Mendel’s Laws

law of segregation

Mendels’ first law. The Law of Segregation states that the two alleles of a given gene will be separate from one another during gamete formation (meiosis).

law of independent assortment

the law that states that genes separate independently of one another in meiosis when forming gametes

dominant allele

an allele whose trait always gets expressed (in the phenotype) in the organism when the allele is present

recessive allele

an allele that is masked (in the phenotype) when a dominant allele is present

codominance

Situation in which the phenotypes produced by both alleles are completely expressed (red flower crossed white flower to produce red & white spotted flower)

incomplete dominance

when one allele is not completely dominant over the other allele (red flower crossed white flower to produce PINK flower)

sex-linked trait

trait related to a gene that is found on the X or Y chromosomes

polygenic traits

traits controlled by two or more genes (ie. human skin color)

multiple alleles

genes that have more than two alleles (ie. human blood types)

probability

the likelihood that a particular event will occur

Hemophilia is a sex-linked, recessive trait. Which of the following describes the probability of
hemophilia in the offspring of a man who does not have hemophilia and a woman whose father is a hemophiliac?

A. Each of their sons will have hemophilia. B. None of their daughters will have hemophilia. C. Their sons have a 25% chance of having hemophilia. D. There is a 50% chance that their daughters will have hemophilia.