Cell Division - 16.3

Question 1

What happens when somatic cells reproduce?

Answer 1

They have the same number of chromosomes as the parent cell (the new cells?

Question 2

How many chromosomes does a zygote have?

Answer 2

23 pairs - one pair from each parent

Question 3

Where are haploid gametes created in?

Answer 3

The ovaries and testes

Question 4

What are the two key outcomes of meiosis?

Answer 4

• Recombination
• Reduction division

Question 5

What is reduction division?

Answer 5

When the daughter cells have fewer chromosomes than the parent cell.

Question 6

What is recombination?

Answer 6

Genetic recombination that gives rise to offspring that are genetically different from one another and thier parents.

Question 7

What are the four distinct phases of meiosis?

Answer 7

Prophase, metaphase, anaphase, and telophase
* Two rounds (meiosis I and meiosis II)

Question 8

Must a germ cells chromosomes be replicated before meiosis?

Answer 8

Yes

Question 9

What is each germ cell of duplicated chromosomes made of?

Answer 9

A pair of identical sister chromatids

Question 10

What happens in prophase 1?

Answer 10

• Each pair of homologous chromosomes line up side by side - synapse
• Homologous chromosomes pair up
• Each pair consists of two sister chromatids - now four - forms a tetrad

Question 11

What happens in metaphase 1?

Answer 11

• Spindle fibers attaches to the centromere of each chromosome
• Spindle fiber attaches to one pair of sister chromatids in the tetrad - other spindle from opposite pole attachés to the other pair of sister chromatids
• Spindle fiber guides each tetrad to the equator of the cell
• At equator they line up in homologous pairs

Question 12

What happens in Anaphase 1?

Answer 12

• Spindle fibers shorten
• Homologous chromosomes separate from one another
• Sister chromatids are held together so centromeres do not split
• A single chromosome (made up of two sister chromatids) moves to each pole of the cell

Question 13

What happens in Telophase 1?

Answer 13

• Homologous chromosomes begin to uncoil and spindle fibers disappear
• Cytoplasm is divided and a nuclei membrane forms around each group of homologous chromosomes - two cells are formed
• Haploid

Question 14

True or false, each cell that enters meiosis 2 is haploid?

Answer 14

True - consists of replicated chromosomes

Question 15

True or false, at the end of meiosis 2 daughter cells are still haploid?

Answer 15

True - single unreplicated chromosomes

Question 16

What does meiosis form?

Answer 16

Formation of genetically distinct haploid gametes

Question 17

What is the copy of chromosomes that are contributed by the female gamete?

Answer 17

Maternal origin

Question 18

What is the copy that is contributed by the male gamete called?

Answer 18

Paternal origin

Question 19

How is genetic variation ensured during meiosis?

Answer 19

• Creation of gametes that carry different combinations of maternal and paternal chromosomes
• Exchange of genetic material between maternal and paternal chromosomes

Question 20

What is independent assortment?

Answer 20

When the chromosomes from the maternal origin points to one pole - chromosome of parental origin is oriented to the other pole

Question 21

When do homologous chromosomes synapse during?

Answer 21

Prophase 1

Question 22

What is crossing over?

Answer 22

When non sister chromatids exchange pieces of chromosome in process

Question 23

What is the result of crossing over?

Answer 23

Individual chromosomes contains some genes of maternal origins and some genes of parental origin

Question 24

What is it called when chromosomes or chromatids do not separate as the should in meiosis?

Answer 24

Nondisjunction

Question 25

When does nondisjunction occur?

Answer 25

In anaphase 1 or anaphase 2

Question 26

When does nonjusdinction occur in anaphase 1?

Answer 26

When homologous pairs do not seperate to their opposite poles

Question 27

How does nonjustinction occur in anaphase II?

Answer 27

When sister chromatids do not seperate to opposite poles.

Question 28

What is monosomy?

Answer 28

When one chromosome is lost due to nondisjunction.

Question 29

What is turner syndrome?

Answer 29

* Missing X chromosome * Female characteristics are underdeveloped

Question 30

What is trisomy?

Answer 30

The gain of an extra chromosome

Question 31

What happens in down syndrome?

Answer 31

Individual is born with an extra chromosome 21

Question 32

What is the process of sperm production called?

Answer 32

Spermatogenesis

Question 33

What is the process of egg production called?

Answer 33

Oogenesis

Question 34

Where does meiosis take place in males?

Answer 34

In the testes

Question 35

What is the diploid germ cell in the male?

Answer 35

Spermatogonium

Question 36

What does puberty stimulate the spermatogonium to do?

Answer 36

Divide by mitosis into two daughter cells

Question 37

What do the two daughter cells then do?

Answer 37

* One replenishes the spermatogonia cell population * The other develops into a primary spermatocyte

Question 38

What then happens to the primary spermatocyte?

Answer 38

Undergoes meiosis 1 to form two secondary spermatocytes

Question 39

What then happens to the secondary spermatocytes?

Answer 39

They undergo meiosis II and form four spermatids.

Question 40

What are the final set of development for sperm?

Answer 40

* Head * Middle piece * Tail like flagellum

Question 41

Where does meiosis take place in females?

Answer 41

In the ovaries

Question 42

What is the diploid germ that oogenesis starts with?

Answer 42

Oogonium

Question 43

What is formed when the oogonium undergoes mitosis?

Answer 43

Two primary oocytes

Question 44

How many oocytes can be formed three months after conception?

Answer 44

Twp million primary oocytes can be found in the ovary

Question 45

When will the primary oocyte be out of prophase 1?

Answer 45

At puberty

Question 46

What kind of cytokinesis occurs in the cytoplasm of the oocyte?

Answer 46

Assymetricaly cytokinesis - first polar body and secondary oocyte (gets more cytoplasm)

Question 47

What happens when the secondary oocyte undergoes meiosis 2?

Answer 47

Second polar body is generated - also cell that will generate into a mature egg

Question 48

What time period separates meiosis I and II?

Answer 48

More than a decade

Question 49

How long is the secondary oocyte arrested till?

Answer 49

Until fertilization occurs

Question 50

How often is a secondary oocyte released?

Answer 50

Each month

Question 51

What does fusion of one ovum and sperm do?

Answer 51

Creates a single zygote

Question 52

Are fraternal twins genetically identical?

Answer 52

No

Question 53

Are identical twins genetically identical?

Answer 53

Yes

Question 54

How are fraternal things born?

Answer 54

* More than one secondary oocyte is released * If both of these oocytes are fertilized and successfully implant in the uterus - fraternal twins may be born

Question 55

How are identical twins born?

Answer 55

* If a single blastocyst or zygote divides into two bodies in the first few days of embryonic development

Question 56

Is being polypoid common in plants?

Answer 56

Yes

Question 57

Do polypoid plants produce larger flowers or fruits?

Answer 57

yes - they also have seedless fruit

Question 58

Is a watermelon diploid?

Answer 58

Yes

Question 59

Are a watermelons gametes haploid?

Answer 59

Yes

Question 60

What does a cross between a 4n watermelon and a 2n watermelon produce?

Answer 60

A triploid watermelon zygote (3n)