reproduction n a lil dna Flashcards
Function of sepal
Enclose and protect the bud
the “leaf” thing below flower
function of Petals
colourful and fragrant, they attract pollinators to the flower
function of Anthers
Sacs where meiosis occurs and pollen grains develop. Pollen grains house the cells that develop into sperm.
function of Carpel
Long slender style with sticky stigma for pollen grain deposition.
style+stigma+ovary
function of Ovary
Reproductive structures called ovules, containing one developing egg (ovum) and cells that support it.
Growth of the pollen tube
Pollen grains germinate in response to sugary fluid produced by mature stigma
A pollen tube grows out of the pollen grain and the male gamete forms in the tube
Pollen tube secretes enzymes to digest stigma and style tissue, growing down style.
Pollen tube enters ovary through micropyle
Tip of the pollen tube absorbs sap and bursts, releasing 2 male gametes.
Nucleus of male gamete fuses with nucleus of ovum to form zygote (fertilisation)
Pollination definition
The transfer of pollen grains from anther to stigma by wind or animal
Self-pollination definition
transfer of pollen grains from anther to stigma of the same flower or in the same plant
Prevent self-pollination
self-incompatibility: Stigma can recognise the pollen of the same flower, pollen grain cannot germinate on stigma of the same plant
Anther ripen first, stigma not ready to receive pollen, so pollen cannot be transferred to stigma of the same plant.
(Male part covering female part and only allow pollination after its own pollen sacs are removed by pollinators)
Cross-pollination definition
transfer of pollen grains from anther of one plant to stigma of another of same species.
Compare insect vs wind-pollinated
Large, brightly colored petals/Small dull petals
Nectar/No nectar
Fragrant/Odourless
Stigmas are small, compact and do not protrude out of the flower/Stigmas are large feathery and protrude out of the flower (to provide a large surface area to trap pollen)
Stamens are not pendulous and do not stick out of flower/Stamens have long pendulous filaments and protruding anthers (Pollen grains easily shaken out of anthers)
Pollen is abundant/Pollen is very abundant.
Pollen grains are large with rough surface (to cling onto insect body)/Pollen grains have smooth surfaces, tiny and light (to be carried by the wind.)
Nectar guide present on petals for insects/No nectar guide
function of Testes
producing testosterone responsible for man’s secondary sexual characteristics, producing sperm
function of Scrotum
muscles contract and relax to control temperature for sperm development warmer or cooler by moving closer or further from the main body to 2degrees cooler than body temp, allowing them to function normally.
function of sperm ducts
delivers sperm from epididymis to urethra during ejaculation.
function of prostate gland
produces fluid that nourishes sperm and provides sperm protection from naturally acidic vagina
function of Urethra
conveys at different times, urine and sperm out of body through penis.
function of Penis
Deliver sperm to vagina
function of Ovaries
produce oestrogen and progesterone, and release eggs in ovulation
function of Fallopian tubes
site of fertilisation, cilia sweep ova (eggs/ovums)
function of Uterus
thick and muscular wall allow it to grow and expand to several times its original size during pregnancy
(Blood-rich endometrium layer) is where embryo implants to draw nutrients.
function of Cervix
allows flow of menstrual blood into the vagina and directs the sperms into the uterus
function of Vagina
repository for sperm
function of Endometrium
thick and muscular wall allow it to grow and expand to several times its original size during pregnancy
Provides blood-rich endometrium layer for embryo to implant to draw nutrients.
Ovary vs testis
Both produce gametes
Ovary is located in the body while testis is located outside the body
All sex cells are produced at birth in the ovary whereas the testis only starts producing sex cells at puberty.
Sperm vs egg
Both carry DNA
Size
Motile
Given Menstrual cycle, possible days fo fertilisation?
Menstrual cycle begins on day__. (where there are dots) as breakdown of endometrium happens on day__.
Ovulation happens on the 14th day of the menstrual cycle,
Making possible days __ and __ as the egg survives one day after ovulation.
Narrate Menstrual cycle
FSH stimulate growth of follicles in ovary (Repair and build-up of endometrium: oestrogen)
Developing follicles secrete oestrogen (stimulates build-up of endometrium, prevents further secretion of FSH) (Negative feedback on the pituitary gland)
High and sudden peak of oestrogen levels stimulate surge in LH and some FSH (Positive feedback on the pituitary gland)
Surge in LH stimulates maturation and rupture of follicles (ovulation)
LH stimulates conversion of follicle tissue to corpus luteum.
