What are the subunits of microtubules?
A microtubule is more rapidly polymerized (or depolymerized) at the
Which cytoskeletal elements are responsible for moving the chromosomes during cell division?
Which type of cytoskeletal filament contains actin?
Motor proteins are able to move along cytoskeletal fibers.
What provides the energy for their movement?
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Hydrolysis of ATP by the motor proteins
Which protein can “walk” toward the plus end of a microtubule?
The structure of a microtubule is best described as
a hollow tube
What are cilia and flagella made of?
Muscle contraction is caused by
interactions between actin and mysoin (in microfilaments)
The extracellular matrix is composed primarily of
proteins and polysaccharides
Which molecules are one of the main components of the plant cell wall?
groups of cells of the same type that work together to perform a common function
two or more tissues that combine and function together
two or more organ that work together to carry out a function
animal tissues (4)
epithelial, connective, nervous, muscle
covers body surface and lines internal structures
contains cells and extracellular matrix
conducts electrical impulses
contracts to provide force
plant tissues (3)
dermal, ground, vascular
forms an outer protective layer
makes up most of the plant body
transports nutrients and water through the plant
prevent passage of molecules across epithelium; not connected to cytoskeleton; create cell polarity
tether adjacent cells together
resist mechanical stress
allow passage of small molecules between adjacent cells
hemidesmosome/focal adhesion junctions
anchor epithelium to basal lamina
“top” side of cell, in contact with external environment or lumen of a tube-like structure
basolateral (basal) membrane
“bottom” or “sides” of cell, in contact with basal lamina and connective tissue
In adherens junctions and desmosomes
cadherin proteins bind to cytoskeletal proteins and to cadherins in neighboring cells
integrin proteins bind to cytoskeletal proteins and to extracellular matrix proteins
genetically identical to each other, result from mitosis and continue to divide by mitosis, 2n diploid ploidy
found in reproductive organs (ovaries, testes), diploid (2n), gametes that result from meiosis are genetically different from each other and from the germ cells they derive from, produce haploid (n) gametes
products of mitosis
1 diploid (2n) –> 2 diploid (2n)SOMATIC CELLS FORMED
products of meiosis
1 diploid (2n) –> 4 haploid (n)GAMETES ARE FORMED
Eukaryotic Cell Cycle
INTERPHASE (G1, S, G2) cell growth and replicationM PHASE (mitosis & cytokinesis) cell division
cell undergo major portion of their growth
chromosomes are replicated
chromosomes begin coiling, centrosomes replicate to prepare spindle apparatus
location on a chromosome where a gene is always found
when does replication occur?
S phase, right before each round of cell division, if mutations occur they are passed down and divided
important to remember about number of chromosomes and replication
replication doubles the amount of DNA, but not the number of chromosomes, so after DNA replication the cell has the same number of chromosomes
replicated chromosomes are made of
two identical sister chromatids attached at their centromeres by cohesin proteins
What is the purpose of mitosis?
division of the nucleus (genetic material)
What are the stages of mitosis?
prophase, prometaphase, metaphase, anaphase, telophase
what is the purpose of cytokinesis?
division of the cell cytoplasm
chromosomes condense and become visible, sister chromatids are held together at centromeres, cytoskeleton is disassembled, spindle begins to form, golgi and ER are dispersed
nuclear envelope breaks down, microtubules attach to kinetochores
chromosomes align witht heir centromeres at the equator of the cell
cohesins (proteins holding centromeres of sister chromatids) break down, releasing individual chromosomes, chromosomes pulled to opposite poles, spindle poles move further apart
chromosomes are clustered at opposite poles and de-condense, two nuclear envelopes form around chromosomes, golgi complex and ER re-form
contractile ring in animals pinches the cytoplasms; cell plate forms for plants
What term refers to the entire set of genetic information in a cell?
Eukaryotic chromosomes are composed of a complex of 60% proteins and 40% DNA. This complex is called
The map displaying the ordered array of chromosomes of an organism is called
What is a cell’s genome made of?
