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What is a Karyotype? Karyotype: picture of an individuals chromosomes arranged in homologous pairs. Chromosomes are usually extracted during METAPHASE.

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Presentation on theme: "What is a Karyotype? Karyotype: picture of an individuals chromosomes arranged in homologous pairs. Chromosomes are usually extracted during METAPHASE."— Presentation transcript:

1 What is a Karyotype? Karyotype: picture of an individuals chromosomes arranged in homologous pairs. Chromosomes are usually extracted during METAPHASE of a cell. Why? You can form a karyotype from any cell that is going through metaphase.

2 You can identify the gender of the person by looking at the sex chromosomes on the karyotype. XX Female XY Male

3 Doctors can also run tests on fetuses to check for chromosomal errors. This test is called an amniocentesis.

4 What happens when things go wrong with the chromosomes?

5 Nondisjunction When homologous chromosomes or sister chromatids fail to separate during meiosis. -Can occur in anaphase I or II; Resulting in gametes with abnormal # of chromosomes. It is not fully understood why nondisjunction occurs. *usually occurs in women over 40

6 Nondisjunction Example of nondisjunction: Trisomy-21 an error most likely during meiosis I, causing 3 of the 21 st chromosome. Commonly known as: Downs Syndrome Symptoms: characteristic facial features, below average height, heart defects, impaired immune system, varying degrees of mental disability.

7 Other forms of Nondisjunction Trisomy-13: (Patau Syndrome) Due to an extra chromosome on The 13 th chromosome. 1 in 10,000 of children born. There are varying degrees. Symptoms: cleft lip, clenched fist, close set eyes, mental Retardation, etc. More than 80% die in the first year.

8 Klinefelters Syndrome: (XXY Male) When a male has an extra X chromosome in most of their cells. Most common symptom is infertility. Most do not know they have it until puberty. Have less testosterone, so lack some male features. **caused by nondisjunction

9 Turner Syndrome: (Monosomy-X) Found in females that do not have the normal XX in their cells. They only have one. 1 in 2000 live births. Symptoms: swollen hands and feet, lack female features after puberty, wide, webbed neck, flat/broad chest, drooping eyes, infertility.

10 Damaged Chromosomes Chromosomes can also be damaged and cause problems. There are 4 types of changes that can occur to chromosomes and cause varying problems to the body.

11 Duplication: when part of the chromosome is repeated. Not always fatal but can cause some developmental abnormalities. Deletion: when part of the chromosome is lost. Inversion: reversing a section of the original chromosome. (not as harmful) Translocation: when a section of one chromosome attaches to a NONhomologous chromosome.

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13 Jumping GENES Transposons: where a section/gene of a chromosome jumps to another chromosome. Disrupting the genes. Barbara McClintock discovered these in the 1940s with variations of corn. She received the Nobel Prize in 1983 for her pioneering work!


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