1. Chapter 11 Section 3: Chromosomes and Human Heredity
Ms. Diana and Ms. Su’ad

2. Karyotype Studies
The study of genetic material does not only involve the study of genes. It also involves whole chromosomes by using images of chromosomes stained during metaphase.
The staining bands identify or mark identical places on homologous chromosomes.
Homologous chromosome is one of two paired chromosomes, one from each parent, that carries genes for a specific trait at the same location.
The pairs of homologous chromosomes are arranged in decreasing size to produce a micrograph called a karyotype.

3. Karyotype Studies
The chromosomes are matched together with one pair of non-matching sex chromosomes.

4. Telomeres
Telomeres – protective caps that are found at chromosome ends.
Telomeres consist of DNA and proteins. The cap is a protective part for the structure of the chromosomes.
Scientists have discovered that telomeres also might be involved in both aging and cancer.

5. Telomeres: A Closer Look

6. Nondisjunction
Nondisjunction – the failure of sister chromatids to separate properly during cell division.
If nondisjunction takes place, then the gametes produced will not have the correct number of chromosomes.
It can result in extra copies of a certain chromosome or one copy of a specific chromosome in the offspring.
Set of three chromosomes: trisomy
Having just one type of chromosome: monosomy

8. Trisomy

9. Down Syndrome
Down syndrome is one of the earliest known human chromosomal disorders that is a result of an extra chromosome 21. “Trisomy-21”
Characteristics of Down syndrome:
Short stature
Heart defects
Mental disability

10. Sex Chromosomes
Nondisjunction occurs in both autosomes and sex chromosomes.

11. Turner’s syndrome
Has only 1chromosome.

12. Fetal Testing
Fetal tests can provide important information to the parents and the physician who is treating them.
Test
Benefit
Risk
Amniocentesis
Diagnosis of chromosome abnormalities
Diagnosis of other defects
Discomfort for expectant mother
Slight risk of infection
Risk of miscarriage
Chorionic villus sampling
Diagnosis of chromosome abnormality
Diagnosis of certain genetic disorders
Risk of infection
Risk of newborn limb defects
Fetal blood sampling
Diagnosis of genetic or chromosome abnormality
Checks for fetal blood problems and oxygen levels
Medications can be given to the fetus before birth
Risk of bleeding from sample site
Amniotic fluid might leak
Risk of fetal death

13. Question