Large and complex organisms always have larger genomes than small, simple organisms (T/F)
What is the diploid (2n) number of chromosomes in a human cell?
How many chromosomes are in a human gamete (egg or sperm cell)?
How many sets of chromosomes are in a haploid (n) cell?
Arrange the sequence of genome, gene, chromosome in order of increasing size
gene, chromosome, genome
Arrange the structures in increasing diameter for chromatin fiber, nucleosome, metaphase chromosome, DNA double helix
DNA double helix, nucleosome, chromatin fiber, metaphase chromosome
Under an electron microscope, chromatin resembles “beads on a string.” What are the beads?
The two “arms” of a chromosome are called
End of a sister chromatid is called
During cell division, which cytoskeletal elements bind to the chromosomes via kinetochore proteins?
What is the name of the process by which prokaryotic cells divide?
During the eukaryotic cell cycle, DNA is replicated during
In a cell that will divide by meiosis, when does DNA replication occur?
before Meiosis I only
Two homologous chromosomes have a total of 4 chromatids, numbered 1-4. Immediately after DNA replication, which chromatid(s) have the same DNA sequence as chromatid #1?
How many copies of the beta-globin gene are in a cell that has just replicated its DNA in preparation for meiosis?
4 (one on each sister chromatid, then the gene is copied because of replication so there are 4 resulting)
homologous replicated chromosomes form pairs, called?
within tetrads, chromatids of homologous chromosomes exchange pieces of DNA, what is this called?
What line up in Metaphase I?
what are separated at anaphase
in the resulting cells of meiosis 1, the cells are what ploidy?
haploid (n) because each cell contains n replicated chromosomes
If a mouse diploid genome contains 40 chromosomes (2n=40)…In a mouse cell at the end of prophase I, how many chromatids, chromosomes, and bivalents are present?
80 chromatids, 40 chromosomes, 20 bivalents
A mouse cell that just completed meiosis I contains.
20 replicated chromosomes
In a mouse cell that just completed meiosis I, how many copies of the beta-globin gene are present?
why is crossing over important?
produces new combinations of alleles in the gametes
A cell containing only one copy of each chromosome
In all sexually reproducing organisms, the diploid phase of the life cycle begins at
If two structures are sister chromatids, their nucleotide sequences are ____
How many double-stranded DNA molecules are found in a chromosome with two sister chromatids?
A pair of homologous chromosomes is two chromosomes that have
the same genes in the same order but possibly different alleles of the same genes
homologous pairs of chromosomes
are identical in size and appearance
A typical eukaryotic cell cycle consists of
interphase, mitosis, and cytokinesis
Mature nerve cells, which are incapable of cell division, are most likely arrested where?
How does G2 differ from G1?
G2 has twice the amount of DNA as the G1 cell (because it has already undergone the S synthesis of DNA cycle)
When dividing cells are examined under a light microscope, chromosomes first become visible during what stage?
Microtubules that form the mitotic spindle originate from ___ and terminate in ___
Taxol is an anti-cancer drug that prevents uncontrolled cell division by stabilizing microtubules, which arrests the cell cycle. If dividing cells are treated with Taxol, at what stage of the cell cycle would the arrest occur?
metaphase, because a drug that stabilizes microtubules will prevent them from shortening, and shortening is what causes sister chromatids to move away from one an other as the cell advances from metaphase to anaphase during mitosis. Therefore, stabilizing microtubules will arrest the cell in mitosis.
When a human cell is in G2 phase, it contains ___ chromosomes, and each of these chromosomes has ___ chromatids.