Corpus Luteum secretes progesterone and some oestrogen, inhibiting secretion of LH and FSH (continues thickening and maintenance of endometrium) (Negative feedback on the pituitary gland)
Falling levels of LH and FSH cause degeneration of corpus luteum. Progesterone and oestrogen level decrease, endometrium breaks down, menstrual cycle restarts.
Describe fertilisation and early development of the zygote simply
formation of a ball of cells which becomes implanted in the wall of the uterus.
State the different stages of embryo development from a zygote.
Fertilised embryo secretes human chorionic gonadotropin (hCG), which maintains the corpus luteum, which continues to secrete oestrogen and progesterone, keeping the endometrium intact.
Outer layer of cells of blastocyst form part of the placenta.
Amnion enclose embryo
Embryo develop finger-like chorionic villi on the placenta that help implant embryo to endometrium
function of amniotic sac
Protection (cushion from external trauma)
Constant temperature
Free movement for foetal muscle development (and lubrication)
Practice swallowing, feeding
function of Plancenta
It has finger-like chorionic villi that increases the surface area to volume ratio for faster diffusion of oxygen and nutrients (and protective antibodies) from maternal blood to foetal blood and diffusion of metabolic waste from foetal blood to maternal blood. (excreted by mother’s kidneys)
Umbilical cord definition
circulatory pathway that connects embryo to chorionic villi of the placenta
function of Umbilical cord
Transport oxygen and nutrients to the foetus (umbilical vein: oxygenated blood) and waste products from the foetus to the placenta (umbilical artery: deoxygenated blood)
Physical, surgical, chemical and behavioural contraception
Physical: Condom, diaphragm
Surgical: Vasectomy, tubal ligation
Chemical: spermicide, IUD, pills
Behavioural contraception: Rhythm method
Features of contraception
require a doctor to be administered
do not protect against STIs
How IUD works
IUD with copper provokes an immune response against sperm and eggs that destroys them
Hormones on IUD inhibit ovulation,
Effect against implantation
How Contraceptive pills works
Contains oestrogen and progesterone
That prevents ovulation by decreasing LH and FSH levels
Low FSH prevents follicle maturation
Low LH prevents ovulation
Describe in vitro fertilisation
in vitro fertilisation as the union of an egg and sperm in a laboratory followed by implantation of the zygote into the uterus.
Relationship between DNA, genes and chromosomes.
Each chromosome is made up of 1 DNA coiled tightly around a core of histone proteins.
1 DNA is made up of several sections of sequences of nucleotides that result in different genes.
Each gene controls formation of a single polypeptide, determining a phenotype.
COMPARE (what elements? in the case of DNA)
Building blocks: peptides vs nucleotides
Elements: CHONS vs CHOPN
Bonds: peptide bonds and phosphodiester bonds
Location: plant storage organ vs animal nucleus
role of condensation reactions in joining the components (nucleotides, di-, poly-)
Nucleotide:
nitrogenous base+pentose sugar (deoxyribose sugar)+phosphate group + 2H2O 2 water molecules formed
Dinucleotide: phosphodiester bond: covalent bond between 5’-phosphate group of one nucleotide and 3’OH group of another nucleotide. 1 water molecule is lost in the process.
Polynucleotide: Condensation reactions between the phosphate group of one nucleotide and the sugar group of another nucleotide form nucleic acid (polynucleotide)
Note: Hydrogen bond is not condensation.
State and explain rule of complementary base pairing, antiparallel orientation and hydrogen bonding in the formation of DNA double helix.
- A-T (2 hydrogen bonds), C-G (3 hydrogen bonds)
- Antiparallel structure
DNA is made up of two antiparallel strands of alternating deoxyribose sugar and phosphate groups
Explain: DNA stability
Explain how DNA molecule structure contributes to DNA stability
Nucleotides are joined together by strong covalent phosphodiester bonds with one base attached to each sugar molecule along the strand to form the sugar-phosphate backbone, contributing to DNA stability.
Antiparallel(asking structure). It allows for complementary base pairing with two hydrogen bonds formed between A and T and three hydrogen bonds formed between C and G. Hydrogen bonds are formed between complementary bases. Although weak by itself, they provide support to DNA structure collectively.
