MCAT Basics Podcast

MCAT Basics 8: Genetics: Chromosomes, Meiosis and Mitosis, and More!

The MCAT Basics Podcast with Sam Smith of MedSchoolCoach covers many topics on the AAMC MCAT. Each podcast covers a different topic, and up to 3 of the 4 MCAT sections. Lesson topics are based on the practice material, including practice tests, question banks.

During mitosis, a cell duplicates all of its contents, including its chromosomes, and splits to form two identical daughter cells. Meiosis also allows genetic variation through a process of DNA shuffling while the cells are dividing. Mitosis and meiosis, the two types of cell division. At each pole of the cell a full set of chromosomes gather together. A membrane forms around each set of chromosomes to create two new nuclei. The single cell then pinches in the middle to form two separate daughter cells each containing a full set of chromosomes within a nucleus. During a mitotic cell cycle, the DNA content per chromosome doubles during S phase (each chromosome starts as one chromatid, then becomes a pair of identical sister chromatids during S phase), but the chromosome number stays the same. A chromatid, then, is a single chromosomal DNA molecule.

Mitosis gives identical cells to each other and to the mother cell, while meiosis leads to genetic variation due to crossing over and independent assortment. Mitosis gives nuclei with the same number of chromosomes as the mother cell while meiosis gives cells with half the number. The main functions of mitosis are growth and repair. Some cells once fully formed do not undergo cell division, such as nerve cells and muscle cells. Since you can never re-grow or repair these types of cells once they are mature, you must take care of the ones you have. The purpose of mitosis is cell regeneration, growth, and asexual reproduction,while the purpose of meiosis is the production of gametes for sexual reproduction. Mitosis is a single nuclear division that results in two nuclei that are usually partitioned into two new daughter cells.

[01:39] Introduction to the show and topics today

[04:23] Purpose of mitosis and meiosis

[11:34] What happens when cells divide

[17:23] Steroid molecule structures

[22:29] Important things to know about chromosomes

[25:39] Biological importance of cell division

[31:39] Sex chromosomes

[35:20] G2 phase of the cell

[39:43] How your hair color is influenced by gene

Quotes:

“The short arm of one chromosome basically flops with the long arm of the other chromosomes. So you take two chromosomes and you trade long arm, short arm, and you basically create one chromosome with two long bits and attach at a centromere. And then another chromosome with two very short bits.“

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