Intro to Genetics PowerPoint Notes



Genetic Disorders Notes

Integrated Science 2 Name: Per.

I. Overview of DNA Structure

A. Review

1. A is a segment of DNA that codes for a particular .

2. Proteins determine the of an organism.

3. In humans, DNA is organized into 23 pairs of chromosomes.

B. DNA Structure

1. The basic building block of DNA is a .

2. Nucleotide chains are held together to form a .

3. Nucleotides are represented using the letters .

II. DNA Based Disorders.

A. Dysfunctional Genes

1. A gene can be some of its nucleotides or some of the nucleotides present may be in

the .

❖ The protein made from that gene may .

B. Missing Genes

1. A person can be born missing or of a gene.

❖ No protein is produced and the trait .

Examples of DNA Based Disorders

1. Sickle-cell anemia

• Caused by a substitution of one nucleotide in the allele for normal .

• Red blood cells become in stressed conditions and die in 10 to 20 days (normal blood cells live for _________ days) leading to ____________.

• These tend to become stuck in capillaries, leading to .

• Most common among individuals with , because it provides a resistance to ,

2. Huntington’s Disease

▪ Produced by a single .

▪ A gradual change of the occurs around the age of .

▪ Marked by a painful, progressing loss of muscle control and mental function until death occurs.

▪ Approximately __________ in 100,000 affected

III. Chromosomal Based Disorders

Causes

1. Nondisjunction

▪ During meiosis I, homologous chromosomes do not .

▪ Results in an extra copy of chromosome in one cell, and a loss of that chromosome from another.

Results

▪ After fertilization, the resulting person will have an .

▪ A cell has one missing chromosome.

▪ A cell has one extra chromosome.

Nondisjunction of Sex Chromosomes

▪ Genes critical to all embryonic development are on the .

o Absence of the X chromosome is , absence of the Y chromosome is lethal.

▪ Individuals can survive if they have an extra chromosome.

▪ Affects approximately 1 birth in every _____________.

Disorders involving Sex Chromosomes

1. Klinefelter Syndrome-

▪ males with extra . Can be XXY or XXXY.

▪ affects 1/500 births.

▪ Abnormal development of the testis, leading to ____________________.

▪ Affected individuals are often ________ and produce relatively small amounts of _______________

2. Triple X syndrome-

▪ females with extra (XXX or XXXX).

▪ Affects 1/1000 female births.

▪ Affected individuals are usually ____________ than average and have ______________ builds.

▪ Normal development of sexual traits and are _____________.

3. Turner Syndrome-

▪ females with only one

▪ affects 1/2000 live female births.

▪ Only 1 in ___________ affected zygotes develops to term.

▪ Individuals are short in stature, generally lack prominent female secondary sexual characteristics, and may be __________________.

▪ Health problems such as __________________, kidney problems, diabetes and thyroid problems.

A. Nondisjunction of Autosomal (non-sex) Chromosomes

▪ Can affect chromosomes .

▪ Only 3 result in a baby that can survive for a time after birth.

▪ Most frequently, the baby dies in utero.

1. Down Syndrome –

▪ one extra . (written as 47, +21).

▪ 1/800 live births

▪ Life expectancy ___________________ but heart problems persist

▪ lower than average mentally.

▪ Decreased muscle tone, flat _________, eyes slanting up, irregular shaped ears, large tongue relative to the mouth.

IV. Diagnosing Gene Disorders

A. Karyotype-a display of all the .

1. The process:

▪ Harvested cells in metaphase are .

▪ Chromosomes are observed under the microscope.

▪ A photograph is taken and enlarged.

▪ Chromosomes are arranged in .

▪ Abnormalities are identified.

B. Prenatal Diagnosis

1. Carrier Identification Tests

▪ CVS (chorionic villus sampling) – a needle is inserted into the mother’s _______________ to test for DNA, gene, and chromosome disorders.

▪ Ultrasound – detects major ___________________ deformations

▪ Amniocentesis – fluid is removed from the sac around the embryo to detect _____________________ abnormalities

▪ Fetal blood sampling – needle is used to remove cells from the fetus to test for ____________ disorders.

V. Preventing Genetic Disorders

A. Blood Test

• Simple blood test in males and females can screen for more than __________ genetic mutations

• Approximately ________ and the results are available in less than a week.

B. In Vitro Fertilization

• Doctors screen embryos after fertilization and only implant those that appear free of ________________

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