Notes and Activity Pages Karyotyping Notes and Activity Pages

Why do scientists study chromosomes? Chromosomal mutations… Additional, missing, or damaged chromosomes cause several human genetic disorders. One way of studying these disorders is to observe the chromosomes themselves.

Karyotypes are treated with chemicals that stops cell division at the metaphase stage. During metaphase, the chromosomes are at the best/longest length for identification.

Karyotyping – tool used to determine the sex of an individual or detect/identify chromosomal abnormalities.

Humans have 46 chromosomes in every diploid (2n) body cell Humans have 46 chromosomes in every diploid (2n) body cell. The chromosomes of a diploid cell occur in HOMOLOGOUS PAIRS. Homologous pairs of chromosomes are similar in size, shape, and the position of their centromere. The cells are stained, placed on glass slides, observed under the microscope, and then photographed. There are 2 chromosomes in each place on a karyotype

In humans, homologous chromosome pairs 1-22 are called AUTOSOMES. Each homologous chromosome is alike (common). Autosomes transmit all genetic traits and conditions. Pair 23 determines the individual’s sex so that pair is referred to as the SEX CHROMOSOMES.

AND NOWWWWW… We are going to view some Karyotypes and determine if there is a disorder and what kind of disorder (mutation)

Normal Female Karyotype (XX at pair 23) Station 1

Normal Male Karyotype (XY at pair 23) 1b Normal Male Karyotype (XY at pair 23)

2 Down Syndrome

Down’s Syndrome Female. Trisomy 21, extra chomosome in pair 21. Down syndrome is one of the most common chromosomal disorders. Physical and mental development is slower. Flat facial profile. Broad forehead. Thick tongue. Upward slant to the eyes. Short arms and legs.

3 Turner Syndrome

Turner Syndrome Females only. Affects pair 23. Results from a missing or incomplete sex chromosome. Turner syndrome can cause a variety of problems: Short stature. Web neck. Failure to begin puberty. Infertility. Heart defects. Learning disabilities.

4 Patau Syndrome

Patau Syndrome Female. Trisomy 13; extra chromosome in pair 13. Least common and most severe of the trisomies. Survival is less than 3 days. Heart defects. Incomplete brain development. Unusual facial features such as small or missing eyes, low set ears. Extra fingers and toes. Spinal defects.

5 Klinefelter Syndrome

Klinefelder Syndrome Males only. Affects pair 23. XXY syndrome. Affects the male hormonal development due to an extra X chromosome. Lack of testosterone can cause less facial and body hair, breast enlargement, and infertility. Taller than the average male; longer arms. Skinny with wider hips and less muscular structure.

6 Edwards Syndrome

Edward’s Syndrome Female. Trisomy 18; extra chromosome in pair 18. More than 130 individual defects of the craniofacial structures, brain, heart, kidneys, and gut. Small mouth, jaw, and short neck. Back of skull is prominent. Malformed ears. Clenched fists with overlapping fingers; flexed legs and feet.

7 Triple-X Syndrome

Triple-X Syndrome Female. Trisomy X; extra X chromosome at pair 23. Taller than average. No unusual physical features. Increased risk of learning disabilities and delayed development of speech and language skills. Weak muscle tone. Behavioral and emotional difficulties.

8 XYY Syndrome

XYY Syndrome Males only. Affects pair 23. Extra copy of the Y chromosome. Taller than average. Increased risk of learning disabilities. Prone to severe acne. May include antisocial or behavioral problems.