1. Bell Work 2. Which cells are NOT formed during meiosis? Somatic cells
Gametes
Sex cells
Sperm cells
Bell Work
Diploid (Body Cell) 2N
Haploid (Sex Cell) 1N 46 50 10 8 20 14 31 28

2. DNA and Chromosomes Chromosomes are found in the nucleus
Chromosomes are made of DNA
Sections of chromosomes are called genes

3. DNA and Chromosomes
Each organism has a distinct number of chromosomes, in humans, every cell contains 46 chromosomes. Other organisms have different numbers, for instance, a dog has 78 chromosomes per cell.
Somatic Cells - body cells, such as muscle, skin, blood ...etc. These cells contain a complete set of chromosomes (46 in humans) and are called DIPLOID.
Sex Cells - also known as gametes. These cells contain half the number of chromosomes as body cells and are called HAPLOID

4. DNA and Chromosomes
Chromosomes come in pairs, called Homologous Pairs (or homologs). Imagine homologs as a matching set, but they are not exactly alike, like a pair of shoes.
Diploid cells have 23 homologous pairs = total of 46
Haploid cells have 23 chromosomes (that are not paired) = total of 23

5. KARYOTYPE Human Chromosomes
To examine human chromosomes, biologist photograph cells in mitosis when the chromosomes are fully condensed
Cut out the chromosomes from the picture and group them together in pairs
This type of picture is called a
KARYOTYPE

8. Karyotypes A karyotype can tell you THREE things:
Sex (male or female)
Irregular numbers of chromosomes
Any mutations in the chromosomes
Basically: all the chromosomes in a cell are displayed and can be examined for any abnormalities

9. Remember… Humans have 46 chromosomes (23 pair)
2 of them are sex chromosomes  they determine what sex you are
XX = female
XY = male
44 of them are autosomes  they do not determine what sex you are

10. Who determines the sex of a child?
The mother or the father?
THE FATHER!!!!

11. Why does the father determine the sex of the offspring???
Mom is XX, she can donate either one X chromosome or the other X chromosome
Dad is XY, he can donate either an X chromosome or a Y chromosomes.
If the offspring receives the father’s X, it is female
If the offspring receives the father’s Y, it is male

12. The Y chromosome If a Y chromosome is present, the person is male
X chromosomes contain genes necessary for growth/development
No cases of a person born with being 45,0Y
Probably spontaneously aborted (miscarriage)

13. Human Genes
The human genome is the complete set of genetic information
Determines characteristics such as eye color and how proteins function within cells

14. Human Chromosomes
Your chromosomes contain about 30,000 genes and 46 chromosomes
Once thought to be over 100,000 genes
That’s about 3 billion base pairs
Remember: genes on the same chromosome are linked together
They tend to be inherited together

15. Chromosomal Disorders
Most of the time, the mechanisms that separate human chromosomes in meiosis work very well, but things can go wrong
The most common error: NONDISJUNCTION
The chromosomes fail to separate
The result? Abnormal numbers of chromosomes
Trisomy 21 (Down Syndrome) is a common example in human genetics

16. Disorders: Down Syndrome – three 21st chromosomes (trisomy 21)
Turner Syndrome – single X chromosome
Klinefelter’s Syndrome – XXY chromosomes
Edwards Syndrome- trisomy 18

18. Edwards Syndrome (Trisomy 18) Frequency: 1 in 6000 births
copyright cmassengale

19. Turner Syndrome single X chromosome Frequency: 1 in 2000 births
copyright cmassengale

20. Klinefelter’s Syndrome XXY chromosome Frequency: 1 in 7000 males
copyright cmassengale

21. Normal Female
copyright cmassengale
2n = 46

22. Normal Male
copyright cmassengale
2n = 46

23. Klinefelter’s Syndrome
Karyotype Notation (total # chromosomes, sex chromosomes and extra or missing autosomal)
copyright cmassengale

24. Male, Trisomy 21 (Down’s)
copyright cmassengale
2n = 47

25. Female Down’s Syndrome (Trisomy 21)
copyright cmassengale
2n = 47

26. Turner’s Syndrome (Single X)
copyright cmassengale
2n = 45