3 - Karyotyping Lab

7/25/2019 3 - Karyotyping Lab

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KARYOTYPING LAB

Background Information:

Scientists have developed several different tools and techniques for studying

chromosomes, genes and base pairs in humans and other organisms. One of the mostuseful techniques is karyotyping.

A karyotype is a photograph of all of an organism's chromosomes. The chromosomes inthe karyotype are arranged in homologous pairs according to size largest to smallest!."omologous pairs can be determined by centromere placement, equal length of top andbottom arms as #ell as similar band placement on each arm.$aryotyping helps doctors diagnose and treat genetic disorders. %octors use a normalhuman karyotype and compare it to the karyotype of a patient to determine if there areabnormalities. Some of the characteristics the physician #ill compare are&

A. Total number of chromosomes normal humans have () chromosomes *+

pairs!, so if the number is higher or lo#er then an abnormality eists

-. "omologous pairs for the first ** pairs of chromosomes autosomes! oncecentromeres are aligned, top and bottom arms are of equal length and if not thenan abnormality eists

. Se hromosomes *+rd pair! if female, then * homologous /chromosomes //! #ill be present and if male, an / chromosome and a 0chromosome /0! #ill be present, so if there are additional or fe#er sechromosomes then an abnormality eists.

Procedure:

1. Arrange the chromosomes into homologous pairs on the 2ayout Sheet, usingyour $aryotype 3eference Sheet as a guide.

*. Once all chromosomes are laid do#n on the 2ayout 4orksheet, ans#er the%iscussion 5uestions using the background information, your karyotype, and6planation of hromosome %isorders "andout.."int& 0ou may have abnormalities in your karyotype more or less than ()chromosomes!, so maintain the number of chromosomes you #ere given.

+. all me over #hen you are completely finished so that 7 may check your #ork.



EXPLANATION OF !RO"O#O"E $I#OR$ER#

ri%du%c&at-abies #ith the 8cry of the cat8 syndrome have a cry #hich sounds like that of a cat indistress because the infant's laryn is improperly developed. The cause of this condition

is a deletion of about half of the short arm of chromosome number five. riduchatbabies are severely mentally disabled, have a small cranium, a small 9a# and a moonshaped face. The incidence of this syndrome is 1:1;;,;;; live births.<<$aryotype& ()// or ()/0 #ith one chromosome => upper arm deletion

$o'n #(ndromeTrisomy *1, one of the most common causes of mental retardation is due to an etrachromosome *1. This results in a number of characteristic features, such as shortstature, broad hands, stubby fingers and toes, a #ide rounded face, a large protruding

tongue that makes speech difficult and mental disabilities. 7ndividuals #ith thissyndrome have a high incidence of respiratory infections, heart defects and leukemia.The average risk of having a child #ith trisomy *1 is 1:?>; live births. @others in theirearly t#enties have a risk of 1:1,>;; and #omen over +> have a risk factor of 1:?;,#hich 9umps to 1:*> for #omen (> or older.<<$aryotype& (?// or (?/0 #ith + of the chromosome =*1

Ed'ard)* #(ndromeThis syndrome, trisomy 1 an etra chromosome 1!, produces severe mental

disabilities and a highly characteristic pattern of malformations such as elongated skull,a very narro# pelvis, rocker bottom feet, malformed heart and a grasping of the t#ocentral fingers by the thumb and little finger. 7n addition, the ears are often lo# set andthe mouth and teeth are small. Bearly all babies born #ith this condition die in earlyinfancy. The frequency of this syndrome is 1:>,;;; live births.<<$aryotype& (?// or (?/0 #ith + of the chromosome =1

Patau #(ndromeThis syndrome trisomy 1+ etra chromosome 1+! causes severely abnormal cerebral

functions and virtually leads to death in early infancy. The baby has very pronouncedclefts of the lip and palate, broad nose, polydactyly etra fingers and toes!, smallcranium and nonfunctional eyes. "eart defects and severe mental disabilities are alsopart of the clinical picture. The frequency is 1:1>,;;; live births.<<$aryotype& (?// or (?/0 #ith + of the chromosome 1+



$i*cu**ion +ue*tion*:

,rite t&e an*'er* to t&e*e -ue*tion* on t&e .ack of t&e Kar(ot(/e La(out,ork*&eet0

1*e Background Information to an*'er t&e fo22o'ing -ue*tion*01. %efine $aryotype.

*. 4hat can karyotypes be used to determineC

+. "o# many chromosomes do normal humans haveC

(. "o# did you kno# if * chromosomes #ere a homologous pair4hat made you pair * chromosomes together!C

>. 4hat does the *+rd pair of chromosomes determineC

). The first ** pairs of chromosomes are homologous in a normal person.7s that 8al#ays true for the *+rd pair of chromosomesC 6plain yourans#er.

1*e (our kar(ot3oe to an*'er t&e fo22o'ing -ue*tion*0?. 4hat is the gender se! of your babyC

. 4as your baby's karyotype normal yes:no!C

D. 7f the karyotype #as abnormal, #hat is the disorder your baby hasuse the 6planation of hromosome %isorders "andout!C

1;. %escribe the disorder your baby has. 7f your baby is normal #rite

8Bormal -aby8.



KARYOTYPE LAYO1T ,ORK#!EET

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3 - Karyotyping Lab

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