1. Cell Reproduction

2. Bell Work
What is the difference between prokaryotic and eukaryotic DNA?
Prokaryotic DNA is circular
Eukaryotic DNA is rod-shaped

3. Chromosomes Describe the structure of a chromosome
Identify the differences in structure between prokaryotic chromosomes and eukaryotic chromosomes
Compare the numbers of chromosomes in different species
Explain the difference between sex chromosomes and autosomes
Distinguish between diploid and haploid cell.

4. Chromosome Structure DNA has several different configurations.
Chromosomes as visible during cell division
Chromosomes are rod shaped structures made of DNA and proteins
Each chromosome is a single DNA molecule
Eukaryotic DNA coils but maintains a straight line
Prokaryotic DNA is in a circular shape (still has a double helix)

5. Chromosome Structure The whole thing is a chromosome
One half is the chromatid
The chromadtids are held together by the centromere
The less tightly coiled DNA-protein complex is called the chromatin
Eukaryotic cells wraps tightly around proteins called histones

6. Example Chromosome = Road Along the road we have houses = genes
Alleles = resident of the houses
Only one allele (resident) can live in a house
Soooo…..we can have green, blue or brown eyes. Only one on these three colors can live in a house (gene).

7. Chromosome Numbers
Each species has a characteristic number of chromosomes in each cell.
All humans have 46 chromosomes

8. Sex Chromosomes and Autosomes
Sex chromosomes – chromosomes that determine the sex of an organism and may also carry other genes for other characteristics
Either X or Y
Females have two X chromosomes: XX
Males have an X and a Y chromosome: XY
Autosomes – all other chromosomes in an organism
In humans, two of the 46 chromosomes are sex chromosomes, the rest are autosomes

9. Homologous Chromosomes
Homologous Chromosomes – every organism produced by sexual reproduction gets a copy of chromosomes from each parent
The organism receives one copy of each autosome from each parent
These are the same size and shape and carry genes for traits

10. Karyotypes
Karyotype – a photomicrograph of the chromosomes in a normal dividing cell found in a human
The 46 human chromosomes exist as 22 homologous pairs of autosomes and 2 sex chromosomes

11. Normal Karyotype vs Down Syndrome

12. Haploid and Diploid
Humans and other mammals many other organisms are Diploid organisms most of their lives
This means that they have one half of their chromosomes from each parent
The only stage that is haploid is the egg/sperm phase of life
Haploid means that there is only one set of chromosomes as in egg/sperm

13. Cell Division In prokaryotes we call this binary fission
it results in two identical cells or clones
DNA replicates and cell divides

15. Cell division In Eukaryotes called MITOSIS Interphase Mitosis
Gap 1 – cell does its job
Synthesis – DNA is copied
Gap 2 – Cell preps for division
Mitosis
Prophase – nucleus breaks down, chromatin coils into chromosomes, centrioles and spindle fiber visible
Metaphase – chromosomes line up in the middle of cell
Anaphase – chromosomes start to pull apart
Telophase – Cleavage furrow forms in animals; cell plate in plant cells and nucleus begins to form again
Cytokinesis – cytoplasm divides completely

16. Meiosis I Meiosis forms gametes
Gametes are sperm and egg cells or in plants can be pollen or spores
Gametes are also called germ cells because they develop into the full organism
Meiosis happens in two stages:
Meiosis I – Takes cells from 2n  2n (diploid to diploid)
Meiosis II – Takes cells from 2n  1n (diploid to haploid)

17. Meiosis I
Prophase I is similar to that of Mitosis but we have an added factor: Crossing-over can occur.
What happens is that the chromosomes pair so that the mom c’some and the dad c’some are next to each other and their legs wrap around
Next part of mom’s c’some is cut and so is dad’s and they swap.
This also allows for genetic recombination
Mom’s hair color is now on dad’s c’some

18. Meiosis I

19. Meiosis I

20. Meiosis I
Metaphase I – similar to mitosis but homologous chromosomes are going to next to each other.
Anaphase I – chromosomes move to opposite sides of the cell.
Independent assortment occurs – the mother’s or father’s c’somes can be on either side of the midline. Increases the number of possible genetic combinations to 2n . So in humans there are 223 possible combinations of genes!

21. Independent Assortment

22. Meiosis I Telophase and cytokinesis – very similar to that of mitosis.
At the end of cytokinesis there are two cells. Each now has one c’some from each homologous pair. (2 sister chromatids)

23. Meiosis II This stage does NOT begin with the coping of DNA!
Sometimes the nuclear membrane reforms and sometimes it doesn’t – depends on the species.
Phases are in the same order but now have a roman number II after them because they are slightly different.
Prophase II– spindle fibers reform and move to opposite sides of the cell and moving c’somes toward the midline

24. Meiosis II
Metaphase II – c’somes move to the midline of the cell, chromatids facing each pole.
Anaphase II – c’somes separate and move to opposite sides of the cell
Telophase II – nuclear membrane begins to form in each of the 4 new cells
Cytokinesis II – 4 new cells have formed each with half of the DNA needed for a new organism

25. Meiosis
Spermatogenesis – forms sperm
Oogenesis – forms eggs

26. Spermatogenesis

27. Oogenesis

28. Chromosome Disorders Trisomy 21 – Down Syndrome
Trisomy X – Little to no effect, menstrual irregularities, higher risk of speech and learning disabilities, delayed motor skills
XXY – Klinefelter’s – male, taller, decreased muscle tone, later speech and walking, 95-99% are infertile.
Fragile X – elongated face, larger ears and low muscle tone, flat feet, stereotypic movements. May meet disability qualifications for Autism