• 7th grade Life Science Tasks - D Cell Cycle



    Task D-1    1-2

    cell cycle -  most cells go through different stages.  

    Growth, development, and division is the normal cycle.


    Interphase - where normal cells spend most of the cycle,

                         growth and development.


    Task D-2   1-3

    Mitotic phase - part of cell cycle that the cell divides.

    The DNA is found in chromatin.

    The DNA is reproduced during the interphase.


    Cell city


    Task D-3   1-6

    During Mitosis:

    The chromatin turns into sister chromatids as the DNA divides.

    Each new cell gets a copy of the chromatid.

    The sister chromatids are held together by a centromere.

    The organelles are duplicated during interphase.





    TASK D-4    1-7

    Mitosis - the nucleus and its contents divide.

    Cytokinesis - the cytoplasm and contents divide.

    The two new cells are daughter cells.


    Task D-5   1-8

    Phases of mitosis: PMAT

    prophase:  nuclear membrane breaks down

                      spindle fibers form

    metaphase: spindle fibers pull chromosomes to line up in middle


    anaphase: sister chromatids seperate, move apart


    telophase:  spindle fibers disappear, nuclear membrane reforms


    TASK D-7    1-9

    Multicellular life starts as a single cell that divides.

    The cells can go through cell differentiation.

    Cell differentiation means those cells become

    different types of cells.


    1.  What different kinds of cells do you have?


    TASK D-8    1-10

    Atoms - macromolecules - cells - tissues - organs - systems - organism

    Stem Cells: unspecialized cells in animals that can 

    develop into any type of cell.

    Stem cells may be used in the future to treat disease.


    TISSUES - groups of similar cells that work together 

                     your organs are made of different types of tissue


    TASK D-9   1-13

    All your systems together form your metabolism.

    ORGANS - Different tissues working together to

                      perform a job.

    organ systems - groups of organs that work together to 

                      perform a job.

    Example:  Digestive system - the stomach, intestines,

    and liver all work together to break down food.


    1.  What other organ systems do you know?




    TASK D-10   1-15

    Meiosis - one diploid cell divides to make 4 haploid cells.

    Diploid - 2 complete sets of chromosomes.

    Haploid - only 1 set of chromosomes, called sex cells, used for                              reproduction, AKA gametes.


    In reproduction, each haploid cell combines the

    DNA with another haploid cell. 

    This is called fertilization.

    Meiosis AS 

    Task D-11  1-16

     Meiosis is like mitosis, but it goes through TWO PMATs.

    You get half your DNA from each parent.

    This is why families tend to look alike.


    Genetic Variation - we all are different because our "genes",

    our DNA, is different.  

    Our genes determine our physical attributes.

    Nature vs. nurture.


    TASK D-12    1-17

    SELECTIVE BREEDING - Humans pick the individual

    with the traits that we want and breed (have kids)

    it with another organism with those traits.

    We have been doing this longer than human history. 

    1.  What different breeds of dogs do you know of?

    2.  What jobs do you think dogs have done for humans?


    Task D-13    1-21


    Plants and animals give half their genes to their offspring.

    Fungus use both.

    Most fungus produce spores, that are haploid cells 

    which combine with another spore to fertilize the cell.

    MItosis Vs Meiosis


    N V N




    TASK D-14   1-23

    Sexual reproduction: half your genes from each parent

    Asexual reproduction: no mixing of genes, like cloning

    Asexual reproduction types:

    Fission - prokaryotes divide.  Identical DNA.

    Budding - Eukaryotes reproduce by mitosis and cell division.

    Regeneration - simple animals reproduce when offspring

                           grows from a piece of the parent.

    A VS S AS


    asexual MM


    Task D-19     1-24

    Cloning - reproduction in a laboratory that produces

    genetically identical cells.


    reproductive cloning -  inserting the genes of different organisms

    to make an individual that is genetically identical.

    theraputic cloning - creating genetically identical cells to treat a            disease or condition, can include making new organs.

    We have not cloned humans yet, but we have cloned mammals.




    TASK D-20   1-27

    Heredity - the passing of traits to offspring.

    Genetics - the study of how traits are passed to offspring.

    Greger Mendel -  the father of genetics, he studied pea plants in the 1850's and discovered that traits are passed to offspring.

    Mendel did NOT know about DNA or chromosomes.




    Task D-21   1-28

    Dominant trait - blocks another trait, this is expressed, seen.

    Recessive trait - blocked by another trait.


    Most traits are controlled by more than one gene.

    Color blindness can be a single gene, and is recessive.

    1.  Name some traits that are inherited....

    eye color



    Task D-22    1-29

    gene is a section of a chromosome that controls one trait.

    We have two genes for each trait.

    If one is dominant, it gets expressed.

    Alleles - different forms of a gene

    phenotype - physical trait that we see

    genotype - allelle for the phenotype


    Allelle and Genes


    TASK D-23  1-30

    We use a Punnett square to figure out the probability of a trait.

    A dominate allele is shown by a CAPITAL letter.  R

    A recessive allele is shown by a lowercase letter.  r

    homozygous - when both alleles are the same type.  RR  rr

    heterozygous - when the alleles are different.  Rr

    1.  Which boxes show heterozygous genes?

    2.  Which boxes show homozygous genes?

    3.  What trait is dominant?

                            1                   2


                                                       3                  4




    DNA & Chromosomes


    Task D-24   1-31

    incomplete dominance - trait is a combination of parents' alleles.

    Eye color and skin color are examples of this.

    codominance - both alleles can be seen.  

    Blood type is an example of this. 

    RHnull Blood type 

    Codominance AS



    Task D-26      2-3

    Polygenetic Inheritence - when multiple genes control a trait.  

    Most traits are polygenetic.

    The environment can also affect traits.

    Acid in the soil makes hydrangea (a flower) blue.

    Nature vs. nurture.



    Heredity CC