Transcript Chapter 11 Complex Inheritance and Human

Chapter 11 Complex Inheritance and
Human Heredity
Section 1: Basic Patterns of Human Inheritance
Section 2: Complex Patterns of Inheritance
Section 3: Chromosomes and Human Heredity
AHSGE CONTENT STANDARD #7: Apply Mendel’s laws to
determine phenotypic and genotypic probabilities of offspring.
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Basic Patterns of Human
Inheritance
(Section 11.1)
MAIN IDEA: The inheritance of a trait over
several generations can be shown in a
pedigree.
11.1 Basic Patterns of Human
Inheritance
Objectives
• Analyze genetic patterns to determine
dominant or recessive inheritance patterns.
• Summarize examples of dominant and
recessive disorders.
• Construct human pedigrees from genetic
information.
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Review Vocabulary
genes – segments of DNA that control the
production of proteins.
dominant – Mendel’s name for a specific trait
that appeared in the F1 generation.
(Webster’s: commanding, controlling, or
prevailing over all others)
recessive – Mendel’s name for a specific trait
hidden or masked in the F1 generation.
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New Vocabulary
carrier
pedigree
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Chapter 11
Complex Inheritance and Human Heredity
11.1 Basic Patterns of Human Inheritance
Recessive Genetic Disorders
 A recessive
trait is
expressed
when the
individual is
homozygous
recessive for
the trait.
Chapter 11
Complex Inheritance and Human Heredity
11.1 Basic Patterns of Human Inheritance
Cystic Fibrosis
 Affects the mucus-producing glands,
digestive enzymes, and sweat glands
 Chloride ions are not absorbed into the
cells of a person with cystic fibrosis
but are excreted in the sweat.
 Without sufficient chloride ions in the
cells, a thick mucus is secreted.
Cystic Fibrosis
(recessive genetic disorder)
Cystic Fibrosis
(recessive genetic disorder)
Approximately 1 in 20 people are carriers of the Cystic
Fibrosis gene and when two carriers parent a child
there is a 1 in 4 chance of the child being born with
Cystic Fibrosis.
Chapter 11
Complex Inheritance and Human Heredity
11.1 Basic Patterns of Human Inheritance
Albinism
 Caused by altered genes, resulting in the
absence of the skin pigment melanin in
hair and eyes
 White hair
 Very pale skin
 Pink pupils
Albinism
(recessive genetic disorder)
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Complex Inheritance and Human Heredity
11.1 Basic Patterns of Human Inheritance
Tay-Sachs Disease
 Caused by the absence of the enzymes
responsible for breaking down fatty acids
called gangliosides
 Gangliosides accumulate in the brain,
inflating brain nerve cells and causing
mental deterioration.
Tay-Sachs Disease
(recessive genetic disorder)
Affects 1 in 2500 people in the United States.
(affects people of Jewish descent)
Tay-Sachs Disease
(recessive genetic disorder)
Tay-Sachs
Disease is often
identified by a
cherry-red spot
on the back of
the eye.
Chapter 11
Complex Inheritance and Human Heredity
11.1 Basic Patterns of Human Inheritance
Galactosemia
Recessive genetic disorder
characterized by the inability
of the body to digest
galactose.
Galactosemia
(recessive genetic disorder)
Chapter 11
Complex Inheritance and Human Heredity
11.1 Basic Patterns of Human Inheritance
Dominant Genetic Disorders
 Huntington’s disease affects the nervous
system.
 Achondroplasia is a genetic condition that
causes small body size and limbs that are
comparatively short.
Achondroplasia
(DOMINANT genetic disorder)
How is achondroplasia inherited?
People with achondroplasia
may pass on the condition to
their children. If one parent is
affected, each child has a onein-two chance of having
achondroplasia, and a one-intwo chance of being average
height. Those born with
achondroplasia may pass the
condition on to their own
children, while those of
average height will not.
Chapter 11
Complex Inheritance and Human Heredity
11.1 Basic Patterns of Human Inheritance
Chapter 11
Complex Inheritance and Human Heredity
Chapter 11
Complex Inheritance and Human Heredity
11.1 Basic Patterns of Human Inheritance
Pedigrees
 A diagram that traces the inheritance of a
particular trait through several generations
Chapter 11
Complex Inheritance and Human Heredity
11.1 Basic Patterns of Human Inheritance
Inferring Genotypes
 Knowing physical traits can determine
what genes an individual is most likely to
have.
Predicting Disorders
 Record keeping helps scientists use
pedigree analysis to study inheritance
patterns, determine phenotypes, and
ascertain genotypes.
Section 11.1 Summary
• Genetic disorders can be caused by dominant or
recessive alleles.
• Cystic fibrosis is a genetic disorder that affects
mucus and sweat secretions.
• Individuals with albinism do not have melanin in
their skin, hair, and eyes.
• Huntington’s disease affects the nervous system.
• Achondroplasia sometimes is called dwarfism.
• Pedigrees are used to study human inheritance
patterns.
Complex Patterns of Inheritance
(Section 11.2)
MAIN IDEA: Complex inheritance
of traits does not follow inheritance
patterns described by Mendel.
Complex Patterns of Inheritance
(Section 11.2)
Objectives
• Distinguish between various complex
inheritance patterns.
• Analyze sex-linked and sex-limited
inheritance patterns.
