MEIOSIS AND SEXUAL LIFE CYCLES:



external image 13_05HumanLifeCycle.jpg
 CHAPTER SUMMARY: CHAPTER 13 OVERVIEW:
  • A living organism is distinguished by their ability to reproduce their own kind. The offspring usually resembles their parents more than they do to their related individuals of the same species you can pick up the resembles of a father and his daughter by The transmission of traits from one generation to the next is called heredity , however some of the offsprings differ from parents and their off spring by demonstrating variation.
  • external image c7.13.2.hydra.jpgCONCEPT 13.1 ( offsprings acquire genes from parents by inhereting chromosome)
  • 1) parents endow with coded info in the form of genes. The gene program is the specific trait hat emerges as we develope from the fertilized egg into adults. This genes inheret by the mother and father are our gentic link to the parents which account for family resemblance such as the shared of eye color or frekle.
  • EX) Genes are the segments of DNA the genetic information is transmitted as a specific sequence from the four deoxyribonucleoties into the DNA. This is a analogous to the symbolic info in which words and sentences are translated in a language of mental images. The cells then just like the brain translates the word "apple" into a mental image of a fruit, yet this cells translate frekles as a feature.
  • 2) Every living species has a characteristic number of chromosomes ( Humans have 46 in almost all of their cells). Each of the chromosomes consist of a single dna molecule, hundreds or thousands of genes, and each have a specific location.

3) Organism who reproduce asexually like the hydra (pictue located on the right) can produce offsprings with exact copies of themselves. A individual who reproduce asexually give rise to a clone. A clone may be genetically fifferent from the result of mutation. Unlike the clone offspring developed as a sexual reproduction  genteically from a sibling and their parents.
CONCEPT 13.2 (FERTILIZATION & MEIOSIS ALTERNATE IN SEXUAL LIFE CYCLES)
    1. the Life Cycle starts at the conception of a oranism until the organism produces their own offspring.
      The 46 human chromosomes arranged in pairs in order of size to produce a karyotype display while homologous chromosome pairs carry genes who control the same inherited characters. Two distinct sex chromosome are the X & Y which are determine by the individual sex
      FEMALE (XX) MALE (XY) the other 22 pair are called autosomes. (Small parts of the X & Y are homologous) . Diploid cells number of chromosomes by (2N).
    2. Both the ova and sperm contain a set of chromosomes, 22 autosomes, a X in the ovum, and a X or Y on the sperm cell. The haploid for humans in the chromosomes is 23(n=23) and the diploid number 46(2n=46).
HUMAN LIFE CYCLE:
  1. The human life cycles begings once a haploid sperm cell fuses a haploid ovum. The cell fuses (syngamy) resulting into fertilization. This fertilized egg(Zygote) is then diploid for containing two haplois sets of chromosomes. As the organism develops from a zygote into a sexually mature adult, mitosis generates the somatic cell of the body.

SEXUAL LIFE CYCLES:
  1. Fertilization and meiosis alternate in all sexual life cycles however, timing in meiosis and fertilization varies among species.
  2. Variation are grouped into three main types of life cycles animals, humans, gametes are the only haploid cell .
  3. Plants and some algea have a scecond type of life cycle the alternation of generations this life cycles include two multicellular stages haploid (sporophyte) and diploid. The meiosis in the sporophyte produces haploid spores.
  4. Fungi and some protist have a third type of life cycle
  5. Either haploid or diploid cells can be divided by mitosis, based on the type of life cycle. However, only diploid cells can undergo meiosis. Although the three types of sexual life cycles are different in the timing of meiosis and fertilization, they share a fundamental feature each of the cycles of chromosome halving and doubling contribute to genetic variation within the offspring

Three types of life cycles:external image sexual_life_cycles.jpg VOCABULARY: in order to comprehend chapter 13 a bit more it is quite important to know the meaning of most biology terms that are been used so here are some substantial vocabulary terms to mainly focus on during the reading.

