Download “Command Center” because it houses all the genetic material in every

Section 3.1 DNA Notes
Learning Outcome
I can explain the differences, and roles involved with chromosomes, genes, and DNA
(1866) Heritable Traits: a scientist monk named Gregory Mendel, noted that parents inherited parents’
traits, and that some traits were more common than others. These traits became known as dominant
and recessive traits. Mendel is known as the father of Genetics
6 Principals of Genetics derived
1) Traits are passed from one generation of a species to the next generation
2) Genes are the units of hereditary and determine traits of living things
3) Living things that reproduce sexually inherit genes in pairs, with one set being contributed by both
parents
4) Some genes are dominant, while others are recessive
5) Dominant genes tend to mask or hide traits of recessive genes when offspring inherit a pair of genes
where one is dominant and the other is recessive
6) Genes may display incomplete dominance that is they may be neither dominant nor recessive
Chargaff’s Rules
First Rule
Number of Guanine units equals the number of Cytosine units, as well as the number of Adenine units
equals the number Thymine units
These are the four bases that help make up DNA
So A = T, and G = C
This strongly hinted towards base pair make up
Second Rule
Composition of DNA varies from one species to another, in particular the amount of A, G, T, and C.
This help add strength to the argument that DNA had the complexity needed to be responsible for
genetic material
Nucleus
The nucleus is known as the “Command Center” because it houses all the genetic material in
every cell
Genes are made up of DNA, and are responsible for determining all of the specific traits of an organism
Deoxyribonucleic Acid (DNA)
This is the inherited material responsible for variation
It was discovered in 1869
It is made up of
2 Backbones made up of alternating phosphate and sugar molecules, which are oriented on the
outside of the molecule
Then Nitrogenous Bases (adenine, guanine, cytosine, thymine), that face towards the inside bonding
with each other (through hydrogen bonds)
The Shape
Looks like a twisted ladder, forming a right handed double helix
The Nitrogenous Bases, form the rungs of the ladder
-Adenine
A only bonds with T
-Thymine
C only bonds with G
-Guanine
-Cytosine
Genes
Gene: is a segment of DNA, located in one particular place on a chromosome, which determines a
specific characteristic of an organism
So a gene is a specific area on the DNA molecule that represents the order of the Nitrogenous bases for
that specific region
The arrangement of these “4 chemicals” (Nitrogenous Bases) determines the genetic code
Genetic Code: Arrangement of the 4 chemical “letters” on a DNA molecule that can be arranged into
words, creating the instructions for an organism
Chromosomes
A single DNA Molecule is arranged into a package known as Chromosome
Chromosome: A structure in which DNA is arranged and in which Genes are located
The total DNA in one cell if spread out would be about the length of 2- 3 meters (1 million times longer
than the cell it came from)
To make it all fit DNA forms these Chromosomes by wrapping the double helix tightly around
some proteins, until a chromosome is formed
So how many chromosomes are there?
Well that depends on what type of organisms
Humans have 46
Fruit Flies have 8
Rice Plants have 24
Dogs have 72
Most Bacteria have one or two circular
Sex Chromosomes, Females are XX, and Males are XY
Genes and Alleles
Genes are located in the chromosomes
Each chromosome has numerous gene locations
Genes come in pairs
Both genes in a pair carry DNA instructions for the same thing
Specific characteristic genes occupy matching locations on the two chromosomes
DNA code may not be exactly the same in both locations
Allele
Is a possible form of a gene
Summary:
DNA is the material that contains the genetic information
The sequencing of the base pairs of the structure of the DNA makes up specific genes located
along the DNA molecule
DNA molecules are packaged up into chromosomes
Chromosomes are found in a cells nucleus
The nucleus carries out the genetic function necessary for the cell