Item 52: Exceptions to the Rule

Incomplete Dominance: The blending of alleles Ex: Red Flower + White Flower = Pink Flower

Incomplete Dominance For a trait, the “dominant” is not completely masking the recessive No lower case letters Get blending in heterozygous

Incomplete Dominance R = red, r = white RR = red, R = red, W = white Normally: Incomplete Dominance: R = red, r = white RR = red, Rr = red rr = white R = red, W = white RR = red RW = pink WW = white

Incomplete Dominance One red and one white flower are cross pollinated (mated), draw the punnett square of their offspring: R R W RW

Incomplete Dominance One red and one pink flower are cross pollinated (mated), draw the punnett square of their offspring: R R R W RR RW

Co-Dominance Both are dominant so both show

Co-Dominance For a trait, you can have 2 dominant options and 1 recessive Can’t use regular upper and lowercase

Co-dominance R = red, r = white RR = red, Rr = red rr = white Normally Co-dominance R = red, r = white RR = red, Rr = red rr = white R= red, W = white, recessive = yellow IRIR or IRi= red IWIW or IWi= white IRIW – red and white ii = yellow

Practice problem…do somewhere in your notes A flower with red and white stripes mates with a homozygous white flower. What is the phenotypic ratio?

Co-dominance Example: Blood types A and B are co-dominant – AB O is recessive Genotypes: A -> IAIA and IAi AB -> IAIB B -> IBIB and IBi O -> ii

Co-dominance Blood transfusions: Must receive blood type you are OR recessive (__O__) O is universal donor AB is universal acceptor

Warm Up 1.) Draw the Punnett square for a man who is heterozygous for B type blood and a woman who has O type blood. What are the blood type possibilities for their children? 2.) Snapdragons are flowers that exhibit incomplete dominance. Show the Punnett square cross between a pink flower and a white flower. What is the phenotypic ratio (pink to white)?

Snapdragons

Karyotypes Karyotype – map of our chromosomes Normal Human karyotypes have 23 pairs of chromosomes – 46 total chromosomes

Karyotypes Pairs 1-22 “autosomes” code for body features Pair 23 “sex chromosomes” determine gender XX  female XY  male

Who decides? X X Mom can give X X Dad can give X or y y X X X X X y SO ____ determines sex of the baby. If dad gives X with mom’s X = girl If dad give y with mom’s X = boy

SEX DETERMINATION XX = female

SEX DETERMINATION Xy = male

Karyotypes Chromosome disorders – when total number of chromosomes doesn’t = 46 Part/whole chromosome is missing or extra

Karyotypes Trisomy – Having 3 chromosomes in a pair because of a nondisjunction Nondisjunction - occurs when sister chromatids fail to separate during anaphase

Down syndrome ____________ TRISOMY 21, nondisjunction

Down syndrome (Trisomy 21) 1 in 800 births Similar facial features Slanted eyes Protruding tongue

Turner syndrome

Klinefelter syndrome XXy

Karyotypes What is the gender? Any chromosomal disorders?

Karyotypes What is the gender? Any chromosomal disorders?

Karyotypes What is the gender? Any chromosomal disorders?

Karyotypes What is the gender? Any chromosomal disorders?

Autosomal (Body) Disorders

Genetic Disorders Autosomal (Body) disorders 2 Types of genetic disorders: Autosomal (Body) disorders Sex-linked (Gamete) Disorders Cystic Fibrosis Colorblindness Sickle Cell Amenia Hemophilia Huntington’s Disease

Genetic Disorders Cystic Fibrosis Inheritance pattern: autosomal recessive Chromosome 7 Symptoms: thick, sticky mucus in lungs

Leads to respiratory and digestive problems More common in Caucasians, but affects all races 30,000 people in the USA have cystic fibrosis

Genetic Disorders Sickle cell Anemia Inheritance pattern – autosomal recessive Chromosome: 11 Symptoms – Mis-shaped red blood cells Relationship to malaria: carriers of sickle cell are immune to malaria

Genetic disorders Huntington’s Disease Inheritance pattern – autosomal dominant Chromosome 4 Symptoms – damage to nerve cells, loss of body movement control

HUNTINGTON’S DISEASE loss muscle control mental Huntington’s brain loss Causes progressive _____ of ________________ and ___________function muscle control mental 1 in 10,000 people in U.S. have Huntington’s disease http://www.scielo.br/img/revistas/bjmbr/v39n8/html/6233i01.htm Normal brain

A person with Huntington’s disease has a _____ chance of passing the disorder on to their offspring. 50%

Review: Huntington’s Disease, Cystic Fibrosis and Sickle Cell are disorders of your body cells – it doesn’t matter if you are male or female Now lets talk about disorders that are sex-linked: the chances of giving the disorder to your children are different if the child is a boy or a girl

Sex-linked traits Found on X chromosome, always recessive Who can get it?  Everyone More likely for males…they only have one X (if it’s recessive, they have no chance of hiding it)

Or Males ONLY HAVE ONE X They either have the They are disorder normal DEFECTIVE NORMAL They either have the disorder They are normal Or

Females have one normal gene that works. FEMALES HAVE TWO X CHROMOSOMES DEFECTIVE NORMAL DEFECTIVE Females have one normal gene that works. need 2 Females __________ defective recessive alleles to show the disorder

Sex-linked traits Male Female XAY – healthy XaY – sick XAXA healthy Females can be carriers Genotypes: Male XAY – healthy XaY – sick Female XAXA healthy XAXa Carrier XaXa -sick

Genetic disorders Colorblindness Inheritance pattern – sex-linked recessive Chromosome X Symptoms – trouble distinguishing between some colors 8% of males; 0.5% of females

Genetic disorders Hemophilia Inheritance pattern – sex-linked recessive Chromosome X Symptoms – blood does not clot normally

XH Xh Y XHY XhY XhXh XHXh Xh How to do a sex-linked problem: Hemophilia is X-linked recessive (so hh is needed to have hemophilia) PROBLEM: cross a carrier mom with an afflicted dad XH Xh XhXh XHXh Xh Y XHY XhY How many girls will have it? Boys? Who are carriers?

Warm Up What percentage of their children will be colorblind? Cross a man who is colorblind with a woman who is a carrier for colorblindness. Answer the following questions: What percentage of their children will be colorblind? What percentage of the males are colorblind? What percentage of the females are carriers? What percentage of the children are not affected and are also not carriers?

Pedigrees Family tree that shows the heredity of a specific trait (usually a disorder) = male = female

Pedigrees If the is filled in = someone with the trait If the is empty = someone without the trait

I II 1 2 III IV http://www.beavton.k12.or.us/sunset/academics/genetics.htm

http://www. ikm. jmu. edu/Buttsjl/ISAT493/Hemophilia/hemophiliaeurope http://www.ikm.jmu.edu/Buttsjl/ISAT493/Hemophilia/hemophiliaeurope.html