BIOL101 Lecture 10: Patterns of Inheritance II- Human Genetics

Incomplete dominance

-Two possible alleles exist for a trait

-No dominance exists

-Heterozygous individuals express both alleles simultaneously, resulting in a third phenotype

-Ex.: AA- red flowers, Aa-pink flowers, aa- white flowers

-Ex.: left- and righthandedness

Multiple alleles

More than two possible alleles for a trait; yielding many possible phenotypes

Ex.: Human blood typing (ABO)

3 alleles: IA "A" allele, IB "B" allele, i "O" allele

Type A blood

IA IA or IA i

Donate to A and AB, only receive A or O

Type B blood

IB IB or IB i

Donate to B and AB, only receive B or O

Type O blood

ii

Universal donor, only receive O

Type AB blood

IA IB

Codominance

Universal acceptor

Antigens

RBC's recognize similar blood types (Antigen A or B)

Antibodies

Proteins produced by WBC's

Reject foreign blood (Anti-A or Anti-B)

Mutations

Any change in DNA sequence

Most are neutral, some beneficial/harmful

Caused by environmental conditions that develop over centuries (mutagen [radiation, UV light])

Karyotype

Photographic display of chromosomes during metaphase

Through amniocentesis or chorionic villus sampling

Detects mutations

Aneuploidy

Abnormal number of chromosomes

Deletion

Cri du chat (cat cry syndrome) caused by deletion of #5

Most dangerous mutation

Inversion

Segment removed, rotated 180 degrees and reinserted

Duplication

Section repeats twice aka "look alike chromosome"

Translocation

Exchange genetic material between two non-homologous chromosomes

Chronic Myelogenous Leukemia (CML)

Caused by translocation between chromosomes (inactive cancer gene on 9) and 22, causes leukemia (production of abnormal/absent WBC's)

Dihybrid cross*

Crosses studying two traits simultaneously

Only can be done with Punnett squares; the two traits are carried on two different chromosomes

[not doing these for test]

Nondisjunction

The failure of tetrads to separate into dyads during anaphase

OR

the failure of dyads to separate into individual chromatids during anaphase 2

Cause of monosomy and trisomy

Monosomy

Chromosomal abnormality consisting of the absence of one chromosome

Most are lethal; offspring is nonviable and apoptosis (abortion) occurs

Trisomy

a condition in which an extra copy of a chromosome is present

Trisomy 21- down syndrome

Some are lethal

Autosome abnormalities

Monosomies of any autosome- lethal

Trisomies of autosomes 1 to 12- lethal

13- Patao syndrome

18- Edward's syndrome

21- Down syndrome

Monosomy sex chromosome abnormalities

YO: missing a second sex chromosome (X)

XO: missing a second sex chromosomes (results in female with Turner's syndrome)

Trisomy sex chromosome abnormalities

XXY- results in male with Klinefelter syndrome

XXX- female with Triplo-X or Metafemale syndrome

XYY- normal male, no disorder

Triplo-X (Metafemale) syndrome

Produces a physically normal, but sterile female

Underdeveloped ovaries and uterus

No ova production and no menstruation

XYY syndrome

Males with XYY are rumored to be more aggressive and produce more testosterone; UNTRUE

A Harvard study attempted to see if criminals in prison were mainly XYY; results were inconclusive