Chapter 2 Flashcards
zygote
the new cell formed by the
process of fertilization.
genes
the basic units of genetic
information.
DNA molecules
the substance that genes are
composed of that determines the
nature of every cell in the body
and how it will function.
chromosomes
rod-shaped portions of DNA that
are organized in 23 pairs.
Why do multiple births occur?
- Some occur when a cluster of cells in the ovum split off within the first two weeks.
- More commonly, two separate ova are fertilized by two separate sperm at roughly the same time.
monozygotic twins
twins who are genetically
identical.
dizygotic twin
twins who are produced when
two separate ova are fertilized
by two separate sperm at roughly
the same time.
dominant trait
the one trait that is expressed
when two competing traits are
present.
recessive trait
a trait within an organism that is
present, but is not expressed.
genotype
the underlying combination of
genetic material present (but not
outwardly visible) in an organism.
phenotype
an observable trait; the trait that is
actually seen.
homozygous
inheriting from parents similar
genes for a given trait.
heterozygous
inheriting from parents different
forms of a gene for a given trait.
polygenic inheritance
inheritance in which a
combination
of multiple gene
pairs is responsible
for the
production
of a particular trait.
reaction range
the potential degree of variability in the actual expression of a trait due to environmental conditions.
X-linked genes
genes that are considered
recessive
and located only on
the X chromosome.
Huntington’s disease
Huntington gene localized to the terminal portion of the short arm of
chromosome 4.
Obsessive-Compulsive
Disorder (OCD)
Several potentially relevant genes have been identified but additional research
is needed to verify.
Fragile X mental retardation
Two genes identified.
Early onset (familial)
Alzheimer’s disease
Three distinct genes identified. Most cases caused by single-gene mutation
on chromosomes 21, 14, and 1.
Attention deficit hyperactivity
disorder (ADHD)
Evidence in some studies has linked ADHD with dopamine-receptor D4 and
D5 genes, but the complexity of the disease makes it difficult to identify a
specific
gene.
Alcoholism
Research suggests that genes affecting the activity of the neurotransmitters
serotonin and GABA likely are involved in risk for alcoholism.
Schizophrenia spectrum
disorder
There is no agreement, but links to chromosomes 1, 5, 6, 10, 13, 15, and
22 have been reported.
behavioural genetics
the study of the effects of heredity
on behavior and psychological
characteristics.
spontaneous mutation
when genes change their form for no known reason.
Down syndrom
a disorder produced by the presence
of an extra chromosome on
the twenty-first pair; once referred
to as mongolism.
fragile X-syndrome
a disorder produced by injury to a
gene on the X chromosome, producing
mild to moderate mental
retardation.
sickle cell anemia
a blood disorder that gets its name
from the shape of the red blood
cells in those who have it.
Tay-Sachs disease
a disorder that produces blindness
and muscle degeneration prior to
death; there is no treatment.
Klinefelter’s disease
a disorder resulting from the presence
of an extra X chromosome
that produces underdeveloped
genitals, extreme height, and
enlarged
breasts.
Genetic counselling
the discipline that focuses on
helping people deal with issues
relating
to inherited disorders.
ultrasound sonography
a process in which high-frequency
sound waves scan the mother’s
womb to produce an image of
the unborn baby, whose size and
shape can then be assessed.
chronic villus sampling (CVS)
a test used to find genetic defects
that involves taking samples of
hair-like material that surrounds
the embryo.
first-trimester screening
Combines a blood test and
ultrasound
sonography in the eleventh to thirteenth week of pregnancy and can identify
chromosomal abnormalities and other disorders, such as heart problems.
amniocentisis
the process of identifying genetic
defects by examining a small
sample
of fetal cells drawn by a
needle inserted into the amniotic
fluid surrounding the unborn
fetus.
