1.
Define and give examples of pleiotropy
2. Explain how epistasis affects the phenotypic ration for a dihybrid cross
3.
Explain how a lethal recessive gene can
be maintained in a population
4.
Distinguish between trisomy
and triploidy
5.
Define genome imprinting and provide
evidence to support this model
Euploidy--->represents the true multiple chromosome condition (n, 2n, 3n)
Aneuploidy-->represents an extra or missing chromosome (2n+1 or 2n-1)
Non-disjunction--->failure of chromosomes to separate usually during meiosis.
. Familial means it can pass on trait.
Translocation--->when a piece of one chromosome moves to another,
Transposition--->when genes moving from one place to another on a chromosome
cause an alteration in expression
. Chromosomal rearrangement--->large segments of chromosomes may change
position.
Spontaneous mispairing-->sequences become misaligned.
Nature vs. nurture
•Phenotypes are often affected by environmental factors.
•Norm of reaction for a genotype = phenotypic range.
•Polygenic factors tend to have broad norms of variation.
•Multifactorial - many factors (genetic, environmental) collectively influence
phenotype.
. Multifactoral Inheritance ...many factors
Polygenetic...many genes several loci with many genes on various chromosomes.
Many human traits clearly influenced by heredity but vary greatly from 1 extreme
to another
1. Genotype is a blueprint
2. environment supplies raw materials
3. cells do the work
Nature / nurture heredity/environment
Heredity determines the upper limit, determines what we can become and its the
interaction between heredity and the environment hat determines what you become.
The environment determines how near the upper limit the organism approaches.
. Many polygenetic congenital malformations express only at a certain threshold
level where a sufficient number of deleterious genes are present to cause the
abnormal phenotype..less than threshold number of bad genes--NORMAL. more than
the threshold number of bad genes--defect
Environmental factors exert significent effects on the threshold level.
. There is a tendency to underestimate the environment when attention is focused
on the gene.
Examples of polygenetic traits in humans
1. stature skin color intelligence finger print pattern blood pressure cleft
palate/lip diabetes mellitus spina bifida/ancephalia congenital heart defects
some allergies
schizophrenia epilepsy club foot
. Assumptions of a Polygenetic model
1. each gene locus is occupied by an ACTIVE (A) and an INACTIVE (a) allele.
2. The alleles at each locus are ADDITIVE in effect..no dominance exhibited.
3. The effect of the active allele at each locus is small and equal to that of
the active allele at every other locus that affects his trait.
. 4. Phenotype is determined by the sum total of active alleles present.
5. The various genes affecting the trait assort independently.
6. Polygenes are qualitatively no different than other genes--they are DNA.
. How multiple alleles operate:
Although there may be only 1 gene locus in an individual, there are more than 2
gene alleles in the population.
A. ABO blood group
1. Gene loci vs. gene alleles in population
2. Number of genotypes and phenotypes possible
. B. Polygnes contrast to multiple alleles
1. Gene loci vs. gene alleles in population
2. Number of genotypes and phenotypes possible
How codominance operates
Both alleles of the gene pair are expressed.
. C. Genetic loci
1. Major: HLA-A and HLA-B on sixth chromosome
2. Minor: 3 on 6th chromosome
Functions--govern histocompatibility
Variations of phenotypes
Probably the most polymorphic loci identified in human genetics.
HLA-A has 15 alleles: B locus has 26: 120 genotypes are possible at A and 231 at
B.
. Immune system/multiple alleles
On chromosome 6 is a cluster of genes called HLA genes which make surface
markers on cells for defence. (tissue compatibility)
They are usually inherited linked together meaning they are close on chromosome.
Halotypes (A3 B18 etc
Priorities for donations
1. monozygotic twin
2. dizygotic twin
3. sibling (match)
4. antigen match sibling
5. child
6. parent
7. 1st order relatives
8. cadavers with greater than 2 antigen matches
Summary
•Importance of genetics. Genetic terminology.
