Meiosis and Abnormal Trisomies

Question 1

why do we need meiosis

Answer 1

sense of genetic diversity

allow 46 chromosomes, to become 23 each,then result in 46 again

Question 2

How to characterize human chrome with karyotype

Answer 2

size

centromere index=short arm length/total chromosome lengthx100

g-bright-low AT/GC ratio, rich in SINE repeats and Allu sees, early rep, contain housekeeping genes, not tissue specific, rich in transcribed genes

Question 3

Meiosis 1

Answer 3

-diplod cells replicate DNA at end of prophase 1 as sister CHROMATIDS

Metaphase/aniphase 1-alignment/disjuction of replicated homologues

Question 4

Meissis 2

Answer 4

separation of sister chromatids

Question 5

Prophase I-pariting of replicated homologous chromosomes at synapse

Answer 5

-pariting of replicated homologous chromosomes at synapse

Question 6

Metaphase I

Answer 6

Chromosomes ordere din middle of cell along metaphase plate

Question 7

Anaphase I

Answer 7

Chiasmama at chromosome edsn. Disjuction

Question 8

Interkinesis I

Answer 8

Formation of nut and 2 daughter cells

Question 9

Meiosis II

Answer 9

Prophase II without DNA synthesis, metaphase II, anaphase II, with 4 final haploid cells

Question 10

Nondisijuction of meiosis I+result

Answer 10

No separation of homologs

Two disomic gametes and two nullisomic gametes

Question 11

Nondisjunc at meiosis II+result

Answer 11

no seperation of chromatids

Two normal gametes and 1 disomic gamete/1 nullisomic gamete

Question 12

Klinefelter syndrome

Answer 12

NDE (non disjunction event)

47, XXY, males, tall , hypogonadism, social pathology, more X=greater risk of mental retardation

Question 13

Edwards syndrome

Answer 13

47, X, +18

IUGR-many organs messed up-clenched hands

Question 14

IUGR

Answer 14

Intra uternine grwoth retardation

Question 15

Patau syndrome

Answer 15

47, X, +13

IUGR, many organs messed up and polydactylyl

Question 16

Downs, diagnosis in baibes and adults

Answer 16

47, XX, +21

Most common cause of mental retardation

Babies-tranverse palmar crease, round head, heart defect

We are doing much better at handling treatment-living to 60 and finding jobs

Question 17

Turner syndrome

Answer 17

45, X

Gonaladal problems and short stature

Question 18

Aneuploidy

Answer 18

Too many/too little chromosomes in zygotes

Question 19

CA repeats

Answer 19

At begging of p-arm or q- arm

differentiate between M1 (heterozygosity for alleles close to centromere) vs M2-homozygosity for allies close to centromere

practice question-if still don’t understand ask

Question 20

Sex difference in meiosis

Answer 20

M1/M2 in puberty-results in 4 spermatids

Meiosis in females-M1 in inauterine development-stops before birth
-oogonia arrested in Dictyotene

M1 is completer with extrusion of 1st polar body at time of ovulation, completion of second occurs at fertilization
-results in 1 mature oocyte and 2 lost polar bodies

Question 21

what results in genetic uniqueness

Answer 21

random distribtion of homo chroms

Formation of chasmatata among non-ssister chromatids resulting in crossing over

Question 22

Balance recriprocol translocation

How many balanced

How to ]ensure does not result in problem baby

Answer 22

Parents are normal, kids probably are not

Translations raise is of aneuploidy because synapsis of translated chrome is driven by DNA homology and messed up chrome-quadi radical (form + shape) will probably not set properly

Only 2 out of 16 segregations would be balanced

Use IVF, PGD, and CVS to ensure not bad child
(preimplantation genetic diagnosis)

Question 23

Acentric/dicentric chromatids

Answer 23

Also coupled with duplications and deletions

In M1

Inversion, synapsis, recombination, two kinetchocres on 1 strand, other will get deleted

Question 24

X inactvation+with mutations+where start

Answer 24

Random @ blastocyte stage for dosage compensation

X-deltions are preferentially methylated

X translocations that are balanced are preferentially NOT methylated

starts at Xic then spreads
-xist vs tsix-xist adds methyation

Females are all mosaic-non-random x inactivation with having x linked disorder

Question 25

How to manifest x linked condition 100% of time for females

Answer 25

Females are all mosaic-non-random x inactivation with having x linked disorder or homozygous

Question 26

Uniparental disomy

Answer 26

Get two chromasomes from 1 parent, and other parents passes a bad one but bad one is lost during mitosis

Fetal phenotype determined y 1. degree of mosaicist, 2. genomic imprinting, 3. non mendelian expression

Basically saying weird shit can happen

Question 27

Duchenne Muscular Distrophy

Answer 27

DMD gene

79 exons

Most people have deletion in 1 or more if have disease

Question 28

Imprinting

Answer 28

Specific parent of originen control on expression of some genes

Question 29

Epienetic

Answer 29

Changes in gene expression due to envrionment

Question 30

PWS vs AS

Answer 30

Prader willi vs angleman

PWS-Paternal deletion-short stature, very fat

AS_readation, inappropriate laguht-maternal deletion of same gene

Often deletion is due to methylation (where a imprinting center gene upstream was mutated/deleted)

Question 31

Screening

Answer 31

Can be done on parents for kids, in second trimester/third

Aminicenteiss, CVS-these all have some fisk associated with them

Let patients deicde what they want