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(Eukaryotic DNA Structure)

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Presentation on theme: "(Eukaryotic DNA Structure)"— Presentation transcript:

1 (Eukaryotic DNA Structure)
Chromosomes (Eukaryotic DNA Structure)

2 When the cell is not dividing, DNA is long and stringy and called chromatin.

3 When the cell is dividing, DNA is tightly coiled around proteins and is called chromosomes.

4 Chromosome Numbers Each species has a specific number of chromosomes in the nucleus in its cells. For example, humans have 46 chromosomes in each body cell, dogs have 78 in each body cell.

5 Chromosome Numbers There is a tongue fern that has 1262 in each body cell! The number of chromosomes that an organism has is NOT related to the complexity of the organism!

6 Chromosome Numbers In body cells, chromosomes come in pairs.
Sex chromosomes are the pair of chromosomes that determine the sex of the organism. In humans, the sex chromosomes are X and Y. Normal females have 2 X chromosomes, and normal males have 1 X and 1 Y.



9 Chromosome Numbers All of the other chromosomes are called autosomes.
So, in humans: 22 pairs or 44 chromosomes are autosomes 1 pair or 2 chromosomes are sex chromosomes There are certain disorders associated with having too little or too many chromosomes.

10 Chromosome Abnormalities
1. Down syndrome – 3 copies of chromosome #21 (trisomy 21)

11 Chromosomes Abnormalities
Turner syndrome – female with only 1X chromosome (XO) (monosomy X)

12 Chromosome Abnormalities
3. Klinefelter syndrome – male with XXY

13 Chromosome Abnormalities
4. Patau syndrome – 3 copies of # 13

14 Doctors can detect these conditions before birth:
Amniocentesis – removes amniotic fluid from around baby … Chromosomes are photographed and organized onto a chart called a karyotype.

15 Chromosomes come in pairs because you inherited one copy of the chromosome from your mother and on copy of the chromosome from your father. The two chromosomes in each pair are called homologous chromosomes because they have the same size and shape and carry the same genes.

16 Most cells in your body are diploid (2n), which means they have 2 sets of chromosomes (one from each parent). The diploid number represents how many chromosomes are in these cells.

17 Sex cells (a. k. a. gametes, a. k. a
Sex cells (a.k.a. gametes, a.k.a. sperm and egg) are haploid (n), which means they only have 1 set of chromosomes. The haploid number will always by half the diploid number.


19 Dog 78 Sand dollar 26 Cat 16 Carrot 18 horse 64 Human 46 Fruit fly 4
Organism # of chromosomes in body cells (diploid number) # of chromosomes in sex cells (haploid number) Human 46 Fruit fly 4 Dog 78 Sand dollar 26 Cat 16 Carrot 18 horse 64

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