[Biology] Ch.2: Reproduction Flashcards
What is the difference between the number of copies of chromosomes in autosomal and germ cells
Autosomal cells are diploid (2n), germ cells are haploid (n)
In humans what is the number of chromosomes in autosomal and germ cells
Autosomal = 46, germ = 23
Why might derangement of the cell cycle lead to the formation of cancer
It can lead to unchecked cell division
What are the four stages of the cell cycle for actively dividing cells
G1, S, G2, and M
Which stages of the cell cycle are known as interphase
G1, S, and G2
What types of cells spend time in G0
Cells that do not divide
What do cells do in G0
They just live and serve their function without preparation for division
What do cells do during the G1 phase (2 things)
- Create organelles for energy and protein production (mitochondria, ribosomes, and endoplasmic reticulum)
- Increase their size
What do cells do during the S stage
Replicate genetic material so that each daughter cell will have identical copies
In the S phase a single chromatid replicates to form two [ 1 ]
Sister chromatids
What quality control checks are done in the G2 stage
- Ensuring there is enough organelles and cytoplasm to divide between two daughter cells
- Ensuring DNA replication proceeded correctly
The M stage consists of [ 1 ] and [ 2 ]
1) mitosis and 2) cytokinesis
What are the four phases of mitosis
Prophase, metaphase, anaphase, and telophase
What is cytokinesis
The splitting of the cytoplasm and organelles into two daughter cells
What is the p53 protein’s role in control of the cell cycle
It is the main protein responsible for putting the cell into arrest if there has been damage to DNA (the arrest lasts until the DNA has been repaired)
What are cyclins and cyclin-dependent kinases
Molecules responsible for the cell cycle
Concentrations of the various [ 1 ] increase and decrease during [ 2 ] of the cell cycle
1) cyclins 2) various parts
What is the relationship between cyclins and CDKs
Cyclins bind to CDKs to form the CDK-cyclin complex that then goes on to phosphorylate transcription factors
[ 1 ] promote transcription of genes required for the next stage of the cell cycle
Transcription factors
One one of the most common mutations found in cancer is mutation of the gene that produces [ 1 ]
p53 (gene is TP53)
What types of cells undergo mitosis
Somatic cells (cells not involved in sexual reproduction)
What is the first step in prophase
The condensation of chromatin into chromosomes
In prophase, once centrioles migrate to opposite poles of the cell they begin to form [ 1 ] which are made of [ 2 ]
1) spindle fibers 2) microtubules
What happens to the nuclear membrane during prophase
It dissolves (allowing the spindle fibers to contact the chromosomes)
What are the kinetochores that appear on the centromeres
Protein structures that serve as an attachment point for specific fibers of the spindle apparatus (kinetochore fibers)
What happens during metaphase
Chromosomes align at the metaphase plate (equatorial plate)
What happens during anaphase
Sister chromatids separate
Telophase is essentially [ 1 ]
The reverse of prophase
What happens during telophase (3 things)
- The spindle apparatus disappears
- Nuclear membrane reforms
- Chromosomes uncoil
How many cell divisions can human somatic cells undergo before programmed cell death
Usually between 20 and 50
Meiosis consists of [ 1 ] round of replication followed by [ 2 ]
1) one 2) two rounds of division
What is the difference between meiosis I and II
- Meiosis I results in homologous chromosomes being separated
- Meiosis II results in separation of sister chromatids
Which meiosis is most similar to mitosis and why
Meiosis II because sister chromatids are being separated
What is the difference between homologous pairs and sister chromatids
Homologous pairs are considered separate chromosomes (you get one from mom and one from pop) but sister chromatids are exactly identical strands of DNA connected at the centromere
What is the major difference between prophase and prophase I
Homologous chromosomes come together and intertwine in a process called synopsis in prophase I
