1. DNA 2. Gene 4. Genome 5. Individual 3. Chromosome 7. Population 6. Family (pedigree) Cell Human Genetics

A karyotype is a set of photographs of chromosomes grouped in ordered pairs.

Human Chromosomes We get 23 pairs of chromosomes. One set from our mom, and one set from our dad, for a total of 46 chromosomes.

Sex Chromosomes The first 44 chromosomes are known as autosomes. The last 2 are called sex chromosomes because they determine an individual’s sex. Females are XX. Males are XY.

What is the probability that a newborn will be male or female? XX XY Female (XX) X X X Male (XY) Y

1 2 A pedigree is a chart that shows the relationships within a family.

Circle = female Square = male Horizontal line connecting a male and female = marriage Vertical line and a bracket connect the parents to their children Half-shaded circle or square = person is a carrier of the trait Completely shaded circle or square = person expresses the trait. Circle or square that is not shaded = person neither expresses the trait nor is a carrier of the trait. Section 14-1 Figure 14-3 A Pedigree Understanding a Pedigree

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Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II Section 14-2 Nondisjunction Nondisjunction is an error in meiosis in which chromosomes fail to separate

Chromosomal Disorders Monosomy occurs when one chromosome from a pair is missing. Trisomy occurs when there is an extra, or third, chromosome for one pair.

Trisomy 21 (Down’s Syndrome)

Trisomy XXY (Klinefelter’s Syndrome)