CHAPTER 11 SKIM READ SECTION 11-1 ON PG._________ GOAL: To understand the relationship between the genes we inherit and human genetic disorders.

CHAPTER 11 Complex Inheritance &Human Heredity

Question: If someone looks more like one parent than the other, did that person inherit more genes from that parent?

No. You inherit the same number of genes from each parent 23 from Mom 23 from Dad You look the way you do based on the pattern of inheritance: Dominant/ Recessive But it is not always so straight forward.

Recessive Traits If you inherit a recessive gene from both parents you will have that recessive phenotype. Eye color Brown- dominant Blue- recessive Bb X Bb bb If you have blue eyes you inherited a recessive gene from BOTH parents

Recessive Genetic Disorders Some genetic disorders are passed on through a recessive allele. The parent may or may not have the genetic disorder. If the parent has the dominant trait they will NOT have the genetic disorder. EX. Gg Since they are heterozygous- they have the recessive allele and are called CARRIERS

Recessive Disorders 1. Cystic Fibrosis 2. Albinism 3. Tay-Sachs disease 4. Galactosemia Who has heard of any of these genetic disorders?

1. Cystic Fibrosis 1 in 3500 births Effects: One of the most common recessive genetic disorders among Caucasians. (Cystic fibrosis is less common in other ethnic groups, affecting about 1 in 17,000 African Americans and 1 in 31,000 Asian Americans.) It affects the mucus producing glands, sweat glands and the digestive enzymes Mucus and fluid build up in the lungs Treatment: physical therapy, special diets, and replacement digestive enzymes Pre-natal Genetic testing is available to see if you are a carrier PG. 297

2. Albinism 1 in 17,000 births Caused: By an altered genes the result in the absence of the skin pigment melanin in hair and eyes A person with albinism has pale skin, white hair and pink pupils Causes vision problems and the person has to be very careful in the sun No treatment- Occurs in other animals PG. 297

3. Tay-Sachs disease 1 in 2500 births Caused: By a recessive gene found on Chromsome 15 More prevalent in Jewish people of eastern European descent Causes an absence of an enzyme that breaks down a fatty acid (gangliodsides) The fatty acid they builds up in the brain Most die before their 5th birthday Treatment: No cure Genetic testing is available for perspective parents PG. 297

4. Galactosemia 1 in 50,000 to 70,000 births Effect: This person has the inability to digest galatose During digestion, lactose from milk is broken down into galactose and glucose. The glucose goes to the cells for energy, but the galactose must be broken down further. People with galactosemia can not break it down further Treatment: Avoid milk. No cure PG. 298

A recessive trait is expressed when the individual is homozygous recessive for the trait.

Dominant Genetic Disorders 1. Huntington’s Disease 2. Achondroplasia Only have to inherit the genetic disorder from one parent. BB and Bb would have the genetic disorder bb would not have the genetic disorder

1. Huntington disease 1 in 10,000 births Effects the person’s nervous system. Between the ages of 30- 50 years old the 1st symptoms appear Symptoms include: loss of brain function, uncontrollable movements, and emotional disturbances Treatment: None Genetic testing is available for this disease

Huntington Disease contin. HD is a familial disease, passed from parent to child through a mutation in a dominant gene. Each child of an HD parent has a 50-50 chance of inheriting the HD gene. If a child does not inherit the HD gene, he or she will not develop the disease and cannot pass it to subsequent generations. A person who inherits the HD gene will sooner or later develop the disease. They could also pass it on to their children PG 298

2. Achondroplasia 1 in 25,000 births Most common form of dwarfism Small body size and comparatively small limb Adult height of 4 feet. Average life expectancy 75% of people with this are born to average sized people- this means that this disorder is most often caused By a mutation on a gene PG. 298

Pedigrees pg 299 Are used to study a family history. The diagram traces a ONE specific trait through several generations of a family

Pedigrees Knowing physical traits can determine what genes an individual is most likely to have. Pedigrees look at physical traits(phenotypes) to infer what the persons genotype is. Keeping track of family history can be used for predicting the pattern of inheritance of different traits/ disorders

CH. 11.2 Complex Patterns of Inheritance Skim read section 11.2 pg. _________. GOAL: To understand to complex patterns of inheritance that lead to variation of phenotypes in populations. To understand the importance of variation in genes. Hmmm…When we say someone has BROWN eyes can you picture EXACTLY what there eye color looks like?

11.2 Complex Patterns of Inheritance In the real world many traits follow a complex pattern of inheritance …..which basically means that the Dominate / Recessive inheritance pattern does not explain how some traits are expressed in offspring

Complex Patterns of Inheritance 1. Incomplete Dominance: When the offspring’s phenotype is a blend of both of the parents. (In the book it is referred to as an “intermediate type.”) 2. Codominance: When both are dominate and are expressed in the offspring’s phenotype. 3. Multiple Alleles: when more than one set of alleles controls the phenotype

What type of inheritance pattern is this an example of? Incomplete dominance OR Co dominance

1. Incomplete dominance: the offspring’s phenotype is a blend of the parents. The dominate R allele does not completely dominate over the r. So a heterozygous genotype Gives you a phenotype that is a Blend of the parents ……in this example Pink

2. Codominance When both are dominate and are expressed in the offspring’s phenotype Example: Sickle- cell disease Sickle Cell Normal Red Blood Cell