  • ASEXUAL REPRODUCTION- Produce exact copies of themselves this way. a single individual is the sole parent and passes copies of all its genes to its offspring
  • AUTOSOMES- A chromosome that is not directly involved in determining sex, as opposed to a sex chromosome
  • ALTERNATION OF GENERATIONS- A life cycle where there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte (characteristic of plants and some algae.)
  • CLONE- A lineage of genetically identical individuals or cells.
  • CHROMOSOME- Develops once crossing over combines with DNA of teo parents to a single chromosome.
  • CROSSING OVER- The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.
  • DIPLOID CELL- A cell with two chromosome sets.
  • FERTILIZATION- The union of haploid gametes to produce a diploid zygote
  • GAMETOPHYTE- The multicellular haploid form in organisms undergoing alternation of generations that mitotically produces haploid gametes that unite and grow into the sporophyte generation
  • GENETICS- The study of heredity and hereditary variation
  • GAMETES- These reproductive cells are the vehicles that transmit genes from one generation to the next. unite and pass on during fertilization
  • GENES- A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).
  • HAPLOID CELL- A cell containing only one set of chromosomes (n)
  • HOMOLOGOUS CHROMOSOMES- Chromosome pairs of the same lenght, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One from the mother, the other from the father.
  • HEREDITY- The transmission of traits from one generation to the next
  • KARYOTYPE- A method to organize the chromosomes of a cell in relation to number, size, and type
  • LIFE CYCLES- Generation-to-generation sequence of stages in the reproductive history of an organism
  • LOCUS- A gene's specific location along the length of a chromosome
  • SEXUAL REPRODUCTION- Two parents give rise to offspring that have unique combinations of genes inherited from the two parents. variations on a common theme of family inheritance
  • MEIOSIS- A two stage cell division in sexually reproducing organisms with half the chromosome number of the original cell
  • MEIOSIS 1 & 2- The first and second stage of process cell division
  • OFFSPRING- A descendant.
  • SOMATIC CELL- Any cell in a multicellular organism except a sperm or egg.
  • SPORES- A spore can divide by mitosis to develop into a multicellular haploid individual, the gametophyte, without fusing with another cell EX) In fungi, a haploid cell, produced either sexually or asexually, that produces a mycelium after germination.
  • SEX CHROMOSOMES- A chromosome responsible for determining the sex of an individual.
  • SPOROPHYTE- Organisms (plants and some algae) that have alternation of generations multicellular diploid form from the union of gametes
  • VARIATAION- Offspring differ somewhat in appearance from parents and siblings
  • ZYGOTE- The diploid product of the union of haploid gametes in conception; (A FERTILIZED EGG) 

FIGURES:
external image independent_assortment.jpg

The figure above represents the number of combinations for a daughter cell formed by meiosis from a diploid cell with two homologous pairs of chromosomes.
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THE MEIOTIC DIVISION OF AN ANIMAL CELLmeiosis I: seperates homologous chromosomes, meiosis II: seperates sister chromatids
Prophase I:
replicated homologous chromosomes (red and blue) pair and exchange segments; 2n=6 in this example
methaphase II:
chromosomes line up by homologous pair
anaphase I:
each pair oh homologous chromosomes seperates
Telophase I and Cytokineses:
Two haploid cells form; each chromosome still consist of two sister chromatids
Prophase II:
A spindle apparatus forms.
Metaphase II:
Chromosomes are positioned n the metaphase plate as in mitosis
Anaphase II:
Sister chromatids seperate.
Telophase II and Cytokinesis:
Haploid daughter cells form.


external image gametes.gif
reproductive cells who transmit genes from one generation to the next they unite and pass on during fertilization  ANIMATIONS AND VIDEOS:In this video the professor explains a bit better the way asexual and sexual reproduction work with a 51:31 minute video .http://www.youtube.com/watch?v=QitJUgbemM0ON-LINE LESSONS:Powerpoint Lectures for. Biology, Lectures by anonymous. Chapter13. Meiosis and Sexual Life Cycles

PowerPoint Presentation - Chapter 13 Meiosis and Sexual Life Cycles


TEST OR QUIZES: in this link the learner will be able to challenge themselves by taking an online quiz based on chapter 13 " Meiosis and sexual Lify Cycles" once answering the seven question that are given make sure to check your answeres on the right hand corner.- The link to the activities, practice test, and quizes are found on the left .


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