University:
York University
Course:
BIOL 2040 | Genetics
Academic year:

2019
Views:

411

Pages:

3
Author:

Nick T.

Chapter 2: Mendel's principles of Heredity Homunculus! A misconception • Believed to see Fetus in head of sperm. Mendel observed Garden Peas. Self-Fertilizing, or breeding". Cross-Fertilizing. * Some traits are caused by a single change in a single gene. →Mendel's Laws Apply to all sexually reproducing organisms. Antagonistic pairs yellow OR Green = "either or" * Monohybrid crosses: P=dominant P X 1 D P P=recessive SsYy Sy SY sy Fi SY Sy SY SsYy sy Mononybrids = 2 different alleles for I trait. ★ LAW OF SEGREGATIONA →The two alleles for each trait segregate during gamete formation, then unite e random. F2 SY product rule: independent events. Probability of event I and 2 = Probability of event I x Probability of event 2 Tossing two coins is still independent events! BECAUSE! The result of one coin will NOT effect the probability of the second one. 1/2 x 1/2 = 1/4 Sum Rule: mutually exclusive events. Probability of Event I OR Probability of Event 2 = P+ Pz Yy x Yy Y YYY YY 3/4 1/4 Law of Independent Assortment: Y allele will give no info of R allele. →There is random shuffling Yyx Yy YY Y = ½ x Y=2 4 YY Parental Recombinant O 9/16 3/4 Yellow< Round 3/4 Wrink 1/4 → 3/16 Round 3/4 3/16 a 1/4 Green< wrink 1/4 1/10 Aa Bb Cc Dd x A a B b Cc Dd A Abb CCDd? Aa x Aa A a a Aa aa AA=1/4 Cc = 1/2 bb = 1/4 Dd = 2 1/4 x 4 x 2 x 2 = 1/64 Aa BbCc Dd x A a B b Cc Dd A-bb C-D- A_ = 3/4 bb = 1/4 3/4 x 1/4 = 27/256 3/4 x 3/4 x 3/4 x 1/4 C- = 3/4 D- = 3/4 Most common Single-gene traits are caused by dominant alleles in humans. Most diseases are linked to recessive alleles. Male (discased) female (deceased) Three key aspects w/ dominant 1. @least one affected parent. 2. Dominant traits show vertical pattern. 3. Two affected parents can have unspecified. an unaffected kid if heterozygous. ★Four key aspects for recessive traits. 1. Affected individuals can have unaffected parents. Consaguines matings. 2. All the children of two affected parents should be affected. 3. Rare recessive traits show a horizontal pattern of inheritance. A