Dominance: Co-Dominance, Incomplete Dominance and Blood Types

Dominance: Co-Dominance, Incomplete Dominance and Blood Types

Lesson Objectives • Minds ON • Yesterday’s Recap • Dominances and Blood Types • Blood Typing Lab • Success Criteria • Homework Take Up • New homework

Minds ON Two rabbits are heterozygous. Brown fur (B) is dominant to white fur (b). Dwarf (small) ears (D) are dominant to floppy ears (d). Draw a Punnett square showing the possibilities. We’ll do it together on the board once you’ve tried it.

Yesterday’s Recap Dihybrid Crosses • Refers to the crossing of two individuals who are both heterozygous for TWO traits (e.g. PpTt x PpTt) • Assumes that these traits are on different genes and can occur at the same time. • E.g. Pod colour and seed colour

Dihybrid Crosses • Parent 1 genotype is: AaBb • Parent 2 genotype is: AaBb

Dominances So far, we have been looking at situations where a dominant trait completely masks the allele Bb/BB = dominant for purple colour

Incomplete Dominance Occurs when: • Neither gene is dominant or recessive • The gene effect is mixed • We use 2 different letters for the homologous pair since neither is dominant.

An Example of Incomplete Dominance With red and white snapdragons, the dominant allele that codes for the colour red is not completely dominant over the recessive allele that produces the white colour. The result is a pink flower.

Using a Punnett Square Red Flower – RR White Flower – WW R = 100% Pink Offspring

Co-Dominance Occurs when: • Neither gene is dominant or recessive • Gene effects are NOT mixed • Therefore, both genes are expressed at the same time! • Examples: Roan cow or Camelia flower

An Example of Co-Dominance Write C (for co-dominance) and a super script (R=Red, W=white) • Red haired = CRCR • White haired = CWCW • Red and White (Roan) =CRCW

Using a Punnett Square Red haired = CRCR White haired = CWCW Red and White (Roan) =CRCW = 100% Roan

Blood Types – A Special Case • There are three alleles: • IA (Type A), IB (Type B) and i (Type O) • A and B are co-dominant • O is recessive • +/- is the Rh (Rhesus) factor (if the Rh blood antigen is present, the person is Rh+; if not, they are Rh-) Predict offspring bloodtypes for: Heterozygous type A mother, type O father

Using A Punnett Square 50% = A 5-% = O IA (Type A), IB (Type B) and i (Type O) -A and B are co-dominant -O is recessive

Blood Types AB universal plasma donors AB+ universal recipients O+ blood most needed O- universal RBC donor

Rhesus Disease • An individual either has, or does not have, the "Rhesus factor" on the surface of their red blood cells. • The status is usually indicated by Rh positive (Rh+ does have the D antigen) or Rh negative (Rh− does not have the D antigen) suffix to the ABO blood type. • Rhesus Disease occurs when there is incompatibility between blood types of mother and fetus. • Untreated, the result can cause death of the child. • Occurs in second and laterpregnancies

Murder Mystery Lab “I THINK THERE’S BEEN…(sunglasses on)..AN ACCIDENT!” (with emphasis) https://www.youtube.com/watch?v=mznsEcZlM2I&noredirect=1 The Jim Carrey shows us… https://www.youtube.com/watch?v=HJSqkwyL1Zo

Lab There’s been a murder. Hortatio needs your help! You have to find out who did it. • Agglutination: refers to the clumping effect of blood when it is mixed with Anti-A , Anti-B or Rh serum . • Go around to each station and sample the blood to find out the blood type and Rh factor to determine who killed One-Eyed Earl!

Dominance: Co-Dominance, Incomplete Dominance and Blood Types