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Bio Chapter 2

Terms in this set (44)

what is interphase

what is G0

what is chromatin
G1, S, G2 part of the cell cycle


not interphase but cells not dividing spend time here and live and carry out function w/o preparing for division


this is the less condensed form chromo are in during interphase, the DNA needs to be accessible to RNA poly to transcribe

makes them not visible with light microscopy
G1 Stage: Presynthetic Gap

what happens in this stage?
cells create organelles for energy and protein production (mito, ER, ribo), while also increasing their size

also there is a restriction point that controls passage to S phase
S Stage: Synthesis of DNA

what happens in this stage
cell will replicate its genetic material so each DC gets an identical copy

after replication, the chromo have 2 identical chromatids that are bound together by a region known as the centromere

rmr even tho chromosomes have 3 chromatids, the number of chromosomes is still 46 (replicated or not) but the cells now have twice as much DNA as the cells in G1
G2 Stage: Postsynthetic Gap

what happens in this stage
cell passes through quality control checkpoint to make sure there are enough organelles and cytoplasm for 2 DC and that DNA replication was correct
M Stage: Mitosis

what happens in this stage
this is mitosis along with cytokinesis happens in somatic cells (nonreproduction cells)

Mitosis has prophase, metaphase, anaphase and telophase

cytokinesis is the splitting of the cytoplasm and organelles b/t the 2 DCs
checkpoints

what happens at the restriction point or the G1/S checkpoint

what protein controls the restriction and G2/M checkpoint

what happens at the G2/M checkpoint
check if DNA is in good condition for synthesis and if damage the cell goes into arrest until DNA repaired


p53


check if cell is at correct size and organelles have been replicated correctly
what are cyclins and cyclin-dependent kinases (CDK) and how are they activated
they are mlcs responsible for the cell cycle

CDKs need the presence of the right cyclin to be activated and the [ ] of these cyclin increases or decreases at different stages of the cell cycle

cyclin binds to CDK to form CDK-cyclin complex and this can phos transcription factors that then promote transcription of genes needed for the next stage
cancer

what is the mutation found in cancer
rmr cancer happens when the quality check fails and inadequate cells replicate

mutation of the gene that makes p53 called TP53

this mutations means the cell cycle is not stopped to repair damaged DNA and mutations can accumulate

= cancerous cells that divide uncontrollably and create tumours
Mitosis: Prophase

what happens in prophase in order?
condensation of chromatin into chromosomes

centrioles pairs separate and move towards opposite poles of the cell

centrioles begin to form spindle fibers (made of microtubules) and this establishes the centrosome has one of the microtubule organizing centers of the cell and the other is the basal body of a flagellum or cilium

spindle fibers radiate out

nuclear membrane dissolves so spindle fibers can contact chromosomes
what are centrioles
located outside the nucleus in regions known as centrosomes and are responsible for correct division of DNA
what are kinetochores
appear at the centrosome

protein structures located on the centromeres that serve as attachment points for specific fibers of the spindle apparatus called kinetochore fibers
Mitosis: Metaphase

what happens in metaphase?
centriole pairs are now on opposite ends of the cell

kinetochore fibers interact with the fibers of the spindle apparatus to align the chromosomes at the metaphase plate

this plate is equidistant from the 2 poles of the cell
Mitosis: Anaphase

what happens in Anaphase?
the centromeres split so that each chromatid has its own distinct centromere which allows the sister chromatids to separate

the sister chromatids are pulled towards opposite poles of the cell by the shortening ogf the kinetochore fibers
Telophase and Cytokinesis

what happens in telophase

what happens in cytokinesis
telophase is just reverse of prophase

spindle apparatus disappears and nuclear membrane reforms around each set of chromosomes and the nucleoli reappear

chromosome uncoil like they are in interphase


happens after telophase, separation of organelles and cytoplasm

rmr that after about 20 to 50 divisions the cell cannot be divided continuously (finite number of divisions)
what cells does meiosis occur in

what is similarity b/t mito and meio

what is difference b/t mito and meio
gametocytes (germ cells) and results in 4 nonidentical sex cells called gamete


genetic material is duplicated, chromatin is condensed to make chromo, MT radiate from centrioles to divide genetic content


mito has one round of replication and division but meio has one round of replication followed by 2 rounds of division

meio 1 homologous chromosomes are separated to make hap DCs (called reductional division)

meio 11 separates sister chromatids w/o a change in ploidy (meaning it doesn't go from dip to hap but rather hap to hap) (called equational division)
Meiosis 1: Prophase 1

what happens in prophase l that is similar to mitosis prophase

what is synapsis

what is crossing over
spindle apparatus forms and the nucleoli and nuclear membrane disappear


homo chromo come together (synapsis), each synaptic pair has has 4 chromatids so its called a tetrad and the homo chromo are held together by group of proteins called synaptonemal complex


chromatids of homo chromo can break at the point of contact called the chiasma and exchange equivalent DNA pieces

can have single or double crossover that occurs

rmr this is b/t homo chromo not sister chromatids because sister chromatids are identical so CO b/t those changes nothing

