Science Exam Study Guide

Meiosis

Purpose: to transmit genetic material from an organism to its offspring to create genetic variation within a population produces sex and germ cells (gametes and spores) divides the amount of genetic material by half, with one haploid set of chromosomes per cell a zygote contains two haploid sets of chromosomes (1 from each parent)

Process:

Interphase I: Chromatin is inside nucleus and chromosomes are duplicating
Prophase I: Nucleus dissolves and centrioles move to opposite sides of the pole, attaching spindle fibers to condensed chromosomes
Homologous chromosomes pair together pair together, forming a tetrad
Metaphase I: Homologous chromosomes line up at the equatorial plate
Anaphase I: Spindle fibers move homologous chromosomes to opposite ends of the cell
Telophase I and Cytokinesis: Nuclear membrane re appears, spindle fibers dissolve and cytoplasm divides

Prophase II: Centrioles move to opposite poles and spindle fibers attach to chromosomes while the nucleus dissolves
Metaphase II: Chromosomes line up at the equatorial plate
Anaphase II: Sister chromatids move to opposite ends of the cell
Telophase II: Nucleus re appears, spindle fibers dissolve and cytoplasm divides resulting in 4 haploid cells

*Reduces chromosome number by half

Spermatogenesis: produces male gametes, which receive equal amounts of cytoplasm and genetic material
Oogenesis: creates an unequal amount of cytoplasm and only one egg matures

DNA (deoxyribonucleic acid): controls the production of proteins within the cell
Shape is a double helix composed of alternating sugar (deoxyribose) and phosphate molecules
4 nitrogen bases include Adenine, Thymine (double hydrogen bond) and Guanine and Cytosine (triple hydrogen bond)
Pyramidines (single ringed) are Thymine and Cytosine and Purines (double ringed) are Adenine and Guanine
Sequence of bases determine which protein is to be made
Chromosomes: microscopic, threadlike strands that contain DNA
Gene: a segment of DNA that codes for a particular protein which codes for a trait
RNA: the chemical that sends the message of the DNA to the ribosomes
Single stranded and had no thymine (uracil instead)
Has sugar ribose
Introns are junk DNA and extrons are DNA that code for a particular protein Non- disjunction: chromosomes don’t separate properly, which results in too little or too many chromosomes in one cell.
(Aneuploidy is a result of this)

2n + 1 = trisomic gamete (down syndrome)
2n – 1 = monosomic gamete (turners syndrome)

Polyploidy: more than 2 complete sets of chromosomes

XXY- Kleinfelter’s syndrome: and extra X chromosome which create feminine traits in males
XYY- Taller than average male
XXX- Meta female: limited fertility, often mentally retarded
XO- Turner’s syndrome: sex organs don’t mature and secondary sexual characteristics fail to develop.

Genetic Mutations
Deletion: removal of a chromosome segment
Duplication: Repeats a segment
Inversion: reverses a segment within a chromosome
Translocation: moves a segment from one chromosome to another, non-homologous one

Process of Respiration:
Breathing in causes air to enter lungs
Causes the exchange of gases (O2 ad CO2) between blood and tissue fluids
External respiration involves the exchange of gases (O2 and C02 between air and blood)
Involves production of ATP

When we inhale, the CO2 and H2O react with carbonic anhydrase to form carbonic acid, which turns into bicarbonate (HCO3) and hydrogen (H)
When we exhale, the bicarbonate and hydrogen become carbonic acid, which separates into CO2 and H2O

All multi-cellular gas exchange systems consist of a:
Moist thin membrane
A structure to maximize surface area
A method of delivering oxygen to the membrane
A surface in which the oxygen can dissolve
4 steps to respiration:
1. Ventilation: movement and exchange of gases between atmosphere and alveoli
2. Exchange of gases: between air in