Human Karyotypes
Human Karyotypes
Karyotypes = pictures of homologous chromosomes lined up during metaphase 1
23 pairs of chromosomes (1 set from the
mother & 1 set from the father) - 22 pairs are autosomes - 1 pair is sex chromosomes
XX = female ♀ & XY = male ♂
About ChromosomesChomosomes = structures of
tightly coiled chromatin (DNA)
Homologous chromosomes = chromosomes of same size & shape carry the same genes for the same traits
Chromosomal Theory of Inheritance
“Genes are located on chromosomes”
Genes- are hereditary units of DNA - control characteristics & abnormalities - exist in different forms called alleles
ALLELES Dominant – shows
whenever present
- designated w/capital letters
T = tall
Recessive – shows only if the organism is homozygous
- masked w/dominant alleles
- designated w/lowercase letterst = short
GENOTYPE = genetic makeup HOMOZYGOUS (Pure) - organism has 2
identical alleles for a trait
TT or tt
HETEROZYGOUS (hybrid)
- organism has 2 different alleles for a trait
Tt
PHENOTYPE Physical appearance an organism develops as
a result of its genotype
Phenotype Genotype
Pure tall plant TT (homozygous dominant)
Pure short plant tt (homozygous recessive)
Hybrid tall plant Tt (heterozygous)
Mendel’s Peas