Recombination

• Sex linked trait


  The gene (pair) that determines a character (e.g. hemophilia) is located on the sex chromosomes
• Y-Linked

  A sex-linked trait is where the gene or allele for the trait is found on the X chromosome
• Color blindness


  An X-linked recessive trait where a affected individual could not distinguish red from green color (red green color blindness)
• Hemophilia


  An X-linked recessive trait where an affected individual suffers from delayed blood clotting during injuries because of the absence of certain blood clotting factors
• Y-linked trait


  A sex-linked trait where the gene or allele for the trait is found on the Y chromosome
• Hypertrichosis pinnae auris


  A Y-linked trait is where affected males have hair growing from their external ears
• Sex-influenced trait


  Any trait in a diploid organism whose expression is affected by an individual's biological sex; a trait that occurs at a higher frequency in one sex over the other
• Sex-limited trait


  Any trait in a diploid organism whose expression is limited to just one biological sex
• Mutation


  A change in the genes of a plant or animal that causes physical characteristics that are different from what is normal. A new form of something that has changed
• Linkage


  Refers to the association and co-inheritance of two DNA segments because they reside close together on the some chromosome
• Recombination


  The process by which pieces of DNA are broken and recombined to produce new combinations of alleles.
• As a result, offspring can have different combinations of genes than their parents
• In humans, males and females are represented by different sex chromosomes
• Females have two X chromosomes in the nucleus of their cells
• Males have one X chromosome and one Y chromosome in the nucleus of their cells
• Depending on whether the trait is dominant or recessive, the expression pattern of the trait differs in males and females
• Color blindness in humans as an example of sex-linked trait, the alleles responsible for color blindness is found on the X chromosome only
• The dominant allele is the normal allele; the recessive allele causes color blindness
• Females need two copies of the recessive allele, one from each of the two X-chromosomes, for the trait to be manifested
• If they only have one copy of the recessive allele, they have normal color vision. However, they are carriers for the trait in that they may pass it on to their offspring
• Males only need one recessive allele in their sole X chromosome for the trait to be expressed
• Sex linkage


  The phenotypic expression of an allele that is dependent on the gender of the individual and is directly tied to the sex chromosome
• In such cases there is a homogametic sex and a heterogametic sex
• Crossovers result in recombination and the exchange of genetic material between the maternal and paternal chromosomes