Benchmark 16.1  By: Danny Ramirez and Alex Esteva

Mendel's Law of Segregation ● Mendel's Law of Segregation states that allele pairs separate or segregate during gamete formation, and randomly unite at fertilization.

Mendel's law of independent assortment ● Mendel's law of independent assortment states that the laws of chance govern which particular characteristics of the parental pairs will occur in each individual offspring.

Vocabulary ● Autosomal: the gene responsible for the phenotype is located on one of the 22 pairs of autosomes. ● X-linked: the gene that encodes for the trait is located on the X chromosome. ● Dominant: conditions that are manifest in heterozygotes. ● Recessive: conditions are only manifest in individuals who have two copies of the mutant allele.

Mendelian Inheritance Patterns  Mendel found the Mendelian Inheritance patterns. The four type of patterns referred to single gene inheritance.

Autosomal Dominant ● Dominant conditions are expressed in individuals who have just one copy of the mutant allele. Affected individual's have one normal copy of the gene and one mutant copy of the gene. So their offspring has a 50% chance of inheriting the mutant allele.

Autosomal Recessive ● Recessive conditions are clinically manifest only when an individual has two copies of the mutant allele. When just one copy of the mutant allele is present, an individual is a carrier of the mutation, but does not develop the condition. Females and males are affected equally by traits transmitted by autosomal recessive inheritance. When two carriers mate, each child has a 25% chance of being homozygous wild-type{not affected ; a 25% chance of being homozygous mutant ; or a 50% chance of being heterozygous.

X-linked Recessive ● All X-linked recessive traits are fully evident in males because they only have one copy of the X chromosome, thus do not have a normal copy of the gene to compensate for the mutant copy. So women are rarely affected by X-linked recessive diseases. Because the gene is on the X chromosome there is no father to son transmission.

X-linked Dominant ● Because the gene is located on the X chromosome, there is no transmission from father to son, but there can be transmission from father to daughter. Children of an affected woman have a 50% chance of inheriting the X chromosome with the mutant allele.

Dominant Inheritance  One parent has a single, damaged dominant gene, who overpowers its normal counterpart, affecting that parent. When the affected parent has sex with an unaffected and non-carrier partner, so the other non- carrier is homozygous recessive, the offspring are either affected or not affected, but they are not carriers

Recessive inheritance  Both parents carry a normal dominant gene and a faulty, recessive, gene. The parents, although carriers, are unaffected by the faulty gene, since their dominant gene overpowers the faulty gene, however when they mate. Their offspring are affected, not affected, or carriers.

codominance  Codominance is when two organisms share a dominant allele, meaning they HAVE to be dominant, they cannot be recessive.  Some examples are: Blood type-- type AB is codominant because both the antigen A and antigen B show up in the genotype. Another example is in cats. If a black cat and tan cat mate, the kitten would have both black fur and tan fur. A dog with white fur and a dog with black fur mate and produce a dog with both white and black fur.

Incomplete dominance  Incomplete dominance is here the Dominant traits of two heterozygotes are are not dominant to the other. An example of this phenomenon is pink snapdragons. If you cross red and white snapdragons, you get pink snapdragons.

Multiple Alleles  Multiple alleles means that there are three or more forms of a gene for a trait. That doesn't mean that a person can have all three of them. The person still only gets two.  (I got this example from the internet) an example of multiple alleles is : it's like having three trays of cookies, each tray having a different kind of cookie. Your instructions are that you may have any two cookies that you want. Can you have two from the same tray? Yes. Can you have two different kinds? Yes, you can have one of one kind and one of a second kind. Can you have one from each of the three trays? No, you can only have two cookies.

Sex linkage  The condition in which a gene responsible for a specific trait is located on a sex chromosome, resulting in sexually dependent inheritance of the trait.  Hemophilia, certain types of baldness, the placement of sweat glands, and color blindness are all different types of sex-linked traits in humans

Polygenic Inheritance  Polygenic inheritance is when a single trait is controlled by 2 or more alleles.  Most human traits are polygenically inherited.  Examples would be skin and eye color.

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