•Mendelian Genetics, Mendel’s Laws (Law of Segregation, Law of Independent
Assortment). Generations, crosses, etc.
•Probability in predicting genetic crosses.
•In humans, pedigree analysis performed to analyze hereditary conditions.
•Many traits are complicated by polygenetic inheritance, pleiotropy,
environmental influences.
•Interactions within genes and between genes and the environment affect
phenotypes.
Huntington’s Disease
•HD symptoms include spasmodic, or jerking, movements of the eyes, face and body
(chorea). Degenerative disorder - symptoms increase with time.
•Gene on short arm of chromosome 4.
– Codes for production of a protein called "huntingtin” (htt); function is still
unknown.
– Defective version of the gene has excessive repeats of a three-base sequence,
"CAG”. (Polyglutamine repeats.)
– In the normal huntingtin gene, this sequence is repeated between 11 and 29
times. In the mutant gene, we see more repeats, from 34 times to > 80.
•Defect causes the resulting huntingtin protein to be malformed, prone to
clumping in the brain and causing the death of nearby nerve cells. Cells of the
basal ganglia and of the cortex are most often affected.
Why late onset?
•NB: Age of onset varies.
•HD involves programmed cell death of certain neurons.
– More repeats - earlier cell death.
– Cell death is complex process.
•Cell death studies in several areas:
– Excitotoxicity. Overstimulation of cells by natural chemicals found in the
brain.
– Defective energy metabolism. A defect in the mitochondria, where energy is
produced.
– Oxidative stress. Normal metabolic activity in the brain that produces toxic
compounds called free radicals.
– Trophic factors. Natural chemical substances found in the human body that may
protect against cell death.
Hope for treatment?
•Recent reports that histone deacetylase (HDAC) inhibitors may be effective in
treatment of HD.
– Promising results seen with HDAC inhibitors in Drosophila, mice.
– Suberoylanilide hydroxamic acid, a histone deacetylase inhibitor, ameliorates
motor deficits in a mouse model of Huntington's disease. Hockly E, et al. Proc
Natl Acad Sci USA. 2003 Feb 18; 100(4): 2041-2046.
– Histone deacetylase inhibitors arrest polyglutamine-dependent
neurodegeneration in Drosophila. Steffan, et al. 2001. Nature 413: 739-743.
– Oxidative stress may play a role in HD cell death.
– Histone deacetylase inhibitors prevent oxidative neuronal death independent of
expanded polyglutamine repeats via an Sp1-dependent pathway. Ryu H, et al. Proc
Natl Acad Sci U S A. 2003 Apr 1; 100(7): 4281-4286.
Chromosomes and Mendelism
•Cytology and genetics converged at beginning of the 20th century.
•We have already mentioned the chromosome theory of inheritance: Mendelian genes
have specific loci on chromosomes, and it is the chromosomes that undergo
segregation and independent assortment.
Morgan and the fruit fly
•Morgan was originally skeptical about Mendelism and chromosome theory, but
performed experiments that provided strong evidence for both!
•Morgan used the experimental organism Drosophila melanogaster, the fruit fly.
Sex linkage
•Morgan mated his white-eyed fly mutant with wild-type flies.
– F1: Red eyes
– F2: 3:1 ratio (red: white)
• BUT white colour only appeared in males!
• All F2 females had red eyes.
• Half the males had red eyes, half had white eyes.
Sex-linked genes
•Genes located on a sex chromosome are called sex-linked genes.
•Reciprocal crosses can reveal sex-linkage.
Example
•In 1906, Doncaster and Raynor studied wing colour in Abraxas moth.
Results in chickens
Mating: Nonbarred (female) x Barred (male)
Progeny: All barred
Mating: Barred (female) x Nonbarred (male)
Progeny: All females nonbarred,
males barred
Hmmm …
•So, in flies we see phenotype differing in males, but in moths and chickens, it
is in females …
Linkage of genes
•Each chromosome has hundreds or thousands of genes.
