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54 Cards in this Set
- Front
- Back
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Describe binary fission. What organisms make use of it?
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DNA attaches to plasma memb, duplicates while cell gros, memb pinches, splits cell into 2 equal halves, each daughter has 1 copy of original chromosome.
Occurs in Prokaryotes |
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In humans, what is the haploid number? Diploid?
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23 = N
2N = 46 |
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What are the 4 basic stages of the cell cycle? Divide them into their two groups.
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G1,S,G2} Interphase (occurs b/t divisions)
M} Mitosis (actual cell division) |
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How would a cell in interphase appear under a microscope?
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Nucleus is membrane bound, chromomsomes are not visible (uncoiled); DNA in form of chromatin (granular)
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What occurs in G1? What is the restriction point?
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Presynthetic Gap: cell doubles in size, new organelles produced usually passing RESTRICTION PT (once past, cell is committed to division, but some cells don't pass and enter G0, such as neurons)
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What occurs in S? What happens to the number of chromosomes?
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Synthesis: each chromosome replicates and get 2 identical sister chromatids held by centromere.
Number of chromosomes stay the same, but now have 2x much DNA. |
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What happens in G2?
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Post Synthetic Gap--cell continues to grow, more organelles assemble
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What occurs in mitosis (generally)?
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Division and distribution of cell's DNA to daughter cells; Cytokinesis allows division of cytoplasm
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How would a cell in mitosis appear under a microscope?
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Chromosomes coil up, become visible
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Where are centrioles located?
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In centrosome
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What are asters?
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Spindle fibers that radiate outward from centrioles; extend toward nucleus to form spindle apparatus
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What occurs in prophase?
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Choromsomes condense, form spindle app, nuc membr dissolves, spindle fibers enter nuc, kineochores appear at centromere
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What occurs in metaphase?
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Kinetochores interact with spindle fibers to align chromosomes at metaphase plate (equitorial plate)
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What occurs in anaphase?
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Centromeres split, sister chromatids separate, chromatids pulled to opp poles by shortening of kinetochore fibers
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What occurs in telophase?
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Spindle app disappears, nuc membrane forms arou each set of chromosomes (chromosomes uncoil to enter telophase)
CYTOKINESIS occurs (cytoplasm divides into 2 daughter cells; in animals have cleavage furrow) |
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Describe budding. Which organisms utilize it?
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Unequal cytokinesis, genetically identical daughter cells
Hydra, yeast |
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Describe regeneration. Which organisms utilize it?
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Regrowth of lost or injured body part; replacement of cells by mitosis
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What is parthenogenesis? What organisms utulize it?
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Development of unfertilized egg into adult organism; orgs develop from haploid cell, therefore all of its cells are also haploid
Bees, ants |
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What occurs during S phase of meiosis?
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replicate chromosomes
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What occurs during interphase of meiosis?
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Centriole duplication
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What cells utilize mitosis? Meiosis?
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Somatic = mitosis
Gametocytes = meiosis |
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What occurs during prophase 1 of meiosis 1?
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Chromatin condenses into chromosomes, spindle app forms, nuc membrane disappears, HOMOLOGOUS chromosomes intertwine via SYNAPSIS (each homologue has sister chromatid, so each pair has 4 chromatids known as TETRAD)
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What is crossing over? What is its effect on linked genes and overall genetic variation. How does the affect the sister chromatids?
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When chromatid secitons break at corresponding parts and exchange DNA
Can unlink linked genes (GENETIC RECOMBINATION), which increases variability. Sister chromatids no longer ID |
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Define chiasmata
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Where chromosomes cross over
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What occurs in metaphase 1 of meiosis 1?
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Tetrads align at equitorial plate, each pair attaches to spindle fiber by kinetechore
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What occurs in anaphase 1 of meiosis 1?
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Homologous pairs separate to opposite poles (DISJUNCTION)
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How does disjunction account for Mendelian law?
