Mitosis and Meiosis

Question 1

G2 checkpoint

Answer 1

Cell replication is complete, if there is a defect not supposed to go past G2

Question 2

Types of Chromosomes

Answer 2

(Big to small) Metacentric –> Submetacentric –>Acrocentric –> Telocentric

Acrocentric has satellite w/ secondary constriction, used for ribosomal genes.
Humans do not have telocentric chromosomes.

Question 3

Chromosome construction

Answer 3

P arm (slightly shorter) connected to centromere and Q arm

Question 4

Karyotype organization

Answer 4

Autosomes organized in longest to shortest (1-22) and sex chromosome 23.

Stain G/C regions.

Question 5

Chromosome Nomenclature

Answer 5

Region –> Band –>Sub-band (RBS)

Chr 16p11.2 = Chromosome 16 Region 1 Band 1 Sub-band 2 on the P arm

Question 6

Cell recombination occurs during sister chromatid exchange

Answer 6

Genetic diversity (meiosis)

Question 7

Cyclins drive cell cycle

Answer 7

Cyclin concentration varies among stages, CDK is constant

Question 8

Mitosis (PMAT)

Answer 8

Prophase – nuclear envelope breaks, spindle fibers appear
Metaphase – chromosomes line up on metaphase plate, spindle fibers connect to centromeres
Anaphase – chromatids separate, go to opposite poles
Telophase – nuclear envelope reforms, chromosomes condense and spindle fibers disappear

Question 9

Count chromosomes by # of centromeres

Answer 9

One centromere = one chromosome

Question 10

Cohesin Complex

Answer 10

Purpose is to keep chromatids attached, facilitates spindle attachment and recombination.

Phosphorylation removes cohesin during prophase to allow chromatids to separate during anaphase.

Question 11

Cornelia de Lange syndrome

Answer 11

Congentital disorder with cohesin complex. Develop synophyrs (unibrow) and long thin filtrum (nose). Poor growth and developmental issues.

Question 12

Chromosome Changes

Answer 12

Due to deletions/additions, duplications, rearrangements

Numerical changes = aneuploidy, most of the time do not live.

Exceptions: Trisomy 13, 18, 21; Turner Syndrome 45x; Klinefelter’s Syndrome 47xxy

Question 13

Chromosome reshuffling can occur at hotspots

Answer 13

Hotspots are areas on chromosome that are weak

Question 14

Karyotype Nomenclature

Answer 14

of chromosomes, sex chromosomes

46, XX
45, XY-15 (missing chromosome 15)
47, XX+21 (extra chromosome 21)
47, XY, upd(15)mat (extra chromosome 15 from maternal)

UPD: Uni Parental Disomy

Question 15

Most important phase of meiosis

Answer 15

Metaphase, phase that is most prone to mistakes (non-disjunction)

Question 16

Trisomy 13 characteristics

Answer 16

Cleft-lip, cleft-palate, low-set ears

Question 17

Chromosome 15 has parent specific methylation patterns

Answer 17

Genomic imprinting happens on chromosome 15

Question 18

What is genomic imprinting?

Answer 18

When genes get turned off due to methylation (Cr15!)

Question 19

Prader Willi Syndrome vs. Angelman Syndrome

Answer 19

If paternal chromosome is deleted = Prader Willi
If maternal chromosome is deleted = Angelman

(Both for chromosome 15)

Question 20

Chromosome Rescue

Answer 20

Mechanism where a non-disjunction produces a trisomy. Body randomly throws one chromosome out but doesn’t know which one is the correct one.

When it’s the wrong one, we get UPD.

Question 21

Turner Syndrome

Answer 21

45X, only one X

Short stature, repro problems

Question 22

Normal females need XX all the way to blastocyst stage to be “normal”

Answer 22

Males only need one X

Question 23

Klinefelter’s Syndrome

Answer 23

47XXY, extra X for the male

Question 24

Hemophilia should only be in men

Answer 24

Lyonization and barr body expression explain pedigree anomalies