Chat transcript: genetics

[Lorena]

20:17:54 [hutals] what are some examples of autosomal recessive disease?

20:17:57 [kmonica26] hi crush

20:17:57 [hutals] hey crush

20:18:09 [jwls29] hi crusher

20:18:22 [jwls29] hemochromatosis, cystic fibrosis

20:18:32 [crusher] mostly enzyme def r examples of AR

20:18:42 [jwls29] agree with crusher

20:18:44 [crusher] phenyl kenuria,tay sac etc

20:19:06 [hutals] yep, very good.

20:19:22 [hutals] what about x linked recessive?

20:19:38 [jwls29] hemophilia A and B

20:19:55 [kmonica26] hemophilia, duchenne

20:20:16 [crusher] g6pd def

20:20:31 [crusher] fabry

20:20:32 [hutals] yep, also lysch nyhan....very good

20:20:43 [crusher] hunters dis

20:20:51 Lorena enters this room

20:20:52 >[Lorena] Welcome to our chat. Please obey the net etiquette while chatting: try to be pleasant and polite.

20:21:17 [crusher] helo lorena

20:21:24 [hutals] yes hunters because a "hunter aims for the X", so X linked recessive

20:21:26 [Lorena] i got disconnected , hi crusher!

20:21:43 [hutals] welcome back lor

20:21:52 [Lorena] thanx

20:22:21 [hutals] which enzyme is deficient in tay sachs?

20:22:50 [crusher] hex amidasa A

20:22:59 [kmonica26] hexoseaminidase

20:23:02 [Lorena] agree

20:23:07 [hutals] tay-saX = heXosaminidase a.....very good

20:23:48 [Lorena] in a family pedigree, what is termed the proband?

20:23:50 [hutals] what enzyme for neimman-picks disease?

20:24:07 [hutals] the patient is the proband

20:24:29 [Lorena] sphingomielinase

20:24:44 [jwls29] sphingomyelinase

20:25:01 [jwls29] agree with hutals

20:26:02 [hutals] "no MAN PICKS his nose with his SPHINGer"

20:26:03 [Lorena] the proband is the first affected individual to be identified

20:26:48 [Lorena] clicicalle hot do you differentiate Nieman picks from Tay sach's?

20:27:15 [Lorena] i mean clinically

20:27:35 [hutals] with hepatospenomegaly is Niemann picks, without hepatospenomegaly is tay sachs

20:27:48 [kmonica26] presence of heaptohegaly in niemann picks

20:28:08 [kmonica26] oops sorry fro the spellings

20:28:22 [Lorena] yes, very good

20:28:59 [hutals] that is very high yield because they know we have our brains set to say "tay sachs" whenever we read "cherry red spots", but they will throw in the hepatospenomegaly somewhere in the question and you might think nothing of it.

20:29:51 [Lorena] in a pedigree of an autosomal dominant inheritance, what would be a raison for an skipped generation?

20:29:53 [hutals] who passes disease to who in mitochondrial inheritance?

20:30:06 acestep1 enters this room

20:30:10 [Lorena] thank you hutals, very HY

20:30:22 [hutals] hey ace

20:30:39 [hutals] incomplete penetrance??

20:30:40 [acestep1] hey guys how r u

20:30:45 [Lorena] mom to kids in mithocondrial

20:30:54 [hutals] either that or somebody was cheating

20:30:57 [jwls29] females pass inheritance to their offspring b/c sperm don't have mitochondria

20:30:58 [acestep1] hi hutals

20:31:00 [Lorena] hi ace, we have missed you

20:31:10 [Lorena] yes hutals very good!!