now each DC has a unique pool of alleles some that are maternal and some paternal
Meiosis 1: Prophase 1

what is genetic recombination

what is Mendels second law (of independent assortment)
can unlink linked genes and increase the variety of genetic recombination that can be produced via gametogenesis

linkage= tendency of genes to be inherited together


CO explains this law

states that the inheritance of one alleles has no effect on the likelihood of inheriting certain alleles for other genes
Meiosis 1: Metaphase 1

what happens in this stage?
tetrads align at the metaphase plate

each pair attaches to a separate spindle fiber by its kinetochore

so in mitosis each chromo has 2 spindle fiber but in meio 1 they only have one
Meiosis 1: Anaphase 1

what happens in this stage?
homo pairs separate to opposite sides of cell

process is called disjunction and it accounts for Mendel's first law (of segregation)

random distribution of maternal and paternal chromo to each DC and this is called segregation
Meiosis 1: Telophase 1

what happens in this stage?
nuclear membrane forms around each new nucleus

cell is haploid

cell divides into DC through cytokinesis

may be short break after M1 called interkinesis where chromo partially uncoil
Meiosis 11

what happens in Prophase 11?

what happens in Metphase 11?

what happens in Anaphase 11?

what happens in Telophase 11?
nuclear envelope dissolves, nucleoli disappear, centriole migrate to opposite poles and the spindle apparatus begins to form

chromo line up on the metaphase plate

centromeres divide, separating the chromosomes into sister chromatids, chromatids are pulled into opposite poles by spindle fibers

nuclear membrane forms around each new nucleus, cytokinesis forms 2 DCs, now have 4 hap DCs per gametocyte
what are the differences b/t mitosis and meiosis
mitosis: 2n to 2n, occurs in all dividing cells, homo chromo do not pair, no CO

meiosis: 2n to n, occurs in only sex cells, homo chromo align on opposite slides of the metaphase plate, CO occurs
the 23rd chromo determines our sex and both the ova and sperm can carry a X chromosomes (sperm can also carry Y)

how does the X chromosomes affect how genetic diseases are inherited?
mutation in X chromo genes cause sex-linked or X-linked disorders

males are hemizygous because they have one copy of X linked genes and will express any X linked mutations

females are homozygous or heterozygous because they have 2 copies of a X linked gene (can be diff allele or same)

for females X linked disorders are recessively inherited and females express these disorders far less freq than males (those who carry but don't exhibit the disease are carriers)
Why do males have the Y chromo
one gene on this chromosome is needed for a human to be male

its called SRY (sex-determining region Y) and it codes fro a transcription factor that initiates testis differentiation and the formation of male gonads
male reproductive anatomy

how are testes created, where are they located and what are their functional components?

explain the function of the functional components
the primitive gonads develop into the testes

the testes have 2 functional comp: the seminiferous tubules and the interstitial cells of Leydig

testes are located in the scrotum, a pouch that changes below the penis


the cells of leydig secrete testosterone and other male hormones or androgens

Sperm are produced in the seminiferous tubules where they are nourished by sertoli cells
male reproductive anatomy

how does ejaculation occur
as sperm are formed they pass to the epididymis, where their flagella gain motility and they are then stored until ejaculation

during ejaculation, sperm travel through the vas deferens and enter the ejaculatory duct at the posterior edge of the prostate gland

the 2 ejaculatory ducts then fuse to form the urethra, which carries sperm through the penis as they exit the body

as sperm pass through reproductive tract they are mixed with seminal fluid, and they mixture is called semen
male reproductive anatomy

sperm and seminal fluid are mixed with the help of seminal vesicles, prostate gland and bulbourethral gland

explain the function of these 3
seminal vesicles contributes fructose to nourish sperm

seminal vesicle and prostate gland give the fluid mild alkaline properties so the sperm can survive in the relative acidity of the female reproductive tract

bulbourethral gland produces clear viscous fluid that cleans out any remnants of urine and lubricates the urethra during sexual arousal
what is a mnemonic to rmr the pathway of the sperm through the male reproductive system
SEVE(N) UP

seminiferous tubules
epididymas
vas deferens
ejaculatory duct
(nothing)
urethra
penis
explain the process of spermatogenesis (process of forming hap sperm through meiosis in the seminiferous tubules)
after the dip stem cells called spermatogonia replicate their genetic material (S stage), they develop into diploid primary spermatocytes

the first meiotic division will result in haploid secondary spermatocytes, which then undergo meiosis 11 to generate hap spermatids

the spermatids undergo maturation to become mature spermatozoa

spermatogenesis results in 4 functional sperm for each spermatogonium
explain the structure of a mature sperm
head (contains genetic material)

head is covered by a cap known as an acrosome


midpiece (generates ATP from fructose)

filled with mitochondria which generate the energy for swimming through the female reproductive tract to reach the ovum in the fallopian tubes


flagellum (for motility)
female reproductive anatomy

how does an egg travel through the female reproductive system
ovaries produce estrogen and progesterone and are in the pelvic cavity

