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Summary of Chapter 3 of the 'Genetics' Course Literature
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An in-depth, but still short, summary of chapter 3 of the course literature. It helped me pass the course with an 8.
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CHAPTER 3 Chromosome Transmission During CellDivision and Sexual Reproduction
3.1 General Features of Chromosomes
3.2 Cell Division
3.3 Mitosis and Cytokinesis
3.4 Meiosis
3.5 Sexual Reproduction
3.6 The Chromosome Theory of Inheritance and Sex Chromosomes
During cell division, eukaryotic cells can sort their chromosomes in two ways. Mitosis sorts
chromosomes so that each daughter cell receives the same number and types of chromosomes
as the original mother cell had. Meiosis results in daughter cells with half the number of
chromosomes that the mother cell had.
, 3.1 General Features of Chromosomes
Chromosome: structure within living cells that contain the genetic material.
Chromatin: the complex between DNA and proteins (provide an organized structure).
Nucleoid: region in the cytoplasm of a prokaryotic cell where the bacterial chromosome is
found (one, circular chromosome, not contained within a membrane-bound nucleus).
The cells of eukaryotic species have internal membranes that enclose highly specialized
compartments. These compartments form membrane-bound organelles.
Most of the genetic material is found within chromosomes in the nucleus, which is bounded by
two membranes (nuclear envelope).
Extranuclear/extrachromosomal DNA: genetic material that is not found within the nucleus, but
in other organelles, such as the mitochondrion and chloroplasts.
Cytogenetics: the field of genetics that involves the microscopic examination of chromosomes.
When a cell is preparing to divide, the chromosomes become more tightly coiled, which
shortens them and increases their diameter. They now become visible with a light microscope.
Somatic cells: any cell of the body that is not a gamete/precursor to a gamete.
Gamete/germ cell: sperm and egg cell or their precursor.
Karyotype: an organizes representation of the chromosomes within a cell. It reveals how many
chromosomes are found within an actively dividing somatic cell.
Diploid: each type of chromosomes is a member of a pair. A diploid cell has two sets of
chromosomes. When a species is diploid, the members of a pair of chromosomes are called
homologs; each type of chromosome is found in a homologous pair. The two chromosomes in
a homologous pair are nearly identical in size, have the same banding pattern and contain a
similar composition of genetic material. However, the two homologs may carry different
versions of a given gene, which are called alleles (dominant/recessive).
It should be emphasized that the sequences of two homologs are not completely identical (more
than 99%) and that this slight difference in DNA sequences provide the allelic differences in
genes.
* the X and Y chromosomes are not considered homologous chromosomes even though they
have short regions of homology.
Locus: the physical location of a gene.
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