20:31:14 [Lorena]

20:31:16 [jwls29] hi ace

20:31:21 [acestep1] same here lor

20:31:24 [kmonica26] hi ace

20:31:37 [acestep1] hi jwls

20:31:39 [crusher] hello ace

20:31:55 [hutals] thats right, females pass to all children, males do not pass to any

20:32:08 [jwls29] incomplete penetrance is when the pt has the genotype but not the phenotype

20:32:13 [crusher] do any of u have q on popular genetics

20:32:23 [acestep1] hi crusher. listen i wont disturb u guys . just wanted 2 make sure u gusy r nto doing biochem . ill joinu guys tom

20:32:29 [crusher] apple

20:32:34 [Lorena] reduced or incomplete penetrance may be a raison why a skipped generation in an autosomal dominant disease, yes jwls

20:32:54 [acestep1] couldnt finish molbio n genetics

20:32:56 sonu12345 enters this room

20:33:04 [hutals] hey sonu

20:33:15 [Lorena] hi sonu

20:33:19 [sonu12345] hi

20:33:21 [acestep1] opk u guys carry on n tc all of u . bye

20:33:23 [sonu12345] all

20:33:29 [Lorena] ok ace, see you tomorrow then

20:33:42 [crusher] hey sonu.u the same sonal

20:33:43 medfan enters this room

20:33:43 [Lorena] what are those q's crush?

20:33:48 [hutals] ok ace, see you tomorrow

20:33:53 [medfan] hi everyone

20:34:04 [Lorena] hi medfan

20:34:06 [crusher] see yaace

20:34:14 [crusher] hi medfen

20:34:17 [hutals] what are popular genetics?

20:34:29 [sonu12345] hi im new to this chat

20:34:31 [hutals] hey medfan

20:35:02 [hutals] welcome sonu, we're discussing genetics tonight. feel free to jump in or observe.

20:35:31 [sonu12345] ya thanku

20:35:35 [crusher] hardyweingburg equations

20:35:42 [hutals] give an example of diseases that display genomic imprinting?

20:36:04 [crusher] parader willi n angleman

20:36:18 [Lorena] angelman (maternal)and prader will (paternal)

20:36:23 [medfan] agree with crusher

20:36:24 [jwls29] angelmann's sx and prader wilil

20:37:21 [hutals] genomic imprinting is when there are differences in phenotype depending on maternal or paternal. angelman (mom is an angel) and P-rader willi (P-aternal) are examples effecting chrom 15

20:37:23 [hutals] good job

20:38:35 [hutals] what are some examples of triplet repeat disorders? how will this effect the future generations?

20:39:07 [medfan] what is genetic drift?

20:39:08 [crusher] fragile x...hungtington...myotonic dystropy

20:39:14 [Lorena] fragile X sx CCG repeats; huntingtons CAG repeats. They show anticipation

20:39:27 [kmonica26] fragile X, myotonic dystrophy, huntington

20:39:29 [crusher] minor changes in influenza genome

20:39:34 [jwls29] agree

20:39:38 [medfan] fragilex, md, hunt.

20:39:47 [jwls29] the greater the number of triplets, the worse the disease

20:39:49 [hutals] Huntingtons, fragile x, friedreichs ataxia, myotonic dystrophy. worsening will future generations (anticipation).....very good all

20:40:18 [hutals] agree with crusher about influenza

20:41:33 [Lorena] or any virus with segmented genomes

20:41:42 [hutals] which trisomy will have polydactyl?

20:41:51 [Lorena] orthomyxovirus

20:42:08 [crusher] roita

20:42:20 [crusher] bunya

20:42:25 [crusher] arena

20:42:49 [jwls29] patau

20:42:49 [crusher] pataua.

20:43:03 [jwls29] which is trisomy 13

20:43:38 [Lorena] i was not sure about patau or edwards but patau then is the one with polydactily and edwards with overlapping fingers

20:43:45 [hutals] patau= trisomy 13 ("13 fingers=polydactyly")

20:46:02 [hutals] if you have high or low alpha fetoprotein (AFP), what might this indicate? (in a preg pt)

20:46:22 [jwls29] down's

20:46:27 [jwls29] low

20:46:32 [crusher] dec in dpown n inc in neural tube def

20:46:36 [jwls29] high is neural tube defect

20:46:51 [kmonica26] A female infant born to a 24-year-old woman has been diagnosed clinically as having Down syndrome. The mother is concerned about her risk of having another child who has a chromosomal abnormality.