each ovary has 1000s of follicles which are multilayered sacs that contain, nourish, and protect immature ova (eggs)

one egg per month is ovulated into the peritoneal sac and then drawn into the fallopian tubes that has cilia to propel the egg forward

fallopian tubes connect to the uterus
female reproductive anatomy

explain the structure of the uterus

what is the vulva
lower end is called the cervix and it connects to the vaginal canal where sperm is deposited during intercourse

this is the external part of the female reproductive system
what is oogenesis

explain how an oocyte is formed
production of female gametes


there is no unending supply of stem cells analogous to spermatogonia but in females all of the oogonia a woman will ever have are formed during fetal development

by birth all of the oogonia have already undergone DNA replication and are considered primary oocytes, these are 2n and arrested in prophase 1

when a woman reaches menarche (first menstrual cycle), one primary oocyte per month will complete meiosis 1 to produce secondary oocyte and a polar body
what 2 layers surround oocytes

What happens when a sperm cell penetrates these layers?
the zona pellucida and the corona radiata

zona pellucida is an acellular mixture of glycoproteins that protect the oocyte and contain compounds necessary for sperm cell binding

corona radiate is outside the zona pellucida, layer of cells that adhered to the oocyte during ovulation


meiosis 11 is only triggered when a sperm cell penetrates these layers

secondary oocyte undergoes the second meiotic division to split into a mature ovum and another polar body, which will eventually be broken down
sexual development

the ability to reproduce is under hormone control

what hormones are involved?
at the start of puberty the hypothalamus stops restricting the production of gonadotropin-releasing hormone (GnRH)

this triggers the anterior pituitary gland to synthesize and release follicle-stimulating hormones (FSH) and luteinizing hormones (LH)

these hormones trigger the production of other sex hormones that develop and maintain the reproductive system
male sexual development

explain how testosterone production changes during puberty

what is the affect of an increase in testosterone
testosterone production is increased during puberty and sperm production begins (FSH and LH are involved in this)

testosterone is involved in the development of secondary sexual characteristics like facial hair, deepening of the voice, increased muscle and bone mass
female sexual development
FSH and LH cause the ovaries to produce estrogen and progesterone


estrogen is secreted in response to FSH and helps develop and maintain the female reproductive system and female secondary sexual characteristics

also estrogen thickens the lining of the uterus in adults each month to prepare for the implantation of a zygote


progesterone is secreted by the corpus luteum in response to LH

this is involved in the development and maintenance of the endometrium so both estrogen and progesterone are needed for generation, development and maintenance of an preg

progesterone is supplied by the placenta while the corpus luteum ceases to function
the menstrual cycle

MCAT will test our ability to identify graphs of the blood [ ] of FSH, LH, estrogen and progesterone through out this cycle

so study the graph on the other side
the menstrual cycle

what is this
estrogen and progesterone will increase and decrease in a cyclic manner

and the endometrial lining will grow and shed aloso

this occurs from menarche to menopause

the 4 stages are follicular phase, ovulation, the luteal phase and menstruation
Menstrual Cycle: Follicular phase

explain this phase in terms of changes in hormone [ ]s
begins with menstrual flow which shed the uterine lining of the previous cycle

GnRH secretion from the hypothalamus increases in response to the decreased [ ] of estrogen and progesterone (these decrease near end of each cycle)

high [ ] of GnRH will increase secretion of FSH and LH

FSH and LH work together to form ovarian follicles and begin to produce estrogen, which has negative feedback and causes the GnRH, FSH and LH to decrease

estrogen stimulates the regrowth of the endometrial lining, stimulating vascularization and glandularization of the decidua
Menstrual Cycle: Ovulation

explain this phase in terms of changes in hormone [ ]s
eventually estrogen levels reach threshold which results now in positive feedback and GnRH, FSH and LH levels spike

LH increase induces ovulation, the release of the ovum from the ovary to the abdominal cavity
Menstrual Cycle: Luteal Phase

explain this phase in terms of changes in hormone [ ]s
LH causes the rupture follicle to form the corpus luteum which secretes progesterone

progesterone levels rise while estrogen levels remain high

high progesterone levels cause neg feedback on GnRH, FSH and LH to prevent the ovulation of multiple eggs
Menstrual Cycle: Menstruation

explain this phase in terms of changes in hormone [ ]s
if implantation doesn't occur, the corpus luteum loses its stimulation from LH, progesterone levels decline and the uterine lining is sloughed pff

loss of high levels of estrogen and progesterone removes the block on GnRH so the next cycle can begin
pregnancy

what happens if fertilization has occured?

what is menopause
the resulting zygote develops into a blastocyte that will implant the uterine lining and secrete human chorionic gonadotropin (hCG)

hCG maintains corpus luteum which produces estrogen and progesterone that are needed to keep uterine lining in place


older woman have ovaries that are less sensitive to FSH and LH and as the estrogen and progesterone levels drop, the endometrium also trophies and menstruation stops

because neg feedback on FSH and LH is removed the blood levels of these 2 hormones rises
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