Bio Ch. 10

• A chromosome number is the number of chromosomes in a cell.
• Most organisms have different chromosome numbers.
• More chromosomes doesn't mean more DNA or that the organism is more complicated.
• A chromosome is a package of DNA.
• More chromosomes could mean that an organism has separated their genes into smaller packages.
• In most organisms, the chromosome number is an even number.
• Chromosomes usually come in pairs.
• Homologous chromosomes are matching chromosomes that carry the same genes but came from different parent.
• Homologous chromosomes carry the same genes, but not necessarily the same versions of those genes.
• For each pair of homologous chromosome, one chromosome came from the father and one chromosome came from the mother.
• A Gamete is a sex cell, or cell used during sex reproduction.
• What type of cells are Sperm cells and Egg cells?

  gametes
• Fertilization is the process by which a sperm cell and egg call combine to form a new individual.
• Gametes do not have homologous chromosome. (they are haploid cells)
• A Zygote is the first cell of a new organism.
• How many gametes are needed for fertilization?

  2
• A diploid cell is a cell/organism with 2 of each chromosome.
• Are most cells diploid or haploid?

  diploid
• A haploid cell is a cell/organism with one of each organism.
• What do scientists use the letter N to represent?

  the number of chromosomes in a haploid cell
• What do scientists use 2N to represent?

  the number of chromosomes in a diploid cell
• Why do scientists use 2N to represent diploid and N to represent haploid?

  Diploid cells will always have twice as many chromosomes as a haploid cell.
• Meiosis is cell division process that creates gametes. (sex cells)
• How many sections does meiosis have?

  2 (Meiosis 1 & Meiosis 2)
• Meiosis starts with a diploid cell. It produces four haploid cells.
• During Prophase 1, homologous chromosomes pair up.
• During Metaphase 1, the homologous pairs line up.
• During Anaphase 1, the homologous chromosome chromosomes are separate.
• Crossing over is the process of homologous chromosomes exchanging segments.
• Crossing over doesnt always occur, but happens quite frequently.
• Crossing over causes genetic recombination (creates new combinations of genes)
• During Metaphase 2, since there are no linger homologous pairs, the chromosomes just line up indivdually.
• During Anaphase 2, the sister chromatids split (just like in mitosis)
• Spermatogenesis is male meiosis.
• Spermatogenesis produces 4 sperm cells.
• Oogenesis is female meiosis.
• Oogenesis produces 1 ovum (egg) and 3 polar bodies (small, useless cells)
• Asexual reproduction is when a single parent produces offspring identical to itself.
• Sexual reproduction is when two mixed DNA to create offspring, unique from the parents and each other.
• A pro of sexual reproduction is that not all members will have a specific defect or disease vulnerability.