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Title: Genes and Inheritance
Description: These notes go over the history of genes and inheritance and the laws of inheritance. These notes were taken for an introductory college biology course.
Description: These notes go over the history of genes and inheritance and the laws of inheritance. These notes were taken for an introductory college biology course.
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Genes and Inheritance
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Eukaryotic cells have chromosomes (a single molecule of condensed DNA)
Portions of the DNA that code for protein are called genes
A gene is a sequence of DNA that is eventually going to code for proteins
o Each gene has different variants, called alleles
▪ Alleles code for the same trait, but the sequence of bases are different
History of Genetics and Inheritance
o 1600s said a premade person was inside of every sperm cell
o Many thought an offspring's traits were combined from each parent
▪ Purple flowers and white flowers combine to make light purple flowers
o Mendel and the Laws of Inheritance
▪ Monk living in the present day Czech Republic in the early 1800s
▪ Experimented on pea plants
• Quick generation time, easy to fertilize and grow, and produce many
offspring
• Chose easily observable traits in pea plants
• Height and flower color
• When he crossed two short plants, the offspring were always
short
• When he crossed two tall plants, the offspring were variable
• Crossed the offspring together
• Sometimes short individuals would disappear for a
generation and then come back
• Inferred the tall trait was somehow obscuring the short
trait
• Tall trait is dominant and short trait is recessive
• Observed the same thing with flower color
• When an individual carries a dominant allele on one chromosome and
the recessive allele on the other chromosome, the dominant mask the
recessive
• Dominant alleles get uppercase letter and recessive allele gets a
lowercase letter
• Changed the way inheritance was viewed
▪ Law of Segregation
• Diploid parents put one of two copies of each trait (one allele) into
each gamete
Laws of Inheritance
o In diploid cells, you have two copies of each gene (homologous chromosomes)
o If you have the same two alleles, you are homozygous for that gene
o If you have two different alleles, you are heterozygous for that gene
▪ Heterozygous individuals will show the dominant trait
o Genotypes are the genetic makeup of an individual (AA, Aa, aa)
o Phenotypes are the outward appearance of a trait
Mendel developed a system to keep track of all of his crosses
o Parental generations is P
Genes and Inheritance
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P's offspring is F1
F1's offspring is F2
So on and so forth
A monohybrid cross is a cross between two heterozygous individuals
A Punnett Square uses the genotypes of the parents to see what alleles the offspring
might inherit
Incomplete dominance
o No dominant allele
o Heterozygous individuals are intermediate between the two homozygous
phenotypes
Polygenic: when a trait is influenced by more than one gene
Title: Genes and Inheritance
Description: These notes go over the history of genes and inheritance and the laws of inheritance. These notes were taken for an introductory college biology course.
Description: These notes go over the history of genes and inheritance and the laws of inheritance. These notes were taken for an introductory college biology course.