LIFESCI 3C03 Chapter Notes - Chapter 3: Cistron, Chromosome, Meiosis

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Published on 27 Jan 2017
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Ecology Selfish Gene Reading Chapter 3
Immortal Coils
Survival machines: all animals, plants, bacteria, and viruses
Replicators (genes) are basically the same kind of molecule in all survival machines
- DNA is made up of a pair of nucleotide double helices (immortal coil)
- Sequence of DNA nucleotides (A, C, T, G) varies between species
Each cell contains its own set of DNA instructions
- Book-case: nucleus
- Volumes: chromosomes (46)
- Pages: genes
DNA molecules do important things:
- Replicate: make copies of themselves
- Protein manufacturing
Genes are at least partially responsible for their survival in the future, because their survival
depends on the efficiency of the bodies in which they live and which they helped to build
- Acquired characteristics are not inherited
- Some genes are able to control clusters of other genes
Sexual reproduction shuffles genes
- Any one individual is a short-lived body for a combination of genes
- 23 pairs of chromosomes, one of each kind from each parent
- Paired chromosomes are not physically together, but they are identical in the sense that
they provide instructions for production of the same protein
E.g. page 6 of volume 13a (from dad) and page 6 from volume 13b (from mom)
are oth aout eye olour, ut oe ight say ro hile the other says blue
- When two genes are rivals for the same slot on a chromosome, they are alleles (e.g.
blue and brown eyes)
Cell division
- Mitosis: splitting of somatic cells to produce identical diploid daughter cells
- Meiosis: occurs during the production of haploid sex cells (sperm or eggs)
Any one sperm or egg is a mosaic of maternal genes and paternal genes due to
crossing over that occurs, which increases genetic diversity of individual sperms
within a male and eggs within a female
Cistron: a sequence of nucleotides between a start and stop codon
Gene: any portion of chromosomal material that potentially lasts for enough generations to
serve as a unit of natural selection
- Replicator with high copying-fidelity (longevity)
- Shorter genetic units are more likely to live longer (less likely to be split by any one
crossing-over)
- Smaller genetic units are more likely to be shared (more likely to have been generated
and more likely to live longer)
Genetic mutations:
- Point mutation: a single nucleotide error in replication
- Inversion: a piece of a chromosome detaches at both ends, inverts, and then re-attaches
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