Genetics Pedigrees and Karyotypes

Karyotype

Karyotype What to look for in a karyotype? When analyzing a human karyotype, scientists first look for these main features: Are there 46 chromosomes? Are there 2 identical pairs of each autosome and 2 sex chromosomes? Are there any rearrangements between chromosomes or large deletions?

Chromosomes Humans have 46 chromosomes 44 chromosomes are autosomes 2 are sex chromosome Females have two X chromosomes Males have one X and one small Y chromosome

Pedigrees FEMALE MALE Half shaded means the person is not “affect”, but is a carrier of the disorder Shaded means the person is “affect” by a disorder Unshaded means the person is not “affect”

Pedigrees MARRIED THE SON & HIS WIFE THEIR KIDS THEIR KIDS

Inheritance of sex chromosomes Egg cells contain one X chromosome Sperm cells contain either one X chromosome or one Y chromosome So in a human population, half are male and half are female

Sex linked Genes Genes located on the sex chromosomes are called sex-linked genes. Males have just one X chromosome, so all X-linked alleles are expressed in Males

Sex-Linked Genes What percent of offspring will be girls? What percent of offspring will be boys? What percent of offspring will have normal vision? What percent of offspring will be colorblind? What percent of offspring will be carriers?

Hemophilia Pedigree

Chromosomal Disorders Nondisjunction

Chromosomal Disorders Down syndrome Trisomy 21 Due to non-disjunction in second stage of meiosis

Chromosomal Disorders Turner’s Syndrome What is missing? Karyotype is (45,X) Only one X chromosome

Chromosomal Disorders Klinefelter’s Syndrome What is extra? Karyotype 47 XXY Extra X chromosome