Transcript Chapter 11

CHAPTER 11
11-1 BASIC PATTERNS IN HUMAN
INHERITANCE
Objectives
1. Analyze genetic patterns to determine dominant
or recessive inheritance patterns
2. Summarize examples of dominant and recessive
disorders
3. Construct human pedigrees from genetic
information
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11.1 Basic Patterns of Human Inheritance
Recessive Genetic Disorders
 A recessive
trait is
expressed
when the
individual
is
homozygous
recessive
for the
trait.
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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.
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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
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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.
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Galactosemia
 Recessive genetic disorder characterized
by the inability of the body to digest
galactose.
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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.
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11.1 Basic Patterns of Human Inheritance
Pedigrees
 A diagram that traces the inheritance of a
particular trait through several
generations
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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.
11-2 COMPLEX PATTERNS OF
INHERITANCE
Objectives
1. Distinguish between various complex inheritance
patterns
2. Analyze sex-linked and sex-limited inheritance
patterns
3. Explain how the environment can influence the
phenotype of an organism
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11.2 Complex Patterns of Inheritance
Incomplete Dominance
 The heterozygous phenotype is an
intermediate phenotype between the two
homozygous phenotypes.
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11.2 Complex Patterns of Inheritance
Codominance
 Both alleles are expressed in the
heterozygous condition.
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11.2 Complex Patterns of Inheritance
Sickle-cell Disease
 Changes in hemoglobin
cause red blood cells to
change to a sickle shape.
Normal red blood cell
 People who are
heterozygous for the
trait have both normal
and sickle-shaped cells.Sickle cell
7766x
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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
ch h
color: C, c , c , and c.
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Coat Color of Rabbits
Chinchilla
Albino
Light gray
Dark gray
Himalayan
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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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Sex Determination
 Sex chromosomes
determine an
individual’s gender.
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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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Sex-Linked Traits
 Genes located on the X chromosome
 Red-green color blindness
 Hemophilia
Sex-Linked
Traits
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Polygenic Traits
 Polygenic traits arise from the
interaction of multiple pairs of genes.
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Environmental Influences
 Environmental factors
 Diet and exercise
 Sunlight and water
 Temperature
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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.
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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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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
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11.3 Chromosomes and Human Heredity
Nondisjunction
 Cell division during which sister
chromatids fail to separate properly
 Down syndrome
Visualizing
Nondisjunction
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