DNA

DNAGenetic Changes

Chapter 11.3

Mutations – any change in the nucleotides of a DNA sequence

Effects of mutations: • Mutations in

body cells – cause problems

for individual – effects all new

cells after cell division

• Mutations in reproductive cells: – become a part of

the genetic makeup of the offspring

– Passed on to children

Types of Mutations

• Point Mutation-change in a single base-Could change an amino acid-May then change structure and/or function of entire protein

Point Mutation

DNA template strand

Point Mutation example: Sickle

Cell Anemia

Frameshift MutationA single base is added or deleted from a DNA strand

- Causes a one base shift in the reading of codons

- Changes all the amino acids after the mutation

Frameshift mutation

Frameshift Mutation - HIV resistance

• Deletion of single nucleotide in CCR5 gene• Problem with the immune cell receptor that

HIV recognizes- HIV can’t recognize cell and infect it

• However, the mutation also affects the normal function of the immune cells

Therefore it is both beneficial and detrimental.

Sentence Analogies

• Point mutation: single change in a nucleotide

THE SUN WAS HOT

THE SON WAS HOT

• Frameshift mutation: addition or deletion of nucleotide that affects all the amino acids after.

THE SUN WAS HOT

THE ESU NWA SHO T - added letter E

THS UNW ASH OT - deleted letter E

Chromosomal Mutations

• Parts of chromosomes break or are lost during mitosis or meiosis

• Parts rejoin wrong (backwards or on different chromosomes)

• Common in plants

Example: Cri du Chat (Cat Cry Syndrome)

–Missing part of Chromosome 5

Causes of Mutations

• Spontaneous: Natural

• Environmental Factors:

Mutagen – any agent that can cause a change in DNA – Radiation (X rays, ultraviolet

rays, nuclear)– Chemicals (dioxins, asbestos)– Viruses

Protection: some enzymes that can repair DNA have evolved

Stopping Point

Protein Synthesis animation