The Human GenomeThe Human Genome

Human ChromosomesHuman Chromosomes

• Karyotype-Karyotype- diagram showing the complete set diagram showing the complete set of chromosomes.of chromosomes.

• A karyotype shows us 46 human chromosomes.A karyotype shows us 46 human chromosomes.

• 22 pairs are 22 pairs are autosomesautosomes (main body parts) (main body parts)

• 1 pair are 1 pair are sex chromosomessex chromosomes

Normal Human KaryotypeNormal Human Karyotype

Determining SexDetermining Sex

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

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

Pedigrees Pedigrees Method of trackingMethod of tracking

traits within a family.traits within a family.

Squares = MalesSquares = Males

Circles = FemalesCircles = Females

Colored = TraitColored = 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 PedigreeTay-Sachs Pedigree

• 1. How many 1. How many generations are there generations are there in this pedigree?in this pedigree?

• 2. Who died in 2. Who died in Generation 2? Generation 2?

• 3. How many kids 3. How many kids were produced from were produced from generation 1?generation 1?

Tay-Sacs PedigreeTay-Sacs Pedigree

• 4. Who got married 4. Who got married in generation 3?in generation 3?

• 5. How many kids 5. How many kids lived in generation 4?lived in generation 4?

It’s in the bloodIt’s in the blood

Your blood cells have protein coats that Your blood cells have protein coats that make them unique to other people’s make them unique to other people’s blood cells. blood cells.

The alleles for blood types are both The alleles for blood types are both multiple allelic and codominant.multiple allelic and codominant.

Phenotype(Blood Type)

GenotypeAntigen on

Red Blood Cell

Safe Transfusions

To From

Human Blood Groups

Genetic DisordersGenetic DisordersRecessive Disorders

Albinism- no pigment

Cystic Fibrosis- mucus in lungs

PKU – inability to break down phenylalanine

Tay-Sachs- breakdown of nervous system

Genetic DisordersGenetic DisordersDominant Allele Disorders

Huntington’s Disease- lose muscle control

& mental function

Achondroplasia- dwarfism

Genetic DisordersGenetic DisordersCodominant Disorders

Sickle Cell Disease- abnormal shaped blood

cells causing blood clots

Sickle Cell AnemiaSickle Cell Anemia

• Found mainly among African-Found mainly among African-Americans.Americans.

• The Hemoglobin that traps oxygen is The Hemoglobin that traps oxygen is deformed so it can’t catch oxygen.deformed so it can’t catch oxygen.

• Deformed cells can also clog small blood Deformed cells can also clog small blood vessels.vessels.

• Caused by a point mutation.Caused by a point mutation.

Cystic FibrosisCystic Fibrosis

• This is caused when 3-bases of your DNA This is caused when 3-bases of your DNA are deleted. are deleted.

• RESULTS:RESULTS:• Wrong protein is made.Wrong protein is made.• Heavy mucus forms in the lungs making it Heavy mucus forms in the lungs making it

difficult to breathe.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 traitsSex linked traits

A trait controlled by an allele on the sex A trait controlled by an allele on the sex chromosomes.chromosomes.

- most found on the X-chromosome- most found on the X-chromosome

- males more likely to express these traits- males more likely to express these traits

Color BlindnessColor Blindness

• Located on the X-chromosome (sex-linked).Located on the X-chromosome (sex-linked).

• The most common form is red-green The most common form is red-green colorblindness.colorblindness.

• You can’t distinguish between colors.You can’t distinguish between colors.

• More common among males.More common among males.

Father(normal vision)

ColorblindNormal vision

Mother (carrier)

Daughter(normal vision)

Son(normal vision)

Daughter(carrier)

Son(colorblind)

Section 14-2

Male

Female

Figure 14-13 Colorblindness

Father(normal vision)

ColorblindNormal vision

Mother (carrier)

Daughter(normal vision)

Son(normal vision)

Daughter(carrier)

Son(colorblind)

Section 14-2

Male

Female

Figure 14-13 Colorblindness

HemophiliaHemophilia

Located on the X-chromosome (sex-linked).Located on the X-chromosome (sex-linked).

Protein for normal blood clotting is Protein for normal blood clotting is missing.missing.

Causes an inability of blood to clot.Causes an inability of blood to clot.

Sex linked traits examplesSex linked traits examplesIf a male cardinal is red and female is brown, If a male cardinal is red and female is brown,

which chromosome is the allele for red feathers which chromosome is the allele for red feathers found?found?

Chromosomal DisordersChromosomal Disorders

• Mutations with chromosomes.Mutations with chromosomes.

• Mostly occur during Mostly occur during meiosis(nondisjunction)meiosis(nondisjunction)

• Examples:Examples:

Down syndromeDown syndrome

Sex Chromosome Disorder.Sex Chromosome Disorder.

Figure 8.21

Meiosis I

Nondisjunction

n + 1 n + 1 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 SyndromeDown’s Syndrome

• Nondisjunction leads to 3 copies of Nondisjunction leads to 3 copies of chromosome #21.chromosome #21.

• No clear understanding on why the extra No clear understanding on why the extra chromosome causes the birth defect.chromosome causes the birth defect.

Sex Chromosome DisordersSex Chromosome DisordersTurner’s syndromeTurner’s syndrome• Nondisjunction leads to only one X Nondisjunction leads to only one X

chromosome being inherited.chromosome being inherited.• Causes females to be sterile.Causes females to be sterile.

Klinefelter’s syndromeKlinefelter’s syndrome• Nondisjunction leads to an extra X Nondisjunction leads to an extra X

chromosme being inherited.chromosme being inherited.• Causes males to be sterile.Causes males to be sterile.

Determining Genetic DisordersDetermining Genetic Disorders

• Doctors look at KaryotypesDoctors look at Karyotypes