First Exam Flashcards
Is embryology or developmental biology older
embryology
How long has embryology been around for
centuries
How long has developmental biology been around for
maybe since the 70’s
What is the focus of embryology
description on what happens in an embryo
What is the focus of developmental biology
explains why things happen throughout development
What age range does embryology focus on
period from conception to 1st trimester
What age range does developmental biology focus on
conception through death
What is the explanation to all the changes occurring throughout development
gene expression changes
Every human being begins as what
a single diploid cell
Where do the diploid chromosomes come from
23 from mom
23 from dad
As development occurred in the embryo, what process led to cell division
mitosis
What very important thing occurred during development to change the egg into an embryo
cell differentiation, specialization
How do the gonads divide
meiosis
What is the germ line concept
a continuity from one generation to the next
As Christians, we believe our continuity can be traced all the way back to what
Adam and Eve
Where does life come from
other than God, only existing life
What is a problem that can result in germline
if mutation in a germline cell, that will be passed down to all the following generations. The mutation will also be in all the embryo’s somatic cells as every cell originates from a germ line cell
What is a technique used to fix mutations in the germline
gene therapy or enhancement on the germ line
What would gene therapy be used specifically for
removing disease causing genes
What would gene enhancement be used for
bettering performance of specific genes
What is the name of the mechanism used for gene therapy
CRISPR
What 4 things are needed for CRISPR to function properly
- errored DNA
- guide RNA
- CAS9 nuclease
- normal sequence
What is the function of the guide RNA
RNA molecule that pairs up with the mistake/errored DNA
What is the function of CAS9
cuts mutated sections out
What is the function of the normal gene sequence
fills in the gap where the error was
What is the biggest danger with using CRISPR
if the guide RNA pairs where it should not be, then the wrong gene is removed=CRISPR induced mutation
How long is the guide RNA
20 bases long
Gene editing in somatic cells leads to what
a cure for that person
Gene editing in germline cells leads to what
prevention of disease for that family line
What is the ethical debate for CRISPR
they must remove more than 1 zygote and manipulate about 57 of them. CRISPR only works on a few of the ones removed and the rest are thrown away. Zygotes are embryos=personhood
What is the con side of CRISPR
could create a new disease from an off target cut
What are the germ cells
spermatogonia and oogonia
What type of cell in reference to chromosomes are spermatogonia and oogonia
diploid
diploid cells have what
pairs of chromosomes
What is the first step that spermatogonia and oogonia undergo
division by mitosis
What is produced due to this division
two diploid cells, one that continues as a primary “cyte” and one that regenerates as a spermatogonia or oogonia
What will the primary oocytes and spermatocytes undergo next
meisosis
What is the very first step in meiosis
duplicating DNA
When a diploid cell duplicates its DNA, it now has how many chromosomes
4C (4 copies of genetic material)
Germ cells are also considered what type of cell
stem cell
Why are germ cells called stem cells
because they generate new cells and regenerate themselves
What is the change that occurs in meiosis I
primary cytes become secondary cytes
What is the order of stages in meiosis
prophase
metaphase
anaphase
telophase
What occurs in prophase I
chromatin folds into chromosomes
What occurs in metaphase I
chromosomes pair up in synapsis along the metaphase plate. Crossing over may occur between the homolog chromosomes
What occurs in anaphase I
homologs seperate and are pulled to opposite poles of the cell
What occurs in telophase I
cytokinesis occurs and nucleus reforms around the chromosomes.
