1. Production of the Sperm and Egg
Meiosis Introduction
Production of the Sperm and Egg

2. Genetics and Heredity
The transmission of traits from one generation to the next is called heredity or inheritance.
However, offspring differ somewhat from parents and siblings, demonstrating variation.
Genetics is the study of heredity and variation.

3. Genes Parents pass on genes to their offspring
Genes program specific traits that emerge as we develop from fertilized eggs into adults.
Example: Your may have a gene for blue eyes, which you inherited from your mother.
Genes are segments of DNA.
In plants and animals, sperm and ova (unfertilized eggs) transmit genes from one generation to the next.

4. Chromosomes Sex chromosomes: determine an individuals sex
XX = Female
XY = Male
Autosomes: any chromosome that is not a sex chromosome

5. Types of cells Somatic cell: any cell other than the sperm or ovum
Contains 46 chromosomes
diploid: has two sets of chromosomes (2n)
Gametes: reproductive cells – the sperm and ovum
Contains 23 chromosomes
haploid: only have one set of chromosomes (1n)

6. Homologous chromosomes
Homologous chromosomes: The chromosomes that make up a pair
Pairs are due to sexual reproduction: we inherit one chromosome of each pair from each parent.
One from mommy one from daddy!  
They carry the same genes controlling the same inherited characteristics
They have the same length,
centromere position, staining
pattern
Also known as “homologues”

7. Purpose of Meiosis
The purpose of meiosis is to produce haploid cells: the sperm and ovum
This way, when the sperm and ovum fuse the baby will have a full set of chromosomes
Sperm (23) + ovum (23) = baby (46 chromosomes)
The fertilized egg (zygote) now has two chromosomes bearing genes from the maternal and paternal family lines.

8. Life Cycle
Fertilization and meiosis alternate in sexual life cycles.

9. Karyotype: a display of the 46 chromosomes (shows 23 pairs of chromosomes)

10. Normal Karyotype

11. Meiosis Gone Wrong
What happens if meiosis does not work correctly?!

12. Down Syndrome
characteristic facial features, short stature; heart defects
susceptibility to respiratory disease, shorter lifespan
prone to developing early Alzheimer's and leukemia
often sexually underdeveloped and sterile, usually some degree of mental retardation.

13. Patau Syndrome
Results in serious eye, brain, circulatory defects as well as cleft palate. 1:5000 live births. Children rarely live more than a few months.

14. Edward Syndrome
Almost every organ system affected 1:10,000 live births. Children with full Trisomy 18 generally do not live more than a few months.

15. Klinefelter Syndrome
Male sex organs; unusually small testes, sterile. Breast enlargement and other feminine body characteristics. Normal intelligence.

16. Turner’s Syndrome
1:5000 live births; the only viable monosomy in humans - women with Turner's have only 45 chromosomes!!! XO individuals are genetically female, however, they do not mature sexually during puberty and are sterile. Short stature and normal intelligence. (98% of these fetuses die before birth)

17. Conclusion It is terribly important that meiosis works correctly!
The homologous chromosomes need to be separated perfectly so the sperm and ovum have 23 different chromosomes.
Let’s see how this takes place…