BSC 2010L. Humans Haploid # of chromosomes: 23 Diploid #: 46 Remember: Have 23 pairs 1 of each pair came from mom 1 of each pair came from.

BSC 2010L

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

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

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

Some Dominant Traits in Humans Widow’s peak Unattached earlobes Freckles

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

Genes located on the sex chromosomes (23rd pair in humans) Examples:

Color-blindness Hemophilia

Males only need 1 gene on X chromosome to have trait – look at boy on far right

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

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

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

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