Download Intro to Genetics and Cell Division

Cell Growth and Division
Purpose of the cell cycle which
includes the mitosis:
-To produce new and identical body cells with identical
copies of DNA.
-Example: 1 skin cell will divide into 2 new and
identical skin cells
-All human body cells contain :
46 chromosomes or pieces of DNA
-23 from your mom
-23 from your dad
Mitosis produces body cells known as
2N or diploid cells.
Known as 2N or
diploid because
they contain 2 of
every chromosome
in each cell.
-one of each from
your mother
-one of each from
your dad
When a sperm with 23
chromosomes (1N)
fertilizes an
egg with 23
chromosomes (1N) it
produces the first body
cell, called the 2N
zygote
which has a total of 46
chromosomes.
Fertilization:
1N sperm by
unitesawith
1N sperm
1 N egg
is
fertilized
1N
egg creating a 2N zygote.
creating a 2N zygote or body cell.
Twin Formation
Identical twins:
-1 sperm and 1 egg unit forming one zygote.
-Zygote goes through mitosis creating two identical cells.
-The two identical cells split apart and both form into a fetus/baby.
-Babies must be of the same sex.
Fraternal twins:
-2 separate sperm fertilize 2 separate eggs forming two separate
zygotes.
-Each zygote goes through mitosis creating 2 separate babies.
-The two babies may be the same sex or of opposite sex.
DNA
-DNA is our
genetic code
-we inherit our DNA from
our parents
-DNA has the code for making
all of our proteins which determine our traits.
Examples of human traits
1. DNA is located in the
nucleus
of every cell in a relaxed,
uncondensed form known
as chromatin.
2. DNA supercoils into
chromatids the loops of
tightly coiled DNA of a
chromosome.
Chromosome:
-1 piece of DNA
Gene:
-1 segment of
DNA on a
chromosome that
codes for a
protein.
Allele:
-a specific form
of a gene
Allele:
A specific form of a gene
Each trait has 2 possible forms
Dominant form or allele:
The overpowering form of a gene
Represented by a capital letter
Recessive form or allele:
The weaker form of a gene
Represented by a lower case letter
2 alleles combine to determine a trait.
1 allele/gene from the sperm
1 allele/gene from the egg
Genetics:
The study of heredity
Heredity:
How traits are passed down generation to generation
History of Genetics:
-Gregor Mendel is known as the
father of Genetics
-1850’s
-Was an Austrian Monk
-Studied mathematics and botany at the
University of Vienna
-Used both of these areas of study to analyze genetic
crosses using pea plants
Pea Plants
Genetic terms you must know:
Phenotype:
A physical trait that you can see
Examples:
Red hair, blue eyes, etc…
Genotype:
The genetic make up /gene or allele
combination
Three types of genotypes:
BB…..
Homozygous dominant
Bb……
Heterozygous
bb…….
Homozygous recessive
Law of Dominance
Anytime a dominant allele is present
the dominant trait will be seen, it
overpowers the recessive allele.
Example:
Black fur is dominant ………… B
White fur is recessive………… b
B
b
B
B
b
b
Bb
BB
b
B
bb
Time to revisit our famous
creature the
CHNOPS
from its conception……
Should This Dog Be Called Spot???
Trait
Hair length
Hair texture
Hair Curliness
Coat Pattern
Dominant Gene
Short (L)
Wiry (T)
Curly (H)
Spotted (A)
Recessive Gene
Long (l)
Silky (t)
Straight (h)
Solid (a)
Punnett Squares: used to determine the
mathematical chance of inheriting certain traits.
Let us review:
Purpose of the cell cycle which includes the
mitosis:
To produce new and identical body cells with
identical copies of DNA.
-Example: 1 skin cell will divide into 2 new and
identical skin cells
One cell cycle is made up of:
1. Interphase
Period of rest
and prep for
Upcoming division
2. Mitosis: Nucleus divides
Prophase
Metaphase
Anaphase
Telophase
3. Cytokinesis: Cell
divides
In humans this process takes place once in every about 20 hours
In bacteria this process takes place once in every 20 minutes
DNA Replicates
Cell divides in half
Key terms:
Chromosomes:
individual pieces of DNA
Chromatin:
loosely coiled DNA in nucleus
Chromatid:
The loops of DNA that are formed when
it has gone through supercoiling
Unreplicated chromosome:
One single loop of a chromosome
Replicated chromosomes:
Two identical loops of a chromosome,
Sister Chromatids:
The two identical loops of a
chromosome, are identical due to DNA
replication.
Centromere:
-center of the chromosomes, holds the
two loops of DNA together.
Nucleus:
-organelle within a cell that contains
the DNA
Nucleolus:
-organelle within the nucleus
that makes ribosomes.
Centrioles:
-organelles only found in cells that aid in cell
division.
Interphase
• 1st phase of the cell cycle, longest phase, takes up 18 out of the 20
hours
– Three major things happen:
– 1. Cell grows and matures from a daughter cell into a parent cell.
– 2. DNA is replicates
– 3. New and needed organelles are formed so when a cell divides
it has all the needed cell structures to survive and function.
During interphase the DNA is in a loosely coiled,
in the form of chromatin.
-Two pairs of centrioles are present outside the
nucleus.
Mitosis
-2nd phase of the cell cycle
-Occurs in 3 subphases
-takes up about 2 of the 20 hours to complete
this section.
Prophase
• A. First phase of
mitosis.
• B. Sets the stage for
the rest of cell
division.
Early prophase
• 1. Nucleus and nucleolus breakdown into
their components of proteins, lipids and
carbs.
• 2. Chromatin supercoils into chromatids.
• 3. Centrioles pairs split apart and move to
opposite sides of the cell/the poles.
• 4. Centrioles stretch spindle
fibers/microtubules across the cell.
Late prophase
Metaphase
• A. Second phase of mitosis
• 1. Replicated chromosomes move to the
middle/equator of the cell.
- 2. Each chromosome attaches to its own
spindle fiber using the centromere.
Metaphase
Anaphase
• A. Third phase of mitosis
• B. Replicated chromosomes split apart and
ASTERS
move away to opposite poles.
1. Sister chromatids
split apart from each
other.
2. One single,
unreplicated copy of
the chromosome is
at each pole.
3. Spindle fibers break
down.
Anaphase
Telophase
• A. Final phase of mitosis
• B. Exact opposite of prophase.
– 1. A nucleus reappears around
each set of chromosomes at the
poles
- 2. A nucleolus reappears in each
nucleus.
- 3. Chromatid uncoils into
chromatin.
Telophase
Cytokinesis
• A. Final phase of the cell cycle
• One cell divides into two new identical daughter
cells.
– Animal cells:
• Cell membrane pinches together forming a cleavage furrow.
• Two ends eventually join separating the one cell into two
cells.
Plant cells:
- The formation of a cell plate occurs.
- The cell plate is a collection of sacks of cellulose that
collect in the center of the cell.
-The cell plate eventually matures into a cell wall.
Cytokinesis
End Result:
One mature parent cell divides into two new and
genetically identical daughter cells.
Cell starts over…………………………hence the cell cycle.
MITOSIS
Cell division video