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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