Chromosome - PowerPoint by WbCO40m7



Mrs. Hoyle
 Chromosome: a very long DNA molecule and associated
proteins, that carry portions of the hereditary information
                      of an organism.
                 Each chromosome has a
                  constriction point called the
Chromosomes       centromere, which divides
                  the chromosome into two
                  sections, or “arms.”
                 The short arm of the
                  chromosome is labeled the
                  “p arm.”
                 The long arm of the
                  chromosome is labeled the
                  “q arm.”
                 The location of the
                  centromere on each
                  chromosome gives the
                  chromosome its
                  characteristic shape, and can
                  be used to help describe the
                  location of specific genes.
    A karyotype is an organized
                                         Karyotype -
    profile of a person's
    chromosomes. In a
    karyotype, chromosomes                  Male
    are arranged and numbered
    by size, from largest to
    smallest. This arrangement
    helps scientists quickly
    identify chromosomal
    alterations that may result in
    a genetic disorder.
   To make a karyotype,
    scientists take a picture of
    someone's chromosomes,
    cut them out and match
    them up using size, banding
    pattern and centromere           Since its discovery back in the
    position as guides.              1960s, karyotyping has been
                                     used as both a `screening tool'
                                     as well as a method to
                                     determine potential genetic
   Autosome refers to
    those chromosomes
    that are not involved
    in sex determination.
    Human diploid cells
    have 22 pairs of
    autosomes and 1 pair
    of sex chromosomes.        Male xy
   Sex chromosomes are        Female xx
    involved in a major
    way in sex
Gregor Mendel
          He made two very
           important generalizations
           from his pea
           experiments, know today
           as the Laws of
           Mendel coined the
           present day terms in
           genetics: recessiveness
           and dominance.
          In 1866 he published his
           work but it didn't take
           affect in the science field
           until 1900, years after his
           death. As the theory of
           evolution spread so did
           his findings and laws.
         Mendel and Pea Plants

   P – pure for trait
   F1- first
   F2- second
                                   Ever wonder how your sister
         Monohybrid                 came out with blue eyes, when
                                    both of your parents have
                                    brown eyes?
   All traits have two genes      Some Ideas Refreshed:
    that represent them.           Genotype: combination of
    Traits come in pairs.           alleles in your DNA (i.e. GG)
   They can be all                Phenotype: the trait that
    dominant (TT)                   shows up based upon the
                                    genotype (i.e. green peas)
   mixed (Tt)                     For each trait you have 2
    or all recessive (tt)          alleles, one comes from each
   This is the basis for
                                    Homozygous: two of the same
    figuring out a Punnett      
    square. When two genes         Heterozygous: two different
    are paired, the dominant        alleles.
    one will take effect.          The dominant allele BLOCKS
   Monohybrid (One-Gene)           the recessive allele (for ALL
                                    cases, unless labeled "mixed
Symbol for
male and
Male is on top
of this punnett
Female is on
the side of the
punnett square
                    Product Rule
                                         A-heads         a- tails
    Chance of two independent
    events occcuring                   AA           Aa
    simultaneously is = to the
    product of the separate          A
   What would be the chance of
    having a AA? One in 4              Aa           aa
   Ex ½ x ½ = ¼ chance
   Ex. If you flip two coins at the a
    same time what would the
    odds be?
   Would it be possible for Aa
    parents to have 4 children with
    aa? YES! Just not as likely.       Ex Aa x Aa
   Aa xAa
                                    ¼ x ¼ x ¼ x ¼ = 1/250
                      Blood Type
   Each of us has two ABO
    blood type alleles,
    because we each inherit     Phenotype   Genotype
    one blood type allele        Type A    AA , Ao
    from our biological          Type B    BB, Bo
    mother and one from
                                 Type AB   AB
    our biological father.
   A description of the pair
    of alleles in our DNA is
    called the genotype.
    Since there are three
    different alleles, there
    are a total of six
    different genotypes
                                            Complete the following
                                             Punnett squares using the
   In some instances, a cross               information. Since dominance
    between two individuals, each            is not operating, a slight
    differently homozygous for a             modification of gene symbols
    particular characteristic, results       is used.
    in partial expression of both           We will use the letter C to
    traits in the F1 phenotype. One          represent color in
    gene incompletely masks the              snapdragons.
    other in the heterozygote.
                                             CR will represent the allele for
                                             red color and
                                             CW will represent the allele
                                             for white color.
                                            The hybrid of a red and a
                                             white snapdragon is pink, so
                                             would be represented as CR
Incomplete Dominance & Codominance
There is no dominant or recessive, the heterozygous
condition results in a "blending" of the two traits.
Example: Snapdragons can be red, white, or pink
           Sex Determination

   Female = XX
   Male = XY
   Male Determines the sex
                  Sex Linked Traits
   The genes for these traits
    are on the X chromosome,
    because boys only receive
    one X chromosome they are
    more likely to inherit
    disorders passed to them
    from their mother who
    would be a carrier.
   Hemophilia and
    Colorblindness are sex
    linked traits, the punnet
    square below shows how a
    woman who is a carrier
    passes the trait to her son,
    but not her daughters.

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