Note Taking Guide Key
Topic # 3032
Inheritance
By: Alisa Amy Kowalski
History of Genetics
1670’s
∙
Scientists believed that...
–
Each sperm contained a “little man” that would develop into a human.
–
Mother only served as an incubator.
1750’s
∙
Scientists believe in the “Blending of Inheritance Theory”
∙
Example: a black animal mated to a white animal would produce a gray animal
1850’s -Gregor Mendel
∙
Austrian monk
∙
Did a series of experiments that would lead to a new understanding of the mechanism of
inheritance
∙
Worked in the monastery garden mating pea plants
∙
Determined that characteristics were inherited by discrete factors that would eventually be
known as genes
∙
He described the principle of segregation & the 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 (without specific control or predetermined plan) during the
formation of gametes.
∙
Since segregation is random, predictable ratios of traits are found in the offspring
∙
During segregation chromosomes go from a pair (2n or diploid) to singles (1n or haploid)
∙
Genes do not blend and are passed intact from one generation to the next and chance
governs the segregation of the chromosomes in the gametes.
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 gamete
∙
There is no predetermined order for the dividing pairs- its every gene for itself (genetic
variation).
Chromosomes
∙
Located in the nucleus
∙
Contain all of the genetic material in the cell
∙
Chromosomes are arranged in pairs
–
Haploid: half the diploid or somatic (non-sex cells or gamete) number of
chromosomes (n or 1n)
–
Diploid: number of chromosomes found in the somatic or body cells (2n). Also
can be considered as twice the number of chromosomes found in the gametes
(sperm or ovum).
Chromosome Numbers
Animal
n
Cattle
30
Sheep
27
Goat
30
Swine
40
Horse
30
Human
23
Chromosomes are made up of a substance called DNA
DNA
∙
Deoxyribonucleic acid
∙
Made up of three components
–
Deoxyribose sugar
–
Phosphate
–
Four nitrogenous bases
2n
60
54
60
80
60
46
Nucleotides
∙
Combination of deoxyribose, phosphate and one of the four bases
∙
Band together to form one strand of the DNA molecule
∙
Two of these strands wind around each other in a double helix to form the DNA molecule
The 4 Nucleotides
∙
The bases of the DNA hold the key to inheritance
∙
The four nitrogenous bases are
–
Adenine (A)
–
Thymine (T)
–
Guanine (G)
–
Cytosine (C)
∙
In the two strands of DNA,
–
A is paired with T
–
C is paired with G
Replication of DNA
∙
The double helix unwinds and pulls apart
∙
A new strand is formed using the old strand as a template
∙
The end result are two identical double helix strands
The Gene
∙
Points of activity found in each chromosome that govern the way in which traits develop.
∙
Specific areas on each chromosome and are made up of DNA
Genetic Codes & Protein Synthesis
∙
Each different possible code represents a protein
∙
RNA (ribonucleic acid) is a group of molecules in charge of reading and translating the
genetic code for the formation of new proteins.
∙
RNA 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
3 Types of RNA
∙
Transfer RNA (tRNA)
–
plays a key role in protein synthesis
–
each tRNA molecule can combine with one amino acid and can transport the
amino acid to the new protein building site in the cytoplasm of the cell
∙
Ribosomal RNA (rRNA)
–
plays a key role in protein synthesis
–
helps control the connecting of the parts of the protein (the amino acids) together.
Messenger RNA -mRNA
∙
Helps complete the building of the protein
∙
Physically sequences the amino acids that are carried to the building site by the tRNA &
chemically connected by the rRNA
∙
Directs the sequence base on the order it obtains from the DNA molecules
RNA Transcription
∙
C is paired with G
∙
T is paired with A
∙
A is paired with U
Comparison to Building a House
∙
tRNA
–
people who haul the building materials to the construction site (cytoplasm - on
the ribosomes)
∙
rRNA
–
People that drive the nails, pour the concrete, etc.
∙
mRNA
–
provides a physical pattern or blueprint for construction
∙
DNA –
the original blueprint that is kept in the main office (nucleus) that directed the
plan