1. 14–1 Human Heredity 14-1 Human Heredity
Photo credit: Richard Hutchings/Photo Researchers, Inc.

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Human Chromosomes
Human Chromosomes
Cells are photographed during mitosis. Scientists then cut out the chromosomes from the photographs and group them together in pairs.
A picture of chromosomes arranged in this way is known as a karyotype.
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Human Chromosomes
Human Karyotype
These human chromosomes have been cut out of a photograph and arranged to form a karyotype. Photo credit: ©CNRI/Science Photo Library/Photo Researchers, Inc.
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Human Chromosomes
Two of the 46 human chromosomes are known as sex chromosomes, because they determine an individual's sex.
Females XX
Males XY
The remaining 44 chromosomes are known as autosomes.
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Human Chromosomes
How is sex determined?
Males and females are born in a roughly 50 : 50 ratio
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Human Traits
Pedigree Charts 
A pedigree chart shows the relationships within a family.
Genetic counselors analyze pedigree charts to infer the genotypes of family members.
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Human Traits
A square represents
a male.
A circle represents
a female.
A vertical line and a bracket connect the parents to their children.
A horizontal line connecting a male and a female represents a marriage.
A shaded circle or square indicates that a person expresses the trait.
A circle or square that is not shaded indicates that a person does not express the trait.
This drawing shows what the symbols in a pedigree represent.
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9. Dominant trait (widow’s peak)
LE 14-14a Ww ww WW or
No widow’s peak
Third
generation
(two sisters)
Widow’s peak
Second generation
(parents plus aunts
and uncles)
First generation
(grandparents)
Dominant trait (widow’s peak)

10. Recessive trait (attached earlobe)
First generation
(grandparents) Ff
FF or Ff ff
Second generation
(parents plus aunts
and uncles)
Third
generation
(two sisters)
Attached earlobe FF or
Recessive trait (attached earlobe)
LE 14-14b
Free earlobe

11. X-Linked Recessive Inheritance

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Human Genes
Blood Group Genes
The best known blood groups are the ABO blood groups and the Rh blood groups.
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Human Genes
The Rh blood group
The positive (Rh+) allele is dominant, Rh+/Rh+ or
Rh+/Rh are Rh-positive.
Rh- alleles are Rh-negative.
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Human Genes
ABO blood group
There are three alleles for this gene, IA, IB, and i.
Alleles IA and IB are codominant.
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Human Genes
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Human Genes
This table shows the major symptoms of some well-known genetic disorders.
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Human Genes
This table shows the major symptoms of some well-known genetic disorders.
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Human Genes
Codominant Alleles
Sickle cell disease is a serious disorder caused by a codominant allele.
Sickle cell is found in about 1 out of 500 African Americans.
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From Gene to Molecule
Malaria and the Sickle Cell Allele
The map on the left shows where malaria is common. The map on the right shows regions where people have the sickle cell allele.
Regions where malaria is common
Regions where the sickle cell allele is common
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14–1
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14–1
A chromosome that is not a sex chromosome is know as a(an)
autosome.
karyotype.
pedigree.
chromatid.
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14–1
Whether a human will be a male or a female is determined by which
sex chromosome is in the egg cell.
autosomes are in the egg cell.
sex chromosome is in the sperm cell.
autosomes are in the sperm cell.
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14–1
Mendelian inheritance in humans is typically studied by
making inferences from family pedigrees.
carrying out carefully controlled crosses.
observing the phenotypes of individual humans.
observing inheritance patterns in other animals.
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14–1
An individual with a blood type phenotype of O can receive blood from an individual with the phenotype O. A.
AB. B.
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14–1
The ABO blood group is made up of
two alleles.
three alleles.
identical alleles.
dominant alleles.
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26. END OF SECTION