DNA and Mutations
Mutation Facts #1-5
• Write down five facts about mutations as we go
through the following videoclips
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•
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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
Down Syndrome
Chromosome 21
“Trisomy 21’
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