Chapter 7 PowerPoint by Jacob Rondinella
7-1 The Human Genetic System A good specimen to study genetics is the fruit fly Drosophila Melanogaster . First studied the fruit fly Why? Thomas Hunt Morgan It can produce a new generation in just a few weeks. Fruit fly is small and you could have many in a small area. Simple genetic system 8 Chromosomes.
Male Drosophila Melanogaster
xy xx ♂ ♀ □ = ♂ (Male) ○ = ♀ (Female) 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 ♂ ♀ 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)
Karyotype
Pedigree Chart
Dominant/Recessive Alleles Ex) Rh Blood group Z alles + (Dominent) - (Recessive) Rh+ Rh+ Rh+ RH - } both show some Phenotype Rh – 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 IAi B - IBIB or IBi AB - IAIB O - ii Universal Rec. AB Universal Donor O
7-2 Sex-Linked Inheritance 23 pairs of chromosomes are found in somatic cells 22 pair are called autosomes They are homologous 1 pair sex chromosomes Sex 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 Color blindness – Inability to see certain colors. 10% of males in U.S. have colorblindness ♂ X Y comes from Dad Comes from mom. Hemophilia – Unable to produce one of the clotting factor proteins that helps blood to clot. 1/1000 Males 1/1,000,000 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 Disorders Found 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 – 1/2500 Defective protein that interferes with chloride ion movement. Thick heavy mucus in lungs.
Albino alligator
Tay-Sachs – Fatal genetic disorder. Common to Jewish families Rapid breakdown of nervous system. Sickle Cell Anemia - Blood disorder where the blood cells look sickle shaped. African ancestry If you are a carrier of sickle cell, you are immune to malaria
PKU - Phenylketonuria 1/15000 recessive Will cause mental retardation There is a test if you have PKU as a baby you are given a special diet. Huntington Disease – Dominant chrom 4 Symptoms occur in late 30’s – 40’s Lose control of muscles Takes 15 years to die.
Chromosome # Disorders Non 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 afflicted Some organs do not develop Other than not being able to have children, the person is fine.
Kline Feter Syndrome – Extra chromosomes (47) XXY Males Underdeveloped sexual organs Slight mental retardation Down Syndrome – Trisomy – nondisjunction on chrom 21 Extra copy of chrom 21 Heart/circ problems slight sever mental retardation. 47 chromosomes
Prenatal Testing Amni0centesis- taking fluid from the placenta Chorionic Villus Sampling- tissue surrounding the fetus is removed and examined