1. January 17, 2017
Journal: Why does DNA replicate?

2. Chromosomes and Karyotypes

3. Chromosomes Usually DNA inside the nucleus is wrapped around proteins
Once the DNA is replicated they appear as X shapes

4. Critical Thinking Question
Why is DNA coiled up and not just a big clump in the nucleus?

5. Chromosome Structure P arm: Short arm of the chromosome
Q arm: Long arm of the chromosome
Centromere: midpoint where the two sides of the ‘X’ cross

6. Sister Chromatids
Two identical halves of a single replicated chromosome
Contain the same DNA on each half

7. Number of Chromosomes Somatic Cells – 46 Chromosomes
Sex Cells – 23 Chromosomes
Same number of chromosomes for entire life

8. Organism
Chromosome numbers
Human 46
Chimpanzee 48
House Mouse 40
Corn 20

9. Human Chromosomes

10. Types of Chromosomes Autosomes Sex Chromosomes 22 pairs
Contain all other traits
Sex Chromosomes
One pair
Determines your gender

11. Identifying Chromosomes
Chromosomes can
be identified by their:
Size
Shape
Gene Banding Pattern

12. Karyotype An organized arrangement of a person’s chromosomes.
Allows you to determine gender and chromosomal abnormalities.

13. Determining Gender Using a Karyotype
Female: XX Male: XY

14. Determining Chromosomal Abnormalities Using a Karyotype
Differences in chromosome number cause disease

15. Chromosomal Abnormalities
Trisomy 21 also known as Down’s Syndrome
Extra chromosome #21

16. Chromosomal Abnormalities
Trisomy 18 also known as Edward’s Syndrome
Extra chromosome #18
Results in heart and mental defects and overlapping fingers

17. Chromosomal Abnormalities
Turner’s Syndrome: XO
Females with underdeveloped ovaries
Typically have short stature

18. Chromosomal Abnormalities
Klinefelter’s Syndrome – XXY
Males with little body hair present.
Typically tall.
Some development of breast tissue normally seen in females.