•Genes located on the same chromosome are often inherited together, and are said
to be linked genes. (Note: Linked genes different from sex-linkage! )
•Linked genes do not generally follow the principle of independent assortment.
X inactivation
•Female mammals inherit two X chromosomes, but in each cell, one X chromosome
becomes inactivated. This ensures that males and females have the same effective
dose (copy) of X-linked genes.
•Condensed chromosome forms Barr body, lies on inside of nuclear envelope.
•Inactivation is random.
Errors and exceptions …
•Chromosome number is important.
•Nondisjunction: a pair of homologous chromosomes fail to separate during
meiosis I OR chromatids of a chromosome do not separate during meiosis II. (Can
also occur in mitosis.)
•If nondisjunction occurs, resulting cells will have too many or too few
chromosomes (a state called aneuploidy).
Aneuploidy
•If a chromosome is present in triplicate (cell has 2n + 1 chromosomes), cell is
trisomic for the chromosome.
•If a chromosome is missing (2n - 1), cell is monosomic for the chromosome.
•Mitosis generally propagates the error.
•Aneuploidy is often fatal. If organism survives, usually there are effects of
the abnormal dose of genes.
Chromosome structure problems
•Deletion: Chromosomal fragment lacking centromere lost during division.
•Occasionally a lost fragment will become attached to a sister chromatid
(producing a duplication in the recipient chromosome).
•Inversion: Chromosomal fragment reattaches to original chromosome but in
reverse orientation.
•Translocation: A segment of one chromosome moved to another, nonhomologous one.
Most commonly, this exchage is reciprocal between chromosomes.
. The exact chromosome number was only figured out in 1956. They thought it was
48 until then. The chromosomes are arranged into 7 groups characterized by their
shape, size and location of centromere.
Problems: Sometimes, one copy of the autosomes can be lost...o survival. In some
cases, an extra autosome can show up..trisomic or trisomy. This can occur in 13,
15, 18, 21, 23.
. The terms involved here are EUPLOIDY AND ANEUPLOIDY Euploidy represents the
true multiple of human chromosome condition (n/2n/3n)
Aneuploidy-extra or missing chromosome (written 2n +1 or 2n-1 trisomy)
ploidy means chromosome set.
. Causes in meiosis, non-disjunction (failure to separate) can occur either in
MI or M2, If non-disjunction occurs during meiosis I, all gametes are effected.
If it occurs in meiosis II, then only 1/2 of the gametes will be effected.
Possible causes would be
1) late maternal age
2) genes predisposed for non-disjunction
3) radiation (UV) causing damage to chromosomes and spindles (#16 common)
4) chromosome abnormalities themselves
5) viruses
Translocation Down is when a piece of #21 goes onto the 14th chromosome
. Familial means it can pass on trait.
Mosaicism (mosic down 1%)
Non-disjunction can occur during mitosis (show) about 16 cell level and then all
cells with 47 and 46 will carry on but those with 45 will die. This can even
happen after differentiation and if so many times there ill be little or no
effect..so you can't even tell.
Sex-chromosomes where this happens called aneuploids. More of these types occur
because they are not as serious as autosomal chromosome problems.
Female XX oo
non-disjunction
xxy xxx x oy xo
. Why are these less severe? Dosage compensation.. The male has a single dose of
X, the female a double dose but it is equal in males and females because only
one X is used.
Murry Barr looked at the LYON hypothesis which showed this about the X's and
noticed that in the nucleus of all female cells the inactive X was tightly
coiled/not in use...a dot called the barr body.
. Lyon suggested that female cells the X's are both active until about 16 cell
stage and then 1 X begins to become inactive. It is at random (so could be
different traits) but permanent. All descents of the cell will be the same as
far as which X is inactive. Now, if more of one is active than the other
(instead of 8 and 8 from the 16 cells 4 and 12), the 12 trait will be expressed
otherwise it is shared.
