Section 7 - Inheritance

• Codominant inheritance occurs when both alleles are expressed equally, resulting in two distinct traits being present at once.
• Define Genotype


  The actual genes an individual possesses
• Define phenotype


  The actual appearance of individuals which is a result of the effects of genotype and environment
• define genotype


  the actual genes an individual possesses
• Define phenotype


  the actual appearance of individuals as a result of the genotype and environment.
• Dominant allele


  An allele whose trait always expressed when the allele is present.
• recessive allele


  An allele that is masked when a dominant allele is present
• codominant allele


  some alleles both expressed as neither is recessive
• explain the nature of multiple alleles

  -if there are more than 2 alleles for a gene

  -organism can only have 2 of the set
• How is a single gene inherited

  monohybrid cross: one gene from mother other from father
• what is dihybrid inheritance

  The inheritance of two characteristics which are controlled by different genes
• How does codominance affect the inheritance of characteristics

  both alleles expressed so both traits appear
• how do multiple alleles affect inheritance?

  no clue?
• How are blood groups inherited in humans

  -allele I A codes for antigen A (codominant)

  -allele I B codes for antigen B (codominant)

  -allele I O doesn't produce antigens (recessive)
• How is sex determined genetically

  XY - Male

  XX - Female
• what is meant by sex linkage?

  Where an allele is located on one of the sex chromosomes, meaning its expression depends on the sex of the individual.
• How are sex linked diseases inherited?

  through one of the sex chromosomes
• What is autosomal linkage?

  2 Genes (characteristics) carried on the same Chromosome
• How does autosomal linkage effect the combination of alleles in gametes?

  Two genes less likely to be separated during crossing over resulting in them being inherited together.
• What is meant by epistasis


  Where two non-linked genes interact, with one gene either masking or suppressing the other gene.
• What are the effects of epistasis? ...
• How do you know a condition is sex linked?

  Only/mainly males have the condition
• How do you know a condition is caused by a recessive allele?

  Two parents that do not have the condition have a child that has the condition (with example from diagram)
• How do you know the condition is caused by a dominant allele?


  two parents that have the condition have a child that does not
• How do you know the condition is NOT sex linked


  father would pass the x chromosome onto the daughter so she is not effected.