1. Mendel and Meiosis
Chapter 10

2. Mendel’s Laws of Heredity
Heredity- Passing on of characteristics from parents to offspring.
TRAITS- Characteristics that are inherited.   
Genetics- STUDY OF HEREDITY
GREGOR MENDEL was the first to succeed in predicting how traits are transferred from one generation to the next.

3. GARDEN PEA EXPERIMENT
Mendel used garden peas to conduct his experiments because:
1.REPRODUCE SEXUALLY (they produce male and female sex cells called _GAMETES)
a. male gamete forms in the pollen grain. SPERM or male sex cell
b. female gamete forms in female reproductive organ. OVUM or female sex cell.
In fertilization the female gamete (ovum) unites with the male gamete (sperm) to form a ZYGOTE which develops into a seed.
2. In pea plants both female and male organs are in the same plant and tightly enclosed by petals, which prevents other pollens form entering.
- Reproduction is PURE AND CONTROLLED

4. TYPICAL FLOWER

5. How he did it: Mendel’s Experiment (fig 10.1) -Removed male organ
-dusted pollen of his choice on female organ CROSSPOLLINATION.
-Sure of what he crossed
-Well CONTROLLED experiment
-Studied ONE trait at a time.
-Analyzed data MATHEMATICALLY.

6. FLOWER POLLINATION

7. MONOHYBRID CROSS
HYBRID offspring of parents that have a different form of a trait
For example: short x tall
MONOHYBRID cross means that he crossed plants that differed in only ONE trait.
What do you get when you cross a gas powered car with and electric car?

8. Monohybrid Punnet squares
Original Parents : P1
1st generation: F1 (F=filial meaning son or daughters)
2nd generation: F2
RR x rr = F 1
Rr x Rr = F 2
Mendel eventually studied 7 traits

9. Mendel’s rules
Rule of Unit Factors: Each organism has 2 factors that control each of its traits.
Genes exist in alternative forms called ALLELES
2 alleles determine one trait. (Tt)
Recessive trait only when tt. Is present

10. Rule of dominance
Rule of dominance- One trait is dominant over another. The trait is expressed as long as it is present in the gene TT or Tt.

11. Law of segregation
Every individual has 2 alleles for each gene and when gametes are produced each gamete only receives one of these alleles. During fertilization these gametes randomly pair to produce 4 combinations

12. PHENOTYPE The way an organism looks and behaves
PHENOTYPE The way an organism looks and behaves. (may have environmental influence)
GENOTYPE- The actual allele make up of the organism.
HOMOZYGOUS traits have the same 2 alleles for a trait. ( TT or tt)
HETEROZYGOUS traits have 2 different alleles for a trait. (Tt) 

13. DIHYBRID CROSSES-crossing two traits at once
Law of independent assortment- Genes for different traits are inherited independently of one another,

14. SEXUAL REPRODUCTION SECTION 2
A cell with 2 of each kind of Chromosome is called a DIPLOID cell or contains 2n for the # of chromosomes.
A cell that produces gametes (sex cells- ovum and sperm cells), contain one kind of each chromosome know and a HAPLOID or n number of chromosomes.
Two chromosomes with identical information are called homologous chromosomes. They are similar structures. They contain the genes for a specific trait, ex. Height.
Genes are arranged in the same order but because there are different alleles (dominant and recessive) they may not be identical.

15. Problem solving lab 10.2

16. Sex linked traits
Traits controlled by genes located on the X and Y chromosome.
Because X and Y are not homologus they do not carry the corresponding allele to each other.
Characteristics carried on X will be expressed and not masked by the other chromosome.
Examples: Male pattern baldness, red-green color blindness, hemophilia (X-linked)

17. Co-dominant Traits
Human traits are often complicated and not expressed purely as either dominant or recessive but rather a mixture of the two traits.
Incomplete dominance
For example: Sickle cell anemia (blood disorder that effects African American population), blood types

18. Recessive Heredity Cystic Fibrosis- White Americans
Tay-Sachs disease- Ashkenasic Jews
Phenylketonuria (PKU)- Tested for at birth
Lesch Nyhan

19. Dominant Heredity Cleft chin Hitchhikers thumb Attached earlobe
Huntington’s disease yoa is expressed.

20. MEIOSIS
If cells reprduced gametes with a complete set of chromosomes (for example 14 chromosomes /7 pairs) each generation would double chromosomes.
F2- 28 chromosomes 14 pairs
F3- 56 chromosomes 28 pairs
F chromosomes 56 pairs
F chromosomes or 102 pairs!!!

21. MEIOSIS
MEIOSIS is cell division that results in HALF the number of chromosomes as the parent’s body cell.
  Male gamete= SPERM
Female gamete= EGGS
When the sperm cell fertilizes the egg the result is a ZYGOTE with a diploid # of chromosomes.

22. PHASES OF MEIOSIS Interphase: Same as mitosis. 1.PROPHASE I
DNA coils, homologous chromosomes line up.
Spindle forms
HOMOLOGOUS structure forms called a TETRAD each made of 2 sister chromatids. ( some crossing over occurs causing an exchange of DNA information.)

23. Prophase 1 cont…
Chromosomes in a tetrad pair so tightly that non sister chromatids can actually break and exchange material. This is called Crossing over.

24. 2.METAPHASE I
Pulled to equator like in Mitosis except the tetrad structure is side by side.

25. Meiosis I cont… 3.Anaphase I 4.Telophase I
Homologous chromosomes separate (tetrad pair separate)
Ensures each new cell will only receive one of the homologous chromosomes.
4.Telophase I
New cells appear with full set of genetic information. One homologous pair in each cell.

26. Meiosis II
Some cells undergo a short resting phase, others go directly into meiosis II.
It is simply mitosis.
Prophase II
Spindle forms and attach to chromosomes
Metaphase II
Sister Chromatids line up at equator
Anaphase II
Centromere splits apart and sister chromatids separate and move to opposite poles.
Telophase II
Nuclei reform, spindles break down
CYTOKINESIS – finishes process

27. Meiosis II 
Same as mitosis EXCEPT chromosomes DO NOT REPLICATE before they divide HAPLOID cells result.

28. Genetic variation
Since each pair can line up at the equator 2 different ways there are a 2N or 2 46 or 7 x1013 or 70, 400, 000,000,000 possibilities, or 70 trillion possibilities.
Genetic recombination- reassortment of chromosomes and the genetic information they carry.

29. Genetic alterations Nondisjunction: Gamete missing : Turner Female XO
Failure of chromosomes to SEPARATE properly.
Ex. Extra chromosomes in one cell or missing one in another. Down’s Syndrome is Trisomy 21.
Gamete missing : Turner Female XO
Tetraploid: 2 complete sets of chromosomes
Polyploidy- Organisms with more than the usual # of chromosomes. Death of zygote in animal cells. Common in plants through genetic engineering.

30. Karyotype