1. Take 5
Which phase in meiosis do the tetrads break and are pulled to opposite poles of the cell?
Which phase in meiosis do the chromosomes (paired chromatids) line at the equator of the cells?
Which phase results in formation of 4 haploid cells?
A haploid cell has ___________ as many chromosomes than a diploid cell.

2. Patterns of Heredity and Human Genetics
Chapter 12.1
Patterns of Heredity and Human Genetics

3. I. Pedigree A graphic representation of genetic inheritance.
Set of symbols that identify male and female relationships and individuals affected by he trait being studied over several generations. For symbols see p. 309, fig. 121.

4. B. Analyzing a pedigree
Physicians may recommend genetic counseling to family members. In some cases, a genetic counselor can prepare a family pedigree
Prenatal Diagnosis -Ways to detect genetic disorders during pregnancy. Often used if after pedigree analyzed a suspected disorder runs in a family or because of older age of female.
Types of prenatal diagnosis:
An amniocentesis, when done a karyotype is prepared and studied to see if all is normal in the embryo (see Fig.12.20, p.329).
Chorionic villi sampling (CVS) is an alternative to the amniocentesis.

5. Karyotype- What gender?

6. II. Simple Recessive Heredity
A. Mutations are changes in genes
1. Mutation = a change in a gene, caused by damage or an error in copying.
Mutations are a source of variation a species needs in order to adapt to changing conditions and thus evolve over time.
Most mutations are harmful or neutral.
2. Most mutations are recessive. A heterozygous individual would not express the condition.
It is unlikely that a person, who is heterozygous for a recessive mutation, will mate with someone who is heterozygous for the same mutation. Therefore, it is less likely for the most recessive mutations to show up in an individual.

7. B. Genetic Disorders
Genetic disorders = the harmful effects that some mutations produce.
1. Cystic Fibrosis
Cystic fibrosis is a recessive genetic disorder, on chromosome #7, caused by a mutation in a gene that codes for a protein responsible for transporting chloride ions. In homozygous conditions, this mutation causes cells in the respiratory system and the digestive system to produce misshapen chloride transport proteins that are unable to function properly.
In these individuals, mucous accumulates in the lungs and pancreas, clogging ducts needed for these organs to function properly. People with CF have difficulty breathing and cannot properly digest their food.
Approximately 1 in 28 white Americans carries the recessive allele; 1 in 2500 inherits the disorder.

8. Genetic Disorders Cont..
2. TaySachs disease
TaySachs is a recessive disorder of the central nervous system. The mutation results in the absence of an enzyme that breaks down lipids produced and stored in central nervous system tissue. Common in the U.S. among Eastern Europe Ashkenazic Jews decendents.

9. Genetic Disorders Cont..
3. Phenylkertonuria (PKU)
A recessive disorder in which affected individuals lack an enzyme that converts the amino acid phenylalanine into the amino acid tyrosine. Because of this build up of phenylalanine in the central nervous system it leads to mental retardation, eczema, and pigment defects that make affected individuals lighter skinned. If diagnosed early enough, the infant can be placed on a low phenylalanine diet until the brain is fully developed.
If a pregnant female is PKU homozygous this can lead to permanent damage to her fetus unless she goes on a PKU low diet during her pregnancy. PKU allele is most common in U.S. in individuals whose ancestors are from Norway, Sweden, or Ireland.

10. III. Simple Dominant Heredity
1. Most dominant traits not deadly.
Simple dominant traits include:
Cleft chin; Widow’s peak; Earlobe type: free hanging dominant; attached earlobes recessive; Hitchhiker’s thumb; Almond shaped eyes (round recessive); Thick lips (thin recessive)

11. B. Huntington’s Disease Is a lethal genetic disorder caused by a rare dominant allele.
Result in breakdown certain areas of the brain. No effective treatment known.
Onset of disorder doesn’t occur until individual affected is in their 30s to 50s, so an individual could have children unknowing they had disorder.
There is a test to determine carriers; however, some individuals choose not to know.