1. 8.3 Human Genetics and Mutations
Key Concepts:
How do chromosomes help determine gender?
How do chromosome mutations occur?
Different genetic diseases
How can scientists test for genetic disease?
Key Vocabulary:
Autosome
Nondisjunction
Monosomy
Trisomy
Karyotype
Amniocentesis

2. The 23rd pair are sex chromosomes that determine an person’s gender
Human Chromosomes
How many pairs of chromosomes do human diploid cells have? 23 pairs (46 total)
The first 22 pairs of chromosomes are autosomes (=body/self) that do not determine sex
The 23rd pair are sex chromosomes that determine an person’s gender
X codes for female
Y codes for male

3. Sex Determination Female cells have two X chromosomes - XX
Male cells have one X and one Y chromosome - XY
In meiosis, the chromosome number is reduced in cells when pairs of chromosomes split
What sex chromosome will females contribute to offspring? ONLY an X
What sex chromosomes will male sperm contribute to offspring? X or a Y

4. Sex Determination **If an X chromosome sperm fertilizes an egg, what will the sex of the offspring be? FEMALE
**If a Y chromosome sperm fertilizes an egg, what will the sex of the offspring be? Male

5. Chromosome Mutations
Changes the number of chromosomes in a cell
What is the normal number of chromosomes in a body cell? A sex cell?
Monosomy occurs when a fertilized egg has only 1 copy of a chromosome
Trisomy occurs when a fertilized egg has 3 copies of a chromosome

6. Nondisjunction
Nondisjunction occurs when chromosomes don’t separate properly during meiosis
What phase of meiosis do the chromosomes separate? ANAPHASE
Causes fertilized eggs to have an abnormal number of chromosomes

7. Nondisjunction

8. Chromosome Diseases
Down’s syndrome – AKA TRISOMY 21
3 chromosomes on 21st pair instead of 2
Kleinfelter syndrome – XXY Syndrome
3 sex chromosomes (this person is male with female characteristics)
Turner syndrome – Monosomy X
One sex chromosome (this person is female)

9. Karyotype
Picture of a person’s chromosomes
Arranged from largest to smallest
Genetic test done with high-risk pregnancies
Used to diagnose genetic diseases and abnormal numbers of chromosomes
Made using a sample of amniotic fluid from mothers womb
Amniocentesis is used to extract the fluid

10. Amniocentesis – a procedure done to extract DNA from the fetus.

11. Amniocentesis

12. Karyotype
Is this karyotype from a male or female?
Female

13. Karyotype
Is this karyotype from a male or female?
Male

14. Karyotype What mutation and disease does this karyotype show?
Down Syndrome

15. Karyotype What mutation and disease does this karyotype show?
Turner Syndrome

16. Turner Syndrome

17. Karyotype What mutation and disease does this karyotype show?
Kleinfelter Syndrome

18. Kleinfelters