Genetic Changes
Mutations- any change in an organism’s
genetic material
•This can occur as a single base pair change or it
can involve an entire chromosome
•Mutations are almost always harmful, although
the harmful effects may not always be apparent
•EX. The skin of the Red Delicious apple became
green as a result of a mutation forming the
Golden Delicious apple
•A mutation that causes death is called a Lethal
Mutation
Gene Mutations
• A GENE MUTATION is the most common type
of mutation
– This is a permanent change in DNA.
– It occurs when there is a change in the sequence
of bases in the segment of DNA that makes up a
gene.
– It can range from a single to a large segment of
a chromosome.
– The effect of a mutation can differ greatly
Gene Mutation: Effects
• No effect- If a gene for eye color mutates in a
finger cell, or any other cell other than an eye
cell, the organism will not experience any
change
• Minor effects- a freckle or spot
• Major effect- skin cancer
Somatic and Germ Mutations
• Somatic mutation- mutations that occur in
body cells.
-These are not passed on to future generations,
so they do not affect the children
• Germ Mutations- mutations that occur in the
gametes (or reproductive cells)
– Germ Mutations are passed down
– Most are recessive so the offspring must have 2
genes to express the mutated gene
Chromosomal Changes
• Chromosomal change- this involves a change
in the number of chromosomes, the number
or the location of genes on a chromosome
– A chromosomal change, unlike other mutations,
does not directly involve the formation of
proteins, but can still change an organisms
expected traits
– Like gene mutations these may be somatic or
occur in the gamete (germ)
Chromosomal Changes
• Chromosomal changes generally occur in sets
• Diploid- having 2 sets for each gene,
chromosomes
– Humans have 2 sets of 23 chromosomes making
46 total
• Ploidy- changes in the number of sets of
chromosomes
Chromosomal Changes: Ploidy
• Seedless watermelons-have 3 instead of 2
sets of chromosomes
• Down Syndrome- a human disorder caused by
a change in ploidy
– There is a 3rd chromosome, one extra, on the 21st
(or 22nd) chromosome
– 47 instead of 46 chromosomes
Chromosomal Changes: Hemophilia
• Hemophilia is a genetic disorder.
– It is called the “bleeder’s disorder” because it
does not allow a person’s blood to clot, leaving a
person susceptible to bleeding to death.
– It occurs as a sex-linked gene, meaning it is carried
on the X chromosome
– Hemophiliacs are rare, 1 in 10,000 males
– Queen Victoria and her royal family were affected
by this disease
Hemophilia Chart
Royal Family Pedigree
Inherited Human Disorders
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Hemophilia- sex-linked
Duchenne muscular dystrophy- sex-linked
Red-green colorblindness- sex-linked
Tay-Sachs disease- recessive, chromosome 15
Cystic Fibrosis- recessive, chromosome 7
Malignant hyperthermia- Usually dominant
Achondroplasia- Dominant, chromosome 4
Achondroplasia
Cystic Fibrosis
Tay-Sachs Disease
Applied Genetics
• Selective breeding- man chooses organisms
with desirable traits and breeds them hoping
that the offspring will have those traits
– Inbreeding- mating of an organism with its close
relatives, or in plants, with itself
• Cross-breeding- method used to produce
organisms with desirable traits (hybridization)
– Breeding individuals from different varieties to
obtain the traits of both parents
Cross Breeding
• Santa Gertrudis cattle is a cross between the
Brahman and a Shorthorn
Biotechnology
• Genetic engineering
• Cloning
– Natural clones= identical twins
– Human genome project
Identical twins
Biotechnology