DNA Abnormal Meiosis Abnormal Meiosis During meiosis sometimes
DNA Abnormal Meiosis
Abnormal Meiosis During meiosis, sometimes chromosomes don’t separate properly resulting in: 1. Non-disjunction occurs where homologous chromosomes fail to separate. • This results in possession of too many or not enough chromosomes. For example, Down’s syndrome is caused when an individual has an extra chromosome, trisomy 21.
2. Translocation occurs when small parts of chromosomes break and rejoin other chromosomes.
Karyotype a micrograph (picture), called a karyotype can be taken for an individual (such as a fetus). A karyotype cannot show errors in individual genes, but it can show if a person has too many, too few, or broken chromosomes.
Homologous chromosomes • Somatic cell nuclei (body cells) are diploid (2 n) • They contain a homologous pair of each chromosome. One pair is paternal, and one pair is maternal. • Homologous chromosomes are the same size and structure. They carry the same genes at the same loci.
typical human karyotype Is this a male or female? FEMALE – 23 rd chromosomes (sex chromosomes) are XX
Typical human karyotype MALE – 23 rd chromosomes (sex chromosomes) are XY
Genetic disorders and human karyotype assignment
Workbreak • Read text pages 161 – 166 • Workbook Section 4. 4 (pages 46 – 47) • Question # 1 – 9
- Slides: 9