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

READING Q’s 1-APPLY: Examine the karyotype. Are these chromosomes for a male or female? -MALE

READING Q’s 2-DEFINE -What happens during nondisjunction? -sister chromatids do not separate properly during cell division.

READING Q’s 3-EVALUATE -Does nondisjunction during meiosis produce any normal genes? -YES EXPLAIN- -nondisjunction during meiosis II produces two normal and two abnormal gametes

READING Q’s 4-LABEL -Circle the pictures that show a trisomy in the sex chromosomes

READING Q’s 5-STATE -The purpose of fetal testing -to test for genetic disorders in the fetus

BACKGROUND INFO -1/2 SHEET NOTES

KARYOTYPE -method of identification of chromosomes HOW WHY -picture taken during mitosis -image enlarged -individual chromosomes cut up -chromosomes matched based on: -size (largest smallest) -centromere position -g-banding WHY -identify abnormalities in chromosomes -identify abnormalities in genes -identify sex of fetus

KARYOTYPE: EXAMPLE A mess of chromosomes…

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

NON-DISJUNCTION WHAT WHEN FACTS -chromosome pair fails to separate -during meiosis -as a result, the gamete that forms has the 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

NON-DISJUNCTION

NON-DISJUNCTION: trisomy Trisomy 21- Down’s Syndrome -most commonly known trisomy -extra chromosomes #21 -1:700 births TRAITS -common facial features -short stature -stubby fingers/toes -large tongue: difficult speech

Trisomy 21

NON-DISJUNCTION: trisomy Patau Syndrome -extra chromosomes #13 -1:1500 births TRAITS -serious eye, brain, and circulatory defects

Trisomy 13

NON-DISJUNCTION: trisomy Edward’s Syndrome -extra chromosomes #18 -10% survive past 1yr TRAITS -many complications

Trisomy 18

NON-DISJUNCTION These are the only known trisonomy genetic disorders that result in offspring surviving for a short period of time

NON-DISJUNCTION: SEX CHROMOSOMES -can be fatal -most survive with specific traits

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

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

XYY

NON-DISJUNCTION: SEX CHROMOSOMES super female -1:1000 live births -XXX TRAITS -no physical problems -normal intelligence

XXX

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

Monosomy XO

GROUP WORK: APPLICATION NOTES -As a cooperative group complete the note sheet using your knowledge from the reading / discussion. HIGLIGHT/MARK supporting info in the text -DISCUSS ideas with group and COMPLETE 11.3 VOCAB

VOCABULARY REVIEW: mitosis -cell division that results in identical cells (DNA replicated) 1- micrograph of chromosomes -KARYOTYPE 2- abnormal number of chromosomes -NONDISJUNCTION 3- withdrawal of tissue from the placenta -CHRONIC VILLI SAMPLING 4- extra chromosome 21 -DOWN SYNDROME 5- protective cap at the end of a chromosome -TELOMERE

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

KARYOTYPES SEQUENCE: how a scientists make a karyotype 1- -chromosomes are removed from a cell in metaphase 2- -chromosomes stained -reveal banding patterns that mark each pair of chromosomes 3- -chromosomes arranged in pairs by size 4- -a microscopic picture is taken

KARYOTYPES INDICATE: the parts of a karyotype of a child born with Down syndrome. TELL: why this karyotype is called trisomy -it has a set of THREE CHROMOSOMES on ONE KIND RECALL:the term for failure of sister chromosomes separate -NONDISJUNCTION STATE: does risk increase with mothers who are younger/older -older XX XXX XX

KARYOTYPES COMPARE/CONTRAST BOTH -used by geneticist to study genetic disorders KARYOTYPES -method used for VISUALIZING chromosomes -used to DETECT abnormalities in chromosome # PEDIGREES -method used for STUDYING inheritance by following traits in family

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 the chromosomes during cell division & against cellular enzymes

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

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 / chronic villi sample / fetal blood sample Embryo death Down’s syndrome Turner’s syndrome Klinefelter’s syndrome

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 Medication/surgery before birth to correct problem infection

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