Download Chromosomes and

Chromosomes and
Human Inheritance
Impacts, Issues:
Strange Genes, Tortured Minds
 Exceptional creativity often accompanies neurobiological disorders such as
schizophrenia, autism, chronic depression, and bipolar disorder
• Examples: Lincoln, Woolf, and Picasso
12.1 Human Chromosomes
 In humans, two ______________________ are the basis of sex – human males
have _______ sex chromosomes, females have __________

All other human chromosomes are ___________________ – chromosomes that
are the same in males and females
Sex Determination in Humans
 Sex of a child is determined by the _____________
• Eggs have an ___ chromosome; sperm have _____________
Sex Determination in Humans
 The ____________ gene on the ______ chromosome is the master gene for male
sex determination
• Triggers formation of testes, which produce the male sex hormone
(____________________)
• Without testosterone, ovaries develop and produce female sex hormones
(_____________________)
Karyotyping
12.1 Key Concepts
Autosomes and Sex Chromosomes
12.2 Autosomal Inheritance Patterns
 Many human traits can be traced to _____________ dominant or recessive alleles
that are inherited in Mendelian patterns
 Some of those alleles cause genetic ____________________
Autosomal Dominant Inheritance
 A dominant autosomal allele is expressed in _______________ and
_____________
• Tends to appear in ____________ generation
• With one homozygous recessive and one heterozygous parent, children
have a _________ chance of inheriting and displaying the trait
• Examples: _________________________________________
Autosomal Recessive Inheritance
 Autosomal recessive alleles are expressed only in _______________;
heterozygotes are ________________and do not have the trait
• A child of two carriers has a _________ chance of expressing the trait
• Example: ____________________
Neurobiological Disorders
 Most neurobiological disorders do not follow _______________ patterns of
Mendelian inheritance
• _____________________________________________

___________________ genes and _________________ factors contribute to
NBDs
12.3 Too Young to be Old
 __________________
• Genetic disorder that results in __________________ aging
• Caused by __________________ mutations in autosomes
12.2-12.3 Key Concepts
Autosomal Inheritance
 Many genes on autosomes are expressed in Mendelian patterns of simple
dominance
 Some dominant or recessive alleles result in genetic disorders
12.4 Examples of X-Linked Inheritance
 _____________________ alleles give rise to phenotypes that reflect Mendelian
patterns of inheritance

Mutated alleles on the X chromosome cause or contribute to over ________
genetic disorders
X-Linked Inheritance Patterns
 More _____________ than _____________ have X-linked recessive genetic
disorders
• Males have only _____ X chromosome and can express a single recessive
allele
• A female heterozygote has ________ X chromosomes and may not show
symptoms
 Males transmit an X only to their ___________________, not to their ________
Some X-Linked Recessive Disorders
 ___________________________
• Bleeding caused by lack of blood-clotting protein

___________________________
• Inability to distinguish certain colors caused by altered photoreceptors in
the eyes

______________________________
• Degeneration of muscles caused by lack of the structural protein
dystrophin
12.4 Key Concepts
Sex-Linked Inheritance
 Some traits are affected by genes on the X chromosome
 Inheritance patterns of such traits differ in males and females
12.5 Heritable Changes
in Chromosome Structure
 On rare occasions, a chromosome’s structure changes; such changes are usually
harmful or lethal, rarely neutral or beneficial

A __________________ of a chromosome may be duplicated, deleted, inverted,
or translocated
_______________________
 DNA sequences are repeated ________ or more times; may be caused by unequal
crossovers in ___________________
_______________________
 Loss of some portion of a chromosome; usually causes serious or lethal disorders
• Example: _______________________
________________________
 Part of the sequence of DNA becomes oriented in the _______________
direction, with no molecular loss
_____________________________
 Typically, ________________________ chromosomes exchange parts (reciprocal
translocation)
Does Chromosome Structure Evolve?
 Changes in chromosome structure can reduce fertility in heterozygotes; but
accumulation of multiple changes in homozygotes may result in new species

