NonMendelian Inheritance and Human Genome Polygenetic Inheritance a

Non-Mendelian Inheritance and Human Genome

Polygenetic Inheritance -a trait is controlled by more than two alleles Ex. Skin color Fig. 14 -13 Aa. Bb. Cc Sperm 1/ Eggs 1/ 8 1/ 1/ 8 8 1/ 64 15/ 8 1/ 1/ 8 8 8 1/ 8 Aa. Bb. Cc 8 1/ Phenotypes: 64 Number of dark-skin alleles: 0 6/ 64 1 15/ 64 2 20/ 3 64 4 6/ 64 5 1/ 64 6

Sex Determination Gametes - -egg & sperm - originate from sex cells haploid -23 chromosomes Zygote - - when sperm & egg unite = fertilization -out of 46 only 2 are sex chromosomes = X & Y - -XX = female, XY = male -44 are autosomes- code for everything else

Sex Linked Genes - -Carried on only the X or Y chromosome - -Ex: Color blindness is a recessive trait carried only on the X chromosome (XCB). A female needs to be XCB to get it, but a male only has to be XCB Y to get it. So more males are color blind.

Numbers That You Should See If You Are In One Of The Following Four Categories: [Some Letter Choices Show No Visible Numbers] 4 Sex-Linked Traits: 1. Normal Color Vision: A: 29, B: 45, C: --, D: 26 2. Red-Green Color-Blind: A: 70, B: --, C: 5, D: -3. Red Color-blind: A: 70, B: --, C: 5, D: 6 4. Green Color-Blind: A: 70, B: --, C: 5, D: 2

Pedigree- a chart showing genetic inheritance

Incomplete Dominance the alleles are blended together to form an intermediate phenotype - example: snap dragon color (red, white or pink)

Incomplete Dominance Flower color RR= Red R’R’= White RR’= Pink

Co-Dominance - Both alleles are expressed in the phenotype (ex. Sickle cell anemia) BB= normal cell bb=sickle cell Bb Both (carrier)

Multiple alleles -Blood Type -Co-dominant -caused by multiple alleles – 3 or more forms - A = has only A carbs. (can act as antigens and cause a immune system reaction) - B = has only B carbs. - AB = both AB carbs. - O = no carbs.

Fig. 14 -11 Allele IA IB Carbohydrate A B i none (a) The three alleles for the ABO blood groups and their associated carbohydrates Genotype Red blood cell appearance Phenotype (blood group) IAIA or IA i A IBIB or IB i B IA IB AB ii O (b) Blood group genotypes and phenotypes

RH factor -Rhesus factor- antigens on the surface of blood cells that can cause an immune response - two types - Positive (+) contain the antigens - Negative (-) do not contain the antigens -a negative mother could harm a positive fetus. -a negative person getting positive blood can be seriously harmed.

Epistasis • A gene at one locus alters the expression of another gene Bb. Cc Sperm Eggs 1/ 1/ 4 BC 1/ 4 b. C Bb. Cc 1/ 4 Bc 1/ 4 bc BBCC Bb. CC BBCc Bb. CC bb. CC Bb. Cc bb. Cc BBCc Bb. Cc BBcc Bb. Cc bb. Cc Bbcc bbcc 4 b. C 4 Bc 4 bc 9 : 3 : 4

Pleiotrophy • Some genes control more than one trait. (ex. Pea flower and seed color are controlled by one gene, a genes for body size affects litter size, in humans a gene linked to eye color also skin tone. )

Multifactorial genetics • Multifactorial traits are affected by genotype and the Fig. 14 -14 environment • Norm of reaction-phenotype range (more acid or aluminum results in darker flowers