Meiosis results in the production of
four haploid daughter cells
The products of meiosis are called
Chromosome number is reduced during meiosis because the process consists of
two cell divisions and only a single round of chromosome replication
During meiosis, the sister chromatids separate during
In an organism with a diploid number of 8, a gamete has ____ chromosome, a liver has ___ chrommosomes, and a sperm cell at meiotic anaphase I has ___ chromosomes
4, 8, 8
In an organism with a haploid number of 9, a skin cell has ____ chromosomes, a developing sperm at prophase II of meiosis has ___ chromosomes, and a newly formed zygote has ____ chromosomes
18, 9, 18
Crossing over occurs during
How does prophase of mitosis differ from prophase I of meiosis?
Synapsis occurs in prophase I of meiosis but not in prophase of mitosis
A pair of homologous chromosomes that have synapsed with one another is called
in a monohybrid cross between two true-breeding strains, the F1 progeny always exhibits
In F2 generation, the recessive phenotype reappears but the ratio is
3 dominant: 1 recessive
7 pairs of traits displayed by Mendel
seed color and shape, pod color and shape, flower color and position, plant height
Why do leaves turn yellow?
enzyme called chlorophyllase, encoded by SGR, breaks down chlorophyll and the yellow carotenoids become visible
both alleles are the same (AA, HbSHbS)
two alleles are different (Aa, HbAHbS)
organism with a heterozygous genotype
What is on the axes of a punnett square
gametes from each parents
How would you identify the genotype of a pea plant with yellow seeds if all you can do is cross with one other pea plant?
cross with homozygous recessive green and if there is a 3:1 ratio, it was heterozygous, if they are all yellow, it was homozygous dominant (testcross)
In humans, the diploid number of chromosomes is 46. How many chromosomes are in a human sperm cell?
23 unreplicated chromosomes
How many copies of the beta-globin gene are in a human sperm cell?
How many chromosomes are in a human zygote immediately after fertilization?
46 unreplicated chromosomes
How many copies of the beta-globin gene are in a human zygote immediately after fertilization?
What happens during crossing over?
non-sister chromatids from the same homologous pair exchange DNA
DNA occurs before
Meiosis I and mitosis
when do homologous chromosomes separate from each other
Fruit flies have a diploid number of 8 chromosomes.
In a fruit fly cell in metaphase I, how many chromosomes, chromatids, and bivalents (tetrads) are found?
chromosomes, 16 chromatids, 4 bivalents
If a person carries both the HbA and HbS alleles of beta-globin gene, when would there be two chromosomes with one of each allele observed?
Meiosis I (because of recombination)
When do sister chromatids separate?
anaphase or anaphase II of meiosis
A pea plant with white flowers that produces offspring that always have white flowers is called
In pea plants, flowers may be purple or white. Flower colors is an example of ___ and purple or white are examples of ___
Mendel crossed pea plants that were pure-breeding for round seeds with pea plants that were pure-breeding for wrinkled seeds. The progeny of this cross always had round seed. The progeny is referred to as the
Mendel crossed pea plants that were pure-breeding for round seeds with pea plants that were pure-breeding for wrinkled seeds. The progeny of this cross always had round seeds. This led him to know what about the phenotypes
round phenotypes are always dominant
a hollow circle on a pedigree is
an unaffected female
an individual on the third row down and the second one out is
upside down Y on a pedigree is
Why is BRCA1 protein abundant in rapidly dividing cells, but not in other cells?
BRCA1 gene is only transcribed in dividing cells (because it’s actually present in all cells, but it just depends on whether or not it is “turned on”)
The mutant BRCA1 allele is lethal in double dose (homozygous BRCA1 mutant embryos do not even develop). Suppose that a man and a woman are both heterozygous for the BRCA1 mutation. What is the likelihood that their (living) child carries one mutant allele of BRCA1?
