Ch. 12: Inheritance Patterns & Human Genetics

18 things you pretty much already know about genetics L6Y L6Y L6Y L6Y

Why don’t we use humans for genetics studies? 1. Too complex 1. Too complex 2. Too long between generations 2. Too long between generations 3. Few offspring 3. Few offspring 4. Takes up too much space 4. Takes up too much space 5. Unethical 5. Unethical

Instead we use Model Organisms Drosophila Melanogaster (fruit fly) Drosophila Melanogaster (fruit fly) Laboratory Mice Laboratory Mice

Other inheritance patterns we will study…. Multiple Alleles Multiple Alleles Sex-Linked Traits Sex-Linked Traits Polygenic Traits Polygenic Traits

Multiple Alleles -Genes with three or more alleles -Genes with three or more alleles

Multiple Alleles for BROWN hair

Blood Type is a Genetic Trait! What are the possible blood types? What are the possible blood types? A B AB AB O

Blood Type Inheritance Multiple Alleles (A, B, O) Multiple Alleles (A, B, O) One gene: multiple alleles One gene: multiple alleles Co Dominance (A & B are co dominant….why there is AB Blood type) Co Dominance (A & B are co dominant….why there is AB Blood type) O is recessive to both O is recessive to both Chart for Possible genotypes for each blood type… Chart for Possible genotypes for each blood type…

To be Positive or Negative Determined by the rH factor… Determined by the rH factor… Complete Dominance: Complete Dominance: If you have the rH factor blood is POSITIVE (+) If you have the rH factor blood is POSITIVE (+) If you do not then blood type is NEGATIVE (-) If you do not then blood type is NEGATIVE (-) Positive is dominant to negative Positive is dominant to negative

Practice Genetic Problems for Blood types

Model Organism: Drosophila melanogaster Common fruit fly used in many genetic experiments Why? Common fruit fly used in many genetic experiments Why? 1. Few weeks between generations 1. Few weeks between generations 2. Small and easy to maintain in lab 2. Small and easy to maintain in lab 3. Only 8 chromosomes 3. Only 8 chromosomes 4. Nobody cares when they are disposed of 4. Nobody cares when they are disposed of

Thomas Hunt Morgan Studied fruit flies and discovered…. Studied fruit flies and discovered…. 1. Traits are inherited on specific locations of chromosomes 2. Some traits are linked (inherited together) if they are close together on the chromosome 3. The SRY gene (there are separate sex Chromosomes) 4. Sex – Linked traits (traits inherited on the sex chromosomes)

Examples of Sex Linked Traits Eye Color Fruit flies Eye Color Fruit flies Color blindness Color blindness Hemophilia (ability of blood to clot) Hemophilia (ability of blood to clot)

Characteristics of Sex – Linked Traits Females will always pass on the X linked trait to their sons Females will always pass on the X linked trait to their sons Males cannot pass Males cannot pass X linked traits to their Sons Males will pass X linked traits To daughters

Example problems for Sex Linked Traits 1. Cross a White eyed fruit fly Male with a homozygous red eyed female 2. Cross a color blind male with a woman carrier for color blindness.

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

Complex Characters traits that are controlled both by the environment and by genetics traits that are controlled both by the environment and by genetics Some types of Cancer Some types of Cancer Heart Disease Heart Disease Skin Color Skin Color

Alzheimer's Disease & Environmental Factors Environmental-factors-and-Alzheimer-s- disease.html Environmental-factors-and-Alzheimer-s- disease.html Environmental-factors-and-Alzheimer-s- disease.html Environmental-factors-and-Alzheimer-s- disease.html

So what does all of this mean? Polygenic Traits & Complex Characters make Human Genetics very complicated Polygenic Traits & Complex Characters make Human Genetics very complicated

Genetic Disorders

MUTATIONS ANY CHANGE IN THE DNA 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: &feature=relmfu

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

Breast Cancer 2 genes associated with breast cancer 2 genes associated with breast cancer BRCA1 (on chromosome17) BRCA1 (on chromosome17) BRCA2 (on chromosome 13) BRCA2 (on chromosome 13) If you have a mutated form of either of these genes you have a greater chance of developing breast or ovarian cancer If you have a mutated form of either of these genes you have a greater chance of developing breast or ovarian cancer

Cystic Fibrosis Affects the lungs & pancreas Affects the lungs & pancreas Body produces thick, sticky mucus that causes infections Body produces thick, sticky mucus that causes infections Mutations in single gene Mutations in single gene

Cystic Fibrosis It is a recessive disorder It is a recessive disorder Not Sex-Linked – it is located on the 7 th chromosome. Not Sex-Linked – it is located on the 7 th chromosome.

Hemophilia Bleeding disorder that slows down the clotting process Bleeding disorder that slows down the clotting process It an X-linked recessive disorder It an X-linked recessive disorder

Hemophilia

Huntington’s Disease Neurological disorder – emotional disturbance & cognitive decline Neurological disorder – emotional disturbance & cognitive decline Mutated gene on chromosome 5 causes this disorder Mutated gene on chromosome 5 causes this disorder It is a dominant disorder It is a dominant disorder Caused by a repeated “CAG” sequence over and over again

The Future of Genetics? 0qw9gq9hQ&feature=relmfu 0qw9gq9hQ&feature=relmfu