Human Chromosomes

Name Class Date

14.1 Human Chromosomes
Lesson Objectives
Identify the types of human chromosomes in a karotype.
Describe the patterns of the inheritance of human traits.
Explainhow pedigrees are used to study human traits.

Lesson Summary
Karyotypes A genome is the full set of all the genetic information that an organism carries in its DNA. Chromosomes are bundles of DNAand protein found in the nucleus of a eukaryotic cell. A karyotype is a picture that shows the complete diploid set of human chromosomes, grouped in pairs and arranged in order of decreasing size. Atypical human diploid cell contains 46 chromosomes, or 23 pairs:
Two of the 46 are the sex chromosomes that determine an individual’s sex: XX = female and XY = male. The X chromosome carries nearly10 times the number of genes as the Y chromosome.
The other 44 are autosomes, or autosomal chromosomes.

Transmission of Human Traits Human genes follow the same Mendelian patterns of inheritanceas the genes of other organisms:
Many human traits follow a pattern of simple dominance.
The alleles for many human genes display codominant inheritance.
Many human genes, including thegenes for blood group, have multiple alleles.
A gene located on a sex chromosome is a sex-linked gene. The genes on sex chromosomes show a sex-linked pattern of inheritance, since females have twocopies of many genes (located on X chromosomes) while males have just one.
In females, most of the genes in one of the X chromosomes are inactivated in each cell.

Human Pedigrees A chart used toanalyze the pattern of inheritance that shows the relationships in a family is a pedigree. Pedigrees can be used to determine the nature of genes and alleles associated with inherited human traits.THINK VISUALLY
Karyotypes
1. Make a sketch of a human karyotype. Number the chromosome pairs. Label autosomes and sex chromosomes.

214
Name Class Date

For Questions 2–8, write...