D3.1 Flashcards

Question

# The Menstrual Cycle Oocyte?

Answer 1

* The term for the **egg before it's matured.** * The **gamete** forming during **meiosis**. * At the **end of Meiosis |, it's called the primary oocye**. * It **begins Meiosis || and is called a secondary oocyte**, and is released and often then called an egg.

Answer 2

* Following fertilization the sperm's nucleus enters the egg, but **the two sets of chromosomes remain separate inside temporary nuclear membranes**. * These are called pronuclei and they undergo DNA replication separately first before merging ahead of mitosis to grow the zygote.

Answer 3

* If a women (for IVF) is given injections of FSH that cause elevated levels of the hormone that **multiple follicles in each ovary are matured --> superovulation.** * Meaning, when the surgeon goes to extract eggs from the ovary to fetilize, they can get many eggs.

Answer 4

* The hormone GnRH is **produced & released by the hypothalamus** and travels just to the **pituitary to stimulate the release of FSH and LH**. * It **controls** the entire process of **sexual development** and **gamete maturation and release.** * **FSH and LH** are then **released from the pituitary** into the bloodstream to travel to the ovaries. * The hormone is regulated by feedback mechanisms - positive and negative at different times.

Answer 5

* Secreted by the **anterior pituitary** * It's target cells are the **follicle cells in the ovary**. * It stimulates **their growth and maturaiton and as they develop, they release estrogen**. * FSH also stimulates sperm production in males

Answer 6

* Released by the **anterior pituitary**, generally in response to a positive feedback loop, whereby the **increasing levels of estrogen stimulate the release of higher levels of LH**. * When **LH levels are high, ovulation is triggered and the matured oocyte is released from the ovary**. * LH levels therefore must be regulated to release the egg at its ideal maturity for fertilization. * The LH surge is very short and used by ovulation tests to predict ovulation within a 1-2 day window.

Answer 7

* *Estrogen is a broader term for multiple sex hormones with different functions like sexual development* * An important hormone is oestradiol, which plays the role in the monthly menstrual cycle. * It **rises in response to maturing follicles and stimulating the further release of high levels of FSH and LH needed for ovulation** * It **thickens the lining for possible fertilization**.

Answer 8

* The hormone **responsible for the luteal phase** (second hald of the cycle). * It rises after ovulation and is **secreted by the corpus luteum** for about 10-12 days post ovulation. * **Retains the thick lining of the endometrium for possible pregnany** and send negative feedback messages to **stop FSH and LH release**. * If **implantation occurs, progesterone levels say high by the embryo.** * If not, they drop post ovulation leading to menstruation.

Answer 9

* IVF is an invasive and expensive medical breathrough that can enable pregnany for couples with infertility. * Women initially **takes birth control** medication to stop her natural cycle. * She then is **injected with FSH to mature many eggs**. * Those **eggs are retrieved from the ovary** and the male provides a semen collection. * Fertilisation **occurs in the lab and a 5-day embryo is then inserted into a uterus** to develop there.

Answer 10

* A group of hormones that are (generally) **released from the anterior pituitary, under the instructinons of GnRH released from the hypohtalams**. * This **stimulates the ovaries and testes to mature gametes**. * The two main gonadotropins are **Follicle Stimulating Hormone (FSH) and Lueinizing Hormone (LH).** * These both stimulate the 'gonad's. *Note that hCG is also a gondadotropin, however is only released during pregnancy.*

Answer 11

As a term it encompasses **meiosis to form the nuclei** as well as **cell differentiation** that causes the **development of the flagella for motility.**

Answer 12

* **Diploid germ cells** that go through **meiosis** to become **mature sperm cells**. * The spermatogonia first goes through mitosis, creating two small diploid cells. * One of those two will enter meioisis to become four sperm, while the other will grow and go through mitosis again in the future. * This keeps number of stem cells consistent.

Answer 13

* **Large, tightly packed cells** inside the seminiferous tubules **that provide nutrients for the developing sperm**. * Also referred to as nurse cells as they take care of the developing sperm * Secrete some proteins that aid in development

Answer 14

* The process by which **egg cells are produced**. * Involves the **meiotic divisions** of the genetic material and the **cell specialization** to form the large and complex structure of an egg cell. * More complex than spermatogensis, as the **oocyte arrests twice during meiosis, in Prophase | and then in Metaphase ||**.