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Each chromosome of paternal origin DISJOINS from those of maternal origin, and can end up in either daughter cell, resulting in daughter cells with unique pool of ALLELES
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What occurs in telophase 1 of meiosis 1?
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Nuclear membrane reforms at each new nucleus, cell divides by cytokinesis, each daughter cell is HAPLOID
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What is interkinesis?
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Pause that may occur between divisions in meiosis
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What occurs in prophase 2 of meiosis 2?
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Centrioles migrate to opposite poles, spindle app forms
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What occurs in metaphase 2 of meiosis 2?
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Chromosomes line up along eq plate, centromeres divide and separate chromosomes into pairs of sister chromatids
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What occurs in anaphase 2 of meiosis 2?
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Sister chromatids pulled to opposite poles by spindle fibers
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What occurs in telophase 2 of meiosis 2?
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Nuc mem forms around new (haploid) nuc; cytokinesis (2-->4 daughter cells)
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What is the purpose of the seminiferous tubules?
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Produce sperm; SERTOLI CELLS nourish sperm
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What is the purpose of interstitial cells?
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AKA CELLS OF LEYDIG; loc't between sem tubules, secrete T AND ANDROGENS
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What is the purpose of the epididymis?
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Acquire motility, mature, and are stored until ejaculation
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Where do sperm travel through during ejaculation?
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Vas deferens to Ejaculatory duct and then Urethra
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What is the pathway of sperm from birth to ejaculation?
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Seminiferous tubules
Epididymis Vas deferens Ejaculatory duct (Nothing) Urethra Penis |
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What is the purpose of the seminal vesicles?
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Provide fructose-rich seminal fluid for sperm, serves as energy
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What is the purpose of the prostate gland?
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Alkaline, milky seminal fluid to protect sperm from acidic env or female reprod tract
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What is the purpose of the bulbourethral gland?
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Viscous fluid of unk fn (pre-ejaculate)
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What is semen?
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Seminal fluid + Sperm
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Where does spermatogenesis occur? Describe the stages sperm take along this process.
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Seminiferous tubules
Spermatagonia (2N)-->Differentiation -->Primary Spermatocytes (2N) -->Meiosis 1 -->Secondary Spermatocytes (N) -->Meisois 1 -->Spermatids (N) -->Maturation -->Spermatazoa (sperm) |
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What is the function of the acrosome?
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Contains enzymes needed to penetrate outer covering of ovum
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What do ovaries consist of?
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1000s of follicles (sac that contains, nourishes, and protects an immature ovum)
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What secretes estrogen?
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Follicle cells
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Describe the path an unferitilized egg will take from the ovary.
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Ovary-->Fallopian tube-->Uterus-->Vaginal canal
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Describe the different stages of oogenesis.
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Primary oocyte (2N)
-->Meiosis 1 -->Secondary oocyte (expelled from follicle during ovulation) and Polar Body (smaller) -->Meiosis 2 AFTER fertilization |
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Describe the layers that comprise oocytes and their relation to reproduction.
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Zona Pellucida = inner
Corona Radiata = outer When both layers penetrated by sperm cell, meiosis 2 is triggered, yielding mature ovum and polar body. |
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What occurs during menopause?
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Ovaries become less sensitive to hormones that stimulate follicle dev't (FSH and LH) and atrophy
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How do sperm overcome the two layers surrounding the oocyte?
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Secretes enzymes to penetrate corona radiata
Acrosome secretes enzymes to digest zona pellucida |
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What occurs once the sperm is in contact with the membrane?
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Sperm forms acrosomal process which penetrates membrane and triggers CORTICAL RXN (ca++ enters initiating formn of FERTILIZATION MEMBRANE which surrounds zygote and prevents multiple fertilizations), sperm nucleus then enters cytoplasm and ovum completes meiosis 2
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How do monozygotic births occur?
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Single zygote splits into 2 embryos
Twins are genetically identical |
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How do dizygotic births occur?
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2 ova released in one ovarian cycle and are fertilized by 2 separatesperm, developing into 2 distinct zygotes
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