DNA and Mutations

Mutation Facts #1-5 • Write down five facts about mutations as we go

through the following videoclips • Video 1• Video 2 – Repair• Video 3 – Repair• Addition and Deletion Mutations

What is a Mutation? • change in the DNA code• Lead to frameshifts – the message is no longer

correctly passed • Protein Outcomes:• 1. changed – different from the original• 2. no change - silent mutations• 3. incomplete - amino acid is changed to a

"stop" codon

3 Types of Mutations:• 1. Substitution - one

base for another• Sickle-cell Anemia• GAG into GUG• Valine becomes

glutamic acid

• 2. Insertion - extra bases

• Huntington's disease – CAG repeat

• fragile X syndrome – CGG repeat

Fragile X syndrome• triplet CGG is repeated

(CGGCGGCGGCGG, etc.).• repeats as few as 5 or as many

as 50 will not cause harm. Even 100 repeats usually cause no harm.

• longer repeats have a tendency to grow longer from one generation to the next (as many as 4000 repeats).

• 3. Deletion - a section of DNA is lost, or deleted.

• Duchenne Muscular Dystrophy (DMD)

• DMD gene codes for dystrophin (protein)

• protein holds skeletal muscle cells together - missing in DMD

Mutations lead to Genetic Disorders

• One Wrong Letter - Tay Sachs • Finding Cures is Hard - Cystic Fibrosis

Chromosome Disorders • Chromosome: Coiled DNA and proteins

Chromosome Arrangement

• Called a Karyotype• Receive one from

mom, one from dad, they are homologs

Chromosome 21“Trisomy 21’

Down Syndrome

Kleinfelter’s syndrome - XXY• Male• Develop some breast

tissue• Little body hair • typically tall• Infertility results - no

sperm

Turner’s Syndrome – X• No Y means Turner’s

people are female. • no ovaries develop don’t undergo puberty and they are sterile.

• Hormone treatment cures all but the sterility.

• Other symptoms: short stature, webbed skin and low hairline at the neck

Mutations – good or bad?• Discuss with your lab partner.

Reflection

1. DNA codes for proteins. If DNA is mutated, how might this cause a disease? (Connect proteins to disease).

2. How is it possible for two identical twins, with identical DNA sequences, have different traits – for instance one gets cancer and one does not.

What is Epigenetics?

• the study of changes in phenotype (appearance) or gene expression caused by mechanisms other than changes in the DNA