What process important to increasing genetic diversity occurs during prophase I
Genetic recombination
True or False: crossing over can occur between sister chromatids
False
What happens during metaphase I
Homologous chromosomes are aligned at the metaphase plate
What happens in anaphase I
Homologous chromosomes are pulled to opposite poles of the cell
At the end of telophase I, each chromosome still consists of [ 1 ] joined at the centromere
Two sister chromatids
What product is produced by completion of meiosis II
Up to four haploid daughter cells
What are carriers
Females carrying a diseased allele on an X chromosome but not exhibiting the disease
What does the SRY (sex-determining region Y) on the Y chromosome code for
A transcription factor that initiates testis differentiation (and thus formation of the male gonads)
In the absence of the Y chromosome all zygotes will be [ 1 ] and in it’s presence a zygote will be [ 2 ]
1) female 2) male
What are the two functional components of the testes
The seminiferous tubules and the interstitial cells (of Leydig)
Sperm are produced in the highly coiled [ 1 ] where they are nourished by [ 2 ]
1) seminiferous tubules 2) Sertoli cells
What do the cells of Leydig do
Secrete testosterone and other male sex hormones (androgens)
Where are the testes located
In the scrotum (external pouch that hangs below the penis)
What happens when sperm pass through the epididymis after they are formed
Their flagella gain motility and they are stored until ejaculation
Seminal fluid is produced through a combined effort by the [ 1 ], [ 2 ], and [ 3 ]
1) seminal vesicles 2) prostate gland 3) bulbourethral gland
What components of seminal fluid come from where
- Fructose —> seminal vesicles
- Mildly alkaline properties —> seminal vesicles and prostate gland
- Clear viscous fluid that clears out urine and lubricates the urethra —> bulbourethral (cowper’s) gland
What is spermatogenesis and where does it occur
Formation of haploid sperm through meiosis; occurs in the seminiferous tubules
What are spermatogonia
Diploid stem cells in males
Why is the midpiece of sperm filled with mitochondria
To generate the energy to be used as sperm swim to reach the ovum in the fallopian tubes
Recite the mnemonic to remember the pathway of sperm through the reproductive system
SEVE(N) UP
- Seminiferous tubules
- Epididymis
- Vas deferens
- Ejaculatory duct
- (Nothing)
- Urethra
- Penis
Ovaries produce [ 1 ] and [ 2 ]
1) estrogen 2) progesterone
What are ovarian follicles
Multilayered sacs that contain, nourish, and protect immature ova (eggs)
One egg per month is ovulated into the [ 1 ] which lines the abdominal cavity. It is then drawn into the [ 2 ]
1) peritoneal sac 2) Fallopian tube / oviduct
Why is the Fallopian tube lined with cilia
To propel the ova/egg forward
The external female anatomy is known collectively as the [ 1 ]
Vulva
True or False: by birth all of the oogonia have already undergone DNA replication and are considered primary oocytes
True
One primary oocyte per month will complete [ 1 ] to produce a secondary oocyte and a polar body
Meiosis I
Secondary oocytes are arrested in [ 1 ] and do not complete the remainder of meiosis II unless [ 2 ] occurs
1) metaphase II 2) fertilization
What are the zona pellucida and the corona radiata
The two layers that surround oocytes
What is the difference between the zona pellucida and the corona radiata
- The zona pellucida surrounds the oocyte itself and is an acellular mixture of glycoproteins and compounds necessary for sperm cell binding
- The corona radiata lies outside of the zona pellucida and is a layer of cells that adhered to the oocyte during ovulation
What is the fate of polar bodies
They get broken down
What is the relationship between the hypothalamus and gonadotropin-releasing hormone (GnRH) prior to puberty
The hypothalamus restricts production of GnRH prior to puberty
When the hypothalamus releases GnRH it triggers the [ 1 ] to synthesize and release [ 2 ] and [ 3 ]
1) anterior pituitary 2) follicle-stimulating hormone (FSH) 2) luteinizing hormone (LH)
