 Studying humans requires alternative methods.  Human geneticists use.  Human are – Deduce the genotypes and phenotypes of individuals in pedigree charts.

Label:

– Deduce the genotypes and phenotypes of individuals in pedigree charts.

Human Pedigree tracing a dominant trait

Human Pedigree tracing a recessive trait

Human Pedigree tracing a sex-linked trait

 Human genetic disorders result from. 1.Gene Mutations –  Hundreds of human genetic disorders involve defects caused by mutations of  Disorders caused by mutated alleles: PKU, cystic fibrosis, sickle cell anemia, Tay-Sachs disease – Define gene mutation – Explain the consequence of a base substitution mutation in relation the process of transcription and translation, using the example of sickle-cell anemia.

 Sickle Cell Anemia is the result of a gene mutation called a  Hemoglobin is found in your.  Each hemoglobin molecule is made up of (  -hemoglobin) and (  -hemoglobin)  The mutation producing sickle cell hemoglobin is in the gene for  -hemoglobin – Explain the consequence of a base substitution mutation in relation the process of transcription and translation, using the example of sickle-cell anemia.

2.Chromosome mutations – Results from nondisjunction – – Explain that non-disjunction can lead to changes in chromosome number, illustrated by reference to Down syndrome (trisomy 21).

Extra chromosomesMissing chromosomes

 Fertilization may result in trisomy or monosomy Trisomy – ○ Example: Down’s Syndrome (Trisomy 21); Klinefelter’s Syndrome (XXY) – Explain that non-disjunction can lead to changes in chromosome number, illustrated by reference to Down syndrome (trisomy 21).

○ Trisomy 21 - Down Syndrome 3 copies of chromosome 21 Mild to severe mental retardation Many lead productive lives

○ Klinefelter Syndrom (XXY condition) Most from non-disjunction in mother Tall, some mental slowness Poor male sex organ development; breast development; usually sterile Personal story

Monosomy – ○ Example: Turner Syndrome (XO) – Explain that non-disjunction can lead to changes in chromosome number, illustrated by reference to Down syndrome (trisomy 21).

○ Turner Syndrome one too few chromosomes (XO) Sterile (cannot have children), shorter than average, heart defects, premature aging, shorter lives ○ YO = LETHAL No babies have been reported being born without an X

Nondisjunction of sex chromosomes

 Some genetic disorders are caused by Examples include: Hemophilia, Color blindness, and Duchenne muscular dystrophy

 Karyotype - refers to both the chromosome composition of an individual and to a photomicrograph showing the chromosomes Uses: ○ To detect genetic disorders ○ For genetic counseling of prospective parents – State that, in karyotyping chromosomes are arranged in pairs according to their size and structure.

Process: ○ Fetal cells, cells from bone marrow, skin, or blood are cultured and then treated with colchicine (arrests the cell in metaphase) ○ Chromosomes are – State that, in karyotyping chromosomes are arranged in pairs according to their size and structure.

 Many birth defects and genetic abnormalities can be detected before birth – State that karyotyping is performed using cells collected by chorionic villus sampling or amniocentesis, for pre-natal diagnosis of chromosome abnormalities.