1. 11.3 CHROMOSOMES & HUMAN HEREDITY
WHAT YOU WILL LEARN
-The role of telomeres
-How nondisjunction leads to Down syndrome and other abnormalities
-The benefits and risks of fetal testing
JUST LIKE ME VIDEO – DOWN’S SYNDROME

2. READING Q’s APPLY: Examine the karyotype.
Are these chromosomes for a male or female?
-MALE

3. READING Q’s DEFINE -What happens during nondisjunction?
-homologous chromosomes do not separate during meiosis 1
-sister chromatids do not separate properly during meiosis 11

4. NON-DISJUNCTION

5. READING Q’s
EVALUATE
-Does nondisjunction during meiosis produce any normal gametes?
-YES
EXPLAIN-
-nondisjunction during meiosis II produces
two normal and two abnormal gametes

6. LABEL -Circle the pictures that show a trisomy in the sex chromosomes
READING Q’s
LABEL
-Circle the pictures that show a trisomy in the sex chromosomes

7. READING Q’s STATE -The purpose of fetal testing
-test for genetic disorders in the fetus
-determine course of action

8. BACKGROUND INFO

9. KARYOTYPE -method of identification of chromosomes HOW WHY
-picture taken during mitosis
-image enlarged
-individual chromosomes cut up
-chromosomes matched based on:
-size
-centromere position
-gene banding
-pairs arranged from largest smallest
WHY
-identify abnormalities in chromosomes/genes
-identify sex of fetus

10. KARYOTYPE: EXAMPLE
A mess of chromosomes…

11. After karyotyping- male or female?
KARYOTYPE: EXAMPLE
After karyotyping- male or female?
NORMAL MALE
NORMAL FEMALE

12. NON-DISJUNCTION WHAT FACTS
-chromosome pair or sister chromatids fails to separate during meiosis
-as a result, the gamete that forms has wrong # chromosomes
-TRISOMY: 1 extra
-MONOSOMY: 1 less
FACTS
-occurs quite often in humans
-impact so severe to zygote: miscarriage occurs very early in pregnancy
-if baby survives, develops a set of traits we call a syndrome

13. Nondisjunction during Meiosis I
Metaphase I
Anaphase I
Failure to separate homologous pairs

14. Nondisjunction during Meiosis II
Metaphase II
Failure to separate Chromatids
Anaphase II

15. NON-DISJUNCTION: trisomy
Trisomy 21- Down’s Syndrome
-most commonly known trisomy
-extra chromosomes #21
-1:700 births
-distinguishing facial features:
flat nose/face, slanted eyes
-lowered IQ
-short stature
-stubby fingers/toes
-large tongue: difficult speech
-heart/respiratory problems
*chances  as mother’s age 

16. Trisomy 21—Down’s syndrome

17. NON-DISJUNCTION: trisomy-13
Patau Syndrome
-extra chromosomes #13
-1:1500 births
-most fetuses don’t develop to term
-serious eye, brain, and circulatory defects

18. Trisomy 13—patau’s syndrome

19. NON-DISJUNCTION: trisomy-18
Edward’s Syndrome
-extra chromosomes #18
-many complications
-severe psychomotor growth/retardation
-malformed ears
-distinctively clenched fingers
95% of conceptions with trisomy 18 don’t survive to term
only 10% born survive beyond 1st year

20. Trisomy 18—Edward’s syndrome

21. NON-DISJUNCTION
These are the only known trisonomy genetic disorders that result in offspring surviving for a short period of time
NON-DISJUNCTION OF SEX CHROMOSOMES
These can be fatal
Most do survive just fine

22. NON-DISJUNCTION: SEX CHROMOSOMES
Klinefelter’s Syndrome - XXY
-1:500 males
-XXY
-tall, sterile male
-normal intelligence
-some female characteristics

23. NON-DISJUNCTION: SEX CHROMOSOMES
Jacob’s Syndrome (super male) - XYY
-1:1000 males
-XYY
-taller than average
-slightly below normal intelligence
-extra testosterone

24. XYY

25. NON-DISJUNCTION: SEX CHROMOSOMES
super female - XXX
-1:1000 female births
-XXX
-no physical problems/fertile
-weakened muscle tone
-may have delayed learning
-taller than average
-most super females unaware they have an extra X chromosome

26. XXX

27. NON-DISJUNCTION: monosomy
Turner’s Syndrome - XO
-1:2700 births
-XO
-females live normal lives
-do not mature sexually at puberty
-sterile
-short stature, short broad neck, broad chest

28. Monosomy XO

29. GROUP WORK: GUIDED NOTES
-As a cooperative group complete the guided note sheet using your knowledge from the reading.

30. VOCABULARY REVIEW: gamete -egg or sperm produced during Meiosis
1- micrograph of chromosomes
-KARYOTYPE
2- abnormal number of chromosomes
-NONDISJUNCTION
3- withdrawal of amniotic fluid from the placenta
-AMNIOCENTESIS
4- extra chromosome 21
-DOWN SYNDROME
5- protective cap at the end of a chromosome
-TELOMERE

31. KARYOTYPES EXPLAIN: how chromosomes are arranged in a karyotype
-in homologous pairs LARGEST to SMALLEST

32. KARYOTYPES SEQUENCE: how a scientists make a karyotype 1-
-chromosomes removed during metaphase 2-
-chromosomes stained
-reveals banding patterns 3-
-chromosomes pairs arranged: largestsmallest 4-
-microscopic picture taken

33. KARYOTYPES
INDICATE: the parts of a karyotype of a child born with Down syndrome.
TELL: why this karyotype is called trisomy
-THREE CHROMOSOMES of ONE KIND
RECALL term for chromosomes failing to separate
-nondisjunction
STATE: does risk increase with mothers who are younger/older
-older XX
XXX XX

34. KARYOTYPES
COMPARE/CONTRAST

35. PROTECT the chromosomes
TELOMERES
DESCRIBE
-Telomeres are made of ____________&______________.
-They are located at the _____________________________________________.
-Their function is to ________________________________________________.
HYPOTHESIZE
DNA
PROTEIN
END of chromosomes
PROTECT the chromosomes
-protection of chromosomes during cell division & against cellular enzymes

36. NONDISJUNCTION MODEL ANALYZE -Klinefelter’s XXY
-nondisjunction in meiosis 1 or 2 :
-Klinefelter’s results when an XX egg is
fertilized with a Y sperm.

37. FETAL TESTING SUMMARIZE the following facts about fetal testing.
-How an abnormal number of chromosomes is identified-
-four possible results of abnormal chromosome numbers
1-_________________________
2-_________________________
3-_________________________
4-_________________________
A sample of cells is taken from the individual / fetus
-amniocentesis / chorionic villi sample / fetal blood sample
Embryo death
Down’s syndrome
Turner’s syndrome
Klinefelter’s syndrome

38. FETAL TESTING
INFER
What might be the benefits of fetal testing? What might be the risks?
BENEFITS RISKS
-________________ -________________
Discovery of genetic problems
Harm to fetus
Prepare / make informed decisions
infection

39. REVIEW 1- What could explain a human karyotype showing 47 chromosomes
trisomy  
2- Why does nondisjunction occur?
The sister chromatids do not separate
3- Which statement concerning telomeres is not true?
They consist of DNA and sugars