20:46:54 [Lorena] aghree with crusher and jwls

20:47:01 [medfan] high nt defect, low trisomy 21

20:47:03 [hutals] high AFP = neural tube defects, low AFP = downs ("low=down")...very good

20:47:08 [kmonica26] The statement that you are MOST likely to include in your discussion is that her risk

20:47:25 [kmonica26] A. can be estimated by determination of maternal serum alpha-fetoprotein in all future pregnancies

20:47:38 [kmonica26] B. cannot be estimated until her infant's chromosome complement has been determined

20:47:47 [kmonica26] C. is increased for Down syndrome, but not for any other chromosomal abnormality

20:47:56 [kmonica26] D. is no greater than that of any other woman her age

20:48:05 [kmonica26] E. is not increased until she reaches the age of 35

20:48:48 [medfan] A?

20:48:56 [hutals] a

20:49:13 [Lorena] a is my guess

20:49:27 [crusher] bhb

20:49:39 [kmonica26] answer is B

20:49:42 [hutals] e is also correct, isn't it?

20:49:44 [kmonica26] In particular, it is important to determine by karyotyping if Down syndrome results from full trisomy of chromosome 21 or from a translocation.

20:50:02 [kmonica26] Approximately 4% of children who have Down syndrome have an unbalanced translocation, and in about 50% of these children, the translocation is familial.

20:51:53 [hutals] ah, just read 5 to 15% risk for parent with a balanced translocation of having another affected child

20:52:11 [Lorena] thnk you, good question

20:53:07 [medfan] good Q

20:53:22 [jwls29] very good question

20:53:27 [kmonica26] another similar question which would have the same answer..

20:53:32 [kmonica26] A newborn has microcephaly; dysmorphic features, including a prominent forehead, protuberant ears, and micrognathia; bilateral hip dislocation; clinodactyly; and simian lines on both hands. Peripheral blood chromosome analysis reveals an unbalanced translocation that results in partial trisomy 9.

20:53:39 [hutals] incidence is normally 1/800, but it increases to 1/385 >35 yo.

20:53:50 [kmonica26] Of the following, the MOST appropriate statement to include when discussing the diagnosis with the parents of this infant is that

20:54:17 [kmonica26] answer would again be..A. chromosome analysis should be obtained on both parents to determine if they are balanced translocation carriers

20:55:09 [hutals] that makes sense because the risk changes dramatically depending on the cause....good questions

20:55:25 [Lorena] thank you monica

20:55:32 [kmonica26] np

20:56:08 sonu12345 enters this room

20:56:44 DrPoon enters this room

20:56:55 [Lorena] what is a robertsonian translocation?

20:57:07 DrPoon exits from this room

20:57:39 DrPoon enters this room

20:57:44 [jwls29] loss of the short arms of the chromosomes and fusion of the long arms

20:58:04 [hutals] type of balanced translocation with reciprocal translocation between 2 homolgous chroms

20:58:07 [kmonica26] agree

20:58:14 [Lorena] yes

20:58:30 [medfan] loss of short arm of two of the chromosomes (13,14,15,21,22) and fusion of the long arm

20:59:25 [Lorena] good jwls, monica, medfan

20:59:36 [hutals] A child is born with multiple fractures and blue sclera what is the diagnosis

20:59:56 [Lorena] OI

20:59:59 [kmonica26] osteogenesis imperfecta

21:00:01 [sonu12345] osteogenesis imperfecta

21:00:07 [medfan] O.I.

21:00:20 [hutals] YEP, Osteogenesis imperfecta;disease of abnormal collagen synthesis resulting in fractures and translucent Conn tiss over chorioid causing the blue sclera....GOOD JOB

21:00:21 [jwls29] agree

21:00:50 [hutals] A congenital deficiency of tyrosinase would lead to what?

21:01:15 [Lorena] albinism?

