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					Human Genetics
         Human Genetic Map
    How many chromosomes are in a
        human sperm or egg?
   23
    How many chromosomes does a
           human have?

   23 pairs
         What is the total human
         chromosome number?
   46
         Do all animals have 23
          chromosome pairs?
   No, different species have different
    chromosome numbers and the number is
    not correlated to the complexity of the
    How can you tell if a human child
      has the correct number of
   By the process of amniocentesis – a
    needle is inserted into the pregnant
    woman’s abdomen into the amniotic sac
    where the fetus is developing and some
    liquid from the sac is removed

   In this liquid are skin cells from the fetus
    How can you tell if a human child
      has the correct number of
   The cells are grown in a nutrient rich liquid
    for about 10 days until they begin to
    divide. When they are dividing the
    chromosomes become visible through a
    microscope and they can then be counted
    and checked for missing or added parts
         Determination of sex

What are sex chromosomes?

     Chromosomes   that determine the sex of an
How many sex chromosomes are there?

    2 – a female X chromosome and a male Y
How is your sex detemined?
    a female has 2 X chromosomes and a male has 1
     X and 1 Y chromosome
               Determination of sex

   How can you predict the expected sex of a
     By using a punnett square
     A female can donate only an X chromosome
     A male can donate either a X or a Y
   What is the chance that the offspring will
    be male or female?
       50 %
Other Facts about
            Autosomes
                Other 44 body
            Karyotype
                A picture of chromosomes
            Pedigree Chart
                Chart that shows the
                 relationship within a family
            Traits are controlled by
              Autosomal Disorders
   Recessive Alleles
       Albinism
       Cystic fibrosis
       PKU
       Tay-Sachs Disease
   Dominant Alleles
       Achondroplasia
       Huntington’s disease
   Codominant Alleles
       Sickle cell disease
      Autosomal Disorders
 Disorders involving the other 22 pairs of
 Can result from an extra chromosome or
  defective genes
        Genetic Autosomnal
1- Angelman’s syndrome
Occurs in about 1 of 10,000 to 15,000 people. It is
  determined by a set of mutated genes on
  chromosome 15.
2- Cystic Fibrosis
A recessive disorder that occurs in about 1 of
  2,500 people of white European ancestry.
  Related to a mutated gene on chromosome
  17. Characterized by excessive secretion of the
  mucus in the body.
Genetic Autosomal Disorders
3- Huntington Disease
A dominant disorder that occurs in about 1
   of 10,000 people. A dominant gene on
   chromosome 4 is responsible.
It causes degeneration of neurons producing
   dementia, and random jerking movements.
Genetic Autosomal Disorders
4- Phenylketonuria (PKU)
A recessive disorder that occurs in about 1
  of 10,000 people. A defective gene on
  chromosome 12 is responsible
5- Prader Willi Syndrome
A recessive disorder that occurs in 1 of
  10,000 to 15,000 people. It is determined
  by a set of mutated genes on
  chromosome 15.
        Genetic Autosomnal
6- Sickle-Cell Anemia
Occurs in about 1 of 12 U.S. blacks. The defective
  gene on chromosome 11 is responsible.
7- Tay-sachs Disease
A recessive disorder that occurs in about 1 of
  5,000 people of European Ashkenazi Jewish
  ancestry. Defective gene on chromosome 15
  is responsible.
                 Sex Linkage
If chromosomes are paired with other
   chromosomes with the same genes, what
   happens when you pair an X and Y

     Females have two forms of the same gene,
      just like on the rest of the chromosomes, but
      men have only the form of the gene found on
      the X chromosome
          Sex-linked Disorders
   Colorblindness
   Hemophilia
   Muscular Dystrophy
Genetic Sex-Linked Disorders
1- Color Blindness
Genetic X-linked recessive disorder. Occurs in 1 of
  10 males
2- Hemophilia A and B
Recessive disorders that affect 1 of 5,000 males.
  These interfere with normal blood clotting and
  occur at different loci (the position on a
  chromosome occupied by a particular gene) on
  the X chromosome.
If color blindness is a trait inherited
   on the X chromosome, why are
 men more likely to be color blind?

   The man doesn’t have a second X
    chromosome to keep recessive genes
    from being expressed
         Chromosomal Disorders
   Down Syndrome
       Extra copy of chromosome at 21
   Sex Chromosome Disorders
       Turner’s Syndrome
            Only One X chromosome (XO)
       Klinefelter’s Syndrome
          Extra   X chromosome (XXY)
    Chromosomal Autosomal
Down Syndrome
Occurs in about 1 in 1,000 live births. An
 extra chromosome is attached to the
 21st pair. Risk increases with maternal
 age. Pregnancies of women over age 35
 accounts for 20% of Down syndrome birth
    Chromosomal Sex-Linked
1- Fragile X Syndrome
Occurs in about 1 of 1,200 males and 1 of
  2,500 females. Results from a breakage of
  the tip of an X chromosome.
2- Klinefelter Syndrome (XXY, XXXY, XXXXY)
Occurs in about 1 of 1,000 males. It is
  caused by an extra X chromosome
      Chromosomal Sex-linked
3- Superfemale Syndrome (XXX, XXXX, XXXXX)
Occurs in about 1 of 1,000 females. Women
  appear normal, but tend to score slightly below
  average in intelligence.
4- Supermale Syndrome (XYY, XYYY, XYYYY)
Occurs in about 1 0f 1,000 males. The men tend
  to be taller than average, with a greater
  incidence of acne and minor skeletal
     Chromosomal Sex-linked
5- Turner’s Syndrome (XO)
Occurs in about 1 of 10,000 females. One of
  the X chromosomes is either missing or
  inactive. These women have immature
  female appearance, do not develop
  secondary sex characteristics, and lack
  internal reproductive organs.

 An individual whose body contains tissue
  of both male and female gonads.
 The ovaries and testes may be present as
  separate organs, or ovarian and testicular
  tissue may be combined in the same
 Causes
     Adrenal Gland imbalance during pregnancy
     Male hormone imbalance
The End