. TURNER'S SYNDROME
What is,,Tumers syndrome?
Turner's syndrome is a chromosome disorder that is congenital (begins at birth).
Normal males have one X and one Y chromosome. Normal females have two X
chromosomes. Patients with Turner's syndrome have only one X chromosome (XO
pattern) in each of their cells and have the appearance of females.
. The XO chromosome presentation occurs in approximately 1 in 3,000 female
births.
What are symptoms of Turner's syndrome?
As a result of the abnormal chromosome status, patients with Turner's syndrome
develop abnormally.
. The characteristic features of Turner's syndrome include immature gonads,
webbed neck, small jaw, high arched palate, widely spaced nipples, short height,
and a flat, shield-like chest.
. Down syndrome,
also called DOWN'S SYNDROME, TRISOMY'21, congenital disorder caused by an extra
chromosome on the chromosome 21 pair, thus giving the person a total of 47
chromosomes rather than the normal 46.
. Persons born with Down syndrome are characterized by several of the following:
broad, flat face; short neck; up-slanted eyes, sometimes with an inner
epicanthal fold; low-set ears; small nose and enlarged tongue and lips; sloping
underchin; poor muscle tone; mental retardation; heart or kidney malformations
or both; and abnormal dermal ridge patterns on fingers, palms, and soles.
. The mental retardation seen in persons with Down syndrome is usually moderate,
though in some it may be mild or severe. Congenital heart disease is found in
about 40 percent of people with Down syndrome.
. Klinefelter's syndrome.
Klinfelter's syndrome (47, XXY seminiferous tubule dysgenesis) is the most
frequent chromosomal disorder (occurring in one in 1,000 males). Symptoms and
features were first described in 1942 by the American physician Harry F.
Klinefelter, a student of Fuller Albright.
. It later became known that affected individuals had an extra X chromosome in
each cell so that the sex chromosome content was XXY and the total number of
chromosomes in each cell was 47 rather than 46.
These patients have the outward appearance of males with firm, small testes.
They cannot generate sperm, and they often have enlarged breasts and buttocks
and inordinately long legs.
. Testosterone production is deficient and there is a compensatory increase in
the pituitary gonadotropin secretion. While normal in intelligence, some of
these persons have difficulties in making social adjustments. Klinefelter's
syndrome occurs more often in the children of mothers over the age of 35 years.
. trisomy 13,
also called PATAU'S SYNDROME, human chromosomal disorder that results from an
extra (third) copy of chromosome 13. Infants born with this disorder have
profound mental retardation and severe developmental malformations that include
a small head, a cleft palate and lip, tiny eyes and eye openings, extra digits
on hands and feet (polydactyly), clenched
. fingers, central nervous system abnormalities, and defects in many internal
organs. There is no cure for this disorder, and most infants die in the first
few months of life. The only treatment is general supportive care. Trisomy 13 is
quite rare, occurring in only one out of 20,000 live births. Its incidence
increases in the offspring of women and men over the age of 32.
.Trisomy 18 also called EDWARD’s syndrome human chromosomal disorder that
results from an extra (third) copy of chromosome 18. Infants born with this
disorder are smaller than average and usually do not survive longer than a few
months.
. Characteristics of the syndrome include severe mental and growth retardation;
congenital heart disease and other internal defects; and a multitude of bodily
deformities, such as low-set and malformed ears, cleft lip and palate, a
receding chin, convex soles of the feet, a webbed neck, and fingers bent in a
unique configuration.
. Trisomy 18 occurs in approximately one in 8,000 live births, and female
infants are affected three to four times as often as males. There is no cure for
this condition. A higher incidence of trisomy 18 is seen in infants born to
women older than 35 years.