Answer 15

* Humans only aim to release one mature egg each month to limit births. * However, meiosis must divide the DNA into 4 nuclei for reduction division to occur. * As only one egg will be matured, **cytokinesis is unequal, with the secondary oocyte keeping majority of the cytoplasm and the polar body being essentially just a nucleus**. * This secondary oocyte only compeltes meiosis || if it's fertilized, if that happens, another polar body is created.

Answer 16

* A **diploid germ cell capable of entering meiosis to develop into a primary oocyte in the ovary**. * The oogonium stalled in Prophase | is still a diploid cell, but called a primary oocyte so oogoniums are only found in utero.

Answer 17

* The event when **more than 1 sperm fertilizes an egg.** * Would **result in a triploid set of chromosomes**, so not a succesful pregnancy. * Hence, there are adaptations in place to prevent polyspermy from occuring to faciliate successful pregnancies.

Answer 18

* A complex **extracellular matrix (glycoprotein layer)** that changes in consistency before and after fertilization. * Before, it's like **jelly, wih accessible sperm binding sites**. * After a sperm breaks through to fertilize the egg, **enzymes are released that causes the zona pellucida to harden**, making it impenetrable to sperm.

Answer 19

* GnRH is released from the hypothalamus during puberty. * It's * It's **triggered by a protein (kisspeptin)** that's released late in childhood to stimulate puberty. * **GnRH then releases FSH and LH that stimulates ovaries and testes.** * They then **release estrogen and testosterone** which lead to the **development of secondary sexual characteristics.** * In women there'a delay (few years) before FSH and LH levels are sufficient to initiate menstruation.

Answer 20

* **Oocytes**: terms for immature eggs that haven't finished meiosis. * **Primary Oocyte**: Cell that has arrested in Prophase | of Meioisis, occurs in utero * The oogoniums begin Meiosis | before birth but stop in Prophase | as a diploid cell. * **Secondary Oocyte**:During puberty this oocyte completes Meiosis | and has entered Meioisis ||, called a secondary oocyte. * It's now a halpoid cell. * It pauses at Metaphase || and is ovulated as such and only finishes Meiois || if fertilized. * Hence, the egg that is ovulated is a secondary oocyte.

Answer 21

* The zona pellucida covers the binding sites for sperm to insert their nuclei into the egg. * This prevents easy penetration of sperm (could otherwise result in polyspermy) * Sperm do however need to be able to get through this layer. * This is done by using the enzymes that are contained in the acrosome head. * **The acrocome head detatches and the enzymes then degrade the coat to reach the binding site.**

Answer 22

* After sperm has inserted its DNA into the egg cells, **cortical granules release enzymes**. * These enzymes cause a reaction that leads to the **hardening of the zona pellucida and resulting removal of attachment sites** * This prevents polyspermy upon fertilizaiton

Answer 23

* Once a fertilized egg, which enters mitosis, **exponentially increases and reaches the uterus** (7-10 days post ovulation). * It's **100 cells big with a distinct shape, consisting of an outer layer of cells**, inner group of cells and fluid cavity. * The stage the **embryo is at for implanting into the endormetrium**.

Answer 24

* The **surrounding layer of cells around the spherical blastocyst.** * These cells will go on to form the **fetal portion of the placenta** and the umbilical cord.

Answer 25

* The **process by which the embryo sinks** into the **highly vacularized endormetrium wall** of the uterus. * Following fertilization, the embryo is 100 cells but very small, and has **limited nutrients used for simple metabolism**. * For growth to occur the embryo must access the mother's blood source. * The **thick, vacularizied layer was sustained by high progesterone levels** to ensure the **embryo can be embedded in the uterus to access the nutrients from blood supply**.

