L37 Meiosis & Chromosomal Aberrations

Question 1

what is meiosis division?

Answer 1

its a specific type of division resulting in the formation of games it reduces the chromosomal number from diploid to haploid in each gamete and it causes recombination of genes ensuring gene variety in the gene pool.

Question 2

MEIOSIS I ?

Answer 2

homologous pairs of chromosomes line up memebers of each part separate and travel to opposite cell poles and the cell divides producing 2 cells with haploid chromosomal number but diploid DNA content because each chromosome have 2 chromatids

Question 3

MEIOSIS II ?

Answer 3

The chromatids of each chromosome are sorted and each chromatid travel to opposite cell pole and cytokinesis occur.
these 2 events produces 4 cells that have haploid chromosome number and haploid DNA content.

Question 4

PROPHASE 1?

Answer 4

it occurs after the s phase where the DNA content is 4n. the chromosomes come close to each other and condense and crossing over occurs with is the exchange of genetic material between homologous chromosomes

Question 5

METAPHASE 1?

Answer 5

the line up of homologous chromosomes on the equilateral plate of the meiotic spindle

Question 6

ANAPHASE 1?

Answer 6

the migration of homologous chromosomes to opposite cell poles

Question 7

TELOPHASE 1?

Answer 7

chromosomes reach opposite cell poles nuclei form and cytokinesis occurs giving rise to 2 daughter cells with haploid number of chromosomes but each chromosome have 2 chromatids which makes the DNA material still diploid.

Question 8

MEIOSIS II ?

Answer 8

occurs without DNA synthesis and rapidly through the 4 phases
chromosomes line up on the equator and spindle fiber attach to the kinetochore and the 2 sister chromatids separate and travel to opposite cell poles and cytokinesis take place.

Question 9

outcome of meiosis II?

Answer 9

1-results in the formation of 4 daughter cells from 1 original cell, each cell contains a haploid number of chromosomes and haploid DNA content.
2-the cells are genetically distinct due to chromosomal reshuffling and crossing over.

Question 10

what Is meant by euploidy?

Answer 10

the normal number of chromosomes in a species humans 46

Question 11

what is meant by polyploidy?

Answer 11

condition in which the number of chromosomes are a simple multiple of the haploid chromosome set.

Question 12

TRIPLOIDY?

Answer 12

it’s a condition where there are 69 chromosomes in the cell 3n.its caused by failure of reduction division of spermatozoon and ovum or due to DISPERMY which is the fertilization of 1 ovum by 2 sperms. it results in early spontaneous miscarriage.

Question 13

TETRAPLOIDY?

Answer 13

a condition where there are 92 chromosomes there are 4n 4 copies of each chromosome occurs due to failure of the first cleavage zygotic division resulting I. Dublin the DNA content immediately after fertilization very rare and always Lethal

Question 14

what’s meant by aneuploidy?

Answer 14

abnormal number of chromosomes due to an extra or missing chromosome.

Question 15

NONDISJUNCTION?

Answer 15

failure of chromosome number due to the failure of separation of homologous chromosomes in meiosis 1 or failure of separation of the sister chromatids in meiosis 2. its mostly due to the aging effect on the primary oocyte in old age moms.

Question 16

ANAPHASE LAG?

Answer 16

its the failure of incorporating homologous chromosome or chromatid in a nucleus during cytokinesis due to the delayed movement during anaphase

Question 17

TRISOMY?

Answer 17

its the presence of 3 copies instead of 2 for an autosome or sex chromosome in an otherwise diploid cell

Question 18

MONOSOMY?

Answer 18

its the absence of a single chromosome, monosomy of an autosome Is almost always fatal. Turner syndrome is where the missing chromosome is the X chromosome in a female. they have near to normal intelligence and have low hairline and webbing of the neck and they are infertile.

Question 19

MIXOPLOIDY?

Answer 19

having 2 or more genetically different cell lineages within one individual, the genetically different cell lineages could arise from the same zygote MOSIACSM or form the fusion of different twin zygote CHIMERISM

Question 20

what is balanced rearrangement of chromosomes?

Answer 20

there has been no loss or gain of genetic material, generally its harmless unless if the breakage occurred at an important gene. carriers of balanced gene rearrangement are prone to having a baby with unbalanced rearragngment.

Question 21

unbalanced rearrangment

Answer 21

the chromosomal complement contains incorrect amount of chromosomal content and clinical effects are usually very serious

Question 22

DELETION (DEL)

Answer 22

deletion of part of a chromosome if more than 2% its lethal

Question 23

INVERSION(INV)?

Answer 23

2 break rearrangement involving only 1 chromosome where the segment is inverted. inversions are balanced rearrangements and mostly unharmful unless break occurred at an important gene.

Question 24

INSERTION(INS)

Answer 24

A segment of 1 chromosome becomes inserted into another chromosome. if the inserted material has moved elsewhere in another chromosomes the karyotype is balanced. otherwise, insertion——->unbalanced

Question 25

DUPLICATION(DUP)

Answer 25

gain of chromosomal material through production if one or mow copies of a gene or region of chromosome

Question 26

TRANSLOCATION(T)

Answer 26

The transfer of genetic material from chromosome to another

Question 27

RECEIPROCAL TRANSLOCATION?

Answer 27

its formed when a break occurs in each chromosome of metacentric and submetacentric types with the segments being exchanged to form 2 new derivative chromosomes chromosome number is still 46.

Question 28

ROBERTSONIAN TRANSLOCATION

Answer 28

it results in the breakage of 2 Acrocentric chromosomes at or close to the centromere with subsequent fusion of both long arms. the short arm of each chromosome are lost but no problem because the only code for ribosomal RNA and other Afrocentric chromosome code for the same ribosomal RNA. the total number of chromosomes is reduced to 45 functionally balanced rearrangement.

Question 29

ISOCHROMOSOME?

Answer 29

abnormal centromeric division that is right angle to the normal division
(centromere is cut transversely not longitudinally). the most encountered isochromosome is that which consists of 2 long arms of the x chromosome

Question 30

RING CHROMOSOME ?

Answer 30

formed when a break occurs on each arm of a chromosome leaving 2 sticky ends on the central portion that reunited as a ring 2 distal chromosomal fragments are lost so that if involved chromosome is an autosome the effects are usually serious.