BISC120 Textbook Notes

BISC120 Textbook Notes - Chapter 14 Mendel and the Gene...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 14 – Mendel and the Gene Idea - Worked with pea plants; “true-breeding” variations –offspring are of the same variety - Hybridization – bringing together two true-breeding varieties o P generation: true-breeding o F1 generation: hybrid offspring (first filial generation) o F2 generation: offspring of F1 hybridization (second filial generation) Two laws generated from studying F2 - Law of Segregation o Purple dominant; white recessive o Four concepts which comprised Mendelian model Alternative versions of genes account for variations in inherited characters Gene for flower color exists in two versions (purple, white) Known as alleles , each residing on a specific chromosome For each character, an organism inherits two alleles, one from each parent Deduced this without knowing chromosomes Genetic locus represented twice in a diploid cell If the two alleles at a locus differ, then the dominant allele determines the appearance while the recessive allele has no impact Law of Segregation: the two alleles for a heritable character separate during gamete formation and end up in different gametes Corresponds to distribution of homologous chromosomes to different gametes in meiosis If identical, then true-breeding Punnett squares useful to understand the possible gene combinations
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
- Homozygous: PP or pp; heterozygous: Pp - Phenotype: observable characteristics and traits; genotype: genetic makup o Ex.: genotype Pp, phenotype purple - Testcross using Punnett square to determine the possibilities - Law of Independent Assortment o Mendel followed a single character Monohybrid: heterozygous for one character (color) Dihybrids: heterozygous for two characters (shape, color) o Law of Independent Assortment: each pair of alleles segregates independently of other pairs of alleles during gamete formation - Laws of segregation/independent assortment reflect same rules of probability, as well as those for multiplication and addition R r R R R Rr R Rr rr - Chance for RR : ¼; chance for Rr : ½; chance for rr : ¼ - Mendelian genetics goes beyond, into hereditary patterns not studied by him o Spectrum of dominance: the different degrees of dominance and recessiveness shown by alleles Complete dominance: one allele dominates; the heterozygous and homozygous are indistinguishable (PP/Pp both are purple) Codominance: both alleles affect the phenotype (AB blood group)
Background image of page 2
Incomplete dominance: heterozygous accounts for both dominant/recessive allele (red and white flowers make pink flowers) - Pleiotropy: when a single gene influences multiple phenotypic traits o Ex.: diseases with many symptoms (cystic fibrosis, sickle-cell disease) - Polygenic inheritance: additive effect of 2+ genes on a single phenotypic character o Indicated by quantitative characters (skin color) - Human traits follow Mendelian patterns of in heritance o Pedigree analysis: determine the available and possible traits for family members
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/18/2011 for the course BISC 120Lg taught by Professor 11:00-01:50pm during the Spring '06 term at USC.

Page1 / 14

BISC120 Textbook Notes - Chapter 14 Mendel and the Gene...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online