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14–1 Human Heredity14-1 Human Heredity
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Human Chromosomes
Karyotype
Visual display of an individual’s chromosomes, which are paired and numbered.
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Human Chromosomes
Human Karyotype: is this a male or female?
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Human Chromosomes
Human and other mammals have two types of chromosomes:
1.Autosomes- Any chromosome other than a sex chromosome.
2.Sex Chromosomes- The X and Y chromosomes which determine gender.
XX= Female
XY= Male
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Human Genes
Let’s talk about Human Blood Types
•Example of multiple alleles.
•Possible phenotypes for human blood types are: A, B, AB, and O.
•There are only 3 alleles for blood types in humans: A, B, and O.
•A & B are codominant.
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Human Genes
The alleles for human blood type are written as:
• IA, IB, and i.
• Alleles IA and IB are co-dominant but both are dominant over i.
• i is recessive.
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Human Genes
• People with the genotype IA IB have type AB blood
• Genotype ii produce blood type O
• Genotypes IAIA or IAi produce blood type A
• Genotypes IBIB or IBi produce blood type B
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1 child = AB1 child = A
2 children = B
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Inherited Diseases
• A disease that is transmitted in the genes an organism inherits from its parents.
• Many result from mutations
• Many are carried on the autosomes and sex chromosomes.
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Inherited Autosomal DiseasesCystic Fibrosis
Huntington Disease
Sickle Cell Disease
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Cystic Fibrosis:
•Affects glands of the body that secrete sweat and
mucus.•Affects the lungs
•Breathing is difficult•Can affect other organs
within your body•Autosomal recessive disease
(caused by a recessive trait that is carried on an
autosome)
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Huntington Disease:
•Degenerative disease of the nervous system
•Progressive (worsens with time)•Breaks down nerve cells in brain
•Causes uncontrollable movements
•Mental Deterioration•Premature Death
•Autosomal dominant disease (you only have to inherit one gene for
the disease to develop)•A child with a parent of
Huntington disease has a 50% chance of inheriting the disease.
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Sickle Cell Disease:
•AKA sickle cell anemia•Changes a person’s hemoglobin•Red blood cells fold or become
distorted in shape•The shapes cause blockages
within blood vessels•Weakness and pain are caused
•Damages brain, heart, and spleen
•Can be fatal•Autosomal recessive disease
•More common in African Americans
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Human Genes
Inherited Sex Chromosome Diseases
•Some traits other than gender are “sex linked traits,” meaning they are determined by alleles located on the sex chromosomes.
•Most sex linked traits are recessive
•Carried on the X chromosome
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• Because males have only 1 X chromosome, a male who carries the recessive allele will show the sex-linked recessive trait.
• Females have 2 X chromosomes, so a female must inherit two recessive alleles for the recessive trait to be expressed.
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Sex linked genetic disorders
Albinism: Albinism is a defect of melanin production that results in little or no color (pigment) in the skin, hair, and eyes
Hemophilia: Body is unable to produce a protein that is needed for normal blood clotting. Bruise easily. Cannot stop bleeding. Usually males
Color Blindness: The inability to see certain colors in the usual way.
Muscular Dystrophy: Is a group of inherited disorders that involve muscle weakness and loss of muscle tissue, which get worse over time.
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Genetics and the Environment
• Note that when it comes to disease, genetics is not always all or nothing.
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Human Traits
So to determine if something is inherited or not, we use a Pedigree.
A pedigree is a chart, or family tree, that traces the inheritance of a trait.
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Human Traits
Pedigree Charts
A person who has at least one copy of an allele is called a carrier whether or not they actually have the trait.
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Human Traits
A circle representsa female.
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 square representsa male. A vertical line and a
bracket connect the parents to their children.
A circle or square that is not shaded indicates that a person does not express the trait.
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Human Genes
Pedigree Charts can determine:
•Harmful or unharmful diseases
•Human blood types
•Any type of trait
