chp 1: introduction Flashcards
genetics
the scientific study of heredity and hereditary variation. it can be studied at the organismal, cellular, and molecular levels
inheritance/heredity
the transmission of traits from one generation to the next
genetics is centered on the study of
genes
gene
unit of heredity
modern definition of gene
a segment of chromosomal DNA that provides info on how to produce a functional product such as a polypeptide or an RNA
genes provide
blueprint that determines the traits of an organism
traits
characteristics of an organism
hippocrates
(500 B.C.) proposed theory of pangenesis and preformationism
theory of pangenesis
“seeds” are produced by all parts of the body in fluids called “humors”
- collected in the reproductive organs
- then transmitted to preformed offspring at moment of conception
theory of epigenesis proposed by
aristotle
theory of epigenesis
blood needed to form semen
semen had
“vital force” to shape and create a new human
how do organisms start out in theory of epigenesis
organisms start out without form and are molded into their final form using a generative force
theory of epigenesis is now referred to as
embryonic development
modern theory of preformationism proposed by
william harvey (1578)
modern theory of preformationism
people using early microscopes thought they saw a miniature human or homunculus in the sperm
with proper nourishment the homunculus will
unfold into its adult proportions
the Spermists believed
the characteristics of the future person were found in the sperm
the Ovists believed
the characteristics of the future person resided in the egg
who refutes the idea of preformation
Embryologist Casper Wolff in 1733
charles darwin
pangenesis = gemmules instead of seeds in humors
gregor mendel
published an explanation of hereditary transmission in plants in 1866
after mendel’s death (1884)
cytologists using the microscope discover chromosomes separating in anaphase in meiosis
friedrich miescher
(1868) discovered nucleic acids