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Gene Linkage and Genetic Disorders
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How Does Gene Linkage Affect Inheritance?
- If genes are located on the same chromosome, they are said
to be linked.
- In Mendelian genetics, alleles assort independently during
meiosis, but linked genes do not.
- Gene linkage can be demonstrated by using a test cross.
- Results that differ from those expected in gene linkage can be explained by crossing over.
- Gene linkage can be demonstrated by using a test cross.
- The frequency of crossing over has been used to construct
linkage maps.
- Genes that are on the same chromosome as those that determine sex are said to be sex-linked.
- The chromosomal basis for sex determination is relatively simple in most organisms.
- Color blindness is an example of a sex-linked gene in humans.
- In mammals, one X chromosome of females is inactivated during development.
- The chromosomal basis for sex determination is relatively simple in most organisms.
What Disorders Are Caused By Gene Defects and Chromosome Abnormalities?
- Genetic disorders can be caused by defective alleles; some examples in humans are as follows.
- Hemophilia is a good example of an X-linked recessive disorder.
- Cystic fibrosis is a serious genetic disorder caused by an autosomal recessive allele.
- Sickle-cell disease results from a defective gene with incomplete dominance.
- Many human abnormalities, such as polydactyly are caused by dominant alleles.
- Hemophilia is a good example of an X-linked recessive disorder.
- Abnormalities in chromosome number can occur due to faulty meiotic divisions.
- Aneuploidy of autosomal chromosomes can cause problems
such as Down syndrome.
- Aneuploidy of the sex chromosomes may alter sexual development.
- Polyploidy is fairly common in the plant kingdom, but is rare in animals.
- Aneuploidy of autosomal chromosomes can cause problems
such as Down syndrome.
- Alterations in chromosome structure can also cause problems.
- Genetic testing can detect many genetic defects before birth.