Q: What is the difference between a diploid and a haploid cell?

Today: Beginning Unit on Cell Reproduction

Power Point Notes: Chromosomes

Homework: 8.2 Section Review 1-6, 8

A haploid cell has half the number of chromosomes in a diploid cell.

Fluorescent In-Situ Hybridization (FISH) identification of human chromosomes

Chromosome - replicated DNA that is condensed, coiled and wrapped around histone proteins - replicates and condenses when the cell is about to divide

Cell Reproduction: Chromosomes

Histones- Proteins that help maintain the shape of the chromosome.

- Aid in tight packing of DNA.

Chromosome Structure

Chromatid - each half of the chromosome

Centromere – point where chromatids attach

Chromatin – Thin, uncoiled strands of

DNA and protein– This form of DNA is

found during interphase of the cell cycle

Chromosome NumbersAutosomes

- all non-sex chromosomes.

- Humans have 22 pairs of autosomes

Sex Chromosomes-Genetic information that determines gender of an organism- In humans, Females have XX chromosome pair; males have an XY pair-1 pair of sex chromosomes-Humans have a total of 23 pairs of chromosomes.

Honeybee (female) – 32

2n Chromosomes

Adder’s Tongue Fern - 1262 Common Frog - 26

Cat - 38 Maize - 20Human - 46

Does more chromosomes mean a bigger or more complicated organism?

Chromosome number does not determine complexity of organism

   Animal  Chromosome number (2n) 1.  Ascaris megalocephala (horse roundworm)  2

 2.  Drosohila melanogaster (fruit fly)  8

 3.  Musca domestica (house fly)  12

 4.  Rana hexadactyla (frog)  26

 5.  Apis mellifera (honey bee — female)  32

 6.  Hydra vulgaris  32

 7.  Fells domestica (cat)  38

 8.  Pattus rattus (rat)  42

 9.  Homo sapiens (man)  46

 10.  Bos indicus (cow)  60

 11.  Canis familiaris (dog)  78

 12.  Columbia livia (pigeon)  80

 13.  Amoeba proteus  250

 14.  Aleucantha (radiolarian)  1600

  Plant  Chromosome number (2n) 1.  Mucorheimalis (bread mold fungus)  2

 2.  Penicillium notatum (fungus)  4

 3.  Pisum sativum (pea)  14

 4.  Zea mays (maize)  20

 5.  Oryza sativa (rice)  24

 6.  Lycopersicon (Tomato)  24

 7.  Solanum tuberosum (potato)  48

 8.  Saccharum offtinalis (sugarcane)  80

 9.  Ophioglossum (Adder’s tongue fern)  1262

Chromosome Numbers cont.

• HOMOLOGOUS CHROMOSOMES– Two chromosomes that are the same size,

shape and DNA makeup

• DIPLOID – contain both chromosomes of a homologous pair. “2N”

• HAPLOID – contain only one of the chromosomes of a homologous pair. “1N”

Karyotype

A photomicrograph of the chromosomes in a normal dividing cell found in a human.

Does this karyotype appear to be male or female?

karyotyping

Trisomy 21, a chromosomal abnormality indicative of down syndrome

Karyotyping Questions:• What characteristics did you use to pair up the

Chromosomes?• How many autosomes are there? How many

sex chromosomes?• Is the organism male or female? What sex

chromosomes do females have? Males?• Why are Karyotypes impt for geneticists?• What disease would be caused if you had

three chromosomes on 21?

Q: What is the difference chromatids, centromeres, and chromatin?

Today Power Point Notes: Cell Division

Prokaryotes vs. Eukaryotes

Homework: draw binary fission p 154, and cell cycle with bulleted

notes p 155.

Chromatids are the halves of the chromosomes, centromeres are where the chromatids are joined, chromatin is the coiled up DNA that makes up the chromatids/chromosomes

Cell Division In Prokaryotes

- Prokaryotes use binary fission, the division of a prokaryotic cell into two offspring cells

- Cell membrane divides

- Prokaryotes do no have a nucleus

Cell Division in Eukaryotes

Mitosis – results in new cells with genetic material identical to the original cell

Asexual reproduction – the production of offspring from one parent

Meiosis – occurs during the formation of gametes

Gametes – haploid reproductive cells

Q: What are the stages of the cell cycle (included in interphase and cell division)

in order?

Today: Cell Cycle, Mitosis

Homework: Draw and label stages of Mitosis and Cytokinesis, with 3-4 notes for each.

