Human genetics Flashcards
determine the pattern of inheritance of man’s traits, the construction of family
history is performed
pedigree analysis
By doing this, one can determine the possible genotypes and phenotypes of the individuals, and can predict if the trait can be possibly transmitted to the next generation.
pedigree analysis
involve the careful compilation of phenotypic records of
the family over several generations
Family histories or pedigrees
affected individual whom the pedigree is discussed is called the ____ (____ if male, ___ if female).
proband;
propositus;
proposita
Analyzing pedigrees can reveal the following: (4)
(a) whether a trait is dominant or recessive
(b) the type of chromosome (autosomal or sex) to which the trait is linked
(c) genotypes of family members
(d) probabilities of phenotypes in future generations
show the presence or absence of a trait as it relates to the relationship among parents, offspring, and siblings.
Pedigrees
If the trait is __, one of the parents must have the trait. ___ traits will not skip a generation. If the trait is ___, neither parent is required to have the trait since they can be heterozygous.
dominant;Dominant
recessive
Common pattern of inheritance in man (5)
-Autosomal dominance
-Autosomal recessive
-Sex-linked dominance
-Sex-linked recessive
-Sex-influenced
The trait for this type of inheritance never skips a generation Affected individual may either be homozygous or heterozygous
Autosomal dominance
Marriage between 2 affected individuals produce affected offspring; May also be produced by both unaffected person heterozygous for the character
Autosomal recessive
Affected male with unaffected wife transmit the trait to daughter only
Sex-linked dominance
Affected female with unaffected husband transmits the trait to sons only; the daughters serve as carrier of the trait
Sex-linked recessive
Gene exhibits high penetrance or expressivity in one sex
Sex-influenced
Give tehir example/s:
Autosomal recessive:
Sex-linked dominance:
Sex-linked recessive: (2)
Sex-influenced: men (2), women
Autosomal recessive: inability to roll tongue
Sex-linked dominance: defective teeth enamel
Sex-linked recessive: colorblindness, hemophilia
Sex-influenced: men (harelip, baldness), women (spina bifida)
One mutated copy of the gene in each cell is sufficient for a person to be affected
Autosomal dominant
an affected person inherits the condition from an affected parent; condition may result from a new mutation in the gene and occur in people with no history of the disorder
Autosomal dominant
both copies of the gene in each cell have mutations.
Autosomal recessive
The parents of an individual with an ____condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition
Autosomal recessive
typically not seen in every generation of an affected family.
Autosomal recessive
In female, a mutation in one of the two copies of the gene in each cell is sufficient to cause the disorder
X-linked dominant
In males, a mutation in the only copy of the gene in each cell causes the disorder.
X-linked dominant
males experience more severe symptoms of the disorder than females
X-linked dominant disorder
In females, a mutation would have to occur in both copies of the gene to cause the disorder
X-linked recessive
Because it is unlikely that females will have two altered copies of this gene, males are affected by ___ disorders much more frequently than females.
X-linked recessive disorders
mutation can only be passed from father to son
Y-linked
two different versions (alleles) of a gene are expressed, and each version makes a slightly different protein.
Co-dominant inheritance
Both alleles influence the genetic trait or determine the characteristics of the genetic condition.
Co-dominant inheritance
Conditions resulting from mutations in ______ can appear in every generation of a family and can affect both males and females, but fathers do not pass these disorders to their daughters or sons.
mitochondrial DNA
Give their example/s:
Autosomal dominant: (2)
Autosomal recessive: (2)
X-linked dominant:
X-linked recessive:
Y-linked:
Co-dominant: (2)
Mitochondrial:
Autosomal dominant: Huntington disease; Marfan syndrome
Autosomal recessive: Cystic fibrosis; Sickle cell disease
X-linked dominant: Fragile X syndrome
X-linked recessive: Hemophilia
Y-linked: Y chromosome infertility
Co-dominant: ABO blood group; alpha-1 antitrypsin deficiency
Mitochondrial: Leber hereditary optic neuropathy (LHON)
, , a type of euploidy has not been observed in humans, and is considered lethal
polyploidy
About ___ of spontaneous abortion and ___ of still births and newborn deaths are due to ___.
17%; 3%; triploidy
Trisomy 21derived from the name of a British physician (____) who first
described the syndrome in 1866.
J. Langdon Down
arises from nondisjunction of chromosome during oogenesis
Triplo – 21
a degenerative disorder of the human central nervous
system resulting in the progressive impairment of the memory
Alzheimer’s Disease (Ad)
It is related to Down syndrome since the genetic region for both disorders is found to be the chromosome 21
Alzheimer’s Disease (Ad)
One feature of this disroder is that they have numerous plaques in the cortical cell
Alzheimer’s Disease (Ad)
is the main component of this plaque; same protein with identical amino acid sequences is found in the aged mongoloid.
