sex chromosomes
the pair of chromosomes that determine the sex of an individual
the 23rd pair in humans are the sex chromosomes
female
xx
male
xy
autosomes
all other chromosomes other than sex cells
1st through 22nd pair in humans
sex-linked
also called x-linked/x-traits; traits that are determined by genes on the x chromosomes
ex of sex-linked diseases: hemophilia, colorblindness, duchenne muscle dystrophy
hemophilia
not able to plot blood correctly -ex: H= normal h=hemophilia -- female X^H X^H - normal X^H X^h - normal but carrier X^h X^h - hemophiliac -- male (can't be carriers) X^H y - normal X^h y - hemophiliac
colorblindness
inability to distinguish between certain colors
red/green colorblindness and blue/yellow colorblindness -- H normal h cb.
bc males only have one x chromosome, any recessive allele on the x chromosome will be expressed -- thus males, are MORE LIKELY to express sex-linked recessive traits
duchenne muscular dystrophy
gradual weakening and wasting away of muscle tissue -- muscle types: skeletal, smooth and cardiac
usual onset before age 6, chair-ridden by 12, dead by 20
incomplete dominance
a blending of traits in which neither allele is completely dominant over the other
ex: snapdragons, hypercholesterolemia (elevated cholesterol) H - normal H^1 - HC.
multiple allele trait
aka codominance; the existence of more than 2 alleles for a given trait
ex: blood type in humans
blood type in humans
3 different alleles: I^A, I^B, i -- corresponds to the presence of antigens on the surface of red blood cells
AB, A, B, and O -- the I^A allele and I^B allele are said to be CODOMINANT to the i allele
AB
phenotype: AB genotypes: I^A I^B antigens (surface): A and B antibodies (in blood): none special: universal recipient
antigen
protein marker on RBC; on surface
antibodies
in blood
A
phenotype: A genotypes: I^A I^A or I^A i antigens: A antibodies: B special: none
B
phenotype: B genotypes: I^B I^B or I^B i antigens: B antibodies: A special: none
O
phenotype: O genotype: ii antigens: none antibodies: both A and B special: universal donor
presence of RH factor
absence of RH factor
RH factor
protein/antigen O+ = 70% A- = 0.8%
pleiotropy
the impact of a single gene on more than one characteristic ex: sickle cell anemia
sickle cell anemia
tow abnormal copies of hemoglobin gene result in a variety of different symptoms including: weakness, organ damage, kidney failure, pain, and others
polygenic inheritance
the additive effects of two or more genes on a single characteristic
skin color, height, eye color in humans
skin color and eye color based on amount of melanin
environmental affects on gene expression and phenotype
himalayan rabbits and siamese (black ears, tail, paws, and nose; keeping warmth) cats carry an enzyme for melanin production that is heat-sensitive
enzyme is less active at the surface of warm body parts
fur color is darker in cooler parts such as ears, limbs, and tail
female
picture
male
picture