Table of Contents:
I. Chromosomes and the Cell Cycle
II. Phases of mitosis
III. Phases of meiosis
IV. Comparison: mitosis vs meiosis
V. Spermatogenesis and oogenesis
VI. Chromosome Inheritance
Compendium Review Chapter 18
I. Chromosomes and the Cell Cycle
A. Chromosomes are long DNA molecules within the nucleus. Each chromosome is wrapped up in proteins that give it its shape. (Frolich PowerPoint Slide 4)
1a. Humans have 46 chromosomes that are made of 23 pairs.
2a. Autosomes comprise 22 of these pairs.
3a. One pair is called the sex chromosomes because they house the genes that decide
gender.
4a. Males: Sex Chromosomes X and Y
5a. Females: Sex Chromosomes X and X
6a. Chromosomes are viewable through the use of a camera attached to the end of
a microscope. (Mader 178)
7a. 23 pairs: humans receive one of each pair from the mother, and one of each pair from the father. (Frolich PowerPoint Slide 4)
(Insert Chromosomes Image: shanghai-ultimate.com / http://rds.yahoo.com/_ylt=A0S0205dYVNIAFYAvS2jzbkF/SIG=11nu2burt/EXP=1213510365/**http%3A//shanghai-ultimate.com/photos)
B. Karyotypes
1b. When a computer arranges chromosomes in pairs, the result is a karyotype of 23 pairs of chromosomes.
2b. A karyotype allows us to see a normal body cell is diploid- full 46 chromosomes.
3b. Mitosis: Duplicate division. Ensures 46 chromosomes.
4b. In dividing cells, every chromosome has 2 parts: sister chromatids.
5b. Each chromatid contains a DNA double helix = same genes.
6b. Centromere: holds the chromatids together until a certain point in the process of mitosis when the centromere splits.
7b. When separated, each sister chromatid becomes a chromasome.
8b. Duplicated chromosome allos for two individual daughter chromosomes. These separate, and each new cell gets one of each, etc. (Mader 379)
C. Cell Cycle
A. 2 parts: Interphase and Cell Division
1a. Interphase: Lasts for about 20 hours: most of cell cycle.
2a. Organelles carry on normal function, and cell gets ready to divide. DNA synthesis occurs.
3a. DNA synthesis: 3 stages: G1 stage: Cell doubles its organelles (mitochondria and ribosomes), and it gets the materials it needs for DNA synthesis. Various proteins needed to change chromatin into chromosomes. S stage: DNA replication occurs. Because of this, every chromosome has two of the same DNA double helix molecules, in sister chromatids. (=duplicated chromosomes) G2 stage: Cell synthesizes proteins needed for cell division.
B. Cell Division: two stages
1b. M: Mitosis- nuclear division. (Duplication division) Each new nucleus contains the same amound and type of chromosomes as the former cell. (Approx. 4 hours) (Mader 379)
(Insert Mitosis Picture / (Frolich PowerPoint Slide 6)
2b. Why does it occur? Growth, replacement and repair. (Frolich PowerPoint Slide 5)
3b. What happens?
•DNA/chrosomes replicate (make exact copies)
•Copies line up at center of cell
•Copies pulled to opposite ends of cells by centromeres/spindles
•Cell membrane pinches off and splits cell into two (Frolich PowerPoint Slide 6)
3b. Cytokinesis: Division of cytoplasm.
4b. Apoptosis: programmed cell death. When cells divide when they shouldn't, they are gotten rid of. (Mader 379)
II. Phases of Mitosis
A. Prophase: A visible indication that the cell is preparing to provide. (Mader 382)
•Chromosomes condense and become visible (Frolich PowerPoint Slide 8) Each is made up of two sister chromatids held together at a centromere. (Mader 382)
•Nuclear envelope fragments
•Nucleolus disappears
•Centrosomes move to opposite poles
•Spindle fibers appear and attach to the centromere (Frolich PowerPoint Slide 8)
B. Metaphase:
•Chromosomes line up at the middle of the cell (equator)
•Fully formed spindle (Frolich PowerPoint Slide 9) for chromosomal movement, by essentially pulling the chromosome apart. (Mader 383)
- Nuclear envelope is fragmented, and the spoindle occupies the region that was occupied by the nucleus. (Mader 382)
C. Anaphase:
•Sister chromatids separate at the centromeres and move towards the poles. (Frolich PowerPoint Slide 10)
- Note: Counting the number of contromeres indicates the number of chromosomes. (Mader 383)
D. Telophase:
•Chromosomes arrive at the poles
•Chromosomes become indistinct chromatin again
•Nucleoli reappear
•Spindle disappears
•Nuclear envelope reassembles
•Two daughter cells are formed by a ring of actin filaments (cleavage furrow) (Frolich PowerPoint Slide 11) These pinch the cell in half. (Mader 383)
(Insert Mitosis 2 image / publications.nigms.nih.gov /)
III. Phases of Meiosis
A. Meiosis: Reduction division. Involves 2 divisions, 4 daughter cells.
1a. At first, the parent cell is diploid, and chromosomes appear in pairs.
2a. Two pairs of chromosomes: short and long.
3a. Members of a pair are called homologous chromosomes, or homologues, since they look alike and carry genes for the same trait.