21:01:22 [crusher] albisnism

21:01:29 [sonu12345] agree

21:01:35 [medfan] albino

21:01:35 [hutals] yep, very good, Albinism, can't synthesize melanin from tyrosine

21:01:55 [hutals] A patient presents with cataracts, hepatosplenomegaly, and mental retardation, what is the Dx?

21:02:24 [crusher] hurlr dis

21:02:28 [Lorena] galactosemia

21:02:47 [kmonica26] agree with lor

21:03:12 [crusher] why is cataract?

21:03:23 [hutals] Galactosemia is correct. hurlers would be corneal clouding and mental retardation

21:03:42 [crusher] oksorry got it

21:03:45 [Lorena] galactitol accumulates and causes osmotical damage

21:04:21 [kmonica26] A female infant is born with unilateral cleft lip and palate. Findings on the remainder of the physical examination are normal, and you inform the parents that this apparently is an isolated birth defect.

21:04:31 [crusher] gactiolo causes lense damage right n enzy is uridyl transferases

21:04:35 [kmonica26] During counseling of the family about their risk for having another similarly affected child, the statement that you are MOST likely to include is that

21:04:47 [kmonica26] A. because the defect is isolated, their risk is no greater than that of any other couple

21:05:00 [kmonica26] B. cleft lip and palate is a multifactorial trait that has a 4% risk of recurrence

21:05:10 [kmonica26] C. the recurrence risk can be estimated only after a chromosome analysis has been obtained

21:05:19 [kmonica26] D. the risk is increased for future females, but not males

21:05:30 [kmonica26] E. the risk would be increased only if one of the parents had cleft lip and palate

21:06:09 [hutals] if isolated, i guess its a??

21:06:12 [medfan] a

21:06:27 [Lorena] i agree with hutals and medfan

21:06:37 [crusher] same is here

21:06:40 [jwls29] b

21:07:06 [kmonica26] Correct jwls..answer is B Isolated cleft lip and palate is inherited as a multifactorial trait that is due to the interaction of genetic and environmental factors.

21:07:32 [medfan] actually,cleft lipis multifacctoria but i don't know about the 4%?

21:08:20 [kmonica26] For cleft lip and palate, the recurrence risks for a family in which neither parent is affected and there is one affected child is approximately 4% in the next pregnancy.

21:08:45 [kmonica26] For most multifactorial birth defects, the recurrence risks for parents who have had one affected child ranges from 2% to 5%, although some traits are associated with higher risks

21:08:51 [Lorena] ok

21:09:11 [hutals] isnt it phenytoin that is one of causes of cleft lip? i thought isolated meant not caused by familial, so i assumed it was same as anyone else.....didnt realize there was an increase risk....good question

21:09:11 [medfan] got it. thanks

21:09:49 [Lorena] thanks

21:10:08 [crusher] good q

21:11:09 [kmonica26] u r welcome

21:11:17 [hutals] you would have thought the parents would have learned that whatever they were doing had an effect on child

21:11:23 [Lorena] what are other factors that are important to consider in recurrence risk of multifactorial diseases?

21:12:27 [hutals] is diet considered multifactorial?

21:12:27 maykel enters this room

21:12:35 [hutals] hey maykel

21:13:31 [jwls29] risk increases as the number of affected individuals increase

21:13:36 [kmonica26] increase as no of affected realtives inc, inc as severity of dis inc, inc if affected person belongs to low risk group

21:13:38 [medfan] so do you have to be genetically predisposed and then have the environmental factor affect it too?

21:13:57 [Lorena] very good

21:14:21 [jwls29] it also increases as the prevalence of the disease increases in the population

21:14:24 [maykel] hi guys

21:14:41 [jwls29] hi maykel

21:14:43 [hutals] A patient presents with 1. Hyperextensible skin 2. Tendency to bleed 3. Hypermobile joints. Dx ?

