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Chapter 14 The Human Genome Page 340 - 360
Lesson 1 Human Heredity
Human Chromosomes
A picture of chromosomes arranged in this way is known as a Karyotype (KAR-ee-uh-typ)
Two of those 46 chromosomes are known as sex chromosomes, because they determine an individual's sex.
To distinguish them from the sex chromosomes, the remaining 44 chromosomes are known as autosomal chromosomes, or autosomes.
Key Point: All human egg cells carry a single X chromosome (23,X) However, Half of all sperm cells carry an X chromosome (23,X) and half carry a Y chromosome (23,Y). This ensures that just about half of the zygotes will be 46,XX and half will be 46,XY.
A pedigree chart, which shows the relationships within a family can be used to help with this task.
Key Point: In both cystic fibrosis and sickle cell disease, a small change in the DNA of a single gene affects the structure of a protein, causing a serious genetic disorder.
Lesson 2 Human Chromosomes
Sex-Linked Genes
Because these chromosomes determine, sex , genes located on them are said to be sex-linked genes.
Key Point: Males have just one X chromosome. Thus, all X-linked alleles are expressed in males, even if they are recessive.
Chromosomal Disorder
This is known as nondisjunction, which means "not coming apart."
Key Point: If nondisjunction occurs, abnormal numbers of chromosomes may find their way into gametes, and disorder of chromosome numbers may result.
Lesson 3 Human Molecular Genetics
Molecular biology has used this biological fact to add a powerful new tool called DNA fingerprinting to the identification of individuals.
Unlike other forms of testing, DNA fingerprinting does not analyze the cell's most important genes, which are largely identical among most people.
Key Point: The Human Genome Project is an ongoing effort to analyze the human DNA sequence.
Key Point: In Gene therapy, an absent or faulty gene is replaced by normal, working gene.
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