South Pontotoc Biology: Unit 9: Cellular Reproduction Concise Notes, Study Guide, and Vocabulary Terms

Vocabulary Terms: https://quizlet.com/_udds9

Study Guide: https://quizlet.com/_1e3zvc

Unit 9: Cellular Reproduction CONCISE Notes

1. Cell Division

a. Growth, repair, and reproduce

b. If a cell grows too large, then it would take too long to get nutrients to all parts of the cell and it would die

c. Cell division is the process in which two cells are produced from one cell.

d. DNA

i. DNA is in the form of chromatin during much of the cells life.

1. Chromatin consists of long, thin, strands of DNA wrapped around proteins.

ii. DNA is in the form of chromosomes during cell division.

1. Chromosomes are strands of chromatin that have become tightly packed.

2. Sister chromatids are the parts of a chromosome - the original and a copy of a chromosome.

a. Sister chromatids are held together by a centromere.

3. We refer to the copied pair of chromatids as a homologous chromosome.

a. Each chromatid is a chromosome.

iii. Humans have 46 chromosomes (23 pairs of chromosomes – the original and a copy of each) during mitosis, which is the only time that chromosomes are visible.

Know the parts of a chromosome

2. The Cell Cycle

a. The order of events that occurs in the life of a cell

b. Controlled by enzymes, which monitor the progress of the cell cycle through its phases

i. The cell cycle may become out of control, either through the failure to produce the correct enzymes or the production of enzymes at the wrong time.

ii. Enzyme production is controlled by genes located on the chromosomes.

1. Gene – segment of DNA that controls the production of a protein

iii. Cancer is one result of uncontrolled cell division (mitosis)

1. A result of changes in one or more of the genes that produce enzymes that are involved in controlling the cell cycle.

2. These changes are expressed as cancer when something prompts the damaged genes into action.

3. Cancerous cells form masses of tissue called tumors that deprive normal cells of nutrients.

4. Metastasis is the process in which cancel cells enter the circulatory system a spread throughout the body to different organs

5. Cancer prevention – the second leading cause of death in the U.S. after heart disease

a. Lung, Colon, Breast, and Prostate cancers most prevalent

b. Diet low in fat and high in fiber – fruits, vegetables, and grains

c. Vitamins and minerals – vitamins A, C, D, and calcium

d. Carotenoids found in yellow and orange foods and green leafy vegetables

e. Daily exercise

f. Limit tobacco and other drug use

c. 3 Parts – interphase, mitosis, cytokinesis

d. Interphase - The period of growth and development of a cell

i. In a multicellular organism, the cell does its particular job

ii. Most of the cell’s life is spent in interphase - longest part of cell cycle

iii. Three Parts of Interphase

1. G1 – (Growth 1) – the cell grows and develops, making proteins, organelles double

2. S – (Synthesis) – DNA (chromatin) is replicated (copied) resulting in twice amount of chromatin

3. G2 – ( Growth 2) – rapid growth, preparing for division

e. Mitosis – Open mitosis - The division of the nucleus (Karyokinesis); Stages - PMAT - Paul Meets Anna Tonight

i. Results in two cells that are identical to the parent cell

ii. Different in unicellular and multicellular organisms

1. At the end of mitosis, unicellular organisms remain as single organisms – this is a form of reproduction

2. Multicellular organisms create groups of cells called tissues that work together to perform a specific function, which then form organs, then form systems, then the whole organism

iii. Fungi cells have a different way to complete some of the steps of mitosis

iv. 4 Parts – Prophase, Metaphase, Anaphase, Telophase

v. Prophase – Pair Up

1. Chromatin condenses into chromosomes – now visible because they shorten and thicken – held together by centromere

2. Nucleolus and nuclear membrane break down

3. In animal cells, centrioles move apart to opposite ends of the cell (to the poles)

a. Small, dark, cylindrical structures made of microtubules

4. Spindle fibers form

a. Made from microtubules

b. Help sister chromatids separate in Anaphase

vi. Metaphase - Middle

1. Chromosomes line up in the center of the cell (in the equator)

2. Spindle fibers attach to the centromere on each side of a chromosome, one for each sister chromatid

vii. Anaphase - Away

1. Sister chromatids are pulled apart at the centromere

2. The chromatids move to opposite poles, pulled by the shortening spindle fibers

3. Cytokinesis begins

viii. Telophase – Two New Nuclei

1. Two identical sets of chromatids are now at each pole

2. The chromatids begin to unwind into chromatin

3. Spindle fibers and centrioles begin to breakdown

4. Two new nuclear membranes form around the chromatin

ix. Fungi Mitosis

1. Closed mitosis - In fungi, the nuclear membrane does not breakdown

2. All of the stages of mitosis occur inside of the nucleus

f. Cytokinesis - The cytoplasm divides and organelles are equally divided between two new cells

i. The parent cell splits into two new daughter cells

ii. Different in plant and animal cells

1. Plant cells form a cell plate between the new cells across the equator

a. A cell membrane forms around each new cell and new cell walls form on each side of the cell plate until separation is complete, dividing the cell in half

