Mendel and the Gene Idea
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All bold-faced terms in the chapter (Do NOT just give a definition of each term. Rather, use the term in your map in “context.”)
Results of a monohybrid cross of P generation “true breeders”
Results of a dihybrid cross of P generation “true breeders”
Explain setting up a monohybrid cross with respect to gametes
Explain setting up a dihybrid cross with respect to gametes
Outline and “map” the concept of all types of inheritance patterns (complete dominance, codominance, incomplete dominance, sex-linked inheritance, pleiotropy, epistasis, polygenic inheritance)-plus give examples of each
Recessively inherited disorders and include examples
Dominantly inherited disorders and include examples
Compare and contrast amniocentesis, chorionic villus sampling
Gregor Mendel
Genetic Testing and Counseling
Inherited Disorders
In 1857, Mendel began breeding garden peas in order to study inheritance.
The Law of independent assortment
Purple or White color for the flowers is called Trait
Heritable feature that varies among individuals is called Character
In Mendel's terminology, Purple flower color is a Dominant trait and White flower color is a recessive trait.
Two or more genes assort independently, each pair of alleles segregates independently or any other pair of alleles during gamete formation.
Monohybrid cross: Cross between heterozygotes
Allele for Yellow seeds is dominant (Y)
Allele for green seeds is recessive seeds (y)
Dihybrids cross: Cross between F1 dihybrids, can determine which of these two hypothesis is correct
F1 plants self pollinate and produce F2 offspring.
F1 hybrids will produce two classes of gametes:
YR
yr
Inheritance Patterns are often more complex than predicted by simple mendelian genetics
Pleiotropy
Epistasis
Codominance
Polygenic Inheritance
Incomplete Dominance
Sex-Linked Inheriance
Complete Dominance
F1 offspring always looked like one of the two parental varieties because one allele in a pair showed more than the other allele.
phenotypes of the heterozygote and the dominant homozygote are indistinguishable.
Allele of incomplete dominance can predict the red or white trait cold not reappear among offspring.
F1 hybrids have a phenotype somewhere between those of the two parental varieties.
Neither allele can complete hide the other.
Variation on dominance relationships between alleles
Ex. Cystic fibrosis & Sickle-Cell Disease
Each gene affects only one phenotypic character
Gene of one parent alters the gene of another parent
Different traits are affected by the genes such as height, weight, and color
Distinct traits over a period of time can vary in population along a continuum
Skin Color for example can be a by product of a trait that varies from environmental factors.
Males carry the XY chromosomes, and Females carry the XX chromosomes
A family's history for a particular trait and assembling this information into a family tree describing the traits of parents and children across the generations.
Passing on the Dominate Gene=A and the recessive gene=a can determine which trait gets passed from the dominate parent.
Dominate Inherited Disorders
Recessively Inherited Disorders
Carriers: Heterozygotes may transmit the recessive allele to their offspring.
Example Disorders range from Albinism, Sickle-Cell Disease and Cystic fibrosis
Allele that causes a genetic disorder codes for either a malfunctioning protein or no protein at all.
(aa) ususally shows up in the homozygous individuals who inherit the recessive gene.
achondroplasia is a form of dwarfism that occurs in one of every 25,000 people.
Multiple human disorders are due to a dominant alleles
Ex: Huntington's Disease is caused by a lethal dominate allele that has no obvious phenotypic effect until the individual is about 35 to 45 years old.
Amniocentesis
Chorionicvillus Sampling
Fetal testing can be tested by the amniotic fluid itself. Tests for disorders including Tay-Sachs disease.
Low risk to Fetus health
Most accurate test procedure for fetal testing by 99%
Needle is inserted into the uterus and extract 10ml of amniotic fluid which is cultured for 3-4 weeks
Testing can begin within 15-20 weeks of pregnancy
Slightly higher risk to fetus health than amniocentesis
Accurate test procedure but can use amniocentesis to confirm results of tests.
Narrow tube is inserted through the cervix into the uterus and suctions out a tiny sample of tissue from the placenta.
Testing can be done within 10-12 weeks of pregnancy