Meiosis & Karyotypes
By Mr. Simonds
EQ: How are traits passed from
parents to offspring?
Vocabulary

Meiosis – A type of cell division that
produces sex cells with half the normal
number of chromosomes.
Meiosis I
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Telophase II
Meiosis II results in four
haploid (N) daughter cells.

Gametes – Sex cells (sperm and eggs)

Haploid – The name for a cell that has
half of its normal number of
chromosomes. Ex. Gametes

Somatic Cells – Every non-sex cell (skin,
nerves, muscle, etc)


Diploid
Diploid – The name for a cell that has
two of every type of chromosome.

Humans have 23 pairs of chromosomes.
That makes a total of 46 chromosomes.


So our diploid number is 46.
In each of our sex cells we have 23
chromosomes, one of each type.

So our haploid number is 23.
Healthy Human Male

If the diploid number of an organism is
10, what is the haploid number?


5
If the haploid number of an organism is
15, what is the diploid number?

Homologous Chromosomes – A pair of
the same type of chromosomes. You get
one from your mom and one from your
dad.
Review

How many chromosomes would one of
your skin cells have?


46
What is the haploid number for humans?

23
Review

What are gametes?


How many chromosomes do human
gametes have?


Sex cells (sperm and eggs)
23
If an organisms haploid number is 20
what is its diploid number?

40
Karyotyping
By Mr. Simonds
What is a Karyotype


Karyotype - a picture of a person’s
chromosomes matched by pairs and arranged
in order.
To make a karyotype you need a picture of a
persons DNA in chromosome form
 Then you match up chromosomes in pairs (23
pairs, including sex chromosomes)
Reasons for Karyotyping

To check for genetic (chromosomal)
disorders such as:
Down syndrome
 Klinefelter syndrome
 Turner syndrome

What are the pairs?

Autosomes – Chromosomes 1-22, they control
most of the traits that make you.
What are the pairs?

Sex Chromosomes – The 23rd pair of chromosomes
(X & Y), they determine your sex (male or female).
Chromosomes & Gender

A female has two X chromosomes.

A male has one X and one Y
chromosome.

As long as there is a Y chromosome the
fetus will become a male.
Karyotype of a Healthy Female
Karyotype of a Healthy Male
What is Down Syndrome?

Down Syndrome – A disorder caused by an
extra 21st chromosome. It causes delays in
physical and intellectual development

Also called Trisomy 21
 Occurs in 1 out of every 800 live births

Down syndrome is not related to race, nationality,
religion or socioeconomic status. The most important
fact to know about individuals with Down syndrome is
that they are more like others than they are different.
Down Syndrome
Turner Syndrome

Turner Syndrome – caused by
having only one X chromosome.
People with Turners become
female.

Occurs in 1 in 2000 to 1 in 2500 live births.

Symptoms include short stature and lack of
ovarian development. (They are sterile.)
Klinefelter Syndrome

Klinefelter Syndrome – Caused by
having two X and one Y chromosome.
People with this become male.

Occurs in 1 in 500 to 1 in 1000 live
births.

They are often tall and usually do not
develop secondary sex characteristics
such as facial hair, or underarm and
pubic hair.
How do these disorders occur?
Prophase II
Metaphase II
*Note that two of
the chromosomes
did not separate
during anaphase
Anaphase II
How do these disorders occur?

Non-disjunction – When chromosomes
fail to separate during meiosis. This
causes most chromosomal disorders.
*Note that two of the
chromosomes did not
separate during
anaphase
Anaphase II
How non-disjunction occurs.
Telephase
Gamete A
Gamete B
* Note that Gamete A has one extra chromosome and Gamete B has
one less chromosome
Review
Mitosis & Karyotypes
(+ a little DNA)
Meiosis

Does the father or the mother cause the
sex of the baby?


Father
Why?

The mother can only donate an X
chromosome
Healthy Human Female
Metaphase
Down Syndrome
Prophase
Nucleus membrane
breaking down
Chromosomes formed
Healthy Human Male
Meiosis

What cells undergo Meiosis?


How much DNA or Chromosomes do
you have after Meiosis?


Sex Cells
Half as much
What cells undergo Mitosis?

Body cells (Everything except for Sex cells)
Meiosis

What does Haploid mean?


An organisms Diploid number is 12. What is
its haploid number?


Half the number of Chromosomes
6
You have two of each type of chromosomes.
Where do you get them from?

One from your mom & one from your dad
Anaphase
Chromosomes
separating
What happened?
Non-Disjunction
Metaphase II
Anaphase II
Telephase/ Cytokinesis
Which ones pair together?
DNA

What do you make during Transcription?


mRNA
What process makes protein from
mRNA?

Translation