Presentation is loading. Please wait.

Presentation is loading. Please wait.

Human Heredity.

Similar presentations

Presentation on theme: "Human Heredity."— Presentation transcript:

1 Human Heredity

2 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 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



6 Who determines the Sex of offspring in Humans?

7 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.

8 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

9 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)

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

11 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

12 The Adams family

13 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

14 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)


16 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

17 normal vision “weak red” “weak green”

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

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

20 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

21 Carrier Mom XHXh XHXH XHXh XHY XhY

22 Royal Hemophilia



25 Sex linkage & calico cats

26 Traits on Y CHROMOSOMES
Ex. Long Hair on Earlobes 3 Muslim brothers from South India.

27 5) Nondisjunction Failure of chromosomes to separate
May cause a variety of birth defects, including trisomy 21 or Down syndrome

28 nondisjunction

29 Trisomy 21


31 Klinefelter’s syndrome

32 Klinefelter’s


34 Super male Super male

35 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


37 6) Pedigree Chart showing family history of a trait
Solid light = homozygous dominant, solid dark = homozygous recessive, half-circle = heterozygous

38 7) Genetic disorders Harmful effects produced by mutated genes, most are recessive and few are lethal Example: sickle cell anemia

39 Normal, with malarial resistance
Same as parents ; normal, no resistance; sickle-cell anemia

40 Polydactyly (multiple fingers and toes)

Download ppt "Human Heredity."

Similar presentations

Ads by Google