Content Objectives The learner will (TLW):
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Essential Questions
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Somatic vs Germ
All cells are divided into two groups:
Somatic cells include all cells of your body with the exception of the sperm and the egg. Somatic cells are also known as body cells and often referred to as being diploid.
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Germ cells include the sperm and ovum only. Germ cells are also known as sex cells, gametes, and often referred to as being haploid.
Gametogenesis: The process by which gametes are produced through the combination of meiosis and other maturation changes.
egg: the female gamete (sex cell) Sperm: the male gamete (sex cell) |
Haploid vs diploid
Sperm cells and Egg cells contain non-homologous chromosomes and therefore are called haploid cells.
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Somatic cells or body cells contain homologous chromosomes and therefore are called Diploid cells
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Mitosis vs Meiosis. What's the difference?
Most somatic cells divide through a process known as Mitosis while sex cells divide through Meiosis.
Meiosis: the making of gametes
Meiosis: a type of cell division that results in four daughter cells, each with half the number of chromosomes (haploid) of the parent cell.
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chromosomes
Every organism's chromosomes will have a pair which are the same length and appearance, and contain copies of the same genes. These two pairs of chromosome are called: Homologous Chromosomes
Sex Chromosomes are not homologous because they contain different genes that are inherited from each parent.
Crossing Over: exchange of chromosome segments between homologus chromosomes during meiosis I
1. Two homologous chromosomes
pair up with each other during pro-phase 1 |
2. In this position some chromatids are very close to each other and segments cross.
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3. Some of these segments break off and reattach to the other homologous chromosome.
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Crossing over is important for genetic diversity. Through Mendel's research we now know that genes located on separate chromosomes assort independently however, some genes that are located close together on the same chromosome will cross over together.
Genetic linkage: tendency for genes located close together on the same chromosome to be inherited together.
Human Karyotype
Humans have 23 pairs of chromosomes in each somatic cell. There are 46 chromosomes in total.
Chromosome Sets 1-22 are known as
Autosomes any chromosome that is not a sex chromosome.
Chromosomes XY are known as
Sex Chromosomes: One of the pair of chromosomes that determines the sex of an individual.
Males: X Y Females: X X
Autosomes any chromosome that is not a sex chromosome.
Chromosomes XY are known as
Sex Chromosomes: One of the pair of chromosomes that determines the sex of an individual.
Males: X Y Females: X X