Presentation on theme: "What is a Karyotype? Karyotype: picture of an individual’s chromosomes arranged in homologous pairs. Chromosomes are usually extracted during METAPHASE."— Presentation transcript:
1 What is a Karyotype?Karyotype: picture of an individual’s 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 FemaleXY 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 NondisjunctionWhen 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 21st chromosome.Commonly known as: Down’s SyndromeSymptoms: 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 13th 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 Klinefelter’s 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 ChromosomesChromosomes 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 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.
13 Jumping GENESTransposons: 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!