- Microtubules from opposite poles attach to each homologue. - Homologues are aligned at the metaphase plate side-by-side

- Microtubules of the spindle shorten (Chiasmata break). - Homologues are separated from each other and move to opposite poles

- Nuclear envelope re-forms - Sister chromatids are no longer identical because of crossing over

Chapter 11- Sexual Reproduction and Meiosis Flashcards by Chloe LaVertu

Sexual life cycle

Made up of meiosis and fertilization

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Diploid cells

Somatic cells of adults have 2 sets of chromosomes

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Haploid cells

Gametes have only 1 set of chromosomes

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Zygote first undergoes ____ to produce ____ ____

Mitosis, diploid cells

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Diploid cells then undergo ____ to produce ____ ____

Meiosis, haploid gametes

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Synapsis

Homologous chromosomes become closely associated

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Synapsis occurs during

Early prophase I

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Crossing over

Genetic recombination between nonsister chromatids

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Crossing over allows for…

Homologues to exchange chromosomal material

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Chiasmata

Site of crossing over

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Interphase period

G1, S, and G2

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Stages of Meiosis I

Prophase I
Metaphase I
Anaphase I
Telophase I

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Stages of Meiosis II

Prophase II
Metaphase II
Anaphase II
Telophase II

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Prophase I

Chromosomes coil tight and become visible. Nuclear envelope disappears, spindle forms

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Chiasmata move to the ____ of the ____ ____ before ____ ____

End, chromosome arm, metaphase I

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Metaphase I

Microtubules from opposite poles attach to each homologue.
Homologues are aligned at the metaphase plate side-by-side

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Fertilization produces new combinations

Over 70 trillion chromosomally different zygotes are possible

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Anaphase I

Microtubules of the spindle shorten
(Chiasmata break).
Homologues are separated from each other and move to opposite poles

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Each pole in Anaphase I

Has a complete haploid set of chromosomes consisting of one member of each homologous pair

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Telophase I

Nuclear envelope re-forms
Sister chromatids are no longer identical because of crossing over

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Cytokensis after Telophase I

May or may not occur

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Meiosis II

Resembles a mitotic division

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Prophase II

Nuclear envelopes dissolve and new spindle apparatus forms

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Metaphase II

Chromosomes align on metaphase plate

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Anaphase II

Sister chromatids are separated from each other

Telophase II

Nuclear envelope re-forms around 4 sets of daughter chromosomes; cytokinesis follows

Final result of Meiosis

Four cells containing haploid sets of chromosomes

Nondisjunction

Failure of chromosomes to move to opposite poles during either meiotic division

Aneuploid gametes

Gametes with missing or extra chromosomes

_____ % of embryos have some form of aneuploidy

1st characteristic of Meiosis

Synapsis and crossing over

2nd characteristic of Meiosis

Sister chromatids remain joined at their centromeres throughout meiosis I

3rd characteristic of Meiosis

Kinetochores of sister chromatids attach to the same pole in meiosis I

4th characteristic of Meiosis

DNA replication is suppressed between meiosis I and meiosis II

Sexual reproduction requires

Meiosis to produce haploid gametes (sperm and eggs)

Gametes united by fertilization to produce

Diploid zygote

Zygote develops by ____ into a new mutlicellular organisim

Mitosis

Asexual reproduction

Genetically identical cells are produced from a single parent cell through mitosis

Parthenogenesis

Females produce offspring from unfertilized eggs

Hermaphroditism

One individual has both testes and ovaries. Some may be able to change sex.

Protogyny

Female-to-male change

Protandry

Male-to-female change

Amphibians

In most species fertilization is external (eggs develop in water).

Oviparity

Fertilized eggs are deposited outside mother’s body to complete their development (like birds)

Ovoviviparity

Fertilized eggs are kept within mother to complete development, young obtain food from egg yolk.

Viviparity

Young develop within mother and obtain nourishment from her blood.

Mammals- Monotremes are ____

Oviparous

Mammals- Marsupials are ____

Vivparous

Mammals- Placentals are _____

Viviparous

Seminiferous tubles

Sites of sperm production

Leydig cells

Produce testosterone

Spermatogonium (germ cells)

Divides by mitosis to produce two diploid cells

Primary spermatocyte

Diploid cell that begins meiosis

Total haploid spermatids produced

Healthy male sperm production per day

100 to 200 millon

#of sperm in each mL

100 million

Granulosa cells

Secrete estrogen

of follicles in ovaries at birth

1 million

Stages of menstrual cycle

1. Follicular phase 2. Ovulation 3. Luteal phase

During follicular phase

Primary oocyte complete meiosis I (forming secondary oocyte)

Secondary oocyte

Starts meiosis II but stops at metaphase II, released at ovulation

Unfertilized oocyte

Disintegrates after 24 hours

Fertilized oocyte

Completes meiosis II and becomes a mature ovum

Mature ovum

Merges with sperm nucleus, forms diploid zygote

Abstinence

100% effectiviness in prevents pregnancy and STD's.

Oral contraception (birth control pill)

Combo of estrogen and progesterone shut down production of LH and FSH (no follicles develop)

Contraceptive implants

Synthetic progesterone prevents ovulation

Female condom

Fits into vagina

Male condom

Better when combined with spermicide

Diaphragm

Latex cup covering cervix

IUD

Fertilization will not occur, implantation cannot take place

Morning-after pill

Disrupts normal menstural period by blocking ovulation

RU-486

Blocks progesterone receptors on endometrial cells

RU-486 induces...

Shedding of lining and menses

Human Embryonic Development

All events that occur from time of fertilization until animal fully formed.

Extraembryonic memebranes

Embryos depend on this to protect and nourish

Average development time for humans

266 days

Induced abortion

Deliverately dislodges embryo from uterus, surgically or by drugs

Fetal side of placenta

Contributed by chorion

Maternal side of placenta

Consits of uterine tissue

Chorionic villi

Surrounded by maternal tissue

Maternal and fetal blood ____ mix

Never, exchange through walls

What moves to maternal blood

Carbon dioxide and wastes

What moves to fetal blood

Nutrients and oxygen

Mature fetal brain

Hypothalamus causes pituitary to stimulate adrenal cortex to secrete androgens

Placenta uses androgens as a...

Precursor of estrogen

Androgens stimulate production of...

Oxytocin and prostaglandin; causes baby to come out

1st stage of birth

Cervix dialtes and amnion bursts

2nd stage of birth

Baby is born and umbilical cord cut

3rd stage of birth

Placenta delivered

First milk produced

Colostrum, yellow fluid rich in nutrients and antibodies

More than ____ diseases are spread primarly through sexual activity

How many STD cases in US each year

15 million new cases

1/2 of STDs occur in

15-24 year olds