Currently available DNA based genetic tests
Alzheimer’s disease - Late-onset variety of senile dementia
Amyotrophic lateral sclerosis (Lou Gehrig’s
disease) - Progressive motor function loss leading to paralysis
and death
Breast and ovarian cancer (inherited) - Early-onset tumors of breasts and ovaries
Charcot–Marie–Tooth - Loss of feeling in ends of limbs
Cystic fibrosis - Thick mucus accumulations in lungs and chronic infections in lungs and pancreas
Duchenne muscular dystrophy (Becker muscular
dystrophy) - Severe to mild muscle wasting, deterioration,
weakness
Dystonia - Muscle rigidity, repetitive twisting movements
Fragile X syndrome - Mental retardation
Hemophilia A and B - Bleeding disorders
Hereditary nonpolyposis colon cancera - Early-onset tumors of colon and sometimes other organs
Huntington’s disease - Progressive neurological degeneration, usually beginning in midlife
Myotonic dystrophy - Progressive muscle weakness
Neurofibromatosis, type 1 - Multiple benign nervous system tumors that can be
disfiguring;
cancers
Phenylketonuria - Progressive mental retardation due to missing enzyme;
correctable
by diet
Sickle-cell disease - Blood cell disorder, chronic pain and infections
Spinal muscular atrophy - Severe, usually lethal progressive muscle-wasting disorder
in children
Tay-Sachs disease - Seizures, paralysis, fatal neurological disease of early
childhood
preimplantation genetic diagnosis (PGD)
to ensure that their next child would be free of Fanconi anemia.
With PGD, a newly fertilized embryo can be screened for a variety of genetic diseases before
it is implanted in the mother’s uterus to develop
germ line therapy
In which cells are taken from an
embryo and then replaced after the defective genes they contain have been repaired.
temperament
patterns of arousal and
emotionality that represent
consistent and enduring
characteristics in an individual.
multifactorial transmission
the determination of traits by a
combination of both genetic and
environmental factors in which
a genotype provides a range
within which a phenotype may
be expressed.
Do we inherit our personality?
At least in part. There’s increasing research
evidence suggesting that some of our most basic personality traits have genetic roots.
For example, two of the key “Big Five” personality traits, neuroticism and extroversion,
have been linked to genetic factors. Neuroticism, as used by personality researchers,
is the
degree
of emotional stability an individual characteristically displays. Extroversion is the
degree to which a person seeks to be with others, to behave in an outgoing manner, and
generally to be sociable.
What personality traits have high contributions of genes?
social potency (the tendency to
be a masterful, forceful leader who enjoys being
the center of attention) and traditionalism
(strict endorsement of rules and authority) are
strongly associated with genetic
factors.
Even less basic personality traits are linked
to genetics. For example, political attitudes,
religious
interests and values, and even attitudes
toward human sexuality have genetic components
fertilization
the process by which a sperm and
an ovum—the male and female
gametes, respectively—join to
form a single new cell.
germinal stage
the first—and shortest—stage of
the prenatal period, which takes
place during the first two weeks
following conception.
placenta
a conduit between the mother and
fetus, providing nourishment and
oxygen via the umbilical cord.
embryonic stage
the period from two to eight weeks
following fertilization during
which significant growth occurs
in the major organs and body
systems.
ectoderm
The outer layer of the embryo which will form teeth, hair, skin, sense-organs, and the brain and spinal cord
endoderm
The inner layer of the embryo which will produce the digestive system, liver, pancreas, and respiratory system.
mesoderm
The layer between endoderm and exoderm. It will form muscles, bones, blood, and circulatory system.
fetal stage
the stage that begins at about
eight weeks after conception, and
continues until birth.
fetus
a developing child, from eight
weeks after conception until birth.
infertility
the inability to conceive after 12
to 18 months of trying to become
pregnant.
artificial insemination
a process of fertilization in which a
man’s sperm is placed directly into
a woman’s vagina by a physician.
in vireo fertilization (IVF)
a procedure in which a woman’s
ova are removed from her ovaries
and a man’s sperm are used to fertilize
the ova in a laboratory.
miscarriage
known as a spontaneous abortion—
occurs when pregnancy ends before the developing child is able to survive outside the
mother’s womb. The embryo detaches from the wall of the uterus and is expelled.
They are usually attributed to some sort of genetic abnormality
abortion
when the mother voluntarily chooses to terminate the pragnency.
teratogen
an environmental agent that
produces
a birth defect.
Fetal alcohol spectrum disorder (FASD)
a disorder caused by the pregnant
mother consuming substantial
quantities of alcohol during
pregnancy,
potentially resulting
in mental retardation and delayed
growth in the child.
fetal alcohol effects (FES)
a condition in which children
display some, though not all,
of the problems of fetal alcohol
syndrome due to the mother’s
consumption of alcohol during
pregnancy.
