Transcript 14–1 Human Heredity

14–1
Human
Heredity
14-1 Human Heredity
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14–1 Human Heredity
Human Chromosomes
Karyotype
Visual display of an individual’s
chromosomes, which are paired and
numbered.
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14–1 Human Heredity
Human Chromosomes
Human Karyotype: is this a male or female?
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14–1 Human Heredity
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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14–1 Human Heredity
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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14–1 Human Heredity
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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14–1 Human Heredity
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 = AB
1 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
Diseases
Cystic 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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14–1 Human Heredity
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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14–1 Human Heredity
• 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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14–1 Human Heredity
Genetics and the
Environment
• Note that when it comes to
disease, genetics is not always all
or nothing.
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14–1 Human Heredity
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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14–1 Human Heredity
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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14–1 Human Heredity
A circle
represents
a female.
A horizontal line
connecting a male and
a female represents a
marriage.
Human Traits
A square
represents
a 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.
A shaded circle or
square indicates that a
person expresses the
trait.
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Human Genes
Pedigree Charts can determine:
• Harmful or unharmful diseases
• Human blood types
• Any type of trait
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