Amyloid protein
multiple malformations;
Low- set ears;
small lower jaw
clenched fingers
deformed skull, face, feet
- Trisomy 18 Edward’s syndrome
cardiac malformations;
Displaced liver
Growth retardation
Severe mental retardation
- Trisomy 18 Edward’s syndrome
Average life expectancy of Trisomy 18 Edward’s syndrome
Ave. 239 days
1 in 6,000 -10,000 births; 3x more frequent in female; Correlated w/ mother’s age
Trisomy 18 Edward’s syndrome
with sloping forehead,
harelip,
palate,
deformed face
polydactyly present
markedly mental retarded
cardiac and internal defects
- Trisomy 13 Patau
syndrome
Average life expectancy of Trisomy 13 Patau syndrome
131 days Live up to 5 years
Fetus spontaneously aborted 0.2:1000;
Frequency: 1 in 10,000 births
Not correlated with mother’s age
Trisomy 13 Patau
syndrome
Mental Retardation;
slanting eyes;
mongolian eye fold;
saddle nose;
swollen tongue;
underdeveloped ears;
slightly flattened face;
Trisomy -21 Down Syndrome
enlarged liver and spleen;
broad and short skull;
thick, short hands, feet and trunk;
mentally retarded;
happy disposition in life
Trisomy -21 Down Syndrome
Reproductive capacity of down syndrome:
Female – __; can produce ___ mongoloid offspring
Male- __
IQ is about ___
fertile; 520%
sterile
25-74
average life expectancy of Trisomy 21
16.2 years
1:665 live births; correlated with mother’s age
Trisomy -21 Down Syndrome
percent of risk of Down syndrome:
39-49 y.o:
40-44 y.o:
45 above:
39-49 y.o: 0.4
40-44 y.o: 1.3
45 above: 1.9-2.5
__ and his associates first described Trisomy 18 in 1960
John H. Edwards
very rare; involves chromosomes 13, 14, and 15.
Patau syndrome Syndrome
Trisomy 13 first described by the group of
Klaus Patau
Human disorders associated with abnormality in the sex chromosomes (5)
-Klinefelter’s syndrome
-Turner’s syndrome
-Triplo-X syndrome
-Jacob Syndrome or Double Y Syndrome
-Hermaphrodi tism
male phenotype of the syndrome:
normal external genitalia;
sparse pubic and facial hair;
rudimentary testes and prostate glands;
No spermatogenesis
Longer arms and legs; large hands and feet
Enlarged breast
High-pitched voice
Normal to slightly retarded socially
inadequate, dependent, & submissive
Klinefelter’s syndrome
General female phenotype of the syndrome:
short stature webbed neck
broad chests
little or no development of 2° sex characteristics
No ovarian development
Abnormal hormonal secretions
Slight mental retardation
Turner’s syndrome
Female sex phenotype of the syndrome:
At 22, infantile external genitalia
With menstrual irregularities, premature menopause
Triplo-X syndrome
Exceptional height;
With acne
Speech and reading problems;
Aggressive and anti-social
Jacob Syndrome or Double Y Syndrome
Have both ovarian and testicular tissues.;
Congenital anomalies;
Mental retardation
Hermaphrodi tism
causes of Klinefelter’s syndrome (2)
- XX female cross with Y male
- X female cross with XY male
cause of Turner’s syndrome
Absence of male
x chromosome
Human Disorders Due to Changes in Chromosome Structure (4)
- Cri-du-chat Syndrome (Deletion)
- Muscular dystrophy (Deletion)
- Robertsonian translocation
- Philadelphia syndrome
results from the deficiency of the short arm of chromosome 5, which is due to the translocation of B/G and B/D chromosome groups.
Cri-du-chat Syndrome (Deletion)
deletion of a small segment of chromosome X, involving the genes for the synthesis of dystrophin
Muscular dystrophy (Deletion)
complex of protein that work together to strengthen muscle fibers and protect them from injury as muscles contract and relax.
Dystrophin
Muscylar dystrophy Deletion results in either:
- Duchenne Muscular Dystrophy or DMD
-Becker Muscular Dystrophy or BMD
no dystrophin synthesis due to frameshift mutation
Duchenne Muscular Dystrophy or DMD
synthesis of smaller but partially functional dystrophin
Becker muscular dystrophy
Recipocal translocation involving chromosomes 2 and 20
Robertsonian translocation
Features: absence of bile ducts in the liver, abnormalities of the eyes and ribs, heart defects and sever itching
Robertsonian translocation
produce symptoms similar to Down syndrome and Patau syndrome occur in 1:500 births
Robertsonian translocation
translocation involving chromosomes 9 and 22
Philadelphia syndrome
Reciprocal translocation activates the oncogenes
Philadelphia syndrome
converts a cell into a tumor cell.
oncogenes
Philedelphia syndrome results to _____ a fatal cancer involving uncontrolled replication of stem cells of the WBC
chronic myelogenous leukemia (CML),
