+ Human Heredity
+ Karyotypes A genome is the full set of genetic information that an organism carries in its DNA. Karyotype: Shows the complete diploid set of chromosomes grouped together in pairs, arranged in order of decreasing size. Does it look like this in the cell?
+ Sex Chromosomes Two of the 46 chromosomes determine sex Females are XX Males XY.
+ Male or Female?
+ Male or Female?
+ Male or Female? Mutation! Turner s Syndrome Female
+ Sex Chromosomes More than 1200 genes are found on the X chromosome The human Y chromosome is much smaller than the X chromosome and contains only about 140 genes Most are associated with male sex determination and sperm development.
+ Autosomal Chromosomes The remaining 44 human chromosomes are known as autosomal chromosomes, or autosomes. The complete human genome consists of 46 chromosomes, including 44 autosomes and 2 sex chromosomes. Genes on autosomes follow inheritance patterns we learned before
+ Sex Linked Gene Gene located on a sex chromosome Genes on Y chromosomes only pass from father to son Tracing male lineage Genes on X chromosome are found in both sexes Remember males only have one.
+ Sex-Linked Inheritance Three genes responsible for color vision all are on the X chromosome They are recessive Males only have one X so if they have one recessive allele they will have some form of color blindness (1 in 12) Females have 2 X chromosomes so they would need both copies of a recessive allele (1 in 200)
+ Ms. Shetler s Family Dad: Not Color Blind Mom: Not Color Blind X N Y X N X n X N X? Ms. Shetler: Not Color Blind Brother: Color Blind X n Y How do we know Mom is a carrier? Is Ms. Shetler a carrier? 50% Chance Is there a way to know for sure? X N Y X N X N X N X N Y X n X N X n X n Y
+ Ms. Shetler s Family Ms. Shetler: Not Color Blind X N X? Husband: Not Color Blind If Ms. Shetler has a color blind son, is she a carrier? Yes If Ms. Shetler does not have a color blind son does that mean she is not a carrier? No X N Y X N Y X N X? X N X N X N X? X N Y X? Y
+ X-Chromosome Inactivation If just one X chromosome is enough for cells in males, how does the cell adjust to the extra X chromosome in female cells? In female cells, most of the genes in one of the X chromosomes are randomly switched off, forming a dense region in the nucleus known as a Barr body. Barr bodies are generally not found in males because their single X chromosome is still active.
+ X-Chromosome Inactivation Also occurs in other mammals like cats One X chromosome has an allele for orange spots Other X chromosome has an allele for black spots Some cells have one X chromosome switched off other cells turns off the other.
+ Sex-Linked Practice In fruit flies, eye color is a sex linked trait. Red is dominant to white. What are the sexes and eye colors of flies with the following genotypes: X R X r Female, red X R Y Male, red X r X r Female, white X R X R Female, red X r Y Male, white
+ Sex-Linked Practice In fruit flies, eye color is a sex linked trait. Red is dominant to white. What are the genotypes of these flies: white eyed, male X r Y red eyed female (heterozygous) X R X r white eyed, female X r X r red eyed, male X R Y red eyed female (homozygous) X R X R
+ Sex-Linked Practice Show a cross between a homozygous red eyed female and a white eyed male. What are the genotypes of the parents: & X r Y X R X R X R X R How many are: 0% 0% 50% 50% white eyed, male white eyed, female red eyed, male red eyed, female X r Y X R X r X R Y X R X r X R Y
+ Human Pedigrees To analyze the pattern of inheritance followed by a particular trait, you can use a chart, called a pedigree, which shows the relationships within a family. A pedigree shows the presence or absence of a trait according to the relationships between parents, siblings, and offspring.
+ Reading Pedigrees
+ Human Pedigrees A pedigree can show you if an allele for a trait is: dominant or recessive autosomal or sex-linked It can also predict the risk of passing a trait onto the next generation
+ Pedigree Example This pedigree shows how one human trait a white lock of hair just above the forehead passes through three generations of a family. The allele for the white forelock trait is dominant. At the top of the chart is a grandfather who had the white forelock trait. Two of his three children inherited the trait. Three grandchildren have the trait, but two do not. Because the white forelock trait is dominant, all the family members in the pedigree lacking this trait must have homozygous recessive alleles. One of the grandfather s children lacks the white forelock trait, so the grandfather must be heterozygous for this trait.
+ Pedigrees Practice
+ Pedigrees Practice
+ Pedigrees Practice