. XYY-Trisomy,
relatively common, human sex chromosome anomaly in which a male has two Y
chromosomes rather than one. It occurs in 1 in 500-1,000 live male births, and
individuals with the anomaly are often characterized by tallness and severe acne
and sometimes by skeletal malformations and mental deficiency.
. X-trisomys
sex chromosome disorder of females, in which three X chromosomes are present,
rather than the normal pair. More common than Turner's syndrome, where only one
X chromosome is present, X-trisomy usually remains undetected because affected
individuals appear normal, experience puberty, and are usually fertile.
Sex chromosome complement
•Klinefelter syndrome occurs when extra X chromosome(s) in a male. Occurs ~
1/2000 births. Affected individuals have male sex organs, but small testes, and
sometimes feminine body characteristics (e.g. breast enlargement).
•Turner syndrome occurs in XO individuals. Phenotypically female, but do not
mature sexually unless estrogen replacement therapy administered. Only known
viable monosomy in humans.
•XYY males don’t show much difference, may be taller. XXX females appear normal.
CML
•Translocations are known to be involved in some human cancers, such as chronic
myelogenous leukemia (reciprocal translocation between 22 and 9).
•Leukemias involve uncontrolled proliferation of white blood cells.
Molecular understanding -> Treatments!
•Until recently, the only successful treatment of CML was to destroy the
patient's bone marrow and then restore blood-cell production by infusing stem
cells from the bone marrow of a healthy donor.
•New treatment, Gleevec© specifically inhibits enzymatic activity of protein
tyrosine kinase encoded by bcr/abl. Effective in 90-98% of patients in drug
trials!
Genomic imprinting
•In some instances, we see differences depending on whether an allele was
provided by the father or the mother.
•Genomic imprinting seems to involve methylation of DNA (-CH3 groups added to
cytosine nucleotides of one of the alleles).
•Normal development apparently requires that some genes have one (and only one!)
active copy.
Extranuclear genes
•We know that mitochondria and chloroplasts carry their own genomes.
•Extranuclear genetic inheritance does not follow Mendelian principles.
Sometimes called cytoplasmic inheritance.
•In most plants and animals, a zygote receives organelles from maternal parent.
Thus, mitochondrial and chloroplast genes are passed from maternal parent.
1.Male genotype XY Female genotype XX
2. Undifferentiated embryo contains:
(a) Undifferentiated gonads
(b) 2 systems of genital ducts Mullerian and Wolffian Ducts. (Mull. is inhibited
in Females)
. 3. Male Y chromosome causes H-Y antigen to be found on all cells of the male.
Gonads become testes. Testes produce Testosterone and Mullerian Inhibiting
Hormone. Mullerian ducts degenerate and Wolffian Ducs in the presence of
testosterone become the epididymis, vasa deferentia, and seminal vesicles.
. 4. Female in the absence of the Y chromosome, there is no H-Y antigen
produced. In the absence of H-Y antigen the gonads become ovaries. No mullerin
Inhibiting Hormone is produced so the Mullerian Ducts become the fallopian
tubes, uterus and the vagina. The Wolffian Ducts degenerate.
. 5. Testicular feminization Karyotype XY External phenotype of well developed
female. Development proceeds as normal up to Mullerian degeneration. Tfm site on
X chromosome makes the tissues non-receptive to testosterone...undescended
testes.
. 6. PPSH (Pseudovaginal Perineoscrotal Hypospadias) XY males develop as female
until puberty. Autosomal recessive gene inhibits the catalyst 5-alpha reductase,
which is necessary to convert testosterone into dihydrotestosterone. At puberty,
virilization of external genitalia takes place.
.B UT THERE'S MORE to a man than testes alone. However, unlike the case of the
testes, the development of secondary sexual structures is not directly specified
by the Y chromosome. Instead, these structures are channeled toward male organs
by secretions of the testes themselves, while a lack of testicular secretions
channels them toward female organs.