2. Animal cells pinch the cell membrane together along the equator

a. A cleavage furrow develops as the animal cell begins cytokinesis until both sides of the cell membrane meet and the cell separates into two new cells

g. The two new cells immediately enter Interphase

h. Mitosis Mistakes

i. Usually occurs during metaphase and results in one cell receiving (or missing) and extra chromosome

ii. The cell may not function and die or may result in a tumor (see 2iii)

3. The Cell Cycle of Sex Cells

a. Two kinds of cells in organisms that sexually reproduce

i. Somatic cells – body cells – all cells except sex cells

1. Formed from Mitosis.

2. Diploid (2n) - Contain all of the chromosomes of the organism

a. Human somatic cells contain 46 chromosomes (23 pairs)

i. Homologous Chromosomes (homologues)- The two chromosomes that make up each pair

1. One of the pair came from the mother, the other from the father

2. One may have the gene for blue eyes, while the other has the gene for brown eyes

ii. Sex cells ( Gametes)

1. Formed from Meiosis.

2. Haploid (n) - Contain half of the chromosomes of the organism

a. Human gametes contain 23 chromosomes

3. Two Kinds – Sperm in males, Egg in females

a. Spermatogenesis – the production of sperm cells

i. One diploid cell produces four haploid sperm cells

ii. Meiosis I – a diploid sperm cell divides equally producing two cells of equal size

iii. Meiosis II – the two diploid cells divide again resulting in four haploid spermatozoa (sperm) of equal size

b. Oogenesis – the production of ova (egg cells) - ovum

i. One diploid cell produces one haploid egg cell and possibly four polar bodies

ii. Meiosis I – a diploid cell egg cell divides unequally producing one cell with most of the cytoplasm and cell organelles, and a smaller cell

iii. Meiosis II – the larger cell divides again a larger haploid egg cell with most of the cytoplasm and organelles, and smaller polar bodies that then disintegrate
Know these diagrams:

iii. Sexual Reproduction Overview

1. One haploid sperm and one haploid egg merge together (fertilization) and form a zygote (fertilized egg that is diploid), resulting in one diploid cell with 46 chromosomes

2. Fraternal Twins – two eggs are fertilized separately (two different sperm) at the same time that have a different set of chromosomes

3. Identical Twins – one fertilized eggs splits and develops two babies that have the same original set of chromosomes

b. Meiosis – the formation of sex cells (Reproductive cells)

i. Two Parts – Meiosis I and Meiosis II, with 4 stages each - 8 stages total

1. Meiosis I is similar to mitosis except that Synapsis occurs and Crossing Over may occur

2. Meiosis II is identical to Mitosis

ii. Allows for genetic variation in a species

iii. Produces haploid cells that are not identical – they have half the normal number of chromosomes

iv. Meiosis I

1. Prophase I

a. Chromatin condenses into chromosomes – now visible

b. Spindle fibers form

c. Centrioles move to the poles

d. Nuclear membrane disintegrates

e. Synapsis – homologous chromosomes pair up

f. Crossing Over may occur between non-sister homologous chromosomes

2. Metaphase I

a. Paired homologous chromosomes move to the equator

b. Spindle connects to the centromeres

3. Anaphase I

a. Homologous chromosomes move to opposite poles

4. Telophase I

a. Spindle disappears

b. Nuclear membranes appear

c. Cell pinches into two (cytokinesis) - 2 Haploid cells are made

v. Meiosis II – identical to mitosis – with the two cells from meiosis I

1. Prophase II

a. Nuclear membranes disappear

b. Spindle forms

c. Centrioles move to the poles

d. Chromatin condenses into chromosomes

2. Metaphase II

a. Non-homologous chromosomes move to the equator

b. Spindle attach to each sister chromatid

3. Anaphase II

a. Spindle pull sister chromatids to opposite poles

4. Telophase II

a. Chromosomes unwind into chromatin

b. Cell membrane pinches - cytokinesis

c. 4 Haploid cells form

vi. Meiosis Mistakes

1. Trisomy – an extra chromosome is present

a. Down Syndrome – an extra chromosome number 21 – the zygote has 47 chromosomes

2. Monosomy – missing a chromosome – most zygotes do not survive

4. Asexual Reproduction – new organism from one parent – genetically identical - usually with the same number of chromosomes

a. Usually results in a large number of identical organisms which may increase the chances of survival if the environment is stable

b. If the environment is changing, then the chance of survival decreases because there is no genetic variation

c. Only requires one parent

d. Many Types

i. Binary Fission – a single cell splits in half – how bacteria and many prokaryotes reproduce; also paramecium

ii. Budding – s small area of cells attached to the parent starts to grow and then detaches when it is a separate organism; many fungi and simple animals like the Hydra reproduce by budding.

iii. Vegetative Propagation - plants send out runners that allow a new plant to grow, or cuttings from a plant can be rooted and grown into mature plants.

iv. Fragmentation – a small broken piece of an organism grows into an adult; eg. Starfish

1. Regeneration – regrowing a missing body part; eg. Starfish, planaria, sponges

v. Parthenogenesis – an unfertilized egg develops into an adult

1. Occurs in some types of insects, some reptiles; eg. Drone honey bees

vi. Spore formation – a spore grows into an adult under favorable conditions; some algae, protozoans, plants, and fungi

1. Spore - a reproductive cell with a tough outer covering – may be diploid or haploid

Budding: