BIOL 80A Final | Gametogenesis

what is gametogenesis and what process does it involve?

the production of sperm and eggs (male and female gametes, respectively), and involves a type of cell division called meiosis

what type of cells does meiosis produce, and how many chromosomes do they contain?

it produces haploid cells (gametes) with one of each chromosome in the genome

how do non-gamete cells in the human body differ in their chromosome count from gamete cells?

all other (non-gamete) cells in the human body have two, or a pair, of each chromosome (making them diploid)

how many unique chromosomes do humans have in total, and what categories are they split into?

humans have 24 unique chromsomes (22 autosomes and two “sex” chromosomes, X and Y)

what types of cells are human egg and sperm?

human egg and sperm are gametes

how many chromosomes are in a human gamete (egg or sperm) cell?

gametes have a complete set of 23 chromosomes (22 autosome, and one sex chromosome, X or Y)

what term describes cells that carry only one copy of each chromosome in their complete set?

haploid

what types of cells are all non-gamete cells in the human body?

somatic cells

what term describes somatic cells, meaning they have a pair (or two copies) of each chromosome?

diploid

how many total individual chromosomes are in a human diploid (somatic) cell?

46 individual chromosomes (two complete sets, one maternal and one paternal)

what are the two types of cell division?

mitosis and meiosis

what is mitosis?

cell division where two resulting cells inherit identical and complete genomes

what is meiosis?

cell division where the four resulting cells inherit half the chromosomes of the parent cell.

what type of human cells undergo mitosis?

somatic cells (body cells, e.g., skin, bone, blood cells) undergo mitosis for growth and repiar

how many chromosomes does a human somatic (mother) cell have before mitosis?

46 chromosomes (diploid)

how many chromosomes do the resulting human daughter cells have after mitosis?

46 chromosomes each (diploid), identical to the mother cell

is the genome of the daughter cells in mitosis identical to the mother cell?

yes, the daughter cells are genetic clones of the parent cells

what type of human cells undergo meiosis?

gametes (sex cells: sperm and eggs) undergo meiosis to produce cells for sexual production

how many chromosomes does a human germline (mother) cell have before meiosis

46 chromosomes (diploid)

how many chromosomes do the resulting human cells have after meiosis I?

23 chromosomes (haploid) with duplicated chromatids in each of the two cells

how many chromosomes do the final resulting human cells have after meiosis II?

23 chromosomes each (haploid) in each of the four final cells

are the daughter cells in meiosis genetically identical to the mother cell?

no, meiosis produces four genetically distinct haploid cells due to processes like crossing over and independent assortment.

what is the purpose of meiosis?

to produce haploid gametes for sexual reproduction and to create genetic diversity

what does meiosis ensure at fertilization?

meiosis ensures a normal complement of paired chromosomes when a haploid sperm and a haploid egg fuse together

what is a zygote?

the zygote is the initial fused cell that results from fertilization (the fusion of a haploid sperm and a haploid egg), which then becomes the developing embryo.

what types of cells fuse together during fertilization?

a haploid sperm and a haploid egg fuse together during fertilization

what is oogenesis?

the process of producing eggs (ova) in the ovaries

what is oogonia (singular: oogonium)?

female germ cells that divide by mitosis during fetal development to produce primary oocytes

what are primary oocytes?

diploid cells (2n) produced from oogonia that are arrested in prophase of meiosis I until puberty

what are the number of primary oocytes at birth vs. puberty?

approximately 1-2 million at birth; declines to approximately 400,000 at puberty, and zero by the end of menopause

what event triggers a primary oocyte to complete the first meiotic divison?

hormones released at puberty cause the development of follicles each month, driving this process.

what are secondary oocytes?

a large, haploid cell (1n) that recieves most of the cytoplasm and organelles after the unequal first meiotic division. it is arrested in metaphase II of meiosis.

what is a polar body?

a small cell produced during the unequal meiotic divisions that dies off and degrades. a second one is formed upon fertilization.

what is ovulation?

the process where the secondary oocyte is released from the ovary and travels through the fallopian tubes

what happens if a secondary oocyte is fertilized?

it completes meiosis II, producing a second polar body and a haploid egg (ovum), which fuses with the haploid sperm to form a diploid zygote (fertilized egg).

what is a diploid (2n)?

a cell containing both sets of chromosomes (46 total in humans)

what is a haploid (1n)?

a cell containing a single set of chromosomes (23 total in humans)

what is an ovarian follicle?

a structure within the ovary that includes the developing oocyte and the supporting cells around it

what is folliculogenesis?

the process of the oocytes growing and developing within the ovarian follicles

what happens to the ruptured follicle after ovulation?

it becomes a corpus luterum, which eventually degrades

what is spermatogenesis?

the process of sperm production?

what is spermatogonia (singular: spermatogonium)?

male germ cells (stem cells) that divide by mitosis in the fetal testes to produce more spermatogonia and primary spermatocytes

when does the production of sperm begin?

it begins during fetal development with germ cell division, but the meiotic process starts at puberty

what are primary spermatocytes?

cells that enter meiosis at puberty to form secondary spermatocytes

what are secondary spermatocytes?

haploid cells formed during meiosis I; they complete meiosis II to give rise to four spermatids

what are spermatids?

haploid cells that are the result of completed meiosis. they undergo spermiogenesis to transform into mature sperm

what is spermiogensis?

the morphological transformation process where early spermatids develop into functional sperm (spermatozoa).

how long does the entire process of spermatogenesis take?

approximate 64 days

how often are sperm produced?

constantly throughout a male’s life starting at puberty, though production declines slowly after age 35

what is the typical daily sperm production rate?

between 100-300 million sperm per day

where in the testes does sperm formation occur?

in the walls of the seminiferous tubules

what are sertoli cells?

cells located within the seminiferous tubules that nourish developing sperm and promote their development

what are interstital cells of leydig?

cells located between the seminiferous tubules that produce testosterone once a male reaches adolescence

where do sperm mature after developing flagella?

in the epididymis, before moving to the vas deferens

how big is a sperm cell vs a female oocyte?

a sperm cells’ volume is 85,000 times less than that of the female oocyte

what does the head of the sperm contain?

it contains the haploid nucleus with very little cytoplasm

what is a acrosome?

a “cap” structure covering most of the sperm head; it is filled with enzymes essential for fertilization

what is inside the mid-piece of the sperm?

tightly packed with mitochondria to produce ATP (energy) for movement

what is the flagellum (tail)?

extension from the neck and mid-piece; powered by ATP to enable the sperm cell to move.