COMPLEX INHERITANCE OF COMPLEX INHERITANCE OF HUMAN TRAITS HUMAN TRAITS Chapter 12.3
Jan 17, 2016
COMPLEX INHERITANCE COMPLEX INHERITANCE OF HUMAN TRAITSOF HUMAN TRAITS
Chapter 12.3
CODOMINANCE IN HUMANSCODOMINANCE IN HUMANSSICKLE CELL ANEMIA
◦If homozygous, red blood cells take on a “sickle” shape
◦If heterozygous, person will produce both normal and sickle shaped red blood cells
◦Sickle cell cause◦slow blood flow◦Block small vessels◦Result in tissue damage and pain
MULTIPLE ALLELES AND BLOOD MULTIPLE ALLELES AND BLOOD TYPETYPE
ABO BLOOD GROUP◦Type A, Type B, Type AB, Type O◦Controlled by 3 alleles
IA, IB, IBlood typing is necessary for blood
transfusions◦So the body doesn’t “reject” the blood
Blood typing is also used to determine paternity of a child
SEX-LINKED HUMAN TRAITSSEX-LINKED HUMAN TRAITSMost genes are located on the X
chromosomeX-LINKED RECESSIVE TRAITS
◦Red-green color blindness◦hemophilia
Red-Green Color BlindnessRed-Green Color BlindnessCaused by inheritance of a recessive
allele on the X chromosomePeople can’t identify red and green traffic
lights by color
HemophiliaHemophiliaX linked recessive disorder that causes
your blood to not be able to clot◦Cuts take a long time to stop bleeding
Females need 2 recessive alleles to show trait, males only need 1
POLYGENIC INHERITANCE IN POLYGENIC INHERITANCE IN HUMANSHUMANS
Skin Color
CHANGES IN CHROMOSOME CHANGES IN CHROMOSOME NUMBERNUMBER
ABNORMAL NUMBER OF AUTOSOMES◦Extra autosomes = “trisomy”
Instead of having 46 chromosomes, they would have 47
Results from “nondisjunction” during meiosis◦Failure of homologous chromosomes to separate
Karyotype:◦chart of chromosome pairs used to identify
unusual chromosome numbers in a cell
Down Syndrome: Trisomy 21Down Syndrome: Trisomy 21The ONLY autosomal trisomy which
doesn’t result in death3rd chromosome present in 21st pairIncidence of this increases in mothers that
give birth over age 40
Abnormal # of Sex ChromosomesAbnormal # of Sex Chromosomes
XO (Missing X chromosome)XXX, XXY, or XYYAs long as there is 1 Y chromosome, the
child will be a maleExtra 23rd pair chromosomes
◦People lead normal lives, however, they can’t have children and some have varying degrees of mental retardation