1. Meiosis
Biology

2. Meiosis
Def: type of cell division that produces 4 cells with half the number of chromosomes as a parent cell
Occurs in the sex organs
Number of chromosomes= 46 or 23 pairs

3. Homologenous Chromosomes
Def: chromosomes that match in shape and size but not necessarily same DNA patterns
Homologous Chromosomes

4. Karyotyping Sex chromosomes Def: arrangement of all 46 chromosomes
The 23rd pair
Determines the organisms sex
XX= girl
XY=boy

5. Male Karyotype

6. Female Karyotype

7. Diploid vs. Haploid Diploid Haploid 2 homologenous sets of chromosomes
Forms the zygote 2n
Haploid
1 set of chromosomes- one from each pair
Occurs in fertilization n

8. Number of Chromosomes
Sex Cells each have half the number of chromosomes (23)
Zygote (fertilized egg) have 46 chromosomes

9. Steps of meiosis Differences between mitosis and meiosis:
Meiosis produces 4 offspring cells
Meiosis involves exchanging of genetic material between the Homologous Chromosomes.
Sister chromosomes- exact copies of DNA
Homologenous chromosomes- DNA does not have to be the same

10. Meiosis 1 Prophase 1 Metaphase 1 Anaphase 1 Telophase 1
Homologenous chromosomes stick together forming a tetrad
Crossing over begins
Metaphase 1
Crossing over is complete
Chromosomes line up in the center
Anaphase 1
Chromosomes migrate towards the opposite poles
Telophase 1
Each pole has a haploid

11. Crossing Over
DEF: Genetic materials is transferred from one chromosome to another
Crossed over

12. Meiosis 2
Follows the exact same steps as Mitosis except the end results in 4 cells instead of 2

16. Chickens have 78 chromosomes in their body cells how many chromosomes do they have in their sex cells?
Cats have 38 chromosomes in their diploid cells. How many do they have in their haploid cells?

17. Birth Defects
Biology

18. Numbers There are 200,000 people born with birth defects every year
To break it down, there are 25 people born with birth defects per hour

19. Causes of Birth Defects
Drugs/Alcohol/Smoking
Radiation/Pollution
STD’s
Inheritance
Malnutrition

20. Detection Blood Test Amniocentesis-
A sample of the amniotic fluid is taken and then the DNA is checked for Chromosomal defects

21. Chromosomes Monosomy- loss of one chromosome
Trisomy- gain an extra chromosome
Sex Chromosomes- X and Y

22. Down Syndrome Occurrence-1/600 births Causes- trisomy 21
Chance with increased age
20’s- 1/1500
40’s-1/44

24. Homozygous Recessive Traits
Found on the X chromosome
Passed on from mother’s to their children
Examples: Muscular Dystrophy and color blindness

25. Mutations
Definition- change in the DNA by changing one or more genes

26. Mutagens Definition- Agents that cause mutations
Examples: Chemicals, x-rays, radiation, genetic

27. Twins
Fraternal- Two fertilized eggs are implanted in the uterus at one time
Identical- one fertilized egg that splits