Human Genetics Inheritance in humans Male/female Multiple Alleles Inherited diseases Twins Sex-linked traits

Single genes (widows peak)

Why is a guy a guy?

Color blindness is also Sex-Linked

Hemophilia

Inheritance in humans  A person receives 23 chromosomes from each parent (46 total)  1 gene for each particular trait from each parent  Genes combine to determine traits (characteristics)  Instruct body cells to make certain chemicals = (proteins)  For example: special proteins (enzymes) make pigment in the iris of the eye

Multiple alleles

Who Has Which Blood Type? TYPES DISTRIBUTIONRATIOS O +1 person in 338.4% O -1 person in 157.7% A +1 person in 332.3% A -1 person in 166.5% B +1 person in 129.4% B -1 person in 671.7% AB +1 person in 293.2% AB -1 person in %

Multiple alleles  Co-dominant – when 2 different genes are both equally dominant–  4 major blood groups = A, B, AB, O.  O is recessive, while A and B are co-dominant

Phenotypes vs. Genotypes  4 major blood groups = A, B, AB, O  Phenotype A could be Genotype AA or Ao  Phenotype B could be Genotype BB or Bo  Phenotype AB can only be Genotype AB  Phenotype O can only be Genotype oo

Inheritance in humans  Allele = each form of a gene Some genes (traits) have multiple alleles  Skin color has 3 or more Controls amount of melanin (pigment) in the skin cells Any one individual inherits only 2

Genetic disorders  Non disjunction = failure of a chromosome pair to separate during meiosis Body cells receive either more or fewer chromosomes than normal  May result in certain disorders  Down’s Syndrome = body cells have an extra chromosome-21 Trisomy-21 (3 instead of 2) May have various physical problems and some degree of mental retardation

Genetic disorders  Down’s Syndrome Trisomy-21 amniocentesis  A karyotype (page 117)is a picture of all the chromosomes in a dividing cell.

 Screening for genetic disorders Amniocentesis  Drawing a small amount of amniotic fluid from the sac surrounding an unborn baby (fetus)  Chromosomes of cells from the fluid can be examined under microscope

twins  Fraternal twins (dizygotic) 2 separate ova are fertilized at same time  Can be same or different sex  Identical twins (monozygotic) Develop from single zygote (fertilized ovum)  Always the same sex Can occur up to 12 days after conception

Identical twins - monozygotic  One fertilized egg splits into two separate people-with the same genes-  A natural clone

Fraternal Twin –Dizygotic  Two – or more eggs which are fertilized by two or more sperm cells  No more alike than any other brother or sister

 Others (include) Muscular dystrophy Huntington disease Cystic fibrosis Hemophila (sex linked)

Sex-linked traits TTraits that are usually carried on X chromosome FFemales less like to inherit Have XX X carries other genes besides feminine traits Recessive genes are hidden by dominant genes of other X MMales more likely to inherit Y carries mostly masculine traits Cannot override genes carried on X

Sex Linked traits

Pedigrees – page 119

Inherited diseases  sickle cell anemia Co dominant gene Caused by mutation of gene for hemoglobin (red pigment in red blood cells that carries O 2 Over time, affected cells become rigid & crescent- shaped

Sickle cell disease/anemia

Sex Determining Chromosomes  Noted different shapes of sex chromosomes: X, Y  Female = XX  Male = XY

Male/Female  XX = normal female  XY = normal male  Sperm determines sex of the individual  X seems to be essential for life No one has been born without at least one X chromosome

Abnormalities of inheriting sex chromosomes  X0 = female in appearance  XXY = male in appearance  Both are sterile –  not able to have children  (There are other abnormalities)  (XYY for example)

Glowing Plant: Natural Lighting without Electricity