1. Karyotypes

2. Several methods help map human chromosomes.
A karyotype is a picture of all chromosomes in a cell.
X Y

3. Human Karyotype
To analyze chromosomes, cells are photographed during mitosis when chromosomes are fully condensed and easy to see.
Chromosomes are cut out of photographs and lined up with homologous chromosome and in order of largest to smallest.
Used to diagnose chromosomal disorders and determine gender.

4. Karyotype : chromosomes are paired
1 from mom & 1 from dad
23 pairs
46 chromosomes
22 pairs – autosomes
1 pair
sex chromosomes
46,XY
Normal male

6. Down syndrome: (Trisomy 21)
47, XX, 21+

7. Is there something wrong on this karyotype?

8. Human chromosomes Let’s look at this again
There are 46 chromosomes (23 homologous pairs) in each somatic cell
22 pairs of autosomes
1 pair of sex chromosomes
XX = Female, XY = Male
Karyotype - chromosomes are arranged according to shape and size
Normal human karyotype

9. Pedigrees
Biology I

10. Pedigrees analysis
Shows the analysis of inheritance in human families

11. Most common signs and symbols used in pedigree analysis

12. Inheritance patterns shown by a pedigree.
Basic patterns of inheritance
autosomal, recessive
autosomal, dominant
X-linked, recessive

13. Autosomal recessive Autosomal dominant X-linked recessive
e.g., PKU, Tay-Sachs, albinism
Autosomal dominant
e.g., Huntington’s Disease
X-linked recessive
e.g., color-blindness, hemophilia

14. Autosomal disorders Recessive disorders Cause: recessive alleles
Albinism, Cystic fibrosis, Sickle-cell anemia, Tay-Sachs disease
More common than dominant disorders
Dominant disorders
Cause: dominant alleles
Dwarfism (Achondroplasia), Alzheimer’s disease, Huntington’s disease
Less common than recessive disorders
Autosomal disorders are more prevalent in certain geographic regions or cultures

15. Autosomal Recessive

16. Autosomal Dominant

17. X- linked Recessive What is the inheritance pattern?
What is the genotype of III-1, III-2, and II-3?
What are the odds that IV-5 would have an affected son?

18. III-1 has 12 kids with an unaffected wife
8 sons - 1 affected
4 daughters - 2 affected
Does he have reason to be concerned about paternity?

19. Sample pedigree - cystic fibrosis
What can we say about I-1 and I-2?
What can we say about II-4 and II-5?
What are the odds that III-5 is a carrier?
What can we say about gene frequency?