Post on 18-Jan-2016
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MUTATIONS
Mutations Changes to DNA are called mutations
change the DNA changes the mRNA may change protein may change trait
DNA TACGCACATTTACGTACG
mRNA AUGCGUGUAAAUGCAUGC
aa aa aa aa aa aa aaprotein
trait
What Causes Mutations?
There are two ways in which DNA can become mutated: Mutations can be inherited.
Parent to child Mutations can be acquired.
Environmental damage Mistakes when DNA is copied
Are Mutations Helpful or Harmful?
Mutations happen regularly
Almost all mutations are neutral
Chemicals & UV radiation cause mutations
Many mutations are repaired by enzymes
Are Mutations Helpful or Harmful?
Some type of skin cancers and leukemia result from somatic mutations
Some mutations may improve an organism’s survival (beneficial)
Types of Chromosomal
Mutations
Chromosome Mutations
May Involve: Changing the structure of a chromosome
Changing the number
Chromosome Mutations
Five types exist: Deletion Inversion Duplication Translocation Nondisjunction
Deletion
Due to breakage A piece of a
chromosome is lost
ABCD-EFGH ABCD-EF
Inversion
Chromosome segment breaks off
Segment flips around backwards
Segment reattaches
ABCD-EFGH ABDC-EFGH
Duplication
Occurs when a gene sequence is repeated
ABCD-EFGH ABCDBCD-EFGH
Translocation
Involves two chromosomes that aren’t homologous
Part of one chromosome is transferred to another chromosomesABCD-EFGH WXY-Z ABCD-EF WXY-ZGH
Translocation
Nondisjunction
Failure of chromosomes to separate during meiosis
Causes gamete to have too many or too few chromosomes
Disorders: Down Syndrome – three 21st chromosomes Turner Syndrome – single X chromosome Klinefelter’s Syndrome – XXY chromosomes
Chromosome Mutation Animation
Chromosome Mutations
Down Syndrome Chromosome 21 does
not separate correctly. Trisomy 21
They have 47 chromosomes in stead of 46.
Children with Down Syndrome develop slower, may have heart and stomach illnesses and vary greatly in their degree of intelligence.
Similar facial features
Chromosome Mutations
Cri-du-chat Deletion of material on 5th
chromosome Characterized by the cat-
like cry made by cri-du-chat babies
Varied levels of mental handicaps
Sex Chromosome Abnormalities
Klinefelter’s Syndrome XXY, XXXY Male Sterility Small testicles Breast enlargement
Sex Chromosome Abnormalities
XYY Syndrome Normal male traits Often tall and thin Associated with antisocial and behavioral
problems*
Sex Chromosome Mutations
Turner’s Syndrome X Female sex organs don't
mature at adolescence
sterility short stature
Sex Chromosome Mutations
XXX Trisomy X Female Little or no visible differences tall stature learning disabilities limited fertility
KARYOTYPE ANALYSIS
Karyotype Pictures of paired
human chromosomes arranged by size, used to identify abnormalities in fetuses
Cells from an amniotic fluid sample are cultured, stained & photographed
1) Autosomes all the chromosomes
except the sex chromosomes (in humans, there are 22 pair)
2) Sex chromosomes The sex-determining
chromosomes, the X & Y
Normal MaleNormal Male
282n = 46
Normal FemaleNormal Female
292n = 46
Male, Trisomy 21 Male, Trisomy 21 (Down(Down’’s)s)
302n = 47
Female DownFemale Down’’s Syndromes Syndrome
312n = 47
KlinefelterKlinefelter’’s Syndromes Syndrome
322n = 47
TurnerTurner’’s Syndromes Syndrome
332n = 45