• Explain how the environment can influence
the phenotype of an organism.
Review Vocabulary
gamete – a mature sex cell (sperm or egg)
with haploid number of chromosomes.
New Vocabulary
incomplete dominance
codominance
multiple alleles
epistasis
sex chromosome
autosome
sex-linked trait
polygenic trait
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Complex Inheritance and Human Heredity
11.2 Complex Patterns of Inheritance
Incomplete Dominance
 The heterozygous phenotype is an
intermediate phenotype between the two
homozygous phenotypes.
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Complex Inheritance and Human Heredity
11.2 Complex Patterns of Inheritance
Incomplete Dominance
…from a different perspective
Codominance
 Both alleles are expressed in the heterozygous
condition.
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11.2 Complex Patterns of Inheritance
Sickle-cell Disease
Normal red blood cell
 Changes in hemoglobin
cause red blood cells to
change to a sickle shape.
 People who are
heterozygous for the trait
have both normal and
sickle-shaped cells.
Sickle cell
7766x
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Complex Inheritance and Human Heredity
11.2 Complex Patterns of Inheritance
Multiple Alleles
 Blood groups in
humans
 ABO blood groups
have three forms
of alleles.
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11.2 Complex Patterns of Inheritance
Coat Color of Rabbits
 Multiple alleles can demonstrate a hierarchy
of dominance.
 In rabbits, four alleles code for coat color:
C, cch, ch, and c.
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11.2 Complex Patterns of Inheritance
Coat Color of Rabbits
Chinchilla
Albino
Light gray
Dark gray
Himalayan
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11.2 Complex Patterns of Inheritance
Epistasis
 Variety is the result of one allele hiding the
effects of another allele.
eebb
eeB_
No dark pigment present in fur
E_bb
E_B_
Dark pigment present in fur
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11.2 Complex Patterns of Inheritance
Sex Determination
 Sex chromosomes determine
an individual’s gender.
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Complex Inheritance and Human Heredity
11.2 Complex Patterns of Inheritance
Dosage Compensation
 The X chromosome carries a variety of
genes that are necessary for the
development of both females and males.
 The Y chromosome mainly has genes that
relate to the development of male
characteristics.
 Chromosome inactivation
 Barr bodies
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11.2 Complex Patterns of Inheritance
Sex-Linked Traits
 Genes located on the X chromosome
 Red-green color blindness
 Hemophilia
Sex-Linked
Traits
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Complex Inheritance and Human Heredity
11.2 Complex Patterns of Inheritance
Polygenic Traits
 Polygenic traits arise from the interaction of
multiple pairs of genes.
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Complex Inheritance and Human Heredity
11.2 Complex Patterns of Inheritance
Environmental Influences
 Environmental factors
 Diet and exercise
 Sunlight and water
 Temperature
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Complex Inheritance and Human Heredity
11.2 Complex Patterns of Inheritance
Twin Studies
 Helps scientists separate genetic contributions
from environmental contributions
 Traits that appear frequently in identical
twins are at least partially controlled by
heredity.
 Traits expressed differently in identical twins
are strongly influenced by environment.
Section 11.2 Summary
• Some traits are inherited through complex
inheritance patterns, such as incomplete
dominance, codominance, and multiple alleles.
• Gender is determined by X and Y chromosomes.
Some traits are linked to the X chromosome.
• Polygenic traits involve more than one pair of
alleles.
• Both genes and environment influence an
organism’s phenotype.
• Studies of inheritance patterns of large families
and twins give insight into complex human
inheritance.
Chromosomes and Human
Heredity
(Section 11.3)
MAIN IDEA:
Chromosomes can be
studied using
karyotypes.
Chromosomes and Human
Heredity (Section 11.3)
Objectives
• Distinguish normal karyotypes from those with
abnormal numbers.
• Define and describe the role of telomeres.
• Relate the effect of nondisjunction to Down
syndrome and other abnormal chromosome
numbers.
• Assess the benefits and risks of diagnostic
fetal testing.
Review Vocabulary
mitosis – a process in the nucleus of a
dividing cell, including prophase, metaphase,
anaphase, and telophase (PMAT!!!).
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New Vocabulary
karyotype
telomere
nondisjunction
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Chapter 11
Complex Inheritance and Human Heredity
11.3 Chromosomes and Human Heredity
Karyotype Studies
 Karyotype—micrograph in which the pairs
of homologous chromosomes are
arranged in decreasing size.
 Images of chromosomes stained during
metaphase
 Chromosomes are arranged in decreasing
size to produce a micrograph.
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Complex Inheritance and Human Heredity
11.3 Chromosomes and Human Heredity
Telomeres
 Telomere caps consist of DNA associated
with proteins.
 Serves a protective function for the
structure of the chromosome.
Chapter 11
Complex Inheritance and Human Heredity
11.3 Chromosomes and Human Heredity
Nondisjunction
 cell division during which
sister chromatids fail to
separate properly
Visualizing Nondisjunction
 Down syndrome
Chapter 11
Complex Inheritance and Human Heredity
Section 11.3 Summary
• Karyotypes are micrographs of
chromosomes.
• Chromosomes terminate in a cap called a
telomere.
• Nondisjunction results in gametes with an
abnormal number of chromosomes.
• Down syndrome is a result of nondisjunction.
• Tests for assessing the possibility of genetic
and chromosomal disorders are available.