4a: Meiosis 1: 1st division. Homolosous chromosomes unite and line up side by side. (AKA synapsis) This leads to the reduction of the number of chromosomes. Only during this time can you view paired chromosomes.
5a. Interkinesis: time between meiosis 1 and meiosis 2.
6a: Meiosis 2: Centromeres divide and sister chromatids separate, becoming chromosomes that are given to a daughter neclei.
7a. Daughter cells in females become gametes (sex cells) that fuse during fertilization.
8a. Zygote: first cell in new idividual. (Mader 385)
(Insert picture of Meiosis / home.hawaii.rr.com / http://genetics.gsk.com/graphics/meiosis-big.gif)
B. Stages of Meiosis:
1b. Part of sexual reproduction. (Production of the sperm and egg.)
2b. Goes through the same 4 stages as mitosis, but a few differences occur in the first two stages. 1. Prophase 1: synapsis occurs, the spindle appears, the nuclear envelope fragments and the nucleolus disappears. While synapsis occurs, the homologous chromosomes come together and line up side by side. Exchange of genetic material may occur. This is called crossing over, and occurs when the chromatids held together by the centromere are no longer identical. Metaphase 1: homologous pairs align at the equator. The things that happen in these two stages ensure that gametes will not have the same combination of chromosomes and genes. (Mader 388)
3b. Asexual reproduction: Uicellular organisms like bacteria reproduce asexually, by binary fission. (Mader 389)
(Insert picture of asexual reproduction / http://www.bio.miami.edu/ /
http://www.bio.miami.edu/chlorophyta/Page%203_files)
4b. Genetic recombination: by producing sexually, genetic recombination ensures that offspring will be genetically different compared to each other and their parents. (Mader 389)
IV. Comparison of Meiosis and Mitosis
(Insert Chart picture / ca.answers.yahoo.com / http://ca.answers.yahoo.com/question/index?qid=20061221172903AA42DMx)
V. Spermatogenesis and Oogenesis
A. Spermatogenesis: the production of sperm in males.
1a. Continual in the testes after puberty. Approx. 300,000 sperm produced daily.
2a. Chromosomes in secondary spermatocytes are duplicated and made up of two chromatids.
3a. Chromosomes in spermatids consist of only one. These mature into sperm. Sperm have 23 chromosomes. (Mader 392)
(Insert picture of spermatogenesis /www.umanitoba.ca / http://www.umanitoba.ca/faculties/science/biological_sciences/lab14/biolab14_2.html)
B. Oogenesis: the production of eggs in females.
1b. Each immature follicle on and ovary contains a primary oocyte aarested in prophase I.
2b. Primary oocyte (diploid) divides during meiosis I into two cells. one is the secondary oocyte, and receives almost all of the cytoplasm. Leaves the ovary during ovulation and may be fertilized by a sperm. First polar body: the "trash can" for discarded chromosomes. (Mader 392)
(Insert picture oogenesis / http://www.csusm.edu/ / http://www.csusm.edu/obrt/events/lectures/boswell01.htm)
VI. Chromosome Inheritance
A. Nondisjunction: "Occurs during meiosis 1, when both members of a homologous paair go into the same daughter cell, or during meiosis II, when the sister chromatids fail to separate and both daughter chromosomes go into the same gamete." (Mader 393)
(Insert picture of nondisjunction / medical-dictionary.thefreedictionary.com / http://medical-dictionary.thefreedictionary.com/Meiotic+nondisjunction)
B. Trisomy: An egg with 24 chromosomes is fertilized. One type of chromosome is prsent in three copies, = "tri"..
C. Monosomy: Egg with 22 chromosomes is fertilized. One tyupe of chromosome is present in a single copy.
D. Barr Body: In normal XX females, one of the X chromosomes becomes a dark mass of chromatin.
E. Trisomy 21: Downs syndrome. 3 copies of chromosome 21 because the egg had two copies instead of 1. Karyotyping can detect this abnormality.
1e. Features: short stature, eyelid fold, stubby fingers, flat face, large tongue, round head, palm crease, mental retardation. (Mader 393-394)
F. Turner Syndrome: Individual has only one sex chromosome, an X. Features: Females are short, broad chest, folds of skin on back of neck. Reproductive organs are small and underdeveloped.
G. Klinefelter Syndrome: Males born with two X chromosomes and one Y. Features: speech and language delays.
H. Poly-X Females: More than two X chromosomes and extra Barr bodies in the nucleus. Tendency to be tall and thin. Some delayed language and speech development.
I. Jacobs Syndrome: XYY males, results from nondisjunction during spermatogenesis. Usually taller than average, acne, speech and reading problems. (Mader 394-396)
VI. Changes in Chromosome Structure
A. Changes in chromosome structure are another form of chromosomal mutation.
1a. Deletion: ocurs when an end of a chromosome breaks off or when two simultaneous breaks lead to the loss of an internal piece.
2a. Duplication: Presence of a chromosomal segment more than once in the same chromosome.
3a. Inversion: Occurrs when a piece of a chromosome is turned around 180 degrees.
4a. Translocation: Movement of a chromosome segment from one chromosome to another homologous chromosome.
No comments:
Post a Comment