2/3 (2 of them will be heterozygous, only out of 3 because the one that was homozygous would not develop and the question specified for living)
What would be result of AAbb x aaBB
What is AAbb x aaBB called?
dihybrid cross (more than one trait)
ratio of the second progeny of dihybrid traits
9:3:3:1 (decreasing dominance)
Independent assortment of genes reflects what fact
nonhomologous chromosomes can orient in either of two ways that are equally likely during meiosis to produce variations
Principle of Segregation
the two alleles of a single gene segregate from one another during gamete formation so that each gamete receives one allele of the gene
Principle of Independent Assortment
the alleles of two different genes segregate independently of one another during gamete formation; the segregation of alleles of one gene does not influence the segregation pattern that will occur for the second gene (applies to two genes located on different chromosomes)
X-linked trait examples
hemophilia/red-green color blindness
describing a pea plant as tall or dwarfed refers to its
The gene that determined height in Mendel’s pea plants has been identified.
This gene (T) encodes an enzyme called gibberellin 3-oxidase. The function of this enzyme is to convert an inactive plant compound into active gibberellin. Gibberellin is a plant hormone that stimulates growth, resulting in taller plants. A point mutation in the T gene resulted in an allele (t) in which a single guanine nucleotide is changed to adenine. This nucleotide substitution results in a protein that contains threonine instead of alanine. This mutation is best described as what?
a point mutation where the codon changes to code for a different amino acid
The T allele codes for the function GA 3-oxidase enzme and is associated with the tall phenotype; the t allele codes for a non-functional version of this enzyme and is associated with the dwarfed phenotype.
Which genotype results in dwarfed plants?
Can a heterozygous (Tt) pea plant produce the active gibberellin molecule?
What does it mean when we say that the T allele is dominant to the t allele?
a plant with the genotype Tt has the same phenotype as a plant with the genotype TT
If a pea plant with genotype Tt is crossed with a pea plant with genotype tt, what phenotypic ratio is observed among the offspring?
1/2 tall and 1/2 dwarfed
What genotypic ratio will result from a pea plant Tt crossed with tt?
1/2 Tt and 1/2 tt
If the ancestors of Mendel’s pea plants all carried the T allele, which codes for a function GA 3-oxidase enzyme, what explains how the first t allele first appeared in the population?
the first t allele first appeared due to an error in REPLICATION
In a pea plant that is Tt, what do we know about meiosis?
T and t separate from each other in meiosis I, when homologous chromosomes separate
The T and t alleles are best describes as
different forms of the same gene (alleles)
When you look at the tall pea plant, what can you infer about its genotype?
It may be possible to know what its genotype is by crossing it with a drwarfed pea plant
The BRCA1 gene is located on Chromosome 17 in humans. BRCA1 encodes a prpotein directly involved in repairing breaks in DNA resulting from exposure to environmental mutagens like radiation or other sources of damage. This gene is primarily expressed in rapidly dividing cells, including breast and ovarian cells. A somatic cell in G1 of interphase has ___ of the BRCA1 gene, located on___.
2 copies, homologous chromosomes
A somatic cell in G2 of interphase has ____ of the BRCA1 gene, located on ______
4 copies, sister chromatids
Give an explanation for why the BRCA1 protein is abundant in rapidly dividing cells, but not in other cells?
The BRCA1 gene is only transcribed in dividing cells.
The X and Y chromosomes are called
X and Y chromosomes do what during meiosis?
In humans, what triggers an embryo to develop as a male?
the presence of a specific gene on the Y chromosome
A human sperm cell always contains
either an X chromosome or a Y chromosome
How many X chromosomes are found in a human egg cell?
How many autosomes are found in a human gamete?
What is the sex chromosome karyotype of a male fruit fly?
What is the sex chromosome karyotype of a female bird?
