Chapter 18:Regulation of Gene Expression

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Chapter 18:Regulation of Gene Expression
2014-12-23 08:18:57
Basic Genetics
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  1. List properties of Prokaryotes and their DNA
    • • One main circularchromosome
    • • DNA is usually naked
    • • Compact genome - mostDNA is coding (genes)
    • • Always HAPLOID
    • • Reproduce by binary fission(asexual) producing clones– Genetic variation comes frommechanisms that are NOT associatedwith reproduction
  2. List properties of Eukaryotes and their DNA.
    Many linear circular chromosomes

    DNA is wrapped around proteins called histones(chromatin)

    Large genomes-­‐less than 3% of DNA codes for genes

    Haploid or diploid

    Animals and higher plants are mostly diploid

    In higher plants and animals, reproduction is usually connected with genetic recombination
  3. Massive File Dump
    • 1.)   
    • Mendel didn’t know
    • about Meiosis, but we do now. State and explain both of Mendel’s laws and
    • identify the event of meiosis that is responsible for each of them. Be sure to
    • mention which phase of meiosis these events occur in..


    • The law of
    • segregation states that each organism has two alleles for each gene. They
    • separate from each other during meiosis I in anaphase.

    • Independent
    • Assortment is when the genes of multiple traits segregate independently when
    • gametes are formed during anaphase II. Each cell receives half of the normal
    • amount of chromosomes.

    • Dominance depends
    • if a chromosome inherits a certain allele. This occurs during crossing over of
    • genetic material in prophase I


    • 2.)   
    • Mendel’s laws can
    • explain the inheritance of many characteristics and combinations of traits. For
    • some other situations, however, the story is more complicated. Give and explain
    • three different situations when certain traits or combinations of traits that
    • are inherited in more complicated ways than what Mendel’s laws would predict.
    • (These must be three separate reasons, not just three different examples of the
    • same phenomenon.


    • Incomplete Dominance is when neither
    • trait is completely dominant to each other. An example is when a red flower and
    • a white flower breed and the genes for red pigments are not dominant or
    • recessive. It has a few pigments of red but not enough for a pure color. The
    • offspring may have a pink color.


    • Overdominance is when a heterozygote can
    • express a phenotype more extreme than the parent generation.  In tomatoes the wild-type genes evenly
    • express fruit and plant growth. The mutant allele produced more leaves. When
    • mixed in a heterozygous offspring the result is much more fruit which is
    • preferable to humans.


    • Codominance happens
    • when two or more alleles influence the phenotype of an organism. An example is
    • human blood types. Blood type 0 codes for no antigen however blood types A and
    • B codes for each antigen. A and B are neither recessive or dominant to each
    • other so both can exist in a person’s body giving us Blood type AB.


    • 3.)   
    • Describe what
    • happens to the DNA of A human somatic cell throughout the course of one
    • complete cell cycle. Tell this like a story where you are a reporter “watching”
    • the DNA. Don’t bother with anything else – just tell the story of the full cell
    • division cycle from the point of view of DNA.


    • The DNA
    • spends most of its time being read like a most to create RNA strands. In fact
    • in certain cells that do not divide DNA will spend all its time in this state.
    • In the S phase DNA replicates with each new strand coming together with a
    • parent strand in the semi conservative model. 
    • During mitosis is where things begin to get more interesting. Prophase
    • is where chromosomes condense and the mitotic spindle begins to form centrosome
    • pairs separate holding some of the microtubules. IN prometaphase the nuclear
    • envelop dissolves exposing the chromosomes and kinetochores are formed for the
    • microtubules to grab onto. Metaphase is where chromosomes line up and the
    • sister chromatids are opposite each other. They form an imaginary line called
    • the metaphase plate down the middle of the cell. During anaphase the sister
    • chromatids are pulled apart as the cell elongates. Finally at telophase the
    • sisters are fully separated and the nuclear envelope beings to form once more
    • of each cell.




    • 4.)   
    • First, make up two
    • traits and two versions of those traits. (For example, you could say height and
    • weight and pretend there were only two versions of each – tall/short and
    • heavy/light. But think of your own examples!) Secondly, give a short
    • explanation, as if to someone with no knowledge of genetics, how They would be
    • inherited if they were located close together on the same chromosome. Third,
    • explain how it would be different if they were located on different
    • chromosomes. Your explanations should include some example scenarios or data.


    • Genetic
    • Recombination  Linkage
    • map

    • Crossing over occurs in
    • Prophase 1 of meiosis

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