Guided Notes: Chromosomes. What type of macromolecule is DNA? DNA stands for: DNA is made up of repeating (the monomer of nucleic acids!

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1 Guided Notes: Chromosomes The Structure of DNA What type of macromolecule is DNA? DNA stands for: DNA is made up of repeating (the monomer of nucleic acids!) 1) Where is it found (use figures 1 and 2 to help!) Figure 1 DNA is in the c of prokaryotes and the n of eukaryotes The nucleus of a human cell contains 30,000 or more g in the form of DNA, called a c. 2) Function of DNA The function of DNA is to s i. This is essential to life! DNA RNA Proteins (The c d of molecular biology! Figure 2: Structure of Chromosomes DNA is packaged tightly into pieces called that are visible ONLY during cell division Each chromosome includes several thousand Most genes contain the directions to make a -Proteins are made up of These proteins play a key role in how we look and grow- It s in your genes! A given gene on a chromosome can have alternative forms called alleles. For now, just know that different alleles of a gene encode the same protein, just slightly different versions of it. Ex: gene that encodes hemoglobin can be normal allele, or a different allele that produces abnormal hemoglobin (causes sickle-cell anemia).

2 Chromosomes and Chromatids Chromosomes are only visible during c d, when they are tightly condensed (wound up). Otherwise they are like long strings. Figure 3: Homologous chromosomes and sister chromatids Humans have chromosomes. These chromosomes come in pairs called h c One member of each pair was inherited from your m. The other was inherited from your f. How many chromosomes do you think the sperm cell that helped create you had? How many chromosomes did your mom s egg cell have? When cells are getting ready to divide, they r their chromosomes (another word for copy). MISCONCEPTION ALERT! When a chromosome has replicated, it is still considered to be ONE chromosome! (Confusing, I know!) The replicated chromosome is composed of two s c. Each sister chromatid is identical to the sister chromatid it is attached to! When the cell divides (we will discuss in detail in mitosis unit), the sister chromatids separate and are then considered to be individual chromosomes. If a cell has 35 chromosomes, then replicates them as it prepares to divide, it will have chromosomes and chromatids. The two cells resulting from the division will have chromosomes each. What is the name of the structure where the sister chromatids are attached to each other?.

3 Synthesize your knowledge! Crystal ponies have 6 chromosomes. That means they have homologous pairs of chromosomes. Draw a crystal pony cell that is getting ready to divide (I have done this for you). Imagine that it glitters and sparkles. Use a different color for maternal (inherited from mom) and paternal chromosomes (inherited from dad). Make each pair of homologous chromosomes a different size. Draw the two resulting cells and their chromosomes (you can depict the chromosomes as still condensed even though in reality they begin to unwind back into long strings as the cell is pinching in two). Assume the two new cells are NOT YET preparing to divide so have NOT replicated their chromosomes yet! Preparing to divide (Chromosomes have replicated) Newly formed cells (Chromosomes have NOT yet replicated)

4 Guided Notes: The Cell Cycle The Cell Cycle The c c describes the life of a cell from birth to death. There are three main parts of the cycle: I : Normal cell activities; broken up into 3 parts. M : Division of the nucleus/separation of the genetic material into 2 new nuclei. C : The division of the cytoplasm following mitosis. Interphase phase : Period of cell growth. Cells can remain in the G1 phase indefinitely, called. phase: Period when DNA replication occurs. Chromosomes replicate and each chromosome is now composed of two s c attached at the c (from chromosome notes!). Once a cell copies its DNA, it prepares to divide. phase: Cell growth and preparation for mitosis. Mitosis Mitosis is a form of a reproduction. Means only organism is required. Occurs in response to the body s need for growth and repair. Refers to division of the n. (The organelle in eukaryotes that contains DNA) stages of mitosis: Prophase, Metaphase, Anaphase, Telophase (will learn more about this soon!). Cytokinesis The cell cycle ends with c : the division of the c (refers broadly to the stuff in the cell excluding the nucleus) Overlaps with the latter part of mitosis. This means one cell has divided into two cells, and those two cells () can continue with their own independent cell cycles!

5 Chromosome appearance throughout the Cell cycle (Dr. Williams will fill in with everyone) Chromosomes are decondensed (long and stringy) during Interphase (G1, S, G2) and do not condense until mitosis begins! We have been drawing them in their condensed form for convenience only! Let s draw the chromosomes throughout the cell cycle using our crystal pony example (cells with 3 pairs of chromosomes).

6 Mitosis Parts of Mitosis 1. Prophase - longest phase of mitosis - chroms. become visible - spindle forms - nuclear envelope breaks down 2. Metaphase - chromosomes line up along middle of cell 3. Anaphase - sister chromatids move apart to opposite sides of the cell 4. Telophase - chroms. disperse - 2 nuclear envelopes reform - nucleolus reappears Cytokinesis - division of cytoplasm - NOT part of mitosis - animal cells: membrane pinches in half - plant cells: cell plate forms - 2 identical daughter cells form