In a non-dividing somatic cell in a human male, there is (are) _____ copy(s) of each gene on the X chromosome
In a non-dividing somatic cell in a human female, there are ___ copies of each X chromosome
epiblast divides and migrates inward and forms three layers of the cell (ectoderm, mesoderm, endoderm)
inner cell mass becomes
outer cell forms
gives rise to many cells
collection of cells that work together to perform a specific function
two or more tissues often combine and function together
4 types of animal tissue
epithelial, connective, nervous, muscle
covers body surface and lines internal structures
contains cells/extracellular matrix
conducts electrical impulses
contracts to provide force
3 types of plant tissue
dermal, ground, vascular
outer protective plant layer
bulk of the plant body
channels that transport nutrients and water
determines/maintains the shape of cells, structural protein network in the cytoplasm of animals
hold adjacent keratinocytes together and connect the bottom layer of keratinocytes to basal lamina
meshwork of proteins and polysaccharides, a properly shaped tissue or organ depends on the ability of cells to adhere to this (it provides a mechanism for cells to adhere and structural/shape support)
2 layers of human skin
epidermis and dermis
outer layer of skin, water-resistant and protective barrier
layer beneath the epidermis and supporting the epidermis physically and by supplying nutrients, provides a bodily cushion
multiple layers of epithelial cells; covers the body and lines internal structures like the digestive tract, specialized for protection, secretion, and absorption
epidermal layer is made of what?
keratinocytes and melanocytes
produce pigment in the epidermal layer
have cytoskeletal filaments that connect to cellular junctions
extracellular matrix underlying and supporting the epithelial tissue
tissue of the dermis with few cells and much extracellular matrix; strong and flexible
cell in the dermis, synthesize extracellular matrix and repairs wounds
two cytoskeletal elements of eukaryotes
microtubules and microfilaments
third cytoskeletal element in animals
hollow, tubelike polymers made of tubulin dimers, have the largest diameter
function of microtubules
radiate outward to the cell periphery from centrosome, can attach to organelles to guide their movement, be tracks for transport of materials from one cell to another
propel movement of materials from one cell to another
the device that microtubules form that separates replicated chromosomes in eukaryotic cell division
polymers of actin monomers in a helix shape (thinnest), present in the cytoplasm in various places, short and branched in the cell cortex (right under plasma membrane)
function of microfilaments
reinforce plasma membrane and organize proteins associated with it
give birth to live young
produce large numbers of offspring without a lot of parental investment
produce few offspring with lots of parental investment
can give rise to a complete organism (fertilized egg)
clump of cells that forms from mitotic divisions within the egg’s outer membrane as the fertilized zygote goes through the fallopian tubes towards the uterus
When does the morula reach the uterus?
4 or 5 days after fertilization
What is different about the cell divisions of the morula?
The cells do not undergo growth, they simply continue to divide and the cytoplasm gets smaller and smaller
hollow sphere formed by the cells of the morula pushing against each other and expanding the membrane
inner cell mass
body of the embryo develops from, group of cells within the blastocyst
what is actually implanted into the uterine wall?
germ layers of the gastrula
ectoderm, mesoderm, endoderm
outer layer of the skin, nervous system, posterior pituitary gland, cornea and the lens of the eye
muscle, bone, connective tissue, circulatory system, kidneys, gonads
lining of respiratory tract/digestive tract, liver, gallbladder, pancreas, thyroid gland
can give rise to any of the three germ layers, or to any cell of the body (inner cell mass/embryonic stem cells)
can form a limited number of types of specialized cells
cells that can differentiated into different cell types (totipotent- complete organism, pluripotent- can give rise to any body cell, multipotent- can give rise to a limited number of types of specialized cells)
hollow glass needle inserts a cell nucleus into an egg cytoplasm whose nucleus has been removed
rapid cell division (mitosis) without growth –> leads to the development of the morula from zygote in human fertilization
natural processes of cell growth and development used to replace diseased or damaged tissues
induced pluripotent cells (iPS)
adult ells can be reprogrammed by activation of just a handful of genes, most of them encoding transcription factors or chromatin proteins
formation of gametes
spermatogenesis: what, where, when
formation of sperm, seminiferous tubules in testes, begins at puberty –> life
entire process of spermatogenesis
diploid spermatogonia undergo mitosis–>diploid primary spermatocyte undergoes meiosis I –>2 haploid secondary spermatocytes undergoes meiosis II –>4 haploid spermatids undergo maturation –>4 sperm gametes
where does the maturation of haploid spermatids into sperm occur?
