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History of Genetics
1670’s Scientists believed
that each sperm contained a “little man” that would develop into a human
Then mother only served as an incubator
History of Genetics cont.
1750’s “Blending of Inheritance Theory”
Example:
Black animal mated to a white animal would produce a gray animal
History of Genetics cont.
1850’sGregor Mendel Austrian monk and worked in the
monastery garden mating pea plants Determined that characteristic were
inherited by discrete factors that would eventually become know as genes
Gregor Mendel
Discovered many principles
Principle of segregation Principle of independent assortment
Principle of Segregation
Every individual carries pairs of factors for each trait and that the members of the genes segregate at random during the formation of gametesSince segregation is random, predictable ratios of traits are found in the offspringDuring segregation, chromosomes go from a pair (2n or diploid) to singles (1n or haploid). Good way to remember:
Principle of Independent Assortment
Members of each pair of genes are distributed independently when the gametes are formed and are unaffected by other gene pairs on other chromosomes
When pairs of genes on different chromosomes separate, they have an equal chance or probability of going to an individual gameteNo predetermined order for the dividing pairs
EVERY GENE FOR ITSELF
Chromosomes
Located in the nucleus of the cell and contain all of the genetic material in the cell
Arranged in pairs
Made up of a substance called DNA
Two Types of Chromosomes
Haploid Half the diploid or
somatic (non-sex cell or gamete) number of chromosomes (n or 1n)
Diploid Number of
chromosomes found in the somatic or body cells (2n).
Twice the number of chromosomes found in the gametes
Chromosomes in Animals
Cattle
Sheep
Goat
Swine
Horse
Human
2n
60
54
60
80
60
46
1n
30
27
30
40
30
23
DNA
Deoxyribonucleic AcidThree Components Deoxyribose sugar Phosphate Four nitrogenous
bases Adenine (A) Thymine (T) Guanine (G) Cytosine (C)
Nucleotides
Combination of the deoxyribose, phosphate and one of the four bases Nucleotides bond together to form
one strand of the DNA molecule Two of the strands wind around each
other in a double helix to form the DNA molecule
The Gene
Genes are points of activity found in each chromosome that govern the way in which traits develop. Genes are specific areas on each chromosome and are made up of DNA
Protein Synthesis
RNA (ribonucleic acid) is a group of molecules in charge of “reading” and “translating” the genetic code for the formation of new proteinsRNA uses the DNA as a template to read the code in order to produce the right protein with the correct order and number of amino acids.
Three Types of RNA
Transfer RNA (t RNA) Plays a key role in protein synthesis (building). Each tRNA molecule can combine with one amino acid and can transport the a. a. to the new protein building site in the cytoplasm of the cell
Three Types of RNA cont.
Ribosomal RNA (rRNA) Also plays a key role in protein
synthesis. It helps control the connecting of the parts of the protein (the amino acids) together.
Three Types of RNA cont.
Messenger RNA (mRNA)Helps complete the building of the proteinPhysically sequencing the amino acids that were carried to the building site by the tRNA and chemically connected by the rRNAThe mRNA directs the sequence based on the order it obtains from the DNA molecule
Activity: Building DNA
Materials Needed: Several of each:
Four different colored gumdrops or other material that a toothpick can be inserted into
Toothpicks
Activity cont.
Instructions: Designate each color of gumdrops a different
base (A=red, T=green, for example) Designate the toothpicks as the bonds
between the bases Give the students a list of bases that ranges
from 10 to 15 bases long The students will then lay out the sequence
using the gumdrops and the sticking toothpicks into the sides
Activity Instructions cont.
The students must then decide the complimentary pair for each base and connect it to the given base
(to make a double helix other toothpicks must be used on the outer sides of the bases to connect the pairs of bases together in a rotating matter)