1. Karyotyping
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
Note that we have 22 pairs of autosomal chromosomes and 1 pair of sex chromosomes

3. Dominant vs. Recessive Traits
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. Dominant vs. Recessive Traits
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. Sex-linked Genes
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