Chapter 8 -

Mendalian Genetics Review https://www.youtube.com/watch?v=cWt1RFnWNzk https://www.youtube.com/watch?v=9AiE9ADkhNM

Incomplete Dominance vs. Codominance Incomplete Dominance: one trait is not completely dominant over the other Two identical copies of a dominant allele are required for expression (homozygous) Heterozygous situations create an intermediate (mixture of traits)

Incomplete Dominance vs. Codominance Codominance: two dominant traits appear in the phenotype Two identical copies of a dominant allele are required for expression (homozygous) Heterozygous situations create a combination of two traits

ABO Blood System ABO blood system uses surface markers (carbohydrates) of red blood cells The system shows relatedness of people ABO blood typing displays: Multiple Allelism: more than two alleles of a gene are in the population Type A, Type B, & Type O Codominance: Type A & B are dominant, Type O is recessive

Polygenic vs. Pleiotropic Traits Polygenic traits: genetic traits affected by many genes Skin Color Eye Color Height: Leg bone height Torso height

Polygenic vs. Pleiotropic Traits Pleiotropic traits: a single gene causing multiple effects Hemophilia – cannot produce clotting factor VIII; unable to form clots to stop bleeding Excessive Bruising Pain Swelling in the joints

Sex Determination For sex chromosomes: Males have one X & one Y Females have two X’s Males produce gametes (sperm cells), half contain one X chromosome and the other half contain one Y chromosome Females produce gametes (egg cells), all contain one X chromosome All fertilized eggs have an X chromosome from the female and either an X or Y chromosome from the male

Sex-linked vs. Autosomal Gene Inheritance Autosomal gene: gene that is located on a chromosome that is not a sex chromosome Sex-linked gene: gene that is located on the X or Y chromosome, which makes it associated with gender Example In hemophilia (h), it is a faulty gene only on the X chromosome The hemophilia gene is a recessive condition Men have the condition if they get the faulty gene since they only have one X chromosome Women only have the condition if they have two faulty genes

X-linked Hemophilia

X-inactivation & Inheritance An extra chromosome on number 21 produces a condition called Down’s Syndrome An extra chromosome on number 18 results in early death in the womb or as an infant Triple X Syndrome occurs when there is an extra X chromsome in females No major development symptoms Why? X-inactivation: genes from multiple X chromosomes are not expressed, resulting in normal developments and phenotypes This occurs normally in females, who have two X chromosomes

Use of Pedigrees in Science Pedigrees are family trees that show inheritance of genetic traits for many generations Scientists use pedigrees to study the inheritance of a genetic traits & genetic disorders https://www.youtube.com/watch?v=YhRxoA_49m8

DNA Fingerprinting DNA Fingerprinting: Process by which DNA from different sources is compared. When small amounts of DNA are available, polymerase chain reaction (PCR) can be used to make millions of copies of the DNA DNA is cut and separated on an gel (made from agarose) with an electric current DNA is compared to show related ness https://www.youtube.com/watch?v=AkBUriMK9u8