Biology 1201A Lecture Notes - Lecture 13: Homologous Chromosome, Gamete, Allele
11 Jun 2018
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Chapter 10
Patterns of Inheritance
Definitions
• Allele- One of two or more versions of a gene.
• Heterozygote- An individual with two different alleles of a gene.
• Homozygous- an individual with two copies of same allele.
• Dominant- allele expressed when more than one allele is present.
• Recessive- allele that is masked by a dominant allele.
• F1 gen- first gen of offspring.
• F2- second gen.
• Genotype- The genetic constitution of an organism.
• Phenotype- outward appearance of an organism.
• Trait- particular variation in a genetic or phenotypic character.
Mendel’s Experiments
- Believed in blending theory of inheritance, offspring’s were a blend of parent’s traits.
- Mendel prevented self-fertilization in his true breeding garden by cutting of anthers
from male peas and he cross pollinated (brought pollen over to fertilize from another
plant).
- Chose true breeding white and purple flowers
- Results- F1 had all purple flowers as if the white trait just disappeared.
- Then, he allowed F1 gen to self- fertilize, Results- both purple and white flowers
appeared.
- About 75% purple flowers and 25% white flowers.
Principle of segregation
- Genes governing genetic characters are present in 2 copies (homologous chromosomes)
- if there are different alleles in a pair of genes, one can be dominant over the other
- alleles of a gene segregate (during meiosis), each gamete receives one of the alleles
- During fertilization fusion of the haploid maternal and paternal gametes produces a
diploid nucleus called zygote nucleus, It receives one allele for the character from male
gamete and one allele for the same character from female gametes.
- During meiosis alleles separate and each gamete gets one allele.
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Document Summary
Believed in blending theory of inheritance, offspring"s were a blend of parent"s traits. Mendel prevented self-fertilization in his true breeding garden by cutting of anthers from male peas and he cross pollinated (brought pollen over to fertilize from another plant). Chose true breeding white and purple flowers. Results- f1 had all purple flowers as if the white trait just disappeared. Then, he allowed f1 gen to self- fertilize, results- both purple and white flowers appeared. About 75% purple flowers and 25% white flowers. During fertilization fusion of the haploid maternal and paternal gametes produces a diploid nucleus called zygote nucleus, it receives one allele for the character from male gamete and one allele for the same character from female gametes. During meiosis alleles separate and each gamete gets one allele. The alleles of the genes that govern the two characters assort independently during formation of gametes.
