Download Heredity and Different Rules Notes

Heredity and Different Rules
Terms:
-Alleles: Different forms of a gene. T=Tall t=short
-Homozygous: two identical alleles. TT or tt
-Heterozygous: two different alleles. Tt
-Phenotype: Physical characteristics. Tall or Short
-Genotype: genetic makeup of alleles. TT/ Tt/ tt
-Simple Mendelian Inheritance: Dominant and Recessive paired
alleles. (most traits are not this simple)
-Rule of Dominance: one trait is expressed when both are present
Tall allele with short allele Tt = the plant is tall
-Rule of unit factors (alleles): Organisms have 2 alleles for each
gene/ 1from each parent. Tall alleles=T Short alleles=t
genotype=Tt
Law of Segregation: genotypes are made up of at least 2 alleles/
one from each parent/ How the alleles separate to form
gametes. (genotypes separating)
(eg. Tt = T t)
Law of Independent Assortment: Random assortment of alleles
during gamete formation. Genes on separate chromosomes
sort independently during meiosis. (two traits/ Random
combinations with more than one trait)
(eg.: YyRr results in 4 possible gametes: YR, Yr, yR, yr)
*Non Mendelian Inheritance: (Incomplete and Co-dominance)
-Incomplete Dominance: Appearance of a third phenotype.
Example: RR red snap-dragon plant x R’R’ white snap
dragon plant = Pink flowers RR’
RR x R’R’
R’
R’
R
RR’
RR’
R
RR’
RR’
-Co-dominance: Expression of both alleles.
Example: Black-feathered chicken BB x White feathered
chicken WW = Black and White feathered chicken BW/
-Blood type IA cross with IB = IAB Both Co-dominant
and Multiple Phenotypes.
BB x WW
B
B
W BW
BW
W BW
BW
-Multiple Phenotypes: Controlled by more than two alleles
Example: Multiple colors of a pigeon. BA /B /b
-Blood type IA cross with IB = IAB Both Co-dominant and
Multiple Phenotypes.
-Sex Determination: Humans have 46 chromosomes, or 23 pairs.
22 pairs are called autosomes and the 23rd pair is called the
sex chromosomes. Either XX for female or XY for male.
-Sex-linked inheritance: Traits controlled by genes on sex
chromosome.
-Polygenic inheritance: Is controlled by two or more genes.
-Environmental Influences:
-External environment Influences: Temp, light, nutrition,
chemicals, and infectious agents. (coloration of artic fox)
-Internal environment Influences: Males and females
(horns on mountain sheep/ Baldness in humans/ Peacock
coloration.