Sickle Cell disease More common in people with African American descent. 9% of African Americans have one form of the trait. Affects red blood cells ability to transport oxygen. The sickle cells get stuck in small blood vessels SS- Normal person SSs- have normal & sickle cells but lead a normal life SsSs – have sickle cell disease

Sickle cell disease & Malaria Sickle cell disease (SsSs ) causes many symptoms such as pain, fever, respiratory failure, and neurological problems. However, someone that is Heterozygous for Sickle- Cell (SSs) has a higher resistance to Malaria Every 30 seconds a child dies of Malaria- the vast majority (90%) from Africa

3. Multiple Alleles Most traits have two versions of alleles BUT multiple allele traits have 3 or more alleles that control the phenotype Examples: Blood type & Fur color of rabbits

Blood groups in Humans IA Codominant IB Codominant (i) Recessive There are 4 blood types: A, B, AB, and O There are 3 alleles that control the blood type: IA Codominant IB Codominant (i) Recessive

Blood Group Alleles Safe to transfuse to: From: A IA IA or IA i A or AB A, O B IB IB or IB i B or AB B, O AB IA IB AB A, B, AB,O O ii A, B, AB, O O Universal Receiver Universal Donor

Rh Factor: This is another part of our blood type. Rh factor follows a dominant / recessive pattern of inheritance. Rh (+) is dominant Rh (-) is recessive

Rabbit fur color has 4 alleles that control fur coat color Rabbit fur color has 4 alleles that control fur coat color. (Multiple Alleles) Has a hierarchy of dominance: C,cch, ch, and c.

Epistasis Variety is the result of one allele hiding the effects of another allele. Lab’s fur color is controlled by 2 sets of alleles One controls if pigment is present and the other controls how dark the pigment will be

Sex Determination Everyone has 23 pairs of chromosomes The first 22 pairs of chromosomes are called autosomes The last pair is called the sex chromosomes and carries the information the determines the sex of an individual Female has two X chromosomes = XX Male has one X and one Y= XY

Sex Linked Traits Sex Linked traits are inherited through the sex chromosomes . Most information is on the X chromosome. It is larger than the Y chromosome. The Y chromosome only provides information to make a male. Two Recessive Sex- linked traits are: 1. Red- green color blindness 2. Hemophilia

1. Red – green color blindness Carried on the X chromosome. More common in males because they only have one X chromosome and if they get a defective X chromosome……. they will be color blind Females would have to inherit 2 defective X chromosomes…….much less likely So most people with color blindness are male

2. Hemophilia This is disease causes a delay in the person’s ability to clot their blood. Again, this is much more common in males because they only have to inherit 1 defective gene (females would have to inherit 2 genes). A person with hemophilia have to be very careful not to injure themselves because they could cause a blood vessel to break and they could bleed to death Before current treatments people with this disease died at an early age

Polygenic Traits These traits arrise from the interaction of multiple pairs of genes. Examples: Skin color Eye color Height Fingerprint pattern

Environmental Influences The environment has an effect on phenotype Epigenetics literally means "above" or "on top of" genetics. It is what control the DNA and what genes are turned "on" or "off." Environmental influences, such as a person’s diet and exposure to pollutants, can impact the epigenome. The epigenome can remain as cells divide and in some cases can be inherited through the generations. Twin studies have helped us discover what role heredity and the environment play in disease

. Environmental Effects on Gene Expression Gene expression can be affected by both the external environment and the internal environment inside an organism. Phenotype is generally a combination of genetic and environmental influences. Example: Japanese goby fish (social environment) 1. The goby fish can change its sex back and forth in response to changes in its social environment. 2. Goby fish exist in schools of many females and only a few males. 3. If a large male goby leaves a population, a female goby will become male. 4. If another large male enters that goby population, this new male turns back into a female. Example: Human height (internal environment)  While human height is a polygenic trait, it is also affected by the nutrients in your diet

CHAPTER 11.3 Skim Read Section 11.3 pg____________ GOAL: To understand the effects mistakes made during gamete formation can create such as, chromosome number disorders.

11.3 Chromosomes & Human Heredity Karyotypes- are used to study chromosomes pg. 311 Images (a picture) are taken of the chromosomes when the cell is in metaphase. The chromosomes images are then arranged in decreasing size Chromosome #1 is the largest and chromosome #22 is the smallest & the sex chromosomes are paired together.

Nondisjunction pg. 312 Can occur during Meiosis I and II. Nondisjuction is when the sister chromatids do not fully separate resulting in one gamete getting too many chromosomes (Trisomy) and another too few chromosomes (monosomy) Alterations in the number of chromosomes someone has causes serious genetic defects and are often fatal (the fertilized egg would die)

Nondisjunction Down’s Syndrome is a nondisjunction disorder called trisomy 21 There is an extra copy of the 21st chromosome Frequency of down’s syndrome is 1 in every 800 births Causes: mental disabilities, heart defects, distinctive facial feature

Nondisjunction can occur in the sex chromosomes XO- Turner’s syndrome The female only has 1 X chromosome. She is not fertile XXY- Klinefelter’s syndrome This male has an extra X chromosome. He is sterile. Five to 10 boys with 47,XYY syndrome are born in the United States each day. XXX- Triple X syndrome Nearly normal female. Most are never know they are triple X XYY- XYY syndrome Nearly normal male. Is fertile

Fetal testing Aminocentesis Choronic villus sampling Fetal Blood sampling Are tests available to determine if the fetus has a genetic disorder or abnormality