Meiosis

What is a gene?

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

diploid cell

(2n) has two sets of chromosomes - body cells (somatic) Human 2n=46

haploid cell

A cell containing only one set of chromosomes (n). - reproductive cells (gametes, sperm, egg) Human n=23

What event must take place during interphase before a cell proceeds to division?

DNA replication

What do gametes do?

Four cells have formed, each nucleus contains a haploid number of chromosomes. (4 different haploid cells)

What cells are left at the end of meiosis I

Four haploid and they are all different

What is the third stage of meiosis I

Anaphase I- homologous chromosomes move to opposite poles (homologous chromosomes separating but sister chromatids stay together)

What is the third stage of meiosis II

Anaphase II- sister chromatids pulled apart, centromeres split

At which stages of meiosis I are the cells diploid and at which stages are they haploid

Haploid- telophase I Diploid- all other stages

In meiosis I, during anaphase I, which structures separated - - homologous chromosomes or sister chromatids

Homologous chromosomes

What's the difference between anaphase I and anaphase II?

In anaphase I, homologous chromosomes separate In anaphase II, centromere's split and sister chromatids separate

Spermatocytes oocytes (2n) — meiosis ——————> Sperm egg (n)

Not sure what this is but she wrote it on the board for notes so I'm assuming it's important

2n / \ <— meiosis I O O / \ / \ <— meiosis II o o o o

Not sure what this is but she wrote it on the board for notes so I'm assuming it's important (I think it's the division of cells)

What cell do you start out with in meiosis I

One diploid

Before fertilization, what happens to the secondary oocyte?

Proceeds to meiosis II

At which stage of meiosis are the chromosomes

Prophase 1

List the stages of meiosis I

Prophase I, Metaphase I, Anaphase I, Telophase I

What is the first stage of meiosis I?

Prophase I- spindle fibers form, nuclear membrane disintegrates, DNA coils, crossing over, pairing of homologous chromosomes

What is the first stage of meiosis II

Prophase II- chromosomes condenses, spindles form each new cell, spindle fibers attached to chromosomes

In meiosis II, during anaphase II, which structures separated -- chromosomes or sister chromatids

Sister chromatids

TRUE OR FALSE The new cells have one copy of half the genetic information in the original cell

TRUE

True or false: The new cells have two copies of half of the genetic information in the original cell

TRUE

What is the fifth stage of meiosis I

Telophase I- spindle fibers break down, chromosomes uncoil in form two nuclei, cell divides

What is the fourth stage of meiosis II

Telophase II- four nuclei form around chromosomes, spindles break down, cell divides

What are crossover points called?

chiasma

What is the ploidy of the zygote produced by fertilization— haploid or diploid

diploid

How many replicated chromosomes does the cell contain during prophase?

four

At the end of meiosis I, are the cells haploid or diploid?

haploid

What are gametes?

sex cells (sperm and egg)

What type of organs are the cells that enter meiosis I found

sex organs

What two structures make up a single replicated chromosome?

sister chromatids

At the end of meiosis II in males, what cells are produced?

spermatids

Once the chromosomes have formed a pair, what are they called?

tetrads

At which stage in meiosis I does the pairs of homologous chromosomes come together?

Late prophase I

Where did each of the cells come from that started meiosis II

Meiosis I

What is the second stage of meiosis I

Metaphase I- line up at the equator, and centromeres attach to spindle fibers

What is the second stage of meiosis II

Metaphase II- centromeres of chromosomes line up randomly at the equator of each cell

Are the genes on a recumbent chromatid the same as the original chromatid

No

Will the cells at the end of telophase I be genetically identical to each other?

No

Describe what happens to the chromatids during crossover

They exchange pieces of chromosome (DNA)

What do spermatids eventually become?

mature sperm

During fertilization which two cells come together?

mature sperm and secondary oocyte

Are the alleles on a recombinant chromatid the same as the original chromatid?

no they are mixed

What phrase is used to describe the chromatids after crossing over takes place in the homologous chromosomes separate

recombinant chromatids

What is the name given to the cells produced at the end of meiosis I in females

secondary oocyte

What is the name given to the cells produced at the end of meiosis I and males

secondary spermatocyte