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Genetic Abnormalities
How do these alterations effect an organism?
Bell Ringer:
Learning Targets:
- Did you meet your weekly goal?
- Why or why not?
- I can analyze a karyotype to determine patterns, such as the presence or absence of a chromosomal disorder.
- I can describe the relationship between human genetic disorders and mutations.
Chromosomal Mutations
Some Examples
How it happens
Down's Syndrome: Trisomy 21
Non-disjunction
Single Chromosome
Large-scale rearrangement
Three copies of chromosome 21
- characteristic facial appearance.
- varying levels of retardation
- other varying effects
"-somy" mutations
- involve individual extra/missing chromosomes
- Usually result in early miscarriage
Segments of chromosomes can also get altered during DNA replication.
There are four major types of chromosomal rearrangements
Why would an extra 21 be tolerated by the organism?
Sex Chromosome "-somy" mutations
Kleinfelter's Syndrome: XXY
Are generally more tolerated by the organism. Don't result in miscarriage
- Phenotypically male.
- Reduced fertility
- Some "female" secondary sexual characteristics (e.g. over-developed breast tissue)
Turner's Syndrome: Monosomy X
In a non-disjunction event, chromosomes do not separate during anaphase.
This leads to gametes with irregular numbers of chromosomes.
- Phenotypically female.
- Sterile
- Associated with heart defects
Multiple Y Chromosomes/Multiple X Chromosomes
Not a problem. Why?
Multiple Y:
Multiple X:
The Y chromosome is the smallest human chromosome.
It contains very few genes.
It's major function is to direct testes formation early in development.
Who is affected by this type of mutation?
The X chromosome is pretty large.
It contains many genes.
BUT: Both males and females have to function with it (and males only get 1 copy).
X-inactivation: Early in development every X chromosome in a cell except for one is turned into an inactive "Barr body".
So multiple X chromosomes are not a problem
Calico cats are always female!
DNA Mutations
How it happens
What it Changes
Frameshift Mutations: can change every amino acid that follows the initial mutation.
- Substitution Replace 1 base with a different one.
- Insertion Add extra base(s) into sequence.
- Deletion Remove base(s) from the sequence.
- Silent: DNA sequence changes but not the amino acid sequence.
- Missense: DNA and amino acid sequence changes.
- Nonsense: DNA changes RNA sequence to a stop codon.
Model the three types of DNA mutations with the following sentence.
THE CAT ATE THE RAT
Graphic Organizer
Create a graphic organizer using the following words.
- Inversion
- Nondisjunction
- Duplication
- Frameshift
- Silent
- Nonsense
- Missense
- Mutation
- Chromosome Mutation
- DNA mutation
- Insertion
- Deletion
- Substitution
- Translocation