Results of Abnormal Meiosis
Bio 30 – Genetics Unit
Mrs. S. Pipke-Painchaud
0405
What is a karyotype?
Chromosomal Mutations:

“changes in genetic material that involve entire chromosomes or pieces of them” (A.W. 157)
Types of Mutations: (structural)

_________________: one or more genes is lost from the chromosome
 ABCDE --> ABDE

_______________: during meiosis an unequal crossover occurs and it receives an extra copy from
its partner chromosome.
 ABCDE --> ABBCDE

________________: a whole or an entire piece of a chromosome attaches to a different pair.
 ABCDE --> ABCXYZDE

_______________: a piece of a chromosome breaks free, turns around and reattaches itself.
 ABCDEFGHI--> ABCDIHGFE
Changing Chromosome Number:

_____________________: “failure of chromatids or chromosomes to separate during cell
division” (Addison Wesley 158).


What happens when this occurs in Mitosis? Or in Meiosis?
Nondisjunction in humans results in gametes with either_____________ or ____________;
chromosomes with ___________ or ____________.
When an abnormal gamete joins with a normal gamete . . .
-
-
_____________________ - “zygote receives only one of a particular type of chromosome
instead of two, as a normal gamete would” (A.W. 158).
- Has ________ chromosomes
____________________ - “the zygote receives three chromosomes of a particular type
instead of two” (A.W. 158)
- Has ________ chromosomes
Human Examples:
 Down Syndrome: ( _____, _____)
Characteristics:
-
Why does the frequency of Down Syndrome increase with the mother’s age?
 Patau Syndrome: (____,____)
Characteristics
 Edward’s Syndrome: (____,____)
Characteristics
Polyploidy:
Define:
 In animals it is often _________________. Plants can tolerate extra sets of chromosomes.
Examples of Polyploid Plant Species:
Plant
Triticum aestivum
Triploid Examples:
Tetraploid Examples:
Other:
Do polyploid animals exist? If so give examples:
Nondisjunction of the Sex Chromosomes:
 Turner’s Syndrome (____,____)
- Monosomy or Trisomy?
- Characteristics:
-
Chance of occurring?
 Klinefelter Syndrome (____,____)
- Monosomy or Trisomy?
- Characteristics:
-
Chance of occurring?
Number of Chromosome Sets
Defective Chromosome Structure:
 Cri-du-chat Syndrome
- Characteristics:
-
Chance of occurring?
Single Allele Disorders:
-
Gene Mutation: (define)
Recessive Genetic Disorders:
List 2 examples and give the key characteristic of each disorder.
Dominant Allele Disorders: Why are they less common?
Example: Huntington’s Disease (briefly describe this disorder)
Codominant Disorders:
-
Sickle Cell Disease:
-
What does this disease cause resistance to?
Is it possible to have an XY female and an XX male?
Autosomal vs Sex Chromosome Trisomies:


In 1961, Mary Lyon proposed that early on in development of a normal female, one X
chromosome in each body cell is inactivated.
She suggested the inactive X chromosome was the darkly staining mass, called a Barr Body that
normally appears in the nuclei of female cells.
-
Thus, one reason sex chromosomes trisomies are less disruptive is because all of the extra
X chromosomes are inactivated except for a few active genes.
Example: Calico and Tortoise Shell cats are always female. WHY?
Examples of Possible Genetic Disorders to research:
Be sure to check out the Genes and Diseases Website NCBI:
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowSection&rid=gnd