Exam 2 - Chapter 6: Meiosis and Mitosis

Question 1

Who first accurately described down syndrome and?

Answer 1

John Langdon Down

Question 2

Who identified Down syndrome as a chromosome condition?

Answer 2

Jérôme Lejeune identifie 47 chromosomes in individuals with Down syndrome

Question 3

What is trisomy 21?

Answer 3

A extra partial or whole copy of chromosome 21 that is associated with causing Down Syndrome

Question 4

What are two causes of trisomy 21?

Answer 4

1) No chiasmata forms and both homologs move to the same pole during meiosis I
2) Chiasmata forms too close to end and doesn’t provide enough resistance to the spindle fiber causing a break

Question 5

Why are older mother more likely to produce offspring with trisomy 21?

Answer 5

Because their primary oocytes have been arrested in prophase I for a longer period of time which may increase frequency of nondisjunction

Question 6

What is mitosis?

Answer 6

a cell divides into two daughter cells

Question 7

What is meiosis?

Answer 7

When cell division occurs twice to produce four, haploid daughter cells

Question 8

What is the order of the cell cycle

Answer 8

G1 > S > G2 > M

Question 9

What occurs during G1 phase?

Answer 9

Regular cell growth and commitment to cell division

Question 10

What 4 things occur during S phase?

Answer 10

1) DNA replication
2) chromosomes condense
3) centromers replicate
4) cohesions are cleaved, except at centromeres

Question 11

What are centrosomes?

Answer 11

the microtubule organizing center that extends microtubules during DNA replication

Question 12

What are asters?

Answer 12

star shaped formations that centromeres form when extending spindle apparatus

Question 13

What centrioles?

Answer 13

Barrel shaped organelles that contribute to microtubule organizing

Question 14

What are centromeres?

Answer 14

Where spindle fibers attach to chromatids

Question 15

What are cohesions?

Answer 15

Protein structures that hold sister chromatids together during cell division

Question 16

What is the structure and function of tubulin?

Answer 16

composed of alpha and beta dimers; make up microtubules and give them a positive and negative end

Question 17

Which charged ends of a microtubule attach where?

Answer 17

The positive end attaches to the kinetochore of chromatin and the negative end is at the centrosome

Question 18

What is the purpose of G2 phase?

Answer 18

Growth to prepare for cell division

Question 19

What is M phase?

Answer 19

the division of a cell into two (mitosis)

Question 20

What 2 things occur during prophase?

Answer 20

1) centrosomes are at the poles
2) microtubules grow from centrosomes to form spindles

Question 21

What 2 things occur during metaphase?

Answer 21

1) Spindles attach at the centromere
2) Spindle tension aligns chromosomes at equator

Question 22

What are kinetochores?

Answer 22

protein complex on a sister chromatid that a spindle binds to

Question 23

What direction do sister chromatid kinetochore poles face during meiosis I?

Answer 23

the same

Question 24

What direction do sister chromatid kinetochore poles face during meiosis II?

Answer 24

opposite

Question 25

What 2 things occur during anaphase?

Answer 25

1) chromatids are unbound from each other by separate by cleaving cohesions 2) Chromosomes segregate to poles rapidly by shortening of spindles

Question 26

What occurs during telophase?

Answer 26

the physical separation of cells

Question 27

In what three ways does meiosis I differ from mitosis?

Answer 27

1) Homologous chromosomes are separated in meiosis I and sister chromatids are separated in mitosis 2) Synaptonemal complex holds homologous chromosomes together during meiosis I, cohesions in meiosis II 3) cross over does not occur in meiosis II

Question 28

When does crossing over occur?

Answer 28

during prophase I

Question 29

What is crossing over?

Answer 29

homologous chromosomes forms chiasmatas and swap DNA segments

Question 30

How does bouquet formation occur?

Answer 30

One end of the each chromosome attaches to the nuclear membrane and the nuclear membrane rearranges with the help of pairing centers to form a bouquet and pair homologs

Question 31

What is the synaptonemal complex?

Answer 31

a protein structure that forms during meiosis I to hold homologous chromosomes together

Question 32

What is a chiasmata?

Answer 32

Point of contact between non-sister chromatids of homologous chromosomes where crossing over occurs

Question 33

Two causes of recombination in meiosis?

Answer 33

crossing over and independent assortment? between homologs or sister chromatids?

Question 34

What does SPO11 do?

Answer 34

make double stranded breaks to facilitate crossing over

Question 35

What is oogenesis?

Answer 35

production of a haploid secondary oocyte via meiosis

Question 36

What is a polar body and its function?

Answer 36

A nonfunctional cell produces during oogenesis that essentially serves to discard chromosomes

Question 37

What stage are female oocytes arrested at when they are born?

Answer 37

Prophase I

Question 38

What stages does a primary oocyte go through and arrest at during ovulation?

Answer 38

meiosis I and arrests at metaphase II as a secondary oocyte

Question 39

What stages does a secondary oocyte go through after fertilization?

Answer 39

completes meiosis II

Question 40

What is non disjunction?

Answer 40

When chromosomes fail to separate properly during cell division resulting in an abnormal amount of chromosomes in daughter cells

Question 41

What is aneuploidy and a common cause?

Answer 41

condition of having an abnormal number of chromosomes in haploid set; disjunction

Question 42

What is euploidy?

Answer 42

variation in the number of sets of chromosomes

Question 43

What is monosomy?

Answer 43

When one chromosome in a haploid set is missing

Question 44

What is trisomy?

Answer 44

an extra chromosome exists in a haploid set

Question 45

what is tetrasomy?

Answer 45

four copies of chromosomes in a set

Question 46

What is alloploidy?

Answer 46

two or more sets of chromosomes come from two different species

Question 47

What is an allodiploid?

Answer 47

There are only 1 homolog of each chromosome and chromosomes come from two different species

Question 48

What is mosaicism?

Answer 48

Organism contains a subset of cells that are genetically different from the rest and results in genetic abnormalities after fertilization

Question 49

What is a bilateral gynandromorph?

Answer 49

half of the body develops as male and the other as female

Question 50

How does a bilateral gynandromorph result?

Answer 50

An XX female loses an X during development

Question 51

What is autoploidy?

Answer 51

When nondisjunction results in an individual having more or extra chromosomes in each set

Question 52

What is translocation?

Answer 52

When a segment of one chromosome is attached to another chromosome

Question 53

What are reciprocal translocations?

Answer 53

two non-homologous chromosomes exchange genetic material

Question 54

What are 2 causes of reciprocal translocation?

Answer 54

1) chromosomal breakage and DNA repair 2) Abnormal crossovers

Question 55

What is a balanced translocation?

Answer 55

translocation where equal amount of genetic material is exchanged

Question 56

Is a reciprocal translocation balanced or unbalanced?

Answer 56

balanced

Question 57

What is a simple translocation?

Answer 57

translocation of genetic material in one direction and is often associated with phenotypic abnormalities or lethality

Question 58

What is a roberstonian translocation?

Answer 58

break occurs near centromeres of two non-homologous chromosomes and larger fragment fuse at centromeres regions to form one large chromosome and smaller segments are lost or form small chromosome

Question 59

What genera is robertsonian translocation associated with?

Answer 59

Transition from great apes to humans