When the hypothalamus releases GnRH it triggers the [ 1 ] to synthesize and release [ 2 ] and [ 3 ]
1) anterior pituitary 2) follicle-stimulating hormone (FSH) 2) luteinizing hormone (LH)
What do FSH and LH do
They trigger the production of other sex hormones that develop and maintain the reproductive system
Where is testosterone produced
The testes
For males testosterone increases dramatically during puberty and [ 1 ] begins
Sperm production
Contrast the effects of FSH and LH on the male gonads
- FSH stimulates Sertoli cells and triggers sperm maturation
- LH causes interstitial cells to produce testosterone
Aside from developing and maintaining the reproductive system what does testosterone do
Results in the development of secondary sex characteristics
What type of feedback does testosterone exert on the hypothalamus and anterior pituitary
Negative feedback
Estrogens are secreted in response to [ 1 ]
FSH
What do estrogens result in
The development and maintenance of the female reproductive system and secondary sex characteristics
What is estrogen’s role in the menstrual cycle
It leads to thickening of the lining of the uterus (the endometrium)
What is the corpus luteum
The remnant follicle that remains after ovulation
What does the corpus luteum do
It secretes progesterone in response to LH
What is the relationship between progesterone and the endometrium
It it involved in development and maintenance of the endometrium (but not in the initial thickening of it)
Can you develop and maintain an endometrium capable of supporting a zygote with only estrogen or progesterone
No. They are both needed
What changes in progesterone secretion by the end of the first trimester of pregnancy
Progesterone is supplied by the placenta and the corpus luteum atrophies and ceases to function
Recite the mnemonic to distinguish the role of estrogen and prgesterone
Estrogen established and progesterone protects the endometrium
When does the follicular phase of the menstrual cycle begin
When the menstrual flow begins
In the follicular phase [ 1 ] secretion from the hypothalamus increases in response to [ 2 ]
1) GnRH 2) decreased concentrations of estrogen and progesterone
Increased [ 1 ] secretion causes increased secretion of [ 2 ] and [ 3 ]
1) GnRH 2) FSH 3) LH
What happens immediately after FSH and LH levels increase
The follicles begin to produce estrogen which has a negative feedback effect and causes GnRH, LH, and FSH concentrations to level off
What happens as follicles secrete higher and higher concentrations of estrogen late in the follicular phase
Estrogen concentrations reach a threshold that results in positive feedback and GnRH, LH, and FSH levels spike
What is ovulation
The release of the ovum from the ovary into the abdominal cavity
What induces ovulation
The spike in LH
What happens in the luteal phase
LH causes the ruptured follicle to form the corpus luteum, which secretes progesterone
High levels of progesterone cause [ 1 ] feedback on [ 2 ], [ 3 ], and [ 4 ]
1) negative 2) GnRH 3) FSH 4) LH
Why is negative feedback necessary in the luteal phase
To prevent the ovulation of multiple eggs
What happens when implantation does not occur
The corpus luteum loses its stimulation from LH, progesterone levels decline, and the uterine lining is sloughed off
If fertilization occurs the zygote will develop into a [ 1 ] that will implant into the uterine lining
1) blastocyst
Why do blastocysts secrete human chorionic gonadotropin (hCG) hormone
It is an analog of LH (similar chemically) and can stimulate LH receptors
Why does hCG production decrease by the second trimester
The placenta has grown to a sufficient size to secrete progesterone and estrogen by itself (the high levels serve as negative feedback to prevent further GnRH secretion)
As a woman ages her ovaries become less sensitive to [ 1 ] and [ 2 ], resulting in [ 3 ]
1) FSH 2) LH 3) ovarian atrophy
Why does the endometrium atrophy as a woman ages
Estrogen and progesterone levels drop
Why are low estrogen and progesterone levels relevant to menopause
The negative feedback control on FSH and LH is gone leading increase in the blood levels of the two hormones
