Phases of Meiosis I Reduction

1. Prophase- tetrad/homologous pair nucleur membrane disappears

2.Metaphase- tetrads line up

3. Anaphase I- tetrads seperate into chromosomes to north and south poles

4. Telophase I- chromosomes reach ending poles

5. Resting phase- in normal 2 cells but double dna 

Phases of Meiosis II Division

-Prophase II- nucleur membrane disappears, chromosomes

-Metaphase II- chromosomes line up

-Anaphase II- chromatids seperate to East and West poles into chromasomes

Telophase II- chromosomes reach the opposite poles

Cytokinesis- 4 genetically different haploid cells

Haploid vs. Diploid

H: n, 1/2 set 23 chromosomes, sex cell

D: 2n, 1 full set 46 chromosomes, somatic cell

-sperm and egg cells

Homologous Chromosomes

-2 chromosomes that match in size, shape, and sequence of genes(one from father, one from mother-may slightly differ)

When does crossing over occur and between what?

-prophase I

-2 tetrads

How many sex and autosome chromosomes in humans?

S: 2

A: 44

What is Independent Assortment?

-the arrangement of homologous chromosome pairs at Metaphase I varies and is a matter of chance

-each pair orients itself independently of the other pair

-results in variety  of resulting gametes

-each pair of alleles segregates independently of the other pairs during gamete formation (meiosis)

Mendels Principle of Segregation

-pairs of alleles seperate during gamete formation (fuse again at fertilization)

Karyotyping

the determination of a karyotype, e.g., to detect chromosomal abnormalities

Chromosomal Disorders

-Down Syndrome- extra 21st chromsome

-Edward syndrome- extra 18 chromosome

-Klinefelter- 1 extra sex chromosome

-Turner- 1 less sex chromosome

Nondisjuction

-chromosomes fail to seperate at Anaphase I or II

-occurs with autosomes or sex chromosomes

Zygote

a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum

Genetic Variation

 variation in alleles of genes, genetic variation provides the genetic material for natural selection.

Dominant vs. Recessive

-dominant overpowers recessive unless incomplete dominance

D- big allele

R- little allele

Genotype vs. Phenotype

-Genotype: the letters/allele outcome

Phenotype: the physical outcome, traits

Homozygous vs. Heterozygous

-HO: either all recessive or all dominant alleles

-HE: both 1 recessive and 1 dominant allele

Hybrid

-offspring of 2 different true breeding varieties, aa and AA

-Aa

Test Cross

-mating between an individual of unknown genotype and a homozygous recessive individual

Sex Linked Diseases

-muscular dystrophy

-color blindness

-hemophilia

-baldness

Blood Typing

-O- ii

-A- I/a I/a or I/a i

-B- I/b I/b or I/b i

-AB- I/a I/b

Pleiotrophy & Polygene

Pl: the impact of a single gene on more than one characteristic ex. sick cell disease

PO: the additive effects of 2 or more genes on a single characteristicex. skin pigment

Incomplete Dominance

-neither dominance or reccesive shows, bloth are blended

-in flowers and sickle cell anemia

Genetic Disorders

-albino, dwarfism, cystic fibrosis, PKU, sickle cell, Tay- Sachs- all recessive

-alzheimers, huntingtons- dominant