Chromosome Mutations

What’s SUPPOSED to happen:  Crossing over (Homologous chromosomes exchange genes)  2 divisions result in genetically unique cells  Each cell has HALF the # of chromosomes as the original cell (1 Diploid  4 Haploid)

Review:  Mutations are changes in DNA  Mutations can happen to 1.Individual genes 2.Chromosomes  This would effect MANY genes  May occur in gametes (eggs & sperm) and be passed to offspring Original Gene: ATC Mutated Gene: AGC

Mutations can happen randomly, but can also be caused by:

Chromosomal mutations are almost always harmful!  Why?  MANY genes are affected  These mutations happen during meiosis  As a result, gametes will have abnormal chromosomes  The child will inherit these abnormal chromosomes through sexual reproduction

Types of Chromosome Mutations

Chromosome Mutation Animation

Nondisjunction  Failure of chromosomes to separate during meiosis  Causes gamete to have too many or too few chromosomes  Most common cause of chromosome disorders

Karyotyping Investigation  You and your partner will play the role of Genetic Counselors.  Your job is to analyze the chromosomes of the baby and determine what chromosomal disorder it has.  You will cut out the chromosomes and match them. Same length Similar pattern of genes

Down Syndrome (Trisomy 21)  Short, broad hands  Stubby fingers  Impotency in males  Cognitive Impairment  Small round face  Protruding tongue  Short Lifespan  1 in 1,250 births  47 chromosomes  3 #21 chromosomes

Turner Syndrome  Short Stature  Premature ovarian failure (many will not complete puberty)  Hypothyroidism  Kidney abnormalities  Heart abnormalities  Chronic ear infections  1 in 2,500 births  45 chromosomes  (one sex chromosome  X)  Female

Klinefelter Syndrome  1 in 1,100 births  47 Chromosomes  XXY  Male  Scarce beard  Longer fingers and arms  Sterile  Delicate skin  Cognitive impairment  Normal lifespan