Genetics

• The Cell Cycle consists of Interphase, which is normal cellular function and preparation for division, and Mitosis, which is division into daughter cells.
• Interphase is regulated by a series of checkpoints.
• Ploidy, represented by 'n', is the number of chromosome sets, with 1n being haploid and 2n being diploid.
• Human Karyotype shows that humans have homologous chromosomes of the same sizes and same genes in same locations (loci).
• Ploidy is maintained during mitosis, meaning that the amount (mass) of DNA, represented by 'c', is the same before and after mitosis.
• In Mitosis, a replicated chromosome donates one of its two identical twin sister chromatids to each daughter cell.
• The correct n (# of sets of homologous chromosomes) and (# of total chromosomes) count for a cell can be determined by the number of chromosomes it has.
• These are separate chromosomes, artificially aligned to be next to each other, not sister chromatids.
• The correct n and total count for a cell can be determined by the number of chromosomes it has.
• Astral microtubules grow toward the membrane of the cell and contribute to cell stability.
• Mitosis involves the division of chromosomes by microtubules, with kinetochore microtubules embedding in the kinetochore at the centromere of each chromatid and being responsible for chromosome movement.
• To maintain species ploidy, gametes must have half the chromosomes.
• Polar microtubules extend toward the opposite pole of the centrosome and contribute to cell elongation and cell stability.
• During prophase I, chromosomes begin to condense and homologous chromosomes synapse, forming a structure known as a synaptonemal complex.
• Meiosis is the creation of gametes and involves the decrease in genetic diversity due to the fusion of two gametes.
• Stages of prophase I include Leptotene, which are "thin/fine threads", Zygotene, which are "joined/yoked threads", and Leptospira bacteria, which have a "thin/fine spiral" chromosome structure.
• Separase degrades cohesin to initiate anaphase.
• Cohesin joins sister chromatids and prevents premature separation of sister chromatids.
• Homologous chromosome synapsis is dependent on DNA sequence similarity/homology, but in males, X and Y are very different.
• Polyploidy does not affect a cell’s ability to undergo mitosis.
• A person born with trisomy 21 (Down syndrome) could not create euploid gametes due to chromosome segregation.
• Chromosome nondisjunction in these hybrids leads to cells with double the number of chromosomes.
• Polyploidy can result from duplication of chromosome sets within a species (autopolyploidy) or from combining the chromosome sets of different species (allopolyploidy).
• Causes of autopolyploidy include meiotic nondisjunction leading to a diploid rather than haploid gamete and mitotic nondisjunction that doubles chromosome number.
• Bread wheat is 6n, Durum wheat is 4n, Banana is 3n, and Citrullus is 2n.
• Each chromosome in these cells has a homolog for pairing, and the hybrid is fertile.
• Many types of polyploidy are possible.
• Colchicine prevents the separation of sister chromatids.
• Plants of odd-numbered ploidy make few to no seeds, while plants of even-numbered ploidy make nice healthy seeds.
• Polyploidy is the presence of three or more sets of chromosomes in the nucleus of an organism.
• Allopolyploids are hybrids with chromosomes from different species and are infertile due to nonhomologous chromosomes that can’t pair in meiosis.
• Meiosis in triploids results in every gamete having a random mix of 1 (correct) or 2 (one extra) homologous chromosomes, making it hard for seeds to develop normally.
• Interphase is characterized by Leptospira bacteria with a "thin/fine spiral".
• Chromosomes begin to condense during Interphase.
• Homologous chromosomes synapse during Interphase.
• Diploid cells enter the G1 phase of the cell cycle during prophase I.
• Pachytene is characterized by "Thick threads".
• Thick-skinned pachyderms are a type of animal that is used to represent stages of prophase I.
• Zygotene is characterized by "Joined/yoked threads".
• Oxen are yoked by their synaptonemal complex during Interphase.