primarily in the testes and then goes on to the epididymis
formation of ova/eggs
entire process of oogenesis
diploid oogonium undergo mitosis –>diploid primary oocyte undergoes meiosis I –>ARRESTED IN PROPHASE I during fetal development until first period, when 10-20 follicles mature due to rising FSH and 1 becomes a dominant secondary oocyte and a polar bodysecondary oocyte undergoes meiosis II and is released from the ovary–>ARRESTED IN METAPHASE II until fertilized, then it produces another polar body and the ootidootid matures –>ovum/egg
changes allowing sperm to fertilize eggs (alters fluidity of plasma membrane, loss of some surface membrane proteins, and change in membrane potential (or charge across membrane))
how the fusion of sperm and egg works (3)
1. sperm penetrates the corona radiata and then the zona pellucida2. sperm head fuses w/plasma membrane of oocyte and releases acrosomal enzymes3. oocyte completes meiosis II to prevent polyspermy
fertilization by more than one sperm
alternate method to fighting against polyspermy
vesicles in the oocyte fuse w/plasma membrane and release contents which alters the zona pellucida
in vitro fertilization
egg and sperm are put in a petri dish where fertilization and cell division occurs, then the embryo is placed in the uterus
how lots of yolk affects cleavage
eggs with lots of yolk have an animal pole (no yolk) and a vegtal pole (lots of yolk) and cell division does not extend the entire egg because the presence of more yolk inhibits it
where do eggs with less yolk get their nutrients from?
WHEN DOES PREGNANCY START?!!!!!??!!!?!?
implantation of the BLASTULA!!!!!!!!!!!!!!! SUCH EXCITE.
MANY BABY. SO INSPIRE.
functions of the placenta
secretes estrogen & progesterone, excretes waste between maternal and fetal blood, made up of the embryonic cells and the maternal cells
BLASTOCYST = inner cell mass –>BILAMINAR EMBYO = epiblast & hypoblast –>GASTRULATION- displaces hypoblast and conforms epiblast into the three germ cells –>TRILAMINAR EMBRYO = ectoderm, mesoderm, endoderm, which produce all the bodily organs and tissue
transformation of germ layers into the bodily organs
how is sex determined
by the presence or absence of a Y chromosome (if Y present, male)
gene on the Y chromosome which encodes a protein called TDF (testis-determining factor), that turns on the developing gonad into testes. If the TDF is not there, the gonad develops into ovaries
3 events of childbirth
cervix shortens and widens, baby is born head-first, face down, placenta is delivered
list in order: blastocyst, morula, gastrula, zygote, fetus
zygote, morula, blastocyst, gastrula, fetus
immediately after fertilization, how many chromosomes are in a human zygote?
46 unreplicated (because mitosis/cleavage hasn’t occurred yet)
How many copies of beta-globin are found in the human zygote immediately after fertilization?
2- 1 for each haploid
During cleavage, cells divide rapidly without growing in size. Which phase(s) of the cell cycle are eliminated or extremely shortened during these cell divisions?
G1 & G2(growth)
The solid ball of cells that results from cleavage is called a
Partial cleavage is most likely to occur in
zygote with a lot of yolk
where does fertilization occur?
At the time of implantation into the uterine wall, the developing embryo is called??
At the time when the embryo implants into the uterine wall, all of the cells that will develop into the new individual’s tissue and organs are found in the
inner cell mass
What is the function of the placenta?
