Heredity not following the Rules Learning Goal: predict possible outcomes of various genetic combinations such as non-Mendelian inheritance

Incomplete dominance=Blending A heterozygous condition in which both alleles are partially expressed, often producing an intermediate or blended phenotype (which is different than either of the homozygous forms). Snapdragons

so they blend their strengths together make a new color. Incomplete dominance so they blend their strengths together make a new color. Both traits are "weak" Snapdragons

Incomplete dominance RR R’R’ RR’ RR RR’ RR’ R’R’ In Incomplete use the SAME letters since they both are weak! Incomplete dominance RR R’R’ RR’ RR RR’ RR’ R’R’

Incomplete dominance H’ H’ H H Palomino horses are a cross between a chestnut horse and a cremello (white) color horse. Practice the cross using a Punnett Square. H’ H’ HH’ H H

Codominance=Both Show Codominance –Both phenotypes are dominant. Instead, the heterozygous individual expresses both phenotypes. Co – both are dominant enough to be expressed!! Dominique chickens

Predict the outcome if BOTH chickens are dominique In CODOMINANCE, use DIFFERENT letters since they both are strong! Codominance BB - Black WW - White BW - Black and White W W Predict the outcome if BOTH chickens are dominique (black and white) ???? BW Cross a black chicken with a white chicken and what to you get if the traits are CODOMINANT? B B

BB=1 BW=2 WW=1 Codominance B W B W BB BW WW BB - Black WW - White BW - Black and White B W BB BW WW B BB=1 BW=2 W WW=1

Codominance Another example of codominance is ABO blood typing. The blood types A and B are codominant to each other; however, type O is actually recessive to A and B.

When both alleles exist, Codominance IBIB or IBi ii IAIB IAIA or IAi When both alleles exist, both are present!

Codominance Universal recipient Universal donor Blood Group Antibodies Which group is the universal recipient? Which group is the universal donor? Codominance Blood Group Antibodies Can give blood to… Can receive blood from AB None A, B, AB, and O A B A and AB A and O B and AB B and O O A and B Universal recipient Universal donor

Practicing Blood Types A man of blood type IAIA marries a woman with blood type IAIB. What is the chance they will have a child with type IAIB blood? IA IB IAIA IAIB IA AB? IA

Practicing Blood Types #2 There could be 2 genotypes for the man: BB or BO Practicing Blood Types #2 O? A man of blood type B marries a woman with blood type O. What is the chance they will have a child with type O blood? i i i i IBi IBi ii IB IB 0% 50% IB i

Codominance Blood Group Antigens Antibodies Can give blood to… Can receive blood from AB A and B None A, B, AB, and O A B A and AB A and O B and AB B and O O

Multiple Alleles Why can you only have 2 genes for each trait? Each individual can only have 2 homologous chromosomes thus 2 alleles for a trait, but there could be more than 2 alleles present in a population. This type of inheritance is known as multiple alleles. Why can you only have 2 genes for each trait? Because… you only have 2 of each type of chromosome!!

Multiple Alleles - examples Blood Type is an example of a trait that has multiple alleles. There are 3 possible alleles that could be inherited – A, B, and O, but you can only inherit 2 of them. Coat color in rabbits is inherited as a series of multiple alleles.

Multiple Alleles - examples How many alleles are there for rabbit coat color? 4

Multiple Alleles - examples Why is dark gray a capital C? What are all of the possible genotypes for a dark-gray coated rabbit? (4) CC Ccch Cch Cc chinchilla rabbit (3) cchcch cchch cchc Himilayan rabbit(2) chch chc White rabbit (1) cc

Multiple Alleles - examples Predict the phenotype for a rabbit with a cchch. Chinchilla Is it possible to obtain a white rabbit if one parent is white and the other is chinchilla? Yes. Only if the chichilla is cchc

Polygenic Inheritance Polygenic inheritance is the inheritance pattern of a trait that is controlled by two or more genes. The genes may be on the same chromosome or on different chromosomes. Height in humans Skin color

Polygenic Inheritance Gametes  ABC   ABc   AbC   Abc   aBC   aBc   abC   abc  ABC 6 5 4 3 ABc 2 AbC Abc 1 aBC aBc abC abc Polygenic inheritance in people showing a cross between two bi-racial parents (AaBbCc x AaBbCc). Skin color is controlled by 3 different genes. The offspring contain seven different shades of skin color based on the number of capital letters in each genotype. Skin color

Sex-Linked Inheritance X and Y Chromosomes are sex chromosomes Remember that genes are located on chromosomes XX are female and XY are male

Sex-Linked Inheritance X and Y Chromosomes The X and Y chromosome carry different genes, so they are NOT homologous.

Sex-Linked Inheritance How Sex is Determined Treat the cross the same as a monohybrid Father has genotype XY Mother has genotype XX The chance of each sex being born is 50% X X XX XY X Y

Sex-Linked Inheritance Traits found only on the X chromosome only are called sex-linked Males will only have one copy of this gene, either the dominant or recessive form Females will have two copies, and can be homozygous dominant, heterozygous, or homozygous recessive

Sex-Linked Inheritance Sex-linked genes The Y chromosome is missing this portion of the X chromosome X chromosome contains over 2300 genes Y chromosome contains only 25 genes, including the sex-determining gene SRY SRY directs the formation of male anatomy

Sex-Linked Inheritance Sex-Linked Crosses Write alleles so X is shown with a superscript for the trait (XH Xh) Y has no superscript (Y) Females who are heterozygous for a recessive trait are called carriers – they will not show the trait, but can pass it to offspring

Sex-Linked Inheritance Sex-linked crosses Practice Problem Hemophilia, a disease where blood does not clot properly, is caused by a recessive sex-linked allele. A female, who is a carrier for hemophilia and a normal male have a child. What is the probability that the child will be born with hemophilia? XH Xh XHXH XHXh XH Y XhY 25% chance XH Y

Hemophilia inheritance

POPQUIZ!! (Just kidding) A roan cow is the product of a red cow and a white cow. What type of inheritance is exhibited? Complete dominance Codominance Incomplete dominance Sex-linked Multiple alleles Polygenic B

POPQUIZ!! C Complete dominance Codominance Incomplete dominance Curly haired people have the genotype HH, while straight haired people have the genotype hh. A wavy haired person is heterozygous. What type of inheritance does this exhibit? Complete dominance Codominance Incomplete dominance Sex-linked Multiple alleles Polygenic C

POPQUIZ!! How well a person performs on an IQ test is controlled by multiple genes. Which of the following types of inheritance does this exhibit? Complete dominance Codominance Incomplete dominance Sex-linked Multiple alleles Polygenic F

POPQUIZ!! Hair loss is a trait caused by a gene located on the X chromosome. This trait would be considered - Complete dominance Codominance Incomplete dominance Sex-linked Multiple alleles Polygenic D

BTW

POPQUIZ!! Kim has always wondered why her 2nd toe is longer than her first. She recently discovered that it is a dominant trait. This trait is considered to exhibit - Complete dominance Codominance Incomplete dominance Sex-linked Multiple alleles Polygenic A

POPQUIZ!! Here is an easy one! Blood types fall under the category of which type of inheritance? Complete dominance Codominance Incomplete dominance Sex-linked Multiple alleles Polygenic E A B HEE HEE