Applied Biology Genetics Notes

Genetics Introduction Genetics is the study of heredity Heredity explains why you look like your parents or siblings (similar traits) Traits (ex. Color, shape) are inherited or passed down to offspring in genetic crosses

Essential Vocabulary! Gene – parts of DNA that control traits Gregor Mendel – “Father of Genetics”, studied inheritable information & performed plant-cross experiments

Dominant vs Recessive Dominant gene – trait ALWAYS shows itself Recessive gene – trait hidden when dominant gene is present Allele – forms of a particular gene (we use caps & lower case letters) (R = round and r = wrinkled…….but both code for shape)

Homozygous vs. Heterozygous Homozygous – 2 of same allele for a trait (RR or rr) Heterozygous – 2 different alleles for a trait (Rr)

Phenotype vs. Genotype Phenotype – physical observable trait (shape, color ect.) Genotype – genetic make-up, combination of alleles (RR, Rr, rr) Genotype Phenotype (purple)

Solving Genetics Problems 1. Designate letters for traits (R=Round, r=wrinkled) 2. Determine parent alleles 3. Set up Punnett square 4. Fill – in Squares 5. Determine possible offspring genotypes & Phenotypes

Practice Problem Black hair (B) is dominant over brown hair (b). A man heterozygous for black hair and a woman with brown hair have children. What are the genotypes and phenotypes of their offspring? Step #1 B = black b = brown Step #2 Dad = Mom = Step #3 (punnett square) Step #4 (fill-in offspring squares) Step #5 (Genotypes & phenotypes)

Blood Typing Genetics (Codominance & Multiple Alleles) In simple genetics…there are usually 2 alleles –1 dominant (R) & 1 recessive (r) In Codominance…neither allele is dominant over the other! Since they are COdominant…they both show up in the heterozygous phenotype!

Blood Typing Genetics (cont.) Usually in simple genetics problems we have: –1 Dominant Allele –1 Recessive Allele R or r In Blood typing, we have: –2 Dominant Alleles = A & B –1 Recessive Allele = o EXAMPLE: Blood Types!

Blood Typing - Codominance In humans, there are 4 possible blood types: A, B, AB, and O. Type O individuals are considered to be the “universal donors”, whereas type AB individuals are said to be “universal recipients”!

Blood Type Genotypes Type A Blood –AA is homozygous –Ao is heterozygous Type B Blood –BB is homozygous –Bo is heterozygous Type AB Blood –AB (this is the co-dominant blood type!) Type O Blood –oo (only 1 way to have Type O blood because o is recessive!)

Blood Typing – Practice Problem A man heterozygous for Type A blood and woman homozygous for Type B blood have children. What are the possible genotypes and phenotypes of their offspring?

Practice Problem #2 Two babies are ready to go home from the hospital…Which baby belongs to which parents? Here’s what you know about the babies: –Baby A bas blood type A –Baby B has blood type O Parents #1 - Father (Homozygous Type A) & Mother (Type O) Parents #2 - Father & Mother (Heterozygous A)

Sex Linkage – Hemophilia Some traits are carried on the X chromosome!! Hemophilia is the most well- known sex-linked disease! Males = X Y Females = X X

Hemophilia Lacking the ability for blood to clot…can’t stop bleeding  Possible Genotypes: Hemophilic Male Genotype = X Y Hemophilic Female = X X Normal Male Genotype = X Y Normal Female Genotypes = X X X X (CARRIER)

Practice Sex Linkage (Hemophilia) Problem A man with hemophilia and a normal women (but carrier for hemophilia) have a child. What are the possible genotypes and phenotypes of their offspring? Man = X Y Woman = X X Offspring Genotypes: Offspring Phenotypes:

Human Genetics Karyotype - the complete set of chromosomes in a species. Can show chromosomal disorders such as: 1.Down Syndrome (Trisomy 21) 2.Turner Syndrome (X missing pieces) 3.Klinefelter Syndrome (XXY) Chromosomal Disorders occur due to NONDISJUNCTION – error in meiosis where chromosomes don’t separate correctly during anaphase!

Human Genetics - Pedigrees