Patterns of Chromosome Inheritance Chapter 24

Karyotyping Karyotype Chromosomal aberration Size-ordered chart of the metaphase chromosomes of an individual cell Chromosomal aberration A mutation that is large enough to see under a light microscope

Amniocentesis

Chorionic villi sampling

Normal male karyotype

Down syndrome karyotype

Changes in Chromosome Number Nondisjunction Result after fertilization: Trisomy Monosomy

Nondisjunction in Meiosis I

Nondisjunction in Meiosis II

Down Syndrome

Changes in Sex Chromosome Number Y chromosome-determines maleness. SRY gene produces a testis-determining factor Caused by non-disjunction

Non-disjunction in Sex Chromosomes Y chromosome-determines maleness. Results of non-disjunction?: XXX XXY XYY X0 0Y Survivable with problems Survivable with problems Survivable with problems Survivable with problems Lethal

Non-disjunction in Sex Chromosomes Turner Syndrome --XO Klinefelter Syndrome—XXY Poly-X Females---XXX Jacobs Syndrome---XYY

Changes in Chromosome Structure Mutation– a permanent genetic change. Chromosome mutation--change in chromosome structure. Types: Inversion Translocation Deletion Duplication

Deletion

Duplication

Translocation

Inversion

WHAT’S HAPPENING??

Sex-Linked Traits Traits controlled by genes on the X or Y chromosomes are sex-linked although most are unrelated to gender. An allele on the X chromosome that is in the region where the Y chromosome has no alleles will express even if recessive; it is termed X-linked. A female would have to have two recessive genes to express the trait; a male would only need one.

X-Linked Alleles The key for an X-linked problem shows the allele attached to the X as in: XB = normal vision Xb = color blindness. Females with the genotype XBXb are carriers because they appear to be normal but each son has a 50% chance of being color blind depending on which allele the son receives. XbXb and XbY are both colorblind.

Cross involving an X-linked allele

X-linked recessive pedigree chart

X-Linked Disorders Red-green color blindness Muscular dystrophy. Hemophilia.

http://perth. uwlax. edu/faculty/howard/BIO101/DNA&translation/sld002 http://perth.uwlax.edu/faculty/howard/BIO101/DNA&translation/sld002.htm

Diana http://brie.medlabscience.med.ualberta.ca/de/genetics/70gen-hemophil.html

Chapter Summary Humans - 22 pairs of autosomes and one pair of sex chromosomes Abnormalities of chromosome number or composition. Males - XY Females -XX. Chromosomal mutations Sex-linked traits