What are the products of meiosis I
two secondary cytes
What type of chromosome number do the secondary cytes have
2C each
In meiosis II what is the process of change
secondary cytes become spermatids or eggs
What occurs in prophase II
chromosomes reappear
What occurs in metaphase II
chromosomes line up between cell poles
What occurs in anaphase II
the identical chromosomes are seperated from each other
What occurs in telophase II
nuclei form
How many copies of chromosomes in the product of meiosis II
one
What are the gonad organs
ovaries
testes
what two things fuse in fertilization to produce a zygote
sperm
oocyte
When are eggs ovulated
at metaphase I (when they are becoming primary secondary oocytes)
What is the major benefit for meiosis
contributes to genetic diversity among offspring
Why is genetic diversity good
God likes genetic diversity
ensures survival of a species=someone will be resistant to a disease and environmental changes
What in meiosis/fertilization leads to genetic diversity
independent assortment of 23 chromosomes, crossing over between homologs, mixing of gametes during fertilization
How many possible combos due to independent assortment of 23 chromosomes alone
8 million
With the mixing of gametes (sperm and egg) how many combinations are possible total
over 64 trillion
What are risks associated with meiosis
non-disjunction
deletions of genes
What is the outcome of non-disjunction
aneuploidies or lethal monosomies
How does a non-disjuction occur
chromosomes don’t separate during division, especially in eggs as they age being held in metaphase I for a long time can result in bonds between the arms of the homologs leading to them not being able to seperate
How does deletions of genes occur during meiosis
during crossing overs, as genes swap, they could delete, translocate or duplicate certain sections and lose another gene
What percentage of fertilized eggs miscarry
50%
50% of the eggs that miscarry (25% total) are due to what
chromosomal problems
The other 50% of eggs miscarried are due to what
hormonal problems
25% of the eggs that miscarry due to chromosomal problems are caused specifically by what chromosomal problem
aneuploidies and monosomies
When does the timing of spermatogenesis begin in humans
at puberty
How long does spermatogenesis last in humans
throughout life
How long does it take for meiosis and sperm maturation
a few weeks, 72 days
How do males have sperm always available
different regions of the testes normally initiate spermatogenesis at different times
Testes contain long tubules called what
seminiferous tubules
What is the function of the seminiferous tubules
is the region where sperm generation occurs
Where are the least mature cells located in the seminiferous tubules
the periphery
where are the most mature cells located
near the central lumen
what are the least mature cells in sperm genesis
spermatogonia
what are the most mature cells in sperm genesis
spermatozoa
What are the cells in order for sperm genesis from least to most mature
spermatogonia primary spermatocyte secondary spermatocyte spermatids spermatozoa
The edge of the seminiferous tubules contain a thick barrier called what
blood testis barrier
what is the function of the blood testis barrier
protects the germline from harmful substances that could be in the blood and cause damage
What are some cytoplasmic changes that occur during spermatogenesis
increase in number cells get smaller formation of acrosome formation of flagellum aggregation of mitochondria condensation synthesis of receptors
Why do the cells get smaller with each division
shedding of extra organelles and cytoplasm
What is the acrosome
a membrane bound organelle that contains enzymes and receptors
Where is the acrosome located
in the head of the sperm
Where does the flagellum originate
from a centriole or centrosome in the tail of the sperm
What is the function of the flagellum
enables the sperm to swim to the egg
Where do mitochondria aggregate
around the tail of the sperm in order to provide ATP to run the motor of the tail
What is condensation
the condensing of the chromosomes into very compack nucleus (extra packing and folding)
Where is the nucleus located
behind the acrosome
Where are the receptors
on the head of the sperm and on the membrane of the acrosome
What are the two main supporting cells for sperm genesis
sertoli cells and interstitial cells
What is the function of Sertoli cells
to move the products of meiosis closer to the central lumen and to provide nutrients for developing sperm
Why do Sertoli cells need to provide the nutrients
because sertoli cells form the blood barrier and block off nutrients that come through the blood to the developing sperm
What is the function of interstitial cells
produce testosterone
What is the function of testosterone
to stimulate development of males and inhibit development of female reproductive organs
When does oogenesis begin in humans
before birth
How many eggs are produced
1-2 million
When does oogenesis end
menopause
How does the level of oogenesis and sperm amount differ
sperm is constantly created
oogenesis gradually declines with time
When eggs are in the process of being produced, they are stalled at what point
metaphase I
How many eggs are ovulated at a time
1 mature egg
When does ovulation occur
it is synched with the monthly hormonal cycle
With eggs and follicles gone, what also disappears and helps push menopause
estrogen
What are the goals of oogenesis
provide a haploid genome stockpile organelles stockpile biomolecules protect egg and embryo incorporate a single sperm during fertilization provide developmental signals for embryo
