Download 1 TT - Brickell Academy Life Science

5/3 Warm-Up
Study quietly for the Nature
of Science (N2) and History
of Genetics (N31) quiz.
HW: DNA Structure Skill Check on 5/5
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What does the
word replication
mean to you?
When does replication occur
in eukaryotic cells?
During the S phase of Interphase.
Let’s see replication in action…
Enzyme
adenine
cytosin
e
thymine
guanine
Let’s see replication in action…
Enzyme
adenine
cytosin
e
thymine
guanine
Let’s see replication in action…
Enzym
e
adenine
thymine
cytosin
e
guanine
What do we
notice?
They are the
EXACT SAME!
Why is this
important?
Allows for the
continuation of
the genetic
information in
new cells made
through mitosis.
adenine
thymin
cytosine
guanin
Fill in your
foldable to
demonstrate
replication.
Why do cells divide?
1. To make
2. To make
old/dead
3. To make
new cells during growth.
new cells to replace or repair
cells.
specialized cells (development)
This occurs through mitosis
and produces body
(somatic) cells.
Would cells need to divide for
any other reason?
Would cells need to divide for
any other reason?
YES! In order for the organism to
reproduce.
How does this happen?
A type of cell division known as meiosis.
What is meiosis?
Meiosis is a type of cell division that
occurs only in reproductive organs to
make gametes (sex cells).
At the end of the process, four
daughter cells are produced with half
of the DNA of the parent cells. Male
gametes are sperm/pollen and
Females produce eggs.
8
chromosomes
(duplicated
)
4 chromosomes in 4
daughter cells
Homologous
pairs line
up in the
middle
How many chromosomes do sex
cells contain?
Sex cells contain half the number of
the organism’s normal number of
chromosomes.
That means that each human gamete
contains 23 chromosomes.
Why is it essential for meiosis to
result in half the total number of
chromosomes?
Why is it essential for meiosis to
result in half the total number of
chromosomes?
During fertilization, the two sex cells
combine and the original number of
chromosomes is restored.
Human egg
cell
23
chromosome
s
Human
zygote
46 ch.
Human sperm
cell
23
chromosomes
Mitosis
2
cell
s
4
cell
s
8
cell
s
So how can
scientists predict
offspring?
Punnett Squares
Parent
How do I set up a Genotype
Punnett square? Tt
In order to set up a Punnett square, you must first
understand that parents can give only one allele for a trait
during meiosis.
Let’s look at plant height in
pea plants to demonstrate:
T
DNA is
copied
T t
Parent DNA
X
T
T
T
t
t
X
t
t
Since 2 of the
4 resulting
daughter cells
have the
same DNA,
we only use 2
of the possible
daughter cells
in setting up
our Punnett
square.
How do I set up a Punnett
Parent One
square?
Parent Genotypes: Tt
X Tt
T t
X
t
t
T
T
T
T
X
t
t
How do I set up a Punnett
Parent Two
square?
Parent Genotypes: Tt
X Tt
T t
T
t
t
T
T
T
X
X
T
t
t
t
How do I set up a Punnett
square?
TT
tt
TT
T T
T t
T t
t t
tt
Parent Genotypes: Tt X Tt
How do I set up a Punnett
square?
T
t
T
T T
T t
Genotypic Ratio:
always written as
purebred
dominant : hybrid
: purebred
recessive and
reduce if needed
1 TT : 2 Tt : 1 tt
t
T t
t t
Parent Genotypes: Tt X Tt
How do I set up a Punnett
square?
T
t
T
T T
Tall
T t
Tall
Phenotypic Ratio:
always written as
dominant :
recessive and
reduce if needed
3 Tall : 1 short
t
T t
Tall
t t
Short
Parent Genotypes: Tt X Tt