Certain duplications may allow one copy of a gene to ______________ while the
other carries out its original function
Differences Among
Closely Related Organisms
 Humans have 23 pairs of chromosomes; chimpanzees, gorillas, and orangutans
have 24
• Two chromosomes _________________________
12.6 Heritable Changes in
the Chromosome Number
 Occasionally, new individuals end up with the wrong
___________________________________
• Consequences range from minor to lethal

______________________________
• Too many or too few copies of one chromosome

___________________________
• Three or more copies of each chromosome
_____________________________
 Changes in chromosome number can be caused by nondisjunction, when a pair
of chromosomes fails to _______________ properly during mitosis or meiosis

Affects the chromosome number at fertilization
• _________________ (n-1 gamete)
• __________________ (n+1 gamete)
Autosomal Change and Down Syndrome
 Only trisomy 21 (________________________) allows survival to adulthood
• Characteristics include physical appearance, mental impairment, and heart
defects

Incidence of nondisjunction increases with _______________________
 Can be detected through ______________________ diagnosis
Change in Sex Chromosome Number
 Changes in sex chromosome number may impair learning or motor skills, or be
undetected


Female sex chromosome abnormalities
• Turner syndrome (__________)
• _______________syndrome (three or more X chromosomes)
Male sex chromosome abnormalities
• Klinefelter syndrome (____________)
• _______________ syndrome
_____________________________
 _______ (one unpaired X chromosome)
• Usually caused by _______________________ in the ______________
• Results in females with undeveloped ovaries
12.5-12.6 Key Concepts: Changes in Chromosome Structure or Number
 On rare occasions, a chromosome may undergo a large-scale, permanent change
in its structure, or the number of autosomes or sex chromosomes may change
 In humans, such changes usually result in a genetic disorder
12.7 Human Genetic Analysis
 Charting genetic connections with ____________________ reveals inheritance
patterns for certain alleles

_____________________
• A standardized chart of _________________ connections
• Used to determine the probability that future offspring will be affected by
a genetic abnormality or disorder
Studying Inheritance in Humans
 Genetic studies can reveal __________________________________ or clues to
past events
• Example: A link between a Y chromosome and Genghis Khan?
Defining Genetic Disorders
and Abnormalities
 ________________________________
• A rare or uncommon version of a trait; not inherently life threatening

Genetic disorder
• An inherited condition that causes mild to severe medical problems,
characterized by a specific set of symptoms (a _________________)
Recurring Genetic Disorders
 Mutations that cause genetic disorders are rare and put their bearers at risk

Such mutations survive in populations for several reasons
• Reintroduction by ______________ mutations
• Recessive alleles are masked in ________________________
• Heterozygotes may have an ____________________ in a specific
environment
A Pedigree for Huntington’s Disease
 A progressive degeneration of the nervous system caused by an autosomal
______________________ allele
12.8 Prospects in Human Genetics
 Genetic analysis can provide parents with information about their future children

_______________________________
• Starts with parental genotypes, pedigrees, and genetic testing for known
disorders
•
Information is used to predict the _____________________of having a
child with a genetic disorder
Prenatal Diagnosis
 Tests done on an ________________ or ___________ before birth to screen for
sex or genetic problems
• Involves risks to mother and fetus

Three types of prenatal diagnosis
• ___________________________
• ____________________________________ (CVS)
• ___________________________
Preimplantation Diagnosis
 Used in in-vitro fertilization
• An _____________________ cell is removed from the early embryo and
examined before implantation
After Preimplantation Diagnosis
 When a severe problem is diagnosed, some parents choose an induced abortion

In some cases, surgery, _______________________, hormone replacement
therapy, or _______________________________ can minimize or eliminate
symptoms of a genetic disorder
• Example: _____________________________________
Genetic Screening
 Genetic screening (_____________________, routine testing for alleles
associated with genetic disorders)
• Provides information on reproductive _____________
• ____________________ family members with a genetic disorder
• Used to ___________________ newborns for certain disorders
• Used to estimate the ________________ of harmful alleles in a population
12.7-12.8 Key Concepts
Human Genetic Analysis
 Various analytical and diagnostic procedures often reveal genetic disorders

What an individual, and society at large, should do with the information raises
ethical questions