1. BSC 2010L

2.  Humans  Haploid # of chromosomes: 23  Diploid #: 46  Remember:  Have 23 pairs  1 of each pair came from mom  1 of each pair came from dad

3.  Each pair of chromosomes is referred to as HOMOLOGOUS CHROMOSOMES  Have the same genes  For each gene there can be 2 alleles (different forms)  Look at picture below:  B = brown eyes  b = blue eyes  Brown is dominant so this person’s phenotype would be brown eyes

4.  Incomplete Dominance  Form of inheritance where heterozygous alleles are both expressed, combined phenotype  Example: a plant with white flowers and plant with red flowers has offspring with pink flowers  Codominant  Both alleles are expressed  Example: Blood types in humans  If a person has the A allele and the B allele, then both A and B are expressed on the surface of the red blood cell

5.  Some Dominant Traits in Humans  Widow’s peak  Unattached earlobes  Freckles

6.  Down Syndrome (Trisomy 21)  3 #21 chromosomes  Sex Chromosomal Abnormalities  Turner Syndrome – XO  Never reaches puberty  Poly-X Syndrome (XXX)  Tend to have learning disabilities  Klinefelter Syndrome (XXY)  Testes underdeveloped, long limbs, poor muscle growth  Jacob Syndrome (XYY)  Taller, speech and reading problems

7.  Genes located on the sex chromosomes (23 rd pair in humans)  Examples:  Color-blindness  Hemophilia  Males only need 1 gene on X chromosome to have trait – look at boy on far right

8.  Method that allows tracking of a genetic disorder within a family  Circles – Females  Squares – Males  Affected individuals – filled in  Carriers – half filled in http://www.sciencegeek.net/Biology/review/Sem1Review.htm

9.  Patterns of inheritance  Autosomal Dominant – many children affected  Autosomal Recessive – few children affected  X-linked recessive – mostly males affected

10.  Patterns of inheritance  Autosomal Dominant – many children affected  Autosomal Recessive – few children affected  X-linked recessive – mostly males affected

11.  Patterns of inheritance  Autosomal Dominant – many children affected  Autosomal Recessive – few children affected  X-linked recessive – mostly males affected