The Human Genome

Human Chromosomes Karyotype- diagram showing the complete set of chromosomes.Karyotype- diagram showing the complete set of chromosomes. A karyotype shows us 46 human chromosomes.A karyotype shows us 46 human chromosomes. 22 pairs are autosomes (main body parts)22 pairs are autosomes (main body parts) 1 pair are sex chromosomes1 pair are sex chromosomes

Normal Human Karyotype

Determining Sex Females are XX, producing only X gametes. Males are XY, producing both X & Y gametes.

Determining Sex Chances of having a boy or girl are always 50%

Pedigrees Method of tracking traits within a family. Squares = Males Circles = Females Circles = Females Colored = Trait

A circle represents a female. A square represents a male. A horizontal line connecting a male and female represents a marriage. A vertical line and a bracket connect the parents to their children. A half-shaded circle or square indicates that a person is a carrier of the trait. A completely shaded circle or square indicates that a person expresses the trait. A circle or square that is not shaded indicates that a person neither expresses the trait nor is a carrier of the trait. Pedigree Example

Tay-Sachs Pedigree 1. How many generations are there in this pedigree?1. How many generations are there in this pedigree? 2. Who died in Generation 2?2. Who died in Generation 2? 3. How many kids were produced from generation 1?3. How many kids were produced from generation 1?

Tay-Sacs Pedigree 4. Who got married in generation 3?4. Who got married in generation 3? 5. How many kids lived in generation 4?5. How many kids lived in generation 4?

It’s in the blood Your blood cells have protein coats that make them unique to other people’s blood cells. The alleles for blood types are both multiple allelic and codominant.

Phenotype (Blood Type) Genotype Antigen on Red Blood Cell Safe Transfusions ToFrom Human Blood Groups

Genetic Disorders Recessive Disorders Albinism- no pigment Cystic Fibrosis- mucus in lungs PKU – inability to break down phenylalanine Tay-Sachs- breakdown of nervous system

Genetic Disorders Dominant Allele Disorders Huntington’s Disease- lose muscle control & mental function Achondroplasia- dwarfism

Genetic Disorders Codominant Disorders Sickle Cell Disease- abnormal shaped blood cells causing blood clots

Sickle Cell Anemia Found mainly among African-Americans.Found mainly among African-Americans. The Hemoglobin that traps oxygen is deformed so it can’t catch oxygen.The Hemoglobin that traps oxygen is deformed so it can’t catch oxygen. Deformed cells can also clog small blood vessels.Deformed cells can also clog small blood vessels. Caused by a point mutation.Caused by a point mutation.

Cystic Fibrosis This is caused when 3-bases of your DNA are deleted.This is caused when 3-bases of your DNA are deleted. RESULTS:RESULTS: Wrong protein is made.Wrong protein is made. Heavy mucus forms in the lungs making it difficult to breathe.Heavy mucus forms in the lungs making it difficult to breathe.

Chromosome # 7 CFTR gene The most common allele that causes cystic fibrosis is missing 3 DNA bases. As a result, the amino acid phenylalanine is missing from the CFTR protein. Normal CFTR is a chloride ion channel in cell membranes. Abnormal CFTR cannot be transported to the cell membrane. The cells in the person’s airways are unable to transport chloride ions. As a result, the airways become clogged with a thick mucus. Cause of Cystic Fibrosis

Sex linked traits A trait controlled by an allele on the sex chromosomes. - most found on the X-chromosome - males more likely to express these traits

Color Blindness Located on the X-chromosome (sex-linked).Located on the X-chromosome (sex-linked). The most common form is red-green colorblindness.The most common form is red-green colorblindness. You can’t distinguish between colors.You can’t distinguish between colors. More common among males.More common among males.

Father (normal vision) Colorblind Normal vision Mother (carrier) Daughter (normal vision) Son (normal vision) Daughter (carrier) Son (colorblind) Section 14-2 Male Female Figure Colorblindness

Father (normal vision) Colorblind Normal vision Mother (carrier) Daughter (normal vision) Son (normal vision) Daughter (carrier) Son (colorblind) Section 14-2 Male Female Figure Colorblindness

Hemophilia Located on the X-chromosome (sex-linked). Protein for normal blood clotting is missing. Causes an inability of blood to clot.

Sex linked traits examples If a male cardinal is red and female is brown, which chromosome is the allele for red feathers found?

Chromosomal Disorders Mutations with chromosomes.Mutations with chromosomes. Mostly occur during meiosis(nondisjunction)Mostly occur during meiosis(nondisjunction) Examples:Examples: Down syndrome Down syndrome Sex Chromosome Disorder. Sex Chromosome Disorder.

Figure 8.21 Meiosis I Nondisjunction n + 1 n - 1 n + 1 n - 1 n n Number of chromosomes Gametes Nondisjunction Meiosis II Nondisjunction in meiosis I Nondisjunction in meiosis II

Down’s Syndrome Nondisjunction leads to 3 copies of chromosome #21.Nondisjunction leads to 3 copies of chromosome #21. No clear understanding on why the extra chromosome causes the birth defect.No clear understanding on why the extra chromosome causes the birth defect.

Sex Chromosome Disorders Turner’s syndrome Nondisjunction leads to only one X chromosome being inherited.Nondisjunction leads to only one X chromosome being inherited. Causes females to be sterile.Causes females to be sterile. Klinefelter’s syndrome Nondisjunction leads to an extra X chromosme being inherited.Nondisjunction leads to an extra X chromosme being inherited. Causes males to be sterile.Causes males to be sterile.

Determining Genetic Disorders Doctors look at KaryotypesDoctors look at Karyotypes