allows the exchange of nutrients and wastes between the mother and the child
forms of asexuality and how they work (3)
budding- bud forms and breaks off (smaller than parent)fragmentation- organism splits and the pieces become organismsparthenogenesis- females produce eggs that develop by mitosis
two processes of sexual reproduction
fertilization (where the zygote is formed) and meiosis (haploid gametes produced with half the number of chromosomes as parent cell)
conditions for species that reproduce both asexually and sexually
sexually- shortage of resources/coldasexually- plentiful resources/warmer environment
twofold cost of sex
sexual reproduction results in slower growth as juxtaposed to asexual reproduction
internal fertilization and strategy type
adaptation for land, fertilization occurs inside the female body, K-strategists (small offspring amount, increased parental care/survival rate)
external fertilization and strategy type
aquatic, eggs and sperm released into water, r-strategists (large offspring amount, decreased parental care/survival rate)
common of external fertilizing eggs, provides all the nutrients the embryo will need until it hatches
membrane surrounding fluid-filled cavity that allows embryo to develop in a watery environment
collects metabolic waste
surrounds embryo and yolk and allantoic sac
yolk sac, allantois, amnion, chorion
placenta is a combination of
allantois and chorion
where are the sperm produced
seminiferous tubules in the testes (scrotum)
path that sperm follow
seminiferous tubules –> epididymis (gain motility) –> vas deferens –> ejaculatory duct –> urethra
what are the glands called that produce semen components?
seminal vesicles contribute
protein and sugar-rich fluid that makes up semen and provides motility
prostate gland contributes
fluid that maintains sperm motility and protects against the acidity of the female reproductive system
neck of the uterus
where do labia minora/majora meet?
how testes and ovaries work with the endocrine system in general
hypothalamus is secretes GnRH that act on the pituitary gland, which releases FSH and LH
How does LH affect males
interacts with Leydig cells to:-secrete testosterone-development of male reproductive structures-development of male secondary sex characteristics-maintenance of adult health
How does FSH affect males
interacts with Sertoli cells to:-produce sperm in the seminiferous tubules
How does FSH affect females
interacts with the follicle cells surrounding the oocyte to:-support developing oocyte-development of female reproductive system-development of female secondary sex characteristics
two phases of the menstrual cycle
follicular and luteal
What occurs during the follicular phase of the menstrual cycle?
FSH acts on granulosa cells (part of follicle cells):-1 oocyte matures and the granulosa cells secrete estradiol that thicken the uterine lining-rapid increase/decrease in LH produced which leads to.
What occurs during the luteal phase of the menstrual cycle?
-ovulation begins because of the sharp increase/decrease in LH-follicle cells are converted to corpus luteum (which secretes progesterone)-corpus luteum continues to secrete while maintained by LH and the hCG secreted by the embryo
menstruation occurs when..
there is no fertiliation, the corpus luteum degenerates, estrogen and progesterone levels go down, and the uterine lining breaks down and sheds
is a result of the decreasing levels of estrogen and progesterone
In spermatogenesis, which cells are haploid?
secondary spermatocytes, spermatids, sperm
What sex chromosomes are found in a primary spermatocyte?
X and Y (meiosis hasn’t occurred yet)
What sex chromosomes are found in a secondary spermatocyte?
Either an X or a Y
Compared to the polar body released after meiosis I, the secondary oocyte contains
How many chromosomes are found in a human oogonium?
46 (prior to division)
During human oogenesis, primary oocytes becomme arrested in
In humans, the division of one primary spermatocyte results in the production of ___ mature gametes; the division of one primary oocyte results in the production of ___ mature gametes
Layer of glycoproteins surrounding a human egg cell
Where does oogenesis occur?
Genes in the same chromosome that fail to show independent assortment are said to be ____
Genes that modify the phenotypic expression of other genes are said to show ____
individuals with a genotype corresponding to a trait do not actually show the phenotype, either because of environmental effects or because of interactions with other genes
particular phenotype is expressed with a different degree of severity in different individuals
identifying the genotype of an individual to find the genes associated with a condition
an X chromosome present in a male in one generation must be transmitted to a female in the next generation, and in the generation after that can be transmitted back to a male. This is called..?
when chromosomes fail to separate normally in meiosis
offspring develop inside mother’s body but inside of eggs
cells in ectoderm, mesoderm, and endoderm contain different
mRNA molecules and protein molecules
ectoderm, mesoderm, and endodern have the same