Karyotypes & Chromosomal Diseases Notes
A karyotype is an organized profile of a person's chromosomes. Two chromosomes specify
gender — XX for female and XY for male. These are known as sex chromosomes. The rest are
arranged in pairs, numbered 1 through 22, from largest to smallest. These are known as
autosomes This arrangement helps scientists quickly identify chromosomal alterations that may
result in a genetic disorder.
To make a karyotype, scientists take a picture of the chromosome from one cell, cut them out,
and arrange them using size, banding pattern, and centromere position as guides.
A regular human has 46 Chromosomes
This is what a normal karyotype looks like
Circle the autosomes
Put a square around the sex chromosomes
Is this a boy or a girl?
What happens when a person has something different, such as too many or too few
chromosomes, missing pieces of chromosomes, or mixed up pieces of chromosomes?
Sometimes chromosomes are incorrectly distributed into the egg or sperm cells during meiosis.
When this happens, one cell may get two copies of a chromosome, while another cell gets
none. Incorrect distribution of chromosomes is called nondisjunction. A zygote with 3 copies of
a chromosome is said to have trisomy. A zygote that is missing 1 chromosome is said to have
monosomy.
Chromosomal Disorders:
Klinefelter Syndrome(XXY) Male: Additional sex chromosome, they are males but male
characteristics are suppressed, they are sterile, have below average IQ and behavior
problems
2. Turner Syndrome (X or XO) Female : They are missing a sex chromosome, sterile,
Average IQ, shorter than normal with incomplete sex characteristics.
1.
Autosomal Disorders:
1. Down Syndrome (Trisomy 21): developmental disorder caused by an extra copy of
chromosome 21, distinct facial features, moderate to severe intellectual disability,
decreased life expectance.
2. Cri-du-Chat Syndrome (Deletion of Chromosome 5): Cat cry
Pedigrees
In these diagrams, people are represented by symbols, usually circles for female and squares
for male, and the bottom line represents the children of the couple above.
C
1. A male
A
2. A female
B
3. A marriage
Shaded in 4. A person who expresses the trait
Not shaded 5. A person who does not express the trait
D
6. A connection between parents and offspring
3
7. How many generations are shown on this chart?