Human Heredity

1) Autosomes 2) Sex chromosomes 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-Limited Traits Genes inherited by both male and female but expressed only in one sex due to SEX HORMONES EX: Beards, breasts, antlers, milk production, feathers on bird

Sex-Influenced Traits 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 man’s index finger, the higher amt of prenatal testosterone (corresponds to physically aggressive behavior)

Sex-Influenced Traits Examples Continued: Hairlip and Gout Dominant in males Recessive in females Spina Bifida: Dom. in females Rec. in Males

Sex-Influenced Traits Other Examples: Baldness: Dom. In Males Rec. in Females B=baldness, B’=normal hair BB=bald (male/female) B’B’=normal hair (male/female) BB’= bald (male) normal (female

The Adams family

Sex Linkage 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

Traits on X Chromosome Red-Green Color Blindness (XR Xr Y°) Hemophilia (inability of blood to clot) XH-normal XHY° XhY°-hemo Muscular Dystrophy (I muscles)

4) Sex-linked traits A recessive gene on the X chromosome Examples: color-blindness & hemophilia Genotypes: Phenotypes: XNY normal male XnY colorblind XNXN normal female XNXn carrier female XnXn colorblind

normal vision “weak red” “weak green”

XN Y XN Xn XNXN XNY XN Xn XnY Cross of carrier female & normal male Phenotypes???

Hemophilia X-linked recessive Most Common in males “Bleeder’s Disease” Missing clotting factor Bleeding spontaneously and in joints

Xh Y XH Xh XHY XHXh Xh Xh XhY Hemophilia Hemophila is sex-linked recessive trait. Normal clotting is dominant. Hemophiliac Male X Carrier (Heter.) Female LET: XH normal Xh hemo YO no trait Xh Y XH XHY XHXh Xh Xh Xh XhY

Carrier Mom XHXh XHXH XHXh XHY XhY

Royal Hemophilia

Sex linkage & calico cats

Traits on Y CHROMOSOMES 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

nondisjunction

Trisomy 21

Klinefelter’s syndrome

Klinefelter’s

Super male Super male

Turner’s syndrome XX 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 . XX XX O

6) Pedigree 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

Polydactyly (multiple fingers and toes)