Ch. 12: Ch. 12: Inheritance Inheritance Patterns & Patterns &

Human Genetics Human Genetics

18 things you pretty 18 things you pretty much already know much already know about geneticsabout genetics

http://www.youtube.com/watch?v=bVk0twJYL6Y

Why donWhy don’’t we use humans t we use humans for genetics studies?for genetics studies?

1. Too complex 1. Too complex 2. Too long between generations2. Too long between generations 3. Few offspring3. Few offspring 4. Takes up too much space4. Takes up too much space 5. Unethical5. Unethical

Instead we use Model Instead we use Model OrganismsOrganisms

Drosophila Melanogaster (fruit fly)Drosophila Melanogaster (fruit fly)

Laboratory MiceLaboratory Mice

Other inheritance Other inheritance patterns we will study….patterns we will study….

Multiple AllelesMultiple Alleles Sex-Linked TraitsSex-Linked Traits Polygenic TraitsPolygenic Traits

Multiple AllelesMultiple Alleles

-Genes with three or more alleles-Genes with three or more alleles

Multiple Alleles for Multiple Alleles for BROWN hairBROWN hair

Blood Type is a Genetic Blood Type is a Genetic Trait!Trait!

What are the possible blood What are the possible blood types?types?

AA BB ABAB OO

Blood Type InheritanceBlood Type Inheritance

Multiple Alleles (A, B, O)Multiple Alleles (A, B, O) One gene: multiple allelesOne gene: multiple alleles

Co Dominance (A & B are co Co Dominance (A & B are co dominant….why there is AB Blood dominant….why there is AB Blood type)type) O is recessive to bothO is recessive to both

Chart for Possible genotypes for each Chart for Possible genotypes for each blood type…blood type…

To be Positive or To be Positive or NegativeNegative

Determined by the rH factor…Determined by the rH factor…

Complete Dominance:Complete Dominance: If you have the rH factor blood is If you have the rH factor blood is

POSITIVE (+)POSITIVE (+) If you do not then blood type is If you do not then blood type is

NEGATIVE (-)NEGATIVE (-)

Positive is dominant to negativePositive is dominant to negative

Practice Genetic Practice Genetic Problems for Blood typesProblems for Blood types

Model Organism: Model Organism: Drosophila melanogasterDrosophila melanogaster Common fruit fly used in many Common fruit fly used in many

genetic experiments Why?genetic experiments Why? 1. Few weeks between generations1. Few weeks between generations 2. Small and easy to maintain in lab2. Small and easy to maintain in lab 3. Only 8 chromosomes3. Only 8 chromosomes 4. Nobody cares when they are 4. Nobody cares when they are

disposed ofdisposed of

Thomas Hunt MorganThomas Hunt Morgan

Studied fruit flies and discovered….Studied fruit flies and discovered….

1. Traits are inherited on specific locations of 1. Traits are inherited on specific locations of chromosomeschromosomes

2. Some traits are linked (inherited together) 2. Some traits are linked (inherited together) if they are close together on the if they are close together on the chromosomechromosome

3. The SRY gene (there are separate sex 3. The SRY gene (there are separate sex

Chromosomes)Chromosomes)

4. 4. Sex – Linked traits (traits inherited on the Sex – Linked traits (traits inherited on the sex chromosomes)sex chromosomes)

Examples of Sex Linked Examples of Sex Linked TraitsTraits

Eye Color Fruit flies Eye Color Fruit flies

Color blindnessColor blindness

Hemophilia (ability of blood to clot)Hemophilia (ability of blood to clot)

Characteristics of Sex – Characteristics of Sex – Linked TraitsLinked Traits

Females will always pass on the X linked Females will always pass on the X linked trait to their sonstrait to their sons

Males cannot pass Males cannot pass

X linked traits to their X linked traits to their

Sons Sons

Males will pass X linked traits Males will pass X linked traits

To daughtersTo daughters

Example problems for Example problems for Sex Linked TraitsSex Linked Traits

1. Cross a White eyed fruit fly Male 1. Cross a White eyed fruit fly Male with a homozygous red eyed femalewith a homozygous red eyed female

2. Cross a color blind male with a 2. Cross a color blind male with a woman carrier for color blindness.woman carrier for color blindness.

Polygenic InheritancePolygenic Inheritance

characteristics that are influenced characteristics that are influenced by SEVERAL genes.by SEVERAL genes.

Complex CharactersComplex Characters

traits that are controlled both by the traits that are controlled both by the environment and by geneticsenvironment and by genetics Some types of CancerSome types of Cancer Heart DiseaseHeart Disease Skin Color Skin Color

Alzheimer's Disease & Alzheimer's Disease & Environmental Factors Environmental Factors

http://www.dnalc.org/view/2144-Environmental-factors-and-Alzheimer-s-disease.html

So what does all of this So what does all of this mean?mean?

Polygenic Traits & Complex Polygenic Traits & Complex Characters make Human Genetics Characters make Human Genetics very complicatedvery complicated

Genetic DisordersGenetic Disorders

MUTATIONSMUTATIONS

ANY CHANGE IN THE DNA ANY CHANGE IN THE DNA SEQUENCE SEQUENCE Germ Cell

MutationSomatic Cell Mutation

• Occur in gametes• Do not affect

organism itself but Can be passed on to

offspring

Ex: Down Syndrome, Huntington’s disease

• Occur in organism’s body cells & affect organism

• Cannot be inherited

• Ex: Skin Cancer, Leukemia

So what does all of this mean for the individual & the protein that is formed if there is a mutation:

Genetic Disorders are often the result of these mutations:

http://www.youtube.com/watch?v=8s4he3wLgkM&feature=relmfu

Down SyndromeDown Syndrome

Caused by one of the sex cells having an extra copy of CHROMOSOME 21

Breast CancerBreast Cancer

2 genes associated 2 genes associated with breast cancerwith breast cancer BRCA1 (on BRCA1 (on

chromosome17)chromosome17) BRCA2 (on BRCA2 (on

chromosome 13)chromosome 13) If you have a mutated If you have a mutated

form of either of form of either of these genes you have these genes you have a greater chance of a greater chance of developing breast or developing breast or ovarian cancerovarian cancer

Cystic FibrosisCystic Fibrosis

Affects the lungs & Affects the lungs & pancreaspancreas

Body produces Body produces thick, sticky mucus thick, sticky mucus that causes that causes infectionsinfections

Mutations in single Mutations in single genegene

Cystic FibrosisCystic Fibrosis

It is a recessive It is a recessive disorderdisorder

Not Sex-Linked – it Not Sex-Linked – it is located on the is located on the 77thth chromosome. chromosome.

HemophiliaHemophilia

Bleeding disorder Bleeding disorder that slows down that slows down the clotting the clotting processprocess

It an X-linked It an X-linked recessive disorderrecessive disorder

HemophiliaHemophilia

Huntington’s DiseaseHuntington’s Disease Neurological disorder Neurological disorder

– emotional – emotional disturbance & disturbance & cognitive declinecognitive decline

Mutated gene on Mutated gene on

chromosome 5 causes chromosome 5 causes this disorderthis disorder

It is a dominant It is a dominant disorderdisorder

Caused by a repeated “CAG” sequence over and over again

The Future of The Future of Genetics?Genetics?

http://www.youtube.com/watch?v=tp0qw9gq9hQ&feature=relmfu