1. Karyotype and Chromosomal Mutation Notes

2. What is a karyotype?
A karyotype is a picture of chromosomes found in a typical human body cell.
The karyotype is the result of a haploid sperm cell, carrying 23 chromosomes fertilizing a haploid egg cell, carrying 23 chromosomes.

3. A Normal Human Karyotype
The chromosomes in a human karyotype are arranged in homologous pairs.
The first 22 pairs of chromosomes are called autosomes.
The 23rd pair of chromosomes are known as the sex chromosomes.

4. Chromosomal Mutation
B. Chromosomal mutations involve changes in the number or structure of chromosomes. Such mutations may change the locations of genes on chromosomes, and may even change the number of copies of some genes.

5. Chromosomal mutations occur during crossing over.
The exchange of genetic material between homologous pairs of chromosomes  

6. IV. Chromosomal Mutation
C. Four types of chromosomal mutations:
Deletion
Duplication
Inversion
Translocation

7. 1) Deletion

8. 2) Duplication

9. 3) Inversion

10. 4) Translocation

11. IV. Chromosomal Mutation
D. Deletions involve the loss of all or part of a chromosome
E. Duplications produce extra copies of all or part of a chromosome
F. Inversions reverse the direction of parts of chromosomes
G. Translocations occur when part of a chromosome break off and attach to another chromosome.

13. IV. Chromosomal Mutation
H. Most mutations are neutral – they do not change the expression of genes or proteins.
I. Some are harmful, some are beneficial.

14. Nondisjunction
J. Nondisjunction occurs during meiosis when homologous chromosomes fail to separate.
Nondisjunction means “not coming apart”.
When it occurs, abnormal numbers of chromosomes may find their way into gametes (sperm or egg), and a disorder of chomosome numbers may result.

15. Nondisjunction

16. Chromosomal Disorders

17. Down’s Syndrome
Defect – autosomal disorder (extra copy of chromosome 21)
Symptoms:
Have delayed mental and social development.
Common problems may include:
Impulsive behavior
Poor judgment
Short attention span
Slow learning

18. Down’s Syndrome Neither! Due to nondisjunction.
Disorder is also called trisomy 21. Have an extra 21st chromosome.
Dominant or Recessive?
Neither! Due to nondisjunction.

19. Down’s Syndrome Interesting Facts:
It is usually the egg that provides the extra copies of chromosome 21
The older the mother, the chances of having a baby with Down’s Syndrome increases
Age 20, 1 in 1500
Age 40, 1 in 60

20. Patau Syndrome- Trisomy 13
Symptoms
Cleft lip or palate
Clenched hands (with outer fingers on top of the inner fingers)
Close-set eyes -- eyes may actually fuse together into one
Decreased muscle tone
Extra fingers or toes (polydactyly)
Low-set ears
Scalp defects (missing skin)
Seizures
Skeletal (limb) abnormalities
Intellectually Disabled

21. Turner’s Syndrome- XO Symptoms:
May be intellectually disabled, some have normal IQ
Short stature
Sterile (cannot have kids)
Webbed neck
Underdeveloped breasts
and ovaries
Defect:
XO (missing a sex
chromosome)

22. Turner’s Syndrome- XO
Frequency: 1 in 2,500 Interesting Fact: Caused by non-disjunction. (Occurs in meiosis when the sister chromatids aren’t pulled apart.

23. Klinefelter’s Syndrome- XXY
Symptoms:
Underdeveloped testes
Inability to produce sperm
Muscle structure, fat and hair distribution similar to that of a female
Breasts develop
Defect: XXY-Male with an extra X chromosome in some cells

24. Klinefelter’s syndrome
Eggs Sperm
Dominant or recessive – chromosomal mutation XXY
Frequency – 1 in 400 males
Interesting fact – often goes undiagnosed. Caused by nondisjunction. Can be treated with male hormones.

25. Double Y syndrome- XYY Signs and symptoms: Often less than average IQ
Tall
High levels of male hormones
Large ears
Sunken chest
Delayed speech and language skills
Defect: Chromosomal mutation - XYY Frequency: 1 in 250 males Interesting fact: Questionable connection to violent tendencies