1. Cell Reproduction & Genetics
Chromosomes
Do Now: Please answer the following questions on your handout:
1. How are genes related to chromosomes?

2. Unit 6: Cell Reproduction & Classical Genetics

4. Chromosomes

6. Chromosome Structure DNA strand Gets wrapped around many
histone proteins
(aka histones)
forming a
coil.
Coils are coiled up even more to form a
supercoil,
which is then packaged
even more to make a
chromosome.

7. What’s the big idea?
Most of the time, DNA is uncoiled, so that it can perform its function of providing instructions to the cell.
Only during cell reproduction does DNA get tightly packed into chromosomes

8. Do Now 1.24 Pre-assessment of knowledge:
In a species of bird, blue feathers are dominant to red. If a red bird is crossed with a pure-breeding (homozygous) blue bird, what will the offspring be like?
If your know how to, attempt a Punnett square

9. Parts of a chromosome The 2 chromatids that make up a chromosome
are called
sister
chromatids,
which are
extremely
similar
to each
other.

10. Quick review
DNA is organized into highly coiled structures called chromosomes.
Each chromosome contains thousands of individual genes.

11. Dogs Have 78 Chromosomes!
Every species of organisms has a characteristic number of chromosomes. 78
Dog
Adder’s Tounge
Fern
1,262
Humans chimps

12. Autosomes and Sex Chromosomes
Human and animal chromosomes are categorized as autosomes or sex chromosomes.
Sex Chromosomes determine an organisim’s sex.
All of the others are called autosomes
Typical human male
44 autosomes,
1 X sex chromosome
1 Y sex chromosome
Typical human female
44 autosomes,
2 X sex chromosomes

13. Homologous Chromosomes
Every cell contains two copies of each autosome.
To put it another way, autosomes come in pairs. These two chromosomes are called
HOMOLOGUS CHROMOSOMES.
Genes for eye color are found at
The same location on both
Chromosomes. The gene for brown
Eyes I got from my dad is in exactly
The same location on one chromosome
As the gene for blue eyes I got from my
Mom on the other homologous
Chromosome.
Specific genes are found in the
Same location on each homolugous
Chromosome.
Consider me for example…

14. Do Now 1.25 Take out HW for checking
How many chromatids are found in typical human cells?
How many pairs of homologous chromosomes are there?

15. Diploid and Haploid Cells
Cells are considered diploid when they have 2 copies of each chromosome. Most of your body’s cells are diploid.
Cells are haploid if they have only one copy of each chromosome pair. This is the case for gametes, like sperm and egg cells, used for reproduction.

16. Diploid vs. Haploid

17. Karyotypes
A karyotype is a picture of all the chromosomes in a dividing cell.
A karyotype of one of your cells might look something like this:

18. Normal Karyotype
Humans almost always have 23 pairs of homologous chromosomes.
Is this karyotype of a male or female?

19. Abnormal Karyotype
Some serious genetic disorders are caused by trisomy – a certain kind of mutation that gives an individual 3 copies of a chromosome.
The karyotype below shows trisomy-21, better known as Down’s Syndrome.

20. Cell Division: 3 types Do Now:
Arrange the following from SMALLEST to LARGEST:
Eukaryotic cell
Chromosome
Atom
Prokaryotic cell
Protein
Multicellular organism

21. Cell Division
Cell division, or reproduction comes in many forms, but there are some important similarities common to all.
The DNA of the cell is copied.
The cell divides one or more times, so 2 or more cells exist after 1 cell divides.

22. Binary Fission Simplest form of division.
Done by prokaryotes and some other unicellular organisms.
Chromosome copied, cell divides.
Results in 2 identical daughter cells.

23. Mitosis
Mitosis is the type of cell division used by humans and other multicellular organisms to produce new body cells.
In this process, one diploid cell copies all of its chromosomes and then divides once to produce 2 new diploid cells identical to the parent cell.
The process involves several stages we will investigate next week.

24. Meiosis is a specialized form of cell division used only by organisms that reproduce sexually.
Meiosis produces gametes, which are haploid cells such as sperm and egg cells required for sexual reproduction.
A specialized diploid cell (in the gonads) copies its chromosomes to become 4n, then divides twice to produce 4 new haploid gametes.
Fertilization is when two haploid gametes combine to form a new diploid individual.

25. The Cell Cycle & Mitosis
Do Now:
Decide whether each example given is an example of binary fission, mitosis, or meiosis:
A paramecium (unicellular eukaryote) splits into 2 new cells.
In the testis of a frog, specialized cells produce sperm.
Cells that line the inside of your digestive tract are constantly scraped off and replaced by new cells
The anthers of a flower produce thousands of grains of pollen, which may be carried by wind or insects to fertilize other flowers.

26. Diploid vs. Haploid
Most of the cells in your body (and in all mammals) are DIPLOID, meaning they have 2 copies of all of your DNA

27. Haploid Cells
Some cells (like animal reproductive cells – sperm and eggs) have only 1 copy of each chromosome. They are haploid.

28. The Cell Cycle
The cell cycle is like a cell’s life cycle.

29. Mitosis
Mitosis is the process of a cell making two identical “daughter” cells.

30. Foldables Make cell cycle and mitosis foldable notes!
Follow instructions carefully
Cell cycle steps on top (G1, S, G2, M)
Mitosis steps on bottom (P, M, A, T)
Details / sketches on the inside.

32. Stages of Mitosis Prophase: chromosomes become visible
Metaphase: chromosomes line up in middle of cell
Anaphase: chromosomes move apart
Telophase: 2 new nuclei begin forming