Inheritance
Mendelian Inheritance –
Mendel figured out Meiosis – how alleles segregate and shuffle during the production of eggs and sperm.
He followed alleles expressed by Complete Dominance
b.1:1, 3:1 (monohybrid cross)
c. 1:1:1:1, 9:3:3:1 (dihybrid cross)
Other Types of Gene Expression:
a. Incomplete Dominance (Heterozygote phenotype is blended)
b. Codominance (ABO blood groups)
a. Inheritance of the alleles is the same using meiosis for both incomplete dom and codom.
b. The phenotype outcome changes, depending on the gene and how it’s regulated
c. Mitochondrial DNA – Pedigree for this shows that whatever Mom has, all of the children have it too. Always check for this before settling on Autosomal Dom or Autosomal Rec
Mendel figured out Meiosis – how alleles segregate and shuffle during the production of eggs and sperm.
He followed alleles expressed by Complete Dominance
- Law of Segregation – refers to the separation of two alleles (on a homologous pair) during meiosis.
- Law of Independent Assortment – refers to the lining up of homologous pairs during meiosis I. how the way one pair lines up is independent of the way a second pair lines up. So when they segregate, the resulting cells get different combinations of alleles. 223 = more than 8 million different combinations of how the homologous pairs can line up.
- Punnet Squares: These represent Meiosis, followed by Fertilization
b.1:1, 3:1 (monohybrid cross)
c. 1:1:1:1, 9:3:3:1 (dihybrid cross)
Other Types of Gene Expression:
a. Incomplete Dominance (Heterozygote phenotype is blended)
b. Codominance (ABO blood groups)
a. Inheritance of the alleles is the same using meiosis for both incomplete dom and codom.
b. The phenotype outcome changes, depending on the gene and how it’s regulated
c. Mitochondrial DNA – Pedigree for this shows that whatever Mom has, all of the children have it too. Always check for this before settling on Autosomal Dom or Autosomal Rec
Punnett Squares
Punnett Square: a diagram used to predict the outcome of a particular cross or breeding experiment.
Youtube video
http://www.youtube.com/watch?v=_ksIajiPUAU&feature=fvwrel
Youtube video
http://www.youtube.com/watch?v=_ksIajiPUAU&feature=fvwrel
Pedigrees
Pedigrees: They are just like a family tree. People are represented by symbols.
O = Female
Square = Male
Youtube Vid
http://www.youtube.com/watch?v=Wuk0W10EveU&feature=related
1 Ask the two questions:
1) Gender Bias? If no, then autosomal
Two unaffected parents having affected offspring? If no, Dominant; if yes, Recessive
2) Gender Bias? If yes, then either X or Y linked
Two unaffected parents having affected offspring? If no, Dominant; if yes, Recessive
Patterns of Affected Individuals
1 Autosomal Dominant
2 Autosomal Recessive
3 X-linked Recessive – Mostly males but not all males; rarely females
4 X-linked Dominant – 2 : 1 bias for females over males
5 Y-linked – all males
6 Mitochondrial – whatever Mom has, all of her children have
*More descriptions of patterns below*
O = Female
Square = Male
Youtube Vid
http://www.youtube.com/watch?v=Wuk0W10EveU&feature=related
1 Ask the two questions:
1) Gender Bias? If no, then autosomal
Two unaffected parents having affected offspring? If no, Dominant; if yes, Recessive
2) Gender Bias? If yes, then either X or Y linked
Two unaffected parents having affected offspring? If no, Dominant; if yes, Recessive
Patterns of Affected Individuals
1 Autosomal Dominant
2 Autosomal Recessive
3 X-linked Recessive – Mostly males but not all males; rarely females
4 X-linked Dominant – 2 : 1 bias for females over males
5 Y-linked – all males
6 Mitochondrial – whatever Mom has, all of her children have
*More descriptions of patterns below*
Black Board Quesitons
What is the pattern of affected individuals you will see on a pedigree for the following modes of inheritance:
- autosomal dominant
- Separated equally between both male and female
- Greater number of individuals affected than non-affected.
- autosomal recessive
- Separated equally between both male and female
- Greater number of individuals not affected than affected
- X linked dominant
- More females affected than males because they have two X’s which gives them twice the chance of displaying the dominate genotype.
- More of the population affected than non-affected.
- X linked recessive
- More males affected than females because males only have on X chromosome which limits the chance of receiving the dominate allele.
- A smaller number of the population affected.
- Often times the recessive phenotype can be hidden for many generations.
- Y linked
- All males in the family line affected.
- Females never affected because they don’t have a Y chromosome.
- Does not skip generations
- mitochondrial
- Trait only inherited from mother because sperm cells do not have a mitochondria.
- All children of a mother are at risk of being affected or carriers.