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biology CH 14 (inheritance patterns (complete dominance (form of dominance…
biology CH 14
inheritance patterns
complete dominance
form of dominance in heterozygous condition wherein the allele that is regarded as dominant completely masks the effect of the allele that is recessive
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codomiance
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a person with type AB blood, which means that both the A allele and the B allele are equally expressed.
two different versions (alleles) of a gene are expressed, and each version makes a slightly different protein.
incomplete dominance
third phenotype in which the expressed physical trait is a combination of the phenotypes of both alleles.
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form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele
sex-linked inheritance
patterns of inheritance and presentation when a gene mutation is present on a sex chromosome rather than a non-sex chromosome
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a recessive gene found in sex chromosomes (the X chromosome of the X and Y chromosomes in humans and drosophila)
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epistasis
often found associated with gene pathways where the expression of one gene is directly dependent on the presence or absence of another gene product within the pathway
example of epistasis is pigmentation in mice. The wild-type coat color, agouti (AA), is dominant to solid-colored fur (aa)
form on non-Mendelian inheritance in which one gene is capable of interfering with expression of another.
polygenic inheritance
height, skin color, eye color and weight
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occurs when one characteristic is controlled by two or more genes. Often the genes are large in quantity but small in effect
inherited disoarders
dominantly
Individuals with autosomal dominant diseases have a 50-50 chance of passing the mutant gene and therefore the disorder on to each of their children.
Examples of autosomal dominant diseases include Huntington disease, neurofibromatosis, and polycystic kidney disease.
neurofibromatosis
It causes tumors to grow on nerves. You can get neurofibromatosis from your parents, or it can happen because of a mutation (change) in your genes.
Type 1 can cause bone deformities, learning disabilities, and high blood pressure.
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Type 2 can cause hearing loss, vision loss, and difficulty with balance. .
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Huntington disease
Adult-onset Huntington disease, the most common form of this disorder, usually appears in a person's thirties or forties
Affected individuals may have trouble walking, speaking, and swallowing. People with this disorder also experience changes in personality and a decline in thinking and reasoning abilities.
is a progressive brain disorder that causes uncontrolled movements, emotional problems, and loss of thinking ability (cognition).
ndividuals with the adult-onset form of Huntington disease usually live about 15 to 20 years after signs and symptoms begin.
Autosomal dominant:
A pattern of inheritance in which an affected individual has one copy of a mutant gene and one normal gene on a pair of autosomal chromosomes.
recessively
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An autosomal recessive disorder means two copies of an abnormal gene must be present in order for the disease or trait to develop
Autosomal recessive is one of several ways that a trait, disorder, or disease can be passed down through families.
examples
tay Sachs disease
is typically found in people with certain ancestry, such as Eastern European Jews. A fatty substance in the brain destroys nerve cells.
Symptoms of slowed development usually appear around six months of age. Symptoms progress until they lead to death, often around age four.
an inherited metabolic disorder in which certain lipids accumulate in the brain, causing spasticity and death in childhood.
sickle cell anemia (SC)
With sickle cell disease, an inherited group of disorders, red blood cells contort into a sickle shape.
The cells die early, leaving a shortage of healthy red blood cells (sickle cell anemia), and can block blood flow causing pain (sickle cell crisi
is an inherited red blood cell disorder in which there aren't enough healthy red blood cells to carry oxygen throughout your body.
Normally, the flexible, round red blood cells move easily through blood vessels.
Cystic fibrosis (CF)
can be life-threatening, and people with the condition tend to have a shorter-than-normal life span
Cystic fibrosis affects the cells that produce mucus, sweat, and digestive juices.
s a hereditary disease that affects the lungs and digestive system. The body produces thick and sticky mucus that can clog the lungs and obstruct the pancreas.
sampling
chorionic villus
CVS utilizes either a catheter or needle to biopsy placental cells that are derived from the same fertilized egg as the fetus
The chorionic villi are wispy projections of placental tissue that share the baby's genetic makeup. The test can be done as early as 10 weeks of pregnancy.
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why its done
reasons:
You had positive results from a prenatal screening test. If the results of a screening test — such as the first trimester screen or prenatal cell-free DNA screening — are positive or worrisome, you might opt for chorionic villus sampling to confirm or rule out a diagnosis.
You had a chromosomal condition in a previous pregnancy. If a previous pregnancy was affected by Down syndrome or another chromosomal condition, this pregnancy may be at a slightly higher risk, too.
You're 35 or older. Babies born to women 35 and older have a higher risk of chromosomal conditions, such as Down syndrome.
You have a family history of a specific genetic condition, or you or your partner is a known carrier of a genetic condition. In addition to identifying Down syndrome, chorionic villus sampling can be used to diagnose many other genetic conditions — including single gene disorders such as Tay-Sachs and cystic fibrosis.
amniocentesis
is a prenatal test. During amniocentesis, an ultrasound transducer is used to show a baby's position in the uterus on a monitor.
A sample of amniotic fluid, which contains fetal cells and chemicals produced by the baby, is then withdrawn for testing.
, is sampled from the amniotic sac surrounding a developing fetus.
detects chromosome abnormalities, neural tube defects, and genetic disorders.
is a medical procedure used primarily in prenatal diagnosis of chromosomal abnormalities and fetal infections as well as for sex determination
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Amniotic fluid is the fluid that surrounds and protects a baby during pregnancy. This fluid contains fetal cells and various proteins.
why its done
reasons :
Genetic testing. Genetic amniocentesis involves taking a sample of amniotic fluid and testing it for certain conditions, such as Down syndrome.
Fetal lung testing. Fetal lung maturity testing involves taking a sample of amniotic fluid and testing it to determine whether a baby's lungs are mature enough for birth.
Diagnosis of fetal infection. he procedure can also be done to evaluate the severity of anemia in babies who have Rh sensitization
Treatment. If you accumulate too much amniotic fluid during pregnancy (polyhydramnios), amniocentesis might be done to drain excess amniotic fluid from your uterus.
Paternity testing. Amniocentesis can collect DNA from the fetus that can then be compared to DNA from the potential father.
cross of p generation
dihybrid
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results
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Mendel designed experiments to determine if two genes segregate independently of one another in dihybrids
Mendel reported the results of some but not all of the "7 choose 2" = (7)(7-1)/(2) = 21 possible dihybrid crosses with seven characters. He performed several trihybrid crosses as well.
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Alleles of genes assort independently, and can thus appear in any combination in the offspring
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monohybrid
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A cross between two parents possessing a pair of contrasting characters is known as monohybrid cross
Generally, the monohybrid cross is used to determine the dominance relationship between two alleles
A Punnett square may be used to predict the possible genetic outcomes of a monohybrid cross based on probability
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results
the result of Experiment 1 shows that the single characteristic of seed shape was expressed in two different forms in the F2 generation: either round or wrinkled
when Mendel averaged the relative proportion of round and wrinkled seeds across all F2 progeny sets, he found that round was consistently three times more frequent than wrinkled
This 3:1 proportion resulting from F1 x F1 crosses suggested there was a hidden recessive form of the trait.
Mendel recognized that this recessive trait was carried down to the F2 generation from the earlier P generation.
Mendel's data did not support the ideas about trait blending that were popular among the biologists of his time. As there were never any semi-wrinkled seeds or greenish-yellow seeds, for example, in the F2 generation
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