LIFESCI 15 Lecture Notes - Lecture 5: Eye Color, Punnett Square, Y Chromosome
1/23/18
I. Who was Mendel?
II. Physical structure of the genome
III. What did Mendel figure out?
IV. Sex-linked traits
Mendel
- 1859: The Origin of Species
o A trait a hage oer tie ithi a speies if…
▪ Variation for a trait
▪ Heritability
▪ Differential reproductive success
- : Medel’s Talk
- The story of his life… fro the logook of The Natural History “oiety of Bru Fe
o Gregor Medel “poke o Iheritae i Pea Plats’
Physical Structure of the Genome
- An organism’s genome is all of its genetic material
- Chromosome – linear strand of DNA
- A hua’s geoe; hroosoes opated oleules of DNA arraged i pairs
- Generic cell
o How many chromosomes? 6
o How many homologous pairs? 3
▪ Homologous – at every physical location they have the same instructions for the gene
• Have 2 chromosome for every gene (maternal and paternal)
- Visualizing the chromosomes
o Karyotype: a picture of all the chromosomes in a cell
▪ Numbered by size
▪ Why would you need one? Before having a kid
▪ Where would you get the cell?
- % of thigs i DNA are juk DNA ad do’t hae gees that ode for aythig
- Diploid: you have 2 sets of chromosomes
- Haploid: only have 1 set of chromosomes
o Ex: gamete
- Not all animals have 46 pairs of chromosomes
- Mitosis: replication of body cells (somatic cells)
o Objective: produce daughter cells with the exact genetic complement of the parent cell
o Replace cells that are worn out
o Diploid → 2 diploids identical to parent cell
- Meiosis: happens in gametes
o Objective: reduce the ploidy of the cell by half (2N → N)
o Each gamete is haploid (N) and has only 1 copy of each set of genes
o When gametes recombine to form zygotes, the original number of chromosomes is restored
(2N)
What did Mendel Figure out?
- Medel’s st law: segregation
o A gamete receives only 1 allele for each gene (even though the organism generally has 2)
o Fertilization reestablishes the diploid number
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