PowerPoint by Jacob RondinellaPowerPoint by Jacob Rondinella

7-1 The Human Genetic SystemA good specimen to study genetics is the fruit

fly Drosophila Melanogaster .

First studied the fruit fly Why?

Thomas Hunt Morgan

1. It can produce a new generation in just a few weeks.2. Fruit fly is small and you could have many in a small area.3. Simple genetic system 8 Chromosomes.

Male Drosophila Melanogaster

Karyotype - pictures of chromosomes grouped together In a human Karyotype 22 pairs of chromosomes are homologous.

Homologous means similar in size, shape, and genetic content.1 pair is your sex chromosomes

xy xx xy xx ♂ ♀ ♂ ♀

In order to study inheritance of human traits Scientists create a family of history in the form of a pedigree chart. Fig 7-4 p. 149

Diagram that follows the inheritance or a single gene through several generations in a family.

□ = ♂ (Male)○ = ♀ (Female)

Dominant/Recessive Alleles

Ex) Rh Blood group Z alles + (Dominent) - (Recessive)

Rh+ Rh+ Rh+ RH - } both show some PhenotypeRh – Rh - Shows reccome phenotype

Multiple Alleles type of gene that is determined by more then two alleles.

EX) ABO Blood group three Alleles Ia, Ib, i

Are codomijent over i the allele does not produce antigens

A - IA IA or IAiB - IBIB or IBiAB - IAIB

O - ii

Universal Rec. ABUniversal Donor O

7-2 Sex-Linked Inheritance23 pairs of chromosomes are found in

somatic cells22 pair are called autosomes They are

homologous

1 pair sex chromosomesSex Linked= inheritance found only on the X

or Y chromosome

Sex linked genes are almost always located on the X chromosomes.

Because males have just one X chromosomes, any X chromosome linked gene a male inherits, recessive or dominant is expressed.

Because males pass their X chromosomes along to their daughter Sex linked genes will tend to move from father to daughter.

Color blindness – Inability to see certain colors. 10% of males in U.S. have colorblindness

♂ X Y comes from DadComes from mom.

Hemophilia – Unable to produce one of the clotting factor proteins that helps blood to clot.

1/1000 Males1/1,000,000 Females

Duchenne Musculer Dystropy - Sudden weakness of muscles because the body produces a defective protein death will result

1/3000 males

7-3 Human Genetic DisordersFound on autosomes (22 pair) ablinism, Cystic Fibrosis

Tay-Sachs, Sickle cell Anemia, PKU, Huntington.Albinism –Chrom 11 (recessive)Unable to produce melanin (skin pigment for skin

color)Cystic Fibrosis- chromosome 7 (recessive)Most common fatal genetic disease.European ancestry – 1/2500Defective protein that interferes with chloride ion

movement. Thick heavy mucus in lungs.

Albino alligator

Tay-Sachs – Fatal genetic disorder.Common to Jewish familiesRapid breakdown of nervous system.

Sickle Cell Anemia -Blood disorder where the blood cells look sickle

shaped.African ancestryIf you are a carrier of sickle cell, you are immune

to malaria

PKU -Phenylketonuria 1/15000 recessiveWill cause mental retardationThere is a test if you have PKU as a baby

you are given a special diet.

Huntington Disease – Dominant chrom 4Symptoms occur in late 30’s – 40’sLose control of musclesTakes 15 years to die.

Chromosome # DisordersNon disjunction – chromosome pair fails to

separate correctly during meiosis.Abnormal numbers of chromosomes are

produced in the sex cells.Tuner Syndrome – a sperm or egg is

produced without a sex chromosome XO in zygote (45 chromosomes only)

Only females can be afflictedSome organs do not developOther than not being able to have children,

the person is fine.

Kline Feter Syndrome – Extra chromosomes (47)

XXYMales Underdeveloped sexual organsSlight mental retardation

Down Syndrome –Trisomy – nondisjunction on chrom 21Extra copy of chrom 21Heart/circ problems slight sever mental

retardation.47 chromosomes

Prenatal TestingAmni0centesis- taking fluid from the

placentaChorionic Villus Sampling- tissue

surrounding the fetus is removed and examined