21:14:46 [medfan] hey maykel

21:15:00 [kmonica26] ehlers dahlos

21:15:04 [Lorena] ehlers danlos

21:15:15 [Lorena] hi maykel

21:15:18 [medfan] agree with kmon and lor

21:15:24 [maykel] what is up medfan and hutals

21:15:37 [hutals] yep, its Ehlers-Danlos syndrome....very good

21:16:05 [hutals] nothing much maykel. we're discussing genetics. feel free to join in or observe

21:16:19 [crusher] ehler dandols def collen gene

21:16:34 [maykel] wow is this a IM conference

21:16:43 [kmonica26] ou have just made the diagnosis of an X-linked recessive disorder in a 3-year-old boy.

21:16:43 [Lorena] what is locus heterogeneity?

21:16:44 [maykel] OH GREAT

21:16:59 [kmonica26] he MOST likely finding in the family history is

21:17:13 [kmonica26] A. a maternal uncle who has the same disorder

21:17:22 [kmonica26] B. a paternal aunt who has two affected sons

21:17:30 [maykel] i am not in the program yet, i got accepted for may 2005

21:17:30 [kmonica26] C. a similarly affected sister

21:17:42 [kmonica26] D. advanced paternal age when the child was conceived

21:17:53 [kmonica26] E. parents who are first cousins

21:17:56 [crusher] A

21:18:09 [jwls29] a

21:18:23 [Lorena] agree

21:18:23 [hutals] a

21:18:42 [hutals] congrats maykel

21:18:48 [kmonica26] correct answere is A

21:19:22 [medfan] why?

21:19:36 [hutals] no male to male transmission and sons of heterozygous moms have 50% chance of being affected

21:19:57 [crusher] cos x.linked is common in male n tranferred by carrier female

21:20:05 [kmonica26] locus hetero exits when the same ds phenotype can be caused by mutations in different loci

21:20:24 [Lorena] he got his X chromosome from mom , mom is a carrier because has 2 x's chromosomes

21:20:25 [medfan] oh yeah...thanks all

21:20:26 [kmonica26] answer to lor question...eg OI

21:20:53 [Lorena] very good monica

21:21:05 [hutals] Absence of Galactosylceramide Beta-galactosidase leads to thebuild up of what compound in what disease?

21:21:21 [Lorena] and what is allelic heterogeneity?

21:21:47 [kmonica26] Krabbe ds

21:22:19 [kmonica26] galactocerebroside accumulated

21:22:39 [jwls29] agree with monica

21:22:44 [hutals] accumulation of galactocerebroside in the brain... Krabbe's disease...very good mon

21:22:52 [hutals] and jwls

21:23:25 [hutals] different mutations at the same locus

21:23:40 [Lorena] yes

21:24:02 [Lorena] give an example of allelic heterogeneity

21:25:49 [Lorena] Duchenne and Becker is an example of allelic heterogeneity

21:26:07 [Lorena] OI is an example of Locus heterogeneity

21:26:17 [medfan] good one lor

21:26:27 [crusher] okthanks lor

21:26:34 [Lorena] sound similar but not the same

21:27:05 [hutals] thanks lor

21:27:17 [Lorena] np

21:27:34 [crusher] wht is linkage disequilebirum?

21:28:14 [hutals] what is the most likely genotype of pt with no barr body, "menopause before menarche", streak gonads, webbed neck, increased FSH and LH?

21:28:37 [kmonica26] turners XO

21:28:41 [Lorena] 45,X...turners

21:28:42 sonu12345 enters this room

21:28:49 [medfan] turners

21:28:51 [crusher] its turner synd=streak gonads

21:28:52 [hutals] tendency for certain alleles at 2 linked loci to occur together more often than expected by chance

21:29:06 [Lorena] linkage disequilibrium is when you see more than expected a combination of 2 alleles?

21:29:19 [hutals] yep turners which is 45 XO

21:29:43 [maykel] hey guys good luck with genetics i am leaving because i guess i need know a little more about genetics lol lol bye good night

21:29:50 [Lorena] how many barr bodies a patient with turner has?