For example, in the eighth week of gestation the testes begin producing the
hormone testosterone, some ofwhich gets converted into the closely related
substance dihydrotestosterone, or DHT. Such hormones are called androgens. DHT
goes on to convert some all-purpose embryonic structures into the male parts
where the lack of DHT would cause those same structures to develop into their
female equivalents.
Embryos also start out with two sets of ducts, known as the Miillerian ducts and
the Wolffian ducts. In the absence of testes the Wolffian ducts atrophy, while
the Miillerian ducts grow into a female's uterus, fallopian tubes, and the inner
part of the vagina. With testes present, the opposite happens: androgens
produced by the testes stimulate the Wolffian ducts to grow into a male's
seminal vesicles, vas deferens, and epididymis.
. At the same time, a testicular protein called Miillerian inhibiting factor
does what its name implies: it prevents the Miillerian ducts from developing
into the internal female organs.
Since a Y chromesome specifies testes, and since the presence or absence of the
testes' secretions specifies the remaining male or female structures, it might
seem as if there's no way that we could end up hermaphrodites.
. Instead, you might think a Y chromosome should guarantee 100 percent male
organs, whereas the lack of a Y chromosome should guarantee 100 percent female
organs.
In fact, a long series of further biochemical steps, programmed by chromosomes
other than the sex chromosomes, is required to produce all the structures other
than ovaries or testes. Every step involves the synthesis of one enzyme,
specified by one gene.
. If any one gene is altered by a mutation, the enzyme for which it's
responsible may be defective or absent. Thus, an enzyme defect may result in a
male pseudohermaphrodite, defined as someone with one X and one Y chromosome,
and hence intrinsically male, but with a mixture of both male and female
structures.
. In the pseudohermaphrodite, some male structures continue to develop normally
because they depend on enzymes and hormones that remain normal. However, male
structures dependent on the defective enzyme are either completely missing or
replaced by their female equivalents. This can be illustrated by a discussion of
two types of male pseudohermaphrodite--one resulting from a defective androgen
receptor, the other from a defect in the enzyme that converts testosterone to
DHT.
THE FORMER type looks like a normal woman. Indeed, "she" often conforms to the
male ideal of feminine beauty even more than the average woman does because her
breasts tend to be well developed and her legs long and graceful. Her complexion
is usually flawless and she tends to have the added height of a man. Hence,
cases have turned up repeatedly among female fashion models.
. Since this type of pseudohermaphrodite looks like a normal baby girl at birth
and externally undergoes normal development and puberty, the problem isn't even
likely to be recognized until the adolescent consults a doctor over her failure
to begin menstruating. At that point the doctor discovers a simple reason for
that failure: the patient has no uterus, fallopian tubes, or uppervagina.
. Instead, the vagina ends blindly without connecting to a uterus (although it
is generally adequate for intercourse). Further examination reveals testes that
are normal except for being buried in the groin or labia; they secrete normal
testosterone and are programmed by a normal Y chromosome. In other words, the
beautiful model is a male who happens to have a genetically determined
biochemical block in the ability to respond to testosterone.
. HERMAPHRODITE
Accepted definition: A person born with both male and female sex organs. This is
a vague, confusing and inaccurate definition. There are 3 labels of
Hermaphrodites: True, Male pseudo and Female Pseudo. All are equally genuine.
. TRUE
A person born with both ovary and testicular tissue, this could be 2 seperate
gonads ( one of each) or a combination of both in one (an ovotestes). The
genitalia can vary from completely male or female, to a combination of both or
even ambiguous looking. The chromosome (karotype) compliment can be XX (female),
XY (male), XX/XY (mosiac) or even XO (extremely rare).
. Those XX with female genitalia are raised female ( some have even given
birth). Those XY with male genitalia are raised male ( a few have fathered
children). The children born XX/XY or XO (with genitalia male or female are
raised in the sex they look most like) ,Those born with ambiguous genitalia have
many medical tests for the doctors to determine which sex they should be
assigned.
