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