Module 3: Non-Mendelian Patterns of Inheritance

• Non-Mendelian - The pattern of inheritance in which traits do not segregate under with Mendel’s laws.
• Incomplete Inheritance - is a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other allele.
• In _, both alleles are expressed equally in the phenotype of the heterozygote.

  Codominance
• Multiple Alleles - Refer to a phenomenon of having more than two forms of the same gene in the population.
• Four blood types In Humans (phenotypes):

  1. A
  2. B
  3. AB
  4. O
• Allele for O is Recessive , two O alleles must be present for a person to have an O blood.

• A and B are _. If a person receives an A allele and a B allele,their blood type is AB.

  Codominant
• Males have 44 body chromosomes and two sex chromosomes. The males determine the sex of their children. Females have 44 body chromosomes and two sex chromosomes, both X. The total number in each cell of an individual is 46. These chromosomes contain genes, which are the factors of heredity.
• Sex-Limited Traits - are those that are expressed exclusively in one sex.
• Sex-Influenced Traits - are expressed in both sexes but more frequently in one than in the other sex.
• Codominance - A heterozygote condition wherein both traits are present simultaneously, rather than one fully determining the phenotype.
• Antigen - A protein- bound to a sugar molecule found on the surface of our red blood cells.
• Complete the table below (ABO System) :

  A) Anti-B

  B) Anti-A

  C) Anti-A and Anti-B

  D) a antigen

  E) b antigen

  F) a and b antigens

  
• Sex chromosomes - This control whether the organism will be a male or a female.
• Both males and females have 22 pairs of autosomal chromosomes and a pair of sex chromosomes. Male brings X and Y chromosomes, while both X chromosomes are in females.
• Three kinds of Sex-related Inheritance:

  1. Sex-linked
  2. Sex-limited
  3. Sex-influenced
• Sex-linked genes - These are genes found either on X or Y chromosomes.
• Hemophilia - an example of an X-linked trait is a rare genetic disorder in which a person lacks enough blood-clotting proteins caused by a change in one of the genes.
• Color-blindness - Another condition of the X-linked trait. These traits will be manifested in females who have two genes of color-blindness.
• Hypertrichosis Pinnae Auris - A Y-linked trait controlled by a Y chromosome and characterized by hairy ear in which are expressed in males alone.
• Lactation - Is an example of a sex-limited trait that is exclusively exhibited among females.
• One classic example of sex-influenced traits is __, which is expressed in females but is more often manifested in males.

  Pattern baldness
• Pedigree - Used to trace a gene as it is passed down throughout a family. This shows the presence or absence of a trait.
• Autosomal traits - Are located on non-sex chromosomes and are inherited equally by males and females.
• Sex-linked traits - Are located on the sex chromosomes and often exhibit different inheritance patterns between males and females.
• The difference between autosomal and sex-linked traits lies in the location of the genes that determine them and how they are inherited relative to an individual's sex.
• How to Read a Pedigree :

  ⮚ Determine whether the trait is dominant or recessive.

  ⮚ Determine if the chart shows an autosomal or sex-linked trait.
• Blood types are controlled by three alleles: A, B, O
• Complete the table bellow:

  A) IAIA or IAi

  B) IBIB or IBi

  C) IAIB

  D) ii

  
• Females have 2 sex chromosomes . Therefore, they can inherit or carry the trait without being affected if it acts in a recessive manner.

• Males have only one X chromosome. Thus, if they inherit the affected X, they will have the disorder.
• Heterozygous 


  Two alleles of a gene are different.
• Homozygous 


  Two alleles of a gene are the same.
• Alleles


  Different forms of a gene. (C,c)
• Genotype 


  Genetic constitution of an individual the alice that control of the phenotype of trait. (Cc)
• Phenotype 


  Set of observable characteristics of an individual resulting from the interaction of its genotype with the environment. (100% curly wings)
• In mendelian patterns of inheritance, the effects of recessive gene are not observed when the dominant gene is present.
• Carl Correns (1864-1933)


  The term incomplete dominance was proposed by the german botanist. he continued research and conducted an experiment of four o'clock flowers.
• Incomplete dominance 


  It is the formation of a third phenotype specifically with traits that results from the combination of parent alleles, none of the alleles from the parent alice express over the other for particular trait.
• Three alleles are responsible for the system:

  1. IA
  2. IB
  3. ii