21:30:00 [hutals] zero

21:30:11 [medfan] none

21:30:17 [crusher] yes in other wirds 2 allel are very close to each other

21:30:22 [hutals] ok maykel, good luck with school

21:30:30 [crusher] one bar body=xx.....

21:30:35 [Lorena] good ...how about a patient with klinefelter's?

21:30:38 [maykel] thanks cya

21:30:56 [kmonica26] 1 barr

21:30:58 [Lorena] bye maykel

21:31:08 [kmonica26] other is inactivated

21:31:09 [hutals] 1 barr body because 47 xxy.....that was my next question

21:31:10 [medfan] bye

21:31:32 [crusher] agree

21:32:21 [jwls29] agree

21:32:30 [medfan] yes

21:32:42 [Lorena] and if the patient's karyotype is 48XXXY? how many barr bodies?

21:32:50 [medfan] two

21:32:58 [crusher] 2

21:33:01 [hutals] 2

21:33:03 [medfan] only one x can be expressed

21:33:12 [Lorena] good job

21:33:12 [jwls29] 2

21:33:34 [Lorena] turners are at increased risk of what neoplasia?

21:33:57 [kmonica26] gonadoblastoma

21:34:03 [crusher] lymphoma

21:34:04 [crusher] ?

21:34:15 [medfan] has to do with gonads? ovarian ca?

21:34:30 [Lorena] gonadoblastoma is right

21:34:33 [hutals] dysgerminoma

21:34:48 [medfan] never mind...i'm totally off!

21:36:10 [jwls29] dysgerminoma

21:36:26 [hutals] i also thought it was ovarian tumor...at least according to golijan

21:36:30 [Lorena] particularly turner's with mosaicism 45X;46XY

21:37:41 sonu12345 enters this room

21:37:41 [medfan] .

21:37:52 [Lorena] are you guys there?

21:38:20 [Lorena] this got frozen

21:38:37 [sonu12345] same here

21:38:38 [Lorena] dysgerminoma and gonadoblastoma is the same tumor?

21:39:51 crusher enters this room

21:40:25 [crusher] hello

21:41:08 [Lorena] no med fan you are not off, these are ovarian tumors

21:41:17 [Lorena] you are right

21:41:33 hutals enters this room

21:41:54 [hutals] comp froze again

21:42:28 [Lorena] same happened to everybody

21:42:54 [hutals] valuemd said they would be working on server all week and would be experiencing slow downs and downtime while they work on server, so i guess its to be expected

21:42:55 kmonica26 enters this room

21:43:35 [kmonica26] sorry got disconnected

21:43:39 [Lorena] ok

21:43:47 [hutals] i think most of us did

21:44:32 [hutals] anything else to discuss? i think it was only genetics on the schedule tonight....right?

21:44:38 [Lorena] yes

21:44:57 [Lorena] tomorrow start with metabolism

21:45:12 [crusher] i,m still looking for hardyweingburg q

21:45:44 [hutals] hardy weinburg eqauation?

21:46:18 [crusher] numerical type Q based on the eqaition

21:46:21 [Lorena] i dont have any of those

21:46:44 [hutals] prevalence of cystic fibrosis is 1 in 2500.....what is the carrier rate of CF?

21:46:50 [hutals] hows that?

21:47:06 [crusher] ya

21:47:21 [crusher] 1/25?

21:47:42 [Lorena] agree

21:48:06 [Lorena] no.... thats not it...

21:48:15 [hutals] number of couples at risk is 1/2500 divided by 1/4= 1/625......carrier rate of CF = 1/sq rt of 625=1/25

21:48:42 [hutals] divide prevalence by 1/2 if auto dom

21:49:18 [crusher] prevelance =q2=1/2500....q= frequ=1/50..so 2pq=2x50=1/25

21:50:00 [crusher] sorry its like =2pq-2x1/50=1/25

21:50:44 [hutals] yes, i was using golijans easier method because i never could really understand the real way to calculate it