8.7 Mutations

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Transcript 8.7 Mutations

8.7 Mutations
KEY CONCEPT
Mutations are changes in DNA that may or may not
affect phenotype.
8.7 Mutations
Mutations
Caused by errors in
• Replication, transcription, cell division, or by external
factors
Germ-cell mutation – occurs in a gamete
• Does not affect the individual but may be passed on to
offspring
Somatic mutation – occurs in a body cell
• Will affect the individual but are not passed on to
offspring
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Lethal Mutations
• Cause death, often before birth
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Gene Mutations
1. Point mutation – substitutes, adds or deletes a single
nucleotide
mutated
base
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Gene Mutations
2. Frame Shift Mutation
• Deletion & addition point mutation cause the remaining
codons to be incorrectly grouped
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Chromosome Mutations
1. Deletion – loss of a piece of a chromosome due to
chromosomal breakage
2. Inversion – chromosomal segment breaks off and then
reattaches in reverse order to the same chromosome
– Orig: ATAGCTA
– Inv:
ATCGATA
3. Translocation – chromosome piece breaks off and
reattaches to another non-homologous chromosome
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4. Nondisjunction – failure of homologous
chromosomes to separate properly during meiosis
Two possible outcomes:
1. Trisomy - Three copies of chromosome
• One gamete has two copies
• Zygote = 3 copies of chromosome
2. Monosomy - One copy of chromosome
• One gamete has no copies
• Zygote - 1 copy of chromosome
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7.4 Human
Genetics and Pedigrees
KEY CONCEPT
A combination of methods is used to study human
genetics.
13.1
Ecologists
Study
Relationships
7.4 Human
Genetics and
Pedigrees
Pedigree – family record that shows how a trait is inherited
over several generations
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Mutations
7.4 Human
Genetics and Pedigrees
Pedigrees
Circles  Girls
Squares  Boys
Carrier – individual with one copy of a recessive allele
• Usually do not express the trait but can pass it along to
offspring
• ½ colored in
• Ex: Autosomal  Hh
Sex-linked  XHXh
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7.4 Human
Genetics and Pedigrees
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Mutations
7.4 Human
Genetics and Pedigrees
• Karyotypes can show changes in chromosomes.
– deletion of part of a chromosome or loss of a
chromosome
– Some translocation changes in chromosomes
– extra chromosomes or duplication of part of a
chromosome
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Mutations
7.4 Human
Genetics and Pedigrees
Detecting Human Genetic Disorders
• Genetic screening – examination of a person’s genetic
makeup
• Genetic counseling – medical guidance that informs
about possible problems that could affect their offspring
Prenatal testing
• Amniocentesis – removes a small amount of amniotic
fluid between the 14th
and 16th week of pregnancy
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7.4 Human
Genetics and Pedigrees
Chorionic villi sampling
• Physician obtains a sample of the chorionic villi
• Tissue that grows between the mothers uterus and the
placenta, between the 8th and 10th week of pregnancy
13.1
Ecologists
5.3 Regulation
of CellStudy
Cycle Relationships
Cancer
Tumor – abnormal group of cells
that result from uncontrolled,
abnormal cell division
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5.3 Regulation
of Cell Cycle
– Benign - tumors remain clustered and can be removed.
– Malignant - uncontrolled dividing cells invade and
destroy healthy tissues elsewhere in the body
– Metastasize - spread of cancer cells beyond their
original site
normal cell
cancer cell
bloodstream
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5.3 Regulation
of Cell Cycle
Kinds of Cancer – based on types of tissue that affect
• Carcinomas – grow in the skin and tissues that line
organs. Ex: lung cancer & breast cancer
• Sarcomas – grow in bone and muscle tissue
• Lymphomas – solid tumors that grow in the tissues that
form blood cells
– Leukemia – tumors that form in blood-forming tissue –
over production of white blood cells
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5.3 Regulation
of Cell Cycle
Causes of Cancer
• Carcinogen – substance that increases the risk of
developing cancer Ex: tobacco, asbestos, X-rays, or UV
rays from sun
• Mutagen – cause mutations to occur within a cell that
leads to cancer
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5.3 Regulation
of Cell Cycle
• Standard cancer treatments typically kill both cancerous
and healthy cells.
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5.3 Regulation
of Cell Cycle
Oncogenes – gene that causes cancer
• Proto-oncogene – normal gene that control cell’s growth.
When mutated  oncogene
• Tumor-suppressor gene – code for proteins to prevent
uncontrolled cell division. When mutated  cancer
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5.3 Regulation
of Cell Cycle
Viruses & Cancer
• Viruses can stimulate uncontrolled cell division
• Cause mutations in proto-oncogenes & tumor suppressor
genes
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How do Cancer cells behave differently from Healthy
ones
• http://www.youtube.com/watch?v=BmFEoCFDiw&list=PLJicmE8fK0Ehrg3meytY7DT8LJiwuU3Th&index
=92
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5.3 Regulation
of Cell Cycle
Cancer Prevention
• Diet high in fiber and low in fat
• Fruits & vegetables are high in fiber
• Vitamins & minerals: carotenoids, vitamins A, C, and E,
and calcium
• Daily exercise
• And lowering exposure to carcinogens (tobacco, UV
rays)