Print: Graphic organizer for Thurs, Meiosis flipbook for Fri.

G1, S, G2, Mitosis, and Cytokinsis. Also G0

Cell CycleInterphase

- the time between divisions

- the cell spends most of its time in interphase

Cell Division

- mitosis and cytokinesis

How long does mitosis take?

It depends on cell type and culture conditions.

Cell Cycle Interphase• G1 stage of interphase

– Cell grows to normal size– Cell carries out regular functions (protein synthesis,

etc…)

• S stage– DNA is synthesized

• G2 stage– Organelles are replicated, preparing for cell division

• G0 stage– Cells stop dividing, sometimes permanently (ex: nerve

cells)

G1 → S → G2 OR G1→ G0

Mitosis

Division of the cell nucleus in which chromosomes of the parent cell divide into two identical daughter cells

http://www.johnkyrk.com/mitosis.html

http://www.cellsalive.com/mitosis.htm

Prophase

1. Nucleolus and nuclear membrane disappear

2. Chromatin condenses to form chromosomes

3. Centrioles and spindle fibers appear

- Centrioles are not in plants.

Metaphase

1. Kinetochore fibers move the chromosomes to the center of the cell

2. Chromosomes line up along the center of the cell

3. kinetochore fibers hold chromosomes in place

Anaphase

1. Chromatids separate at the centromere

2. Chromatids move, centromere first, toward opposite poles

3. Chromatids are considered to be individual chromosomes after separation.

One chromosome (unduplicated)

One chromosome (duplicated)

one chromatid two sister chromatids

one chromatid

Telophase and Cytokinesis1. Centrioles and spindle

fibers disappear2. chromosomes unwind into

chromatin “spaghetti”3. nuclear membrane forms

around set of chromatin and the nucleolus appears

4. Cytoplasm divides (cytokinesis), forming two new cells

5. Organelles are separated into two new cells

Control of Cell Division• signals from the cell can

trigger the next phase of the cell cycle

• 3 checkpoints:– Cell growth (G1) checkpoint

• decide whether cell should divide or not.

– Yes - cell begins G2 phase– No - cell goes into G0 phase

– DNA synthesis (G2) checkpoint

• signal the cell to enter mitosis– Mitosis checkpoint

• signal the cell to exit mitosis

Application

1.Growth

2.Self Healing

3.Cancer - uncontrolled growth of cells - error at G1 checkpoint

Which stage?

Mitosis

• http://www.biologycorner.com/flash/mitosis.html

Mitosis vs. Meiosis

MEIOSIS

– Takes place in two sets of divisions, meiosis I and meiosis II

– Occurs in Germ cells found in the ovaries and testes

• Meiosis I– Reduces the number of chromosomes from

diploid to haploid

• Meiosis II– Produces four haploid daughter cells

http://www.johnkyrk.com/meiosis.html

Prophase I• Like Mitosis:

–DNA is coiled into chromosomes

–Spindle fibers appear–Nucleolus and nuclear

membrane disassemble

• Different than Mitosis•Synapsis - homologous

chromosomes pair up•Crossing over -

exchange genetic information, or genetic recombination

Meiosis I continuedMetaphase I:tetrads line up at the

nucleustetrad – a pair of homologous chromosomes

Anaphase I: Independent assortment - tetrads move to opposite sides of the cell (random)

Telophase I and Cytokinesis: chromosomes reach opposite sides of the cell and the cell divides

Meiosis II- Begins with the two cells

formed in Meiosis I- DNA is NOT copied

before Meiosis II

Prophase II, Metaphase II,and Anaphase II – similar to

Meiosis I, but each half receives only half of the genetic information

Telophase II and Cytokinesis II - Like Meiosis I

- Ends with four cells instead of two

- Cells are haploid instead of diploid

Meiosis I

Meiosis II

Gametes

• In animals, gametes are the only cells that use meiosis.

• Spermatogenesis – produces 4 sperm cells

• Oogenesis – produces 1 egg cell, or ovum, and three polar bodies, which degenerate.

What is crossing over?

Crossing over occurs when pieces of chromatids break off and attach to the homologous chromosome by it.

What are some key differences and similarities between mitosis and

meiosis?• Mitosis is used by regular cells, meiosis is

used by reproductive cells

• There is one division in Mitosis, and two divisions in Meiosis

• Mitosis ends with two diploid cells, Meiosis ends up with four haploid cells

• In both Mitosis and Meiosis DNA is doubled just once.