Contact Inhibition & Genetics Vocab

• Living organisms can reproduce with their own kind.

Contact Inhibition

• Cells stop growing and repairing when they touch other cells.
• Tumor suppressor genes (p53) on chromosome 17, specifically at locus 17p53223, halt growth when cells touch, which is known as contact inhibition.
• Specific regions, like the ends of bones, receive specific growth stimuli.
• Tumors develop if inhibition is lost, leading to cancer.

Vocab Definitions

• Genetics: The scientific study of heredity and variation.
• Heredity: The transmission of traits from one generation to another.
• Genes: Units of heredity made of DNA segments (A, T, C, G), determine traits, and are found on chromosomes.
  • Normal:
    • 46 chromosomes.
    • 23 pairs of chromosomes.
    • 92 chromatids.
    • 22 pairs of autosomes.
    • 1 pair of sex chromosomes.
• Gametes: Reproductive cells pass genes to the next generation and combine through fertilization, the goal of every organism to reproduce sexually.
• Locus: The specific location of genes, indicated by numbers.
• DNA: Mostly packaged into chromosomes and one set of chromosomes is inherited from each parent.
• Somatic Cells: Body cells other than gametes, containing 46 individual chromosomes, 23 pairs of chromosomes, 22 pairs of autosomes, and one pair of sex chromosomes.
• Homologous Chromosomes (Homologs): Each pair has 4 chromatids (tetrad), and they carry genes for the same inherited characters.
  • They line up as a matching pair (tetrad).
  • In mitosis, only individual chromosomes line up.
• Sex Chromosomes:
  • X and Y, one from each parent.
  • XX for female and XY for male.
• Diploid Cell (2n): Two sets of chromosomes, 2n=46 in humans with 2 produced in mitosis.
• Haploid (n): Half the normal amount (diploid).
  • 4 produced in meiosis.
  • Sex cell with a single set of chromosomes.
• Meiosis (Chromosome Reduction): Sexual reproduction process in 2 sets of cell divisions, resulting in 4 non-identical daughter cells (haploid).
  • Each cell has half the number of chromosomes as the parent cell.
  • Only sex organ cells undergo meiosis to produce gametes and reduces the number of chromosomes.
• P-generation: Parent generation aiming for 23 chromosomes each from sperm and egg resulting in a 46 cell offspring.

Meiosis I (Reduction Division)

• Only one interphase occurs and in Prophase I, homologous chromosomes pair up (synapsis) and exchange genetic material (crossing over).
• Metaphase I: Homologous pairs align at the cell's equator.
• Anaphase I: Homologous chromosomes separate and move to opposite poles.
• Chromosomal reduction occurs.
• Telophase I & Cytokinesis: Two haploid daughter cells form, each with half the original chromosomes.

Meiosis II (Equational Division)

• Similar to mitosis occurs with half the number of chromosomes.

• Breaks into single strands.

• Prophase II: Chromosomes condense and the spindle forms.

• Metaphase II: Chromosomes align at the equator.

• Anaphase II: Sister chromatids separate to opposite poles.

• Telophase II & Cytokinesis: Four non-identical haploid cells form.

• Mitosis: Asexual reproduction that conserves the number of chromosomes.

• Germinate: To put out roots.

• Ova/Ovum: the creation of sperm cells male.

Spermatogenesis

• Immature germ cells lead to a fertilized egg, or zygote, and develop into sperm.
• The initial cell is spermatogonia, stimulated by testosterone.
• Spermatogonia replicates its DNA
• A primary spermatocyte forms at the conclusion of Meiosis 1.
• Secondary spermatocytes produce 4 haploid spermatids.
• Further development forms the cell structure, including the acrosome.

Oogenesis

• Production of female gametes, or eggs in the ovaries during fetal development, continuing through puberty and ovulation.
• Primary oocytes are halted at Prophase 1 and reactivate after hormonal stimulation post-puberty.
• One secondary oocyte is arrested a second time at metaphase 2, until LH stimulates the ovary for ovulation.
• Rarely, two or more oocytes can result in two sperm.
• Fertilization: Combination of two haploids to diploid
• Sister Chromatid Cohesion: Allows sister chromatids of a single chromosome to stay together through meiosis 1
• Interphase:
  • Mitosis cleave happens at the end
  • In meiosis cohesions
  • In mitosis, the S phase produces two identical daughter cells.
  • Meiosis, the S phase leads to two rounds of division, resulting in four haploid daughter cells.
  • Resulting cells each have half the chromosome number of the parent cell due to crossing over.
  • This process occurs during prophase I of meiosis.