Presentation on theme: "Human Heredity. 1) Autosomes –all the chromosomes except the sex chromosomes (in humans, there are 22 pair) 2) Sex chromosomes –The sex-determining chromosomes,"— Presentation transcript:
1) Autosomes –all the chromosomes except the sex chromosomes (in humans, there are 22 pair) 2) Sex chromosomes –The sex-determining chromosomes, the X & Y
3) Karyotype –Pictures of paired human chromosomes arranged by size, used to identify abnormalities in fetuses –Cells from an amniotic fluid sample are cultured, stained & photographed
Who determines the Sex of offspring in Humans?
Sex-Limited, Influenced Traits and Sex Linked Some traits are carried on the sex chromosomes = X and Y Most Traits are on X Y is smaller, so few genes located.
SEX HORMONESGenes inherited by both male and female but expressed only in one sex due to SEX HORMONES EX: Beards, breasts, antlers, milk production, feathers on birdEX: Beards, breasts, antlers, milk production, feathers on bird
Autosomal genes influenced by sex. Genes DOMINATE in one sex and RECESSIVE in other Males and females with the same genotype will have different phenoypes EX: Index vs Ring finger Short index finger: Dom. in Males Rec. in Females (FYI: Shorter mans index finger, the higher amt of prenatal testosterone (corresponds to physically aggressive behavior)
Examples Continued: Hairlip and Gout Dominant in males Recessive in females Spina Bifida: Dom. in females Rec. in Males
Other Examples: Baldness: Dom. In Males Rec. in Females B=baldness, B=normal hair BB=bald (male/female) BB=normal hair (male/female) BB= bald (male) normal (female
The Adams family
Controlled by GENES on SEX CHROMOSOMES. X chromosome is larger than y more genes carried on the X X-Linked Genes: genes found on X chromosome Appear mostly in males Only one copy of X; nothing to counteract bad gene Females would need two copies to express trait
Red-Green Color Blindness (X R X r Y°) Hemophilia (inability of blood to clot) X H -normal X H Y° X h Y°-hemo Muscular Dystrophy (I muscles)
4) Sex-linked traits –A recessive gene on the X chromosome –Examples: color-blindness & hemophilia –Genotypes:Phenotypes: – X N Ynormal male – X n Ycolorblind – X N X N normal female – X N X n carrier female – X n X n colorblind
normal vision weak red weak green
Phenotypes??? Cross of carrier female & normal male XNXN XnXn XNXN XNXNXNXN XNYXNY X N X n XnYXnY Y
X-linked recessive Most Common in males Bleeders Disease Missing clotting factor Bleeding spontaneously and in joints
Hemophila is sex-linked recessive trait. Normal clotting is dominant. Hemophiliac Male X Carrier (Heter.) Female LET: X H normal X h hemo X h hemo Y O no trait Y O no trait XhXh Y XHXH XhXh XHXhXHXh XHYXHY X h XhYXhY
XHXhXHXh X H X H X H X h X H Y X h Y Carrier Mom
Sex linkage & calico cats
Ex. Long Hair on Earlobes 3 Muslim brothers from South India.
5) Nondisjunction –Failure of chromosomes to separate –May cause a variety of birth defects, including trisomy 21 or Down syndrome
Turners syndrome XX O Only 1 sex chromosome is present. *Associated with underdeveloped ovaries, short stature, webbed neck, and broad chest. *Individuals are sterile, and lack secondary sexual characteristics. *Mental retardation typically not evident.
6) Pedigree6) Pedigree Chart showing family history of a trait Chart showing family history of a trait –Solid light = homozygous dominant, –solid dark = homozygous recessive, –half-circle = heterozygous
7) Genetic disorders –Harmful effects produced by mutated genes, most are recessive and few are lethal –Example: sickle cell anemia
Normal, with malarial resistance Same as parents ; normal, no resistance; sickle-cell anemia