1. Introduction to Genetics & Meiosis
HONORS BIOLOGY

2. Genetics – study of heredity
Heredity – passing on characteristics from parents to offspring
Traits – inherited characteristics

3. Gregor Mendel 19th Century Austrian Monk
First important studies of heredity

4. Monohybrid Crosses Two parents, differing by a single trait
Parents = P1
First Generation is called F1 – Filial 1
Second Generation is F2

5. How information is transferred
Gametes – sex cells
Fertilization – uniting male and female sex cells
Genetic information is located in genes, which are located on chromosomes.
Each trait is represented by two alleles.
Rule of Unit Factors-one factor(allele) from each parent

6. Rule of Dominance
An allele can carry either a Dominant or a Recessive trait.
For a recessive trait to be “expressed” , both alleles must carry it.
A dominant trait is represented by a capital letter, recessive by a lower case.

7. Law of Segregation
The two alleles for a trait separate when a gamete is formed.
The parent passes on, at random, one allele to each off-spring.

8. Gene expression Phenotype – the way an organism “looks”.
Genotype – the actual gene combination an organism carries.
Homozygous – two alleles for a trait are the same.
Heterozygous – two alleles for a trait are different.

9. B b BB bB Bb bb

10. Punnett Squares of all Possible crosses:
BB x BB
BB x Bb
Bb x Bb
Bb x bb
bb x bb B BB b Bb bB bb

11. PART II
MEIOSIS

12. Diploid Cell Cell that contains two of each chromosome
Supports Mendel’s conclusion that organisms have two factors (alleles) for each trait
One allele is on each of the paired chromosomes

13. Homologous Pairs
Together the two chromosomes of each pair in a diploid cell help determine what the individual organism looks like.
These paired chromosomes are called homologous pairs or homologous chromosomes.

14. Have genes for the same traits arranged in the same order, but there are different possible alleles for the same gene.
Two chromosomes in a homologous pair are not identical

15. Haploid cells A cell with one of each kind of chromosome - gamete
Male gametes are called sperm
Female gametes are called eggs
When a sperm fertilizes an egg the resulting off-spring is called a zygote

16. Meiosis
Cell division which produces gametes containing half the number of chromosomes of the parent
Two separate divisions - Meiosis I & Meiosis II
Meiosis I begins with 1 diploid cell and Meiosis II ends with four haploid cells

17. Interphase Cell carries out its normal functions
Sex cells replicate their chromosomes
Each chromosome then consists of two identical sister chromatids held together by a centromere

18. Prophase I Chromosomes coil up and spindle forms
Each pair of homologous chromosomes comes together top form a four-part structure called a tetrad
Pair so tightly that crossing-over can occur
resulting in new allele combinations

20. Metaphase I
Tetrads line up on mid-line of spindle

22. Anaphase I
Homologous chromosomes separate and move to opposite ends of the cell

24. Telophase I Spindle is broken down Chromosomes uncoil
Cytoplasm divides to form two new cells
each cell has only half the genetic information of the original cell because it has only one chromosome from each homologous pair

26. Second Phase of Meiosis
The newly formed cells must divide again to create the haploid cells

27. Comparing Meiosis and Mitosis
Chromosome behavior
Mitosis: Homologous chromosomes independent
Meiosis: Homologous chromosomes pair forming bivalents until anaphase I
Chromosome number- reduction in meiosis
mitosis- identical daughter cells
meiosis- daughter cells haploid
Genetic identity of progeny:
Mitosis: identical daughter cells
Meiosis: daughter cells have new assortment of parental chromosomes
Meiosis: chromatids not identical, crossing over