Presentation on theme: "11.3 CHROMOSOMES & HUMAN HEREDITY"— Presentation transcript:
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 testingJUST 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
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 smallestWHY-identify abnormalities in chromosomes/genes-identify sex of fetus
11 After karyotyping- male or female? KARYOTYPE: EXAMPLEAfter karyotyping- male or female?NORMAL MALENORMAL 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 lessFACTS-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 IAnaphase IFailure to separate homologous pairs
14 Nondisjunction during Meiosis II Metaphase IIFailure to separate ChromatidsAnaphase 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
21 NON-DISJUNCTIONThese are the only known trisonomy genetic disorders that result in offspring surviving for a short period of timeNON-DISJUNCTION OF SEX CHROMOSOMESThese can be fatalMost do survive just fine
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
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-KARYOTYPE2- abnormal number of chromosomes-NONDISJUNCTION3- withdrawal of amniotic fluid from the placenta-AMNIOCENTESIS4- extra chromosome 21-DOWN SYNDROME5- 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 metaphase2--chromosomes stained-reveals banding patterns3--chromosomes pairs arranged: largestsmallest4--microscopic picture taken
33 KARYOTYPESINDICATE: the parts of a karyotype of a child born with Down syndrome.TELL: why this karyotype is called trisomy-THREE CHROMOSOMES of ONE KINDRECALL term for chromosomes failing to separate-nondisjunctionSTATE: does risk increase with mothers who are younger/older-olderXXXXXXX
35 PROTECT the chromosomes TELOMERESDESCRIBE-Telomeres are made of ____________&______________.-They are located at the _____________________________________________.-Their function is to ________________________________________________.HYPOTHESIZEDNAPROTEINEND of chromosomesPROTECT 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 isfertilized 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 numbers1-_________________________2-_________________________3-_________________________4-_________________________A sample of cells is taken from the individual / fetus-amniocentesis / chorionic villi sample / fetal blood sampleEmbryo deathDown’s syndromeTurner’s syndromeKlinefelter’s syndrome
38 FETAL TESTINGINFERWhat might be the benefits of fetal testing? What might be the risks?BENEFITS RISKS-________________ -________________Discovery of genetic problemsHarm to fetusPrepare / make informed decisionsinfection
39 REVIEW 1- What could explain a human karyotype showing 47 chromosomes trisomy 2- Why does nondisjunction occur?The sister chromatids do not separate3- Which statement concerning telomeres is not true?They consist of DNA and sugars
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