Transcript Document
Human Genetics
Vocabulary—Woo Hoo!
1. Sex-linked trait 2. Linked gene 3. Chromosome map 4. Deletion 5. Inversion 6. Translocation 7. Nondisjunction 8. Point mutation 9. Substitution 10. Frameshift mutation 11. Insertion mutation 12. Pedigree 13. Carrier 14. Genetic disorder 15. Polygenic 16. Multiple allele 17. Amniocentesis 18. Genetic counseling 19. Gene therapy
Sex Chromosomes and Autosomes
• The sex chromosomes contain genes that determine the gender of the individual.
• Autosomes are the remaining chromosomes that do not affect the gender of the individual.
• Males= XY • Females = XX
Gender Determination—What are the chances of having a girl or a boy??
Gene Location
• Genes located on the X-Chromosome are called X-Linked
Genes.
• Genes located on the Y-Chromosome are called Y-Linked
Genes.
• The X Chromosome is much bigger than the Y Chromosome and therefore there are more genes on it.
• A male with a recessive allele on the X chromosome will exhibit the recessive trait since there is not a counter-part on the smaller Y Chromosome.
Punnett Squares with Sex Chromosomes
Linked Genes
• Pairs of genes that tend to be inherited together are called LINKED GENES.
• The genes are linked together because they are found on the same chromosome • During crossing-over the genes can be swapped.
• Video Clip—Crossing Over
Chromosome Mapping
• The farther apart 2 genes are located on a chromosome, the more likely a cross over will occur.
• Chromosome Map—a diagram that shows the linear placement of genes on a chromosome.
• One MAP UNIT = 1% chance of crossing-over
Mutations
• A MUTATION is a change in the nucleotide base sequence of DNA (the letters) Germ-Cell • In the Gametes • Do not affect the organism but can be passed on to offspring Somatic-Cell • In the body cells • Can affect the organism, but are not passed on Lethal • Causes death; usually before birth
Chromosome Mutations
•
CHROMOSOME MUTATIONS
are changes in the structure of a chromosome or the loss/gain of an entire chromosome Deletion Inversion •Loss of a piece of a chromosome • A chromosomal segment breaks off, flips backwards, and reattaches Translocation Nondisjunction • A piece of one chromosome breaks off and reattaches to another chromosome • A chromosome fails to separate during meiosis, therefore one gamete receives an extra copy and one gamete receives no copy
Gene Mutations
Point Mutation • Substitution, addition, or removal of a single nucleotide (letter) • Change occurs within a single gene Substitution • One nucleotide replaces another • If this occurs in a codon, the amino acid can be changed Frameshift Mutation • Loss of a nucleotide resulting in the incorrect grouping of codons, making all the amino acids change Insertion Mutation • One or more nucleotides are added to a gene • Can also cause a Frameshift mutation
Mutation Video Clip • Give an example of an addition • Give an example of a deletion
Inheritance of Traits
• A PEDIGREE is a diagram that shows how a trait is inherited over several generations • Squares = males, Circles = females • Filled symbol = has the trait, empty symbol= no trait • Horizontal line =mating, vertical line = offspring
Pedigree Handout
Family Pedigree Practice!
• • Create a pedigree for eye color for the following family!
Children: • • • •
Suzy has brown eyes, Jose has brown eyes, Hiram has blue eyes, Damien has brown eyes.
Mom has blue eyes, Dad has blue eyes On mom’s side: Grandma has brown eyes, grandpa has blue eyes On dad’s side: grandma has blue eyes, grandpa has blue eyes
Genetic Disorders
• GENETIC DISORDERS are diseases or disabling conditions that are passed down from parent to offspring • POLYGENIC are traits that are influenced by multiple genes rather than a single allele • COMPLEX CHARACTERS- human conditions that are influenced by a combination of genes and environmental factors.
• Skin color, height, heart disease
Genetic Disorder Pedigree—Hemophilia Case STudy
Multiple Alleles
• Genes with 3 or more alleles. Example: Blood types, ABO • Multiple alleles often lead to codominance (both traits expressed) or incomplete dominance (an in-between trait is expressed, ie wavy hair).
Blood Types
• 4 types • Type A, Type B, Type O, Type AB • A and B are dominant • O is recessive • AO= A blood type • BO=B blood type • AB=genes are CODOMINANT, blood type is AB • Brain Pop –Blood Types
Blood Typing
• Complete the squares below to determine the different possible genotype combinations for offspring:
A B A
Father’s Genotype
B
Make Punnett Squares for these as well: 1. Mom—OO Dad—AB 2. Mom—AA Dad—BB 3. Mom—AA Dad—AO 4. Mom—BB Dad AO 5. Mom—AB Dad OO 6. Mom—AO Dad BO
Codominance, ABO practice
X-Linked Traits
• X-Linked traits are traits found on the X chromosome and often only males will exhibit the recessive trait (since they don’t have a counterpart on the Y to dominate it).
• Colorblindness is an X-linked trait and therefore more common in males • X-Linked Practice!
Single Allele Traits
• More than 200 human traits are controlled by a single allele.
• Huntington’s Disease is a single allele, dominant, disease.
Genetic Screening and
Genetic Disorders • Many people seek GENETIC SCREENING before having children.
• GENETIC SCREENING is an examination of a person’s genetic makeup to see what traits may be passed on to an offspring.
• GENETIC COUNSELING is when a person seeks professional, medical guidance about the risks of passing on traits to children • AMNIOCENTESIS is a procedure to test the amniotic fluid during pregnancy to analyze fetal DNA and check for genetic disease.
Gene Therapy • In your own words, what is gene therapy?
• Gene therapy cures blindness?
Genetic Disorder Powerpoints and Presentations
Choose a disorder and complete the presentation. You may choose one from below or find your own.
• • • • Barth Syndrome Bicuspid Aortic Valve Cerebral Palsy Cleft Palate • Huntington’s Disease • Alexander Disease • • Cystic Fibrosis Down Syndrome • Alzheimer’s • Autism • Hemophilia • Marfan Syndrome • Long Q-T Syndrome • Progeria • • Sickle Cell Anemia Spina Bifida • Williams Syndrome