. Doctors then recommend early surgery to make the child look physically like
the sex assigned to them.
CAUSES
The causes are not known, The medical community does know this is a very rare
condition but do not have accurate figures to how many people have this
condition (depending on the literature between 350-450 known cases).
FEMALE PSEUDO
A person born XX with normal female internal organs but with "masculanized"
genitalia. They can appear more male then female or a combination of each.
CAUSES
The most common is Congenital Adrenal Hyperplasia (CAH) it occurs approximately
1:14,000 births.This is when the adrenal glands overproduce testosterone.
. It also has been recorded that some persons with this disorder had been
exposed to progesterone-like drugs before they were born.
MALE PSEUDO
A person born XY with testes (usually in the abdominal cavity). The external
genitalia are usually female but can be ambiguous.
CAUSES
The most common cause is Androgen Insensitivity Syndrome (AIS). This is when the
body doesn't respond to the androgen being produced. There are different
variations: Complete (CAIS) , and Partial (PAIS). This condition has a variety
of names and occurrence rates
. CAUSES
The most common cause is Androgen Insensitivity Syndrome (AIS). This is when the
body doesn't respond to the androgen being produced. There are different
variations: Complete (CAIS) , and Partial (PAIS). This condition has a variety
of names and occurrence rates
Paternity.
The genes make up only a tiny fraction of the DNA. The rest, the great
bulk-about 97 percent-has no known function. It is sometimes referred to as
"junk DNA." Nevertheless, these nongenic regions show the same genetic
variability that genes do, in fact usually more. These differences are not
overt, but can be detected by laboratory tests.
.. Regions of DNA that are used for forensic analysis are usually not genes, but
rather are located in those parts of the chromosomes without known functions, or
if part of a gene, not in the part that produces a detectable effect. (One
reason for this choice has been to protect individual privacy.)
.. Nevertheless, the words commonly used for describing genes (e.g., allele,
homozygous, polymorphic) are carried over to DNA regions used for
identification. It is customary to call the genotype for the group of loci
involved in a forensic analysis a profile
.. Question: My question is what do these genetic systems represent? Skin
pigment? Height, weight? For instance here are our test results: D351358
16,17,15,16,15,17. MA 18,19,15,18,15,16. D165539 9,11, 9,11, 9,13. 0251338
18,19,17,19,16,17. 0851179 14,15,13,14,13,14. 021511 30, 30, 30. D 18S51
16,17,12,16,12,17. D195433 14,15.2,14,14,10,14. THO1 6, 7, 6, 7, 7, 9. FGA 22,
22, 20, 22,19, 20. I am interested in all the traits of the genetic systems but
really interested in the D195433 system where the child has 14 from both mom and
dad. And lastly what is the paternity index?
.. Answer: These genetic systems do not represent any known traits which is one
of the reasons they were selected for testing identity. They represent regions
of DNA with no known function but that differ between unrelated individuals. In
the case of 0195433, both the mother and the tested man happen to carry an
allele (form of the gene) designated 14. The child in this case appears to have
inherited a copy of the 14 from both the mother and the father.
.. The paternity index (PI) is the genetic odds in favor of paternity. It is a
measure of just the genetic evidence and should generally be at least 100.
A PI of 100 means that given the type of the mother, the tested man is 100 times
more likely to produce a child of that type than would a randomly selected man
of the same ethnic background as the tested man.
.. There are many labs that mistakenly confuse the probability of paternity with
accuracy. They incorrectly
claim that their test is 99.9%-99.99% accurate. What they are reporting is the
probability of paternity. The probability of paternity cannot be substituted for
accuracy. The probability of paternity is a simple odds ratio. The generally
accepted minimum standard for an inclusionary is 99.0%. This means that the
alleged father has a 99 to 1 better chance of being the father than a random
man.