NOTEPACKET INFORMATION ON GAMETE FUSION AND TWINS:
Please don’t take this paper. I only have a class set and need them for all my classes!
Write in your notes the items that are underlinedGamete Fusion
Gametes are AKA: Gametes are specialized reproductive cells made by the cell division process that occurs in the ovaries or testes. That process is known as MEIOSIS and does not occur in our body cells.
These reproductive cells are known as sperm/egg cells.
Gamete fusion: when a sperm fuses with an egg
Gamete fusion is AKA: when the sperm fuses with the egg cell, now all the chromosomes, and information, are present to make a new organism. We call this fertilization.
Zygote: after the egg cell is fertilized by the sperm cell, this single cell is called a zygote. sperm + egg
cell = new “baby” cell
The zygote goes through mitosis and the one cell becomes two. The two cells go through mitosis and become four cells, and this continues on until you are the approximately 75 trillion cells that make you who you
are.
During fertilization or gamete fusion: the egg cell fuses with the sperm cell. This results in a single cell,
called a zygote, with all the chromosomes now that can develop into a new individual organism
Gamete Fusion
Egg cell
Twins
Sperm cell
fertilization
zygote
mitosis
mitosis
mitosis
And so on, until you get to the 75 trillion
cells that make you you !
Twins will happen as the result of one or two things… two
eggs being fertilized, or one single celled zygote splitting into
two separate zygotes with all the same genetic information (or
the same chromosomes) and those two zygotes grow into two
individuals.
Two eggs being fertilized are called fraternal twins. These
two individuals are siblings born at the same time. They can
be two boys, two girls, or a boy and a girl. They are NOT genetically identical.
One fertilized egg (zygote) splitting into two and becoming
two genetically identical individuals are called identical
twins. They have identical DNA. This means that they have
the same chromosomes, including the 23rd chromosome, and
that means they will be the same gender. So you cannot have
boy - girl twins be identical twins.
If one fertilized zygote cell splits into two zygotes, but not
completely, and grow into two individuals that are connected
together somewhere on their body, you have a type of twins
that we call conjoined twins. This is sometimes called Siamese twins. But the proper term is conjoined twins.
In the boxes on your notepacket, fill in your boxes as these boxes below are filled in below
Fraternal Twins
Egg cell
Sperm cell
Egg cell
Identical Twins
Egg cell
Sperm cell
Sperm cell
fertilization
fertilization
zygote
fertilization
zygote
zygote
zygote
mitosis
mitosis
zygote
mitosis
mitosis
mitosis
mitosis
mitosis
mitosis
mitosis
mitosis
mitosis
mitosis
And so on
And so on
Results in two babies from two fertilized cells that
are not genetically identical
And so on
And so on
Results in two babies from one fertilized egg cell that
divided into two zygotes that are genetically identical
Conjoined Twins
Egg cell
Sperm cell
fertilization
zygote
Zygote splits into two
zygotes
zygote
zygote
mitosis
mitosis
mitosis
And so on
And so on
Conjoined twins:
Results in two babies from one fertilized egg cell that divided
into two zygotes that do not completely split in two. Resulting in
a part of the two bodies being connected.
Read in a Big Biology Book (or the online book) on page 313 about non-disjunction disorders.
Non-disjunction will occur when chromosomes fail to separate during Meiosis, resulting in gametes that have too many chromosomes, or too few chromosomes. (Non-disjunction means failure to separate.) There are a only a few that will result in an infant.
All others will be terminal to the fetus and will not result in a child (a miscarriage would occur). The X chromosome and Y chromosome can have copies and still result in a child (XXY, X, XXX, XYY). But you have to have an X chromosome to be a viable fetus. So
you could not have a baby with only a Y chromosome and no X chromosome (Y only) This would result in a miscarriage because
the X chromosome carries so much information and codes for so many different proteins that are critical for development in a
person.
Fill in your notepacket about these Non-junction syndromes from the information below. Downs syndrome occurs when the 21
chromosome fail to separate correctly and there is an additional copy of the 21 chromosomes in the cell, also called Trisomy 21.
Edwards Syndrome occurs when you have an extra 18th chromosome, trisomy 18. And Patau’s Syndrome occurs when there is an
extra 13th chromosome, trisomy 13.