Genetics 3.2

• Pedigrees reveal patterns of inheritance of human traits
• Pedigree- Shows a family tree with respect to a given trait, the analysis reveals patterns of inheritance
• Dr. Victor McKusick (1921-2008)
• 2565+ single traits and diseases for humans
• 2281+ loci are not fully known yet
• McKusick-Kaufman syndrome - a condition that affects the development of the hands and feet, heart, and reproductive system.
• In a pedigree,

  •Parents are connected by a single horizontal line, and vertical lines lead to their offspring

  •If the parents are related (consanguineous), such as first cousins, they are connected by a double line

  •Offspring are called sibs (siblings) and are connected by a horizontal sibship line

  •Twins are indicated by diagonal lines stemming from a vertical line connected to the sibship line

  •For identical (monozygotic) twins, the diagonal lines are linked by a horizontal line

  •Fraternal (dizygotic) twins lack this connecting line
• Pedigree

  ●   ■ ♦  - Aborted or stillborn individuals

  • □┬○ - Parents

  •    │ -generation

  •o  Proband  -  person who prompted  pedigree check                      

  •   Vertical dotted line = adoption
• Pedigree analysis of human traits has been an extremely valuable tool in human genetic studies
• We can use pedigrees to help find who has a genetic defect, who has that defective allele
• DNA molecules have fixed nucleotide sentences, cannot change it

  But the environment/conditions can alter if it shows or now. It can slow or stop protein production
• Epigenetics is the study of how your behaviors and environment can cause changes that affect the way your genes work
• •Recessive Traits:

            1. Albinism – absence of Melanin

            2. Cystic Fibrosis 

              - production of mucus       

                in the pancreas and Lungs

              - common recessive disease  

                among Caucasians 1/2500 births 
• I – 1st gen

  II – 2nd gen

  III – 3rd gen
• Pedigree analysis of human traits has been an extremely valuable tool in human genetic studies. We can use pedigrees to help find who has a genetic defect, who has that defective allele.
• DNA molecules have fixed nucleotide sentences, and cannot change it. But the environment/conditions can alter if it shows or now. It can slow or stop protein production.
• Epigenetics – environment/condition can affect how a gene functions
• Recessive traits

  • Albinism: absence of melanin
  • Cystic fibrosis: production of music in the pancreas and lungs. Common recessive disease among Caucasians 1/2500 births
• Some recessive alleles are very defective and dangerous. Sometimes having a homozygous recessive allele is an issue, especially if it carries a disease.
• For recessive traits:

  • Parents are generally unaffected (heterozygous)
  • Approximately 1/4 of the sibling are affected (25%)
  • Probability that an additional child will be affected is 1/4
  •  Recessive traits often result from consanguineous mating
  • Two affected parents CAN NOT have unaffected offspring. 
  • Can skip a generation
• Dominant traits:

  • Achondroplasia - dwarfism
  • Huntington disease- a degenerative neurological disorder
• Dominant traits seldom skip generations, affected individuals all have an affected parent
• For dominant traits:

  • Traits occurs EVERY generation (at least 1 person is affected)
  • When one parent is affected, approximately 1/2 of the progeny are affected
  • The probability that an additional child will be affected is 1/2 
  • Two unaffected parents don’t produce affected offspring
  • Two affected parents can produce unaffected offspring
• Wild alleles are normal alleles

  Null alleles are genes with only one allele, a nonfunctional allele

  A normal gene has (+), (++) means both alleles are present

  Missing an allele (+-)

  E+ both alleles, E- absence of an allele.

  1 -  dom allele, 2- recessive allele