Answer 26

* Lab produced anitbodies (proteins, not living cells) that are **made from pure cultures of B cells** that are cloned and will mass produce in a **single type of antibody** that is sensitive to **one single antigen**. * Created for targeted specific tools to treat disorders * Produced and used in home pregnancy tests

Answer 27

* **Specialized tissues that arises from the trophoblast** of the embryo and material uterine tissue. * The 'pancake' shaped (flattened disc) structure that **enables a connection between maternal and fetal blood vessels**. * Necessary, as the embryo grows to **maintain the surface area to volume ratio needed for efficient diffusion of materials**. * The **maternal blood leaves its capillairies** to best **faciliate diffusion with embryonic capillaries**.

Answer 28

* A **protective sheath that covers the important fetal blood vessels**, which carry blood to and from the placenta for material exchange. * Forms two vessels that **deliver deoxygenated blood to the placenta**, and one larger vessel that **returns oxygentated blood to the fetus's heart** (a vein).

Answer 29

* The **fetal blood vessels** branch into numerous projections (placenta villi) that are **surrounded by maternal blood** (outside of vessels in intervillous spaces). * These projections are **spread out to maximise the surface area** for **rapid diffusion of materials** between mum and baby.

Answer 30

* A peptide hormone that faciliates bonding - **made in the hypothalamus and released by the posterior pituitary**. * Has a role in attachment, but specifically for reproduction as it **stimulates labour/birth and the onset of breastfeeding**. * Operates by positive reinforcement loops in both birth & breastfeeding.

Answer 31

* The period in a female's life when her mentrual cycle first becomes **less predictable** and then eventually stops altogether. * Generally begins in a woman's 40s, but there's variation. * Occurs becuase **ovaries stop producing estrogen & progesterone, usually because there's no viable follicles maturing to trigger the release anymore**. * Hormone changes cause symptons: trouble sleeping, hot flushes, muscle & hair loss.

Answer 32

* The **trophoblast cells of the embryo secrete hCG** and later the embryonic placenta cells secrete it. * Remember that the **corpus luteum will secrete progesterone** for about 12 days post ovulation and then will break down and **progesterone levels drop, stripping the endometrium**. * If pregnancy is **successful**, the embryo must signal the **corpus luteum to continue producing progesterone** until placenta is fully formed.

Answer 33

* Monoclonal antibodies can be made that specifically **bind to the anigen on hCG.** * These antibodies are attached to pregnancy tests. * If **hCG is present it binds to these antibodies.** * Often a second antibody with a dye has been mixed in (often urine) * So, if **hCG is present the dyed antibodies will stick to it and then it will also bind to the anitbodies attached to the stick** creating a visable dye if hCG is present.

Answer 34

* During the menstrual cycle progesterone contributes to the **maintaining of the uterine wall**. * During early pregnancy its necessary to help the embryo stay implanted in the uterus * When placenta has formed it continues to release progesterone **that inhibits uterine contractions to prevent labour**. * As the fetus approaches a full term of pregnancy it stops producing as much hormone, allowing for contractions to occur which releases oxytocin.

Answer 35

* Fetus **grows larger, causes strain on walls of uterus** which then increases. * The production of **progesterone decreases, the uterus starts to contract** which pushes the baby's head into the cervix. * This causes the **cervix to signal the hypothalamus** to **signal the pituitary to release oxytocin**. * Oxytocin then **causes the uterine muscle contractions** (more strain on the cervix and thus more oxytocin) * This positive loop continues with rising oxytocin levels until birth is completed

Answer 36

HRT is supplementary oestrogen and progesterone that helps increase low levels at menopause. **Advantages**: Can alleviate symptoms like hot flushes, mood swings, and emotional changes. The added estrogen can strengthen bones and reduce the risk of osteoporosis. **Disadvantages**: Higher estrogen is linked to breast cancer, and correlation to CDH.

Answer 37

* Refers to the fact that flowers **contain both male and female reproductive structures**. * One flower produces **male and female gametes**. * Male parts are called the **staMEN** * Female parts are called **carpel or pistil.**

Answer 38

* The food source of the seed. * The female ovule maintains polar bodies/nuclei * Then when pollen enters, one fertilizes the ovule to make a 2n zygote and another pollen nucleus fertilizes the two polar bodies and this triploid mass develops into the endosperm.

