, chemicals.

Chernobyl

Base (Small-Scale) Mutations l There are 2 main types of small scale mutations.

1. Point mutation -Point mutation- change in one base pair in a DNA sequence (substitution). -A point mutation cause an amino acid to change, which may change the structure of the protein being made. Example: AUG=Met AAG=Lys -Only one letter was changed (the A to a U) and one amino acid changed (from methionine to lysine). -Point Mutations- AT MOST, one amino acid changes. -QUESTION: Can a point mutation occur without changing an amino acid? ANSWER: Yes- called a silent mutation -Point mutations, in general, have the least consequences. But there are some exceptions…

Picture of A Point Mutation m. RNA Normal Protein Stop Replace G with A m. RNA Point mutation Protein Stop

Point mutations in our lives! -Sickle cell anemia is a blood disease caused by a point mutation. -A single nucleotide is changed from “A” to “T” which causes the amino acid to change from glutamic acid to valine: Amino acids: Thr – Pro – Glu Normal: ACT CCT GAG Sickle cell: ACT CCT GTG GAG Amino acids: Thr – Pro – Val – Glu

Point mutations in our lives! -People with sickle cell anemia often experience a lot of pain and swelling and have trouble exercising. thly o. o d o s sm l cell ots. e v a o cl m m d r t o o o n like n se bl d ells ssels d cau c e kl od ve ck an c i S Sickle cells also can’t carry blo et stu h g g u s Oxygen as effectively as normal thro le cell k Cells. Sic

2. Frameshift mutation -Frameshift mutation-adding or deleting nucleotides to a DNA sequence. -A frameshift mutation is usually worse than a point mutation because it causes the entire DNA sequence to be shifted over, so many amino acids are affected! Example: DNA: ATTAAACCG Delete this T ATAAACCG

V. Frameshift mutation Deletion of U Frameshift mutation m. RNA Protein

Frameshift Mutations l Crohn’s Disease is caused by a frameshift mutation. l It causes inflammation to the digestive tract.

Point mutation and Frameshift mutations

Questions: Is this a point mutation or a frameshift mutation? -It’s a point mutation because only one nucleotide changed!

Questions: THE CAT ATE THE RAT THE CAR ATE THE RAT Point or frameshift?

Questions THE DOG BIT THE CAT THE DOB ITT HEC AT Point or frameshift?

2) Chromosome Mutations

Chromosome Mutations l May Involve: l Changing the structure of a chromosome l The loss or gain of part of a chromosome, usually during cell division

Chromosome Mutations l Four types: l Deletion l Inversion l Translocation l Duplication

Deletion l Due to breakage l A piece of a chromosome is lost during cell division

Inversion l Chromosome segment breaks off l Segment flips around backwards l Segment reattaches

Duplication l Occurs when a gene sequence is repeated

Translocation l Involves two chromosomes that are NOT homologous l Part of one chromosome is transferred to another chromosome l Ex- part of c’some #1 translocated to c’some #2

Translocation

Chromosome Mutation Animation