Human genetics unit 4

Human Genetics

I. Human Chromosomes, Genes, and Human Inheritance

I. Human Chromosomes, Genes, and Human Inheritance

A. Human genome

1. All the DNA of the human species

I. Human Chromosomes, Genes, and Human Inheritance

2. The DNA is divided into thousands of genes on 23 pairs of chromosomes

I. Human Chromosomes, Genes, and Human Inheritance

a. Autosomes are chromosomes that contain genes for characteristics that are unrelated to sex 22 pairs

b. Sex chromosomes are

the remaining pair of

human chromosomes

consists of the, X and Y

I. Human Chromosomes, Genes, and Human Inheritance

c. Humans have an estimated 20,000 to 22,000 genes

I. Human Chromosomes, Genes, and Human Inheritance

B. Linkage

1. Genes that are located on the

same chromosome

2. Alleles for these genes tend to

segregate together during

meiosis, unless they are

separated by crossing-over

I. Human Chromosomes, Genes, and Human Inheritance

C. Genetic traits

1. Characteristics that are encoded in DNA

2. Autosomal traits are controlled by genes on one of the 22 human autosomes

3. sex-linked traits are controlled by genes on the sex chromosomes

I. Human Chromosomes, Genes, and Human Inheritance

D. multiple allele traits are controlled by a single gene with more than two alleles

I. Human Chromosomes, Genes, and Human Inheritance

E. Polygenic traits are when human traits are controlled by more than one gene

I. Human Chromosomes, Genes, and Human Inheritance

F. Pleiotropy are when a single gene may affect more than one trait

I. Human Chromosomes, Genes, and Human Inheritance

G. Epistasis is when one gene affects the expression of another gene

I. Human Chromosomes, Genes, and Human Inheritance

H. Genetic Disorders

1. Genetic disorders caused by mutations

a. This is mutation is the DNA on a chromosome

b. Few genetic disorders are controlled by dominant alleles, most are recessive alleles

I. Human Chromosomes, Genes, and Human Inheritance

2. Chromosomal Disorders

a. This is the failure of replicated chromosomes to separate during meiosis

b. If such gametes are fertilized and form zygotes, they usually do not survive

c. If they do survive,

the individuals are

likely to have

serious genetic

disorders

I. Human Chromosomes, Genes, and Human Inheritance

I. Treating Genetic Disorders

1. The symptoms of genetic disorders can sometimes be treated, but cures for genetic disorders are still in the early stages of development

2. gene therapy involves inserting normal genes into cells with mutant genes