Answer 39

* Pollen from a flower can sometimes land on a stigma of the same plant. * To reduce inbreeding, this often fails to create the pollen tubes necessary for it to reach the ovary. * This is done through evolution of alleles. * **Plants can't create pollen tubes if the same incompatibility alleles are present**. * **Alleles are an adaptation to prevent self-pollination**

Answer 40

* The stages of early growth in a seed that will allow it to develop into a plant. * An **adaptation plants have to manage harsh environments** is for seeds to remain dormant until favourable conditions for successful growth. * When this happens, seeds begin to germinate.

Answer 41

* The **uptake of water from the soil** via a small opening (micropyte). * Water **triggers the start of metabolic pathways** which break down food stores to increase rates of cell resp. and protein synthesis. * This **allows plant embryo inside seed to grow**. * The growing plant & absorbed **water both exert pressure for the embryo to sprout out** of tough seed coat.

Answer 42

* The endosperm becomes used for plant growth - the original endosperm becomes a cotyledon, **which sprout off from the developing stem - they are the first 'leaves'** and can photosynthesize after sprouting. * Not as effective as mature leaves that develop later in growth. * If it splits into two leaves - dicot, one leaf - monocot.

Answer 43

* **Male**: Pollen. Pollen consists of individual pollen grains which is actually two haploid nuclei to faciliate the double fertilization. * **Female**: Ovule. One Ovary contains multiple ovules, which can each be fertilized and become on embryo --> seed. * Ovary becomes the fruit (many seeds in a fruit) * Each ovule contains many haploid nuclei (one will be fertilized and others will contribute to the endosperm & seed structure.

Answer 44

* **Cross Pollintation**: the landing of pollen from one flower onto the flower of ANOTHER PLANT (not just another flower). * Generates more genetic diversity & the hybrid offspring are often healthy and stronger. * **Self Pollination**: Still creates non identitical offspring, as the gametes are unique, but is associated with inbreeding challenges (reduced health due to greater genetic similarity.)

Answer 45

* Purpose: **To attract pollinators**. * Often colourful, scented and sometimes contain guidelines that attract the pollinator into the center of the flower.

Answer 46

* Purpose: **Surrounds the developing flower bud, protecting it and photosynthesizing for it.** * Often green and will often fall back and look small after blooming.

Answer 47

* Purpose: **The top part of the stamen & contains pollen sacs that make & release pollen** * Appear large and green before pollination and then shrivelled and furry when covered in pollen.

Answer 48

* Purpose: **stalks that hold up anthers, and elevate them away from the stigma (female part) of the plant.** * This helps ensure that pollen is picked up by an approaching pollinator and transferred without landing on its own stigma.

Answer 49

Purpose: **The top external part of the pistil/carpel (female part of the plant) that often excretes a sticky subtance/is spread out to increase surface coverage, which sticks pollen grains on it from travelling pollinators/wind.**

Answer 50

* Purpose: **The tube that connects the stigma to the ovary, which allows the stigma to be help higher to increase the chance of pollenation.** * Once pollen lands, pollen tubes are formed in the style that **transport the pollen grains** down to the ovary containing the ovules.

Answer 51

* Purpose: **Produces and stores the female gamete (ovules).** * The ovary contains ovules that can be fertilized at once. * When ovules are fertilized, the ovary will ripen into a usually edible fruit intended to attract herbivores to help dispere the seeds.

Answer 52

* Mature the pollen and ovules at **different times, so that ovules are immature** at the time of pollen release. * Use of **wind/water** can move pollen away, as are animal pollinators (bees, birds, bats). * Self-incompatability mechanisms assist if pollen does land on a flower of the same plant.

Answer 53

* Done by **herbivores, water or wind** - some seeds can be ejected out/have prickles to stick on fur. * Seeds need to be in an envrionment that has nutriends for growth. * It's often beneficial for the new offspring plant to be away from parent plant that's already utilizing that location's resources --> hence dispersal/movement of seeds away.

Answer 54

1. Water to initiate germination 2. Oxygen for cell. resp for ATP to allow for growth. 3. Appropriate temperature & pH for the enzymes involved in the metabolic processes to function.

D3.1 Flashcards

Reproduction (78 cards)