What are oocytes surrounded by
granulosa cells
What do granulosa cells and oocyte form
primordial follicle
How do you get a women to ovulate more than one egg
FSH injections
Why does providing a haploid genome become a goal for the egg
it is fertilized during metaphase I and needs to retain the diploid state
How is the haploid genome ensured
through meiosis
How does the egg stockpile organelles
uneven cytokinesis
What does uneven cytokinesis form
a daughter cell with most of the cytoplasm and another daughter cell with very little cytoplasm
What is the daughter cell without cytoplasm called
polar body
Do both daughter cells contain some genome
yes, in first division one is 2C, and then second is 1C for polar bodies
How do polar bodies contribute to a more ethical pre implantation genetic diagnosis
the polar bodies should contain identical genome to the real egg, these could be analyzed as they are unable to turn into humans in the end
How does IVF still have ethics to it
women must still hyperovulate, fertilize that egg and then implant . Fertilization under IVF conditions still is harsh
How does the egg stockpile RNAs
as a primary oocyte it has 4 sets of chromosomes that are available for transcription into RNA, mRNAs are stockpiled in the egg
What about rRNA stockpiling
hundreds of rRNA are located on chromosomes, duplicated in a process called gene amplification
How does egg stockpile proteins
female synthesizes proteins, released in bloodstream and taken up by the ooctye by endocytosis
Why does the egg stockpile lipids
to form membranes
Why does egg stockpile glycogen
for glucose to form ATP
What other cells can help synthesize molecules
follicle cells
What is an accumulation of the stockpile materials called
yolk
The yolk contributes what most
to the large size of the egg
How does the egg protect itself and the developing embryo
zona pellucida
What composes the zona pellucida
a thick layer of glycoproteins
Some eggs have what alternative layer protecting them
chorion
When the egg is ovulated, the egg is surrounded by what other protection layer
follicle cells (granulosa cells)
How does a single sperm fertilize the egg
receptors expressed in zona pellucida and plasma membrane
cortical granules contain enzymes to destroy sperm receptors after fertilization
How does a egg provide developmental signals to influence cell fate
TFs switch certain genes on stimulating embryo development,
What is the time it takes from primordial to ovulation
120 days to mature
What must sperm undergo to become activated
capacitation
What does capacitation do
moves the sperm from a dormant, pampered, inactive state to an activated state
What occurs during capacitation
ATP production
flagellum movement
loss of coat
What is the loss of coat do
expose the egg-binding proteins/receptors
What induces capacitation
substances in the vagina
How long does capacitation take
2-3 days
How long do flagellum move
48 hours maximum
What occurs to aid in the movement of sperm to egg
muscular contractions and cilia of oviducts
Why does the sperm need aid
sperm don’t know where to swim to
What also occurs to help attract the sperm to the egg
chemotaxis
What is chemotaxis
movement of sperm toward the source of a chemical signal produced by the egg
When are these chemical signals released
after ovulation
What are the chemical sources originating from
granulosa cells or the fluid of the follicular antrum
Do all eggs have the same chemical
no
What does the chemical from the egg match
receptors on different species’ sperm
how many sperm typically reach the egg when released in the vagina
100
What are the 3 barriers of an egg
granulosa cells
zona pellucida
plasma membrane
How does the sperm cross the granulosa cells
sperm have an enzyme that digests the ECM between the granulosa cells
What is the enzyme that degrades the ECM between granulosa cells
ph20
What also aids the sperm in getting past the granulosa cell layer
the flagellum helps it wriggle between to get in contact with the zona pellucida
How does the sperm get past the zona pellucida
uses a receptor to bind to the receptor on the zona pellucida
What is the name of the receptor on the sperm
ZRK
Where is ZRK location on the sperm
head of the sperm
What does ZRK stand for
Zona Receptor kinase
What is the name of the receptor on the zona pellucida
ZP3
What does the binding of the ZRK to ZP3 initiate
the initiating the opening of calcium channels in the sperm’s head to open
What happens when calcium channels open
calcium influx
What does penetrating the zona pellucida require
the acrosome reaction
When does the acrosome reaction occur
front of acrosome and the plasma fuses at several points
What does this fusing of the acrosome and PM cause
disintegration of the acrosome to release enzymes
What are the enzymes released
proteases and glycosidases
What do proteases and glycosidases do
dissolve holes in the zona pellucida by breaking down the glycoproteins
What does the sperm do next to finish crossing zona pellucida
wiggle its way through
What is the second receptor on the inside of sperm
Izumo-1
What does Izumo-1 attach to
Juno receptor on the eggs PM
What happens when Izumo-1 and Juno attach
PM will fuse, sperm becomes parn of the evv
How many copies of chromosomes are in egg when the sperm fuses with it
3C total
What must the egg do
get rid of 1 chromosome copy through another polar body (end of meiosis 2)
What is formed at the end of meiosis
single cell
What is this single cell called
zygote
Where did most of the zygotes membrane come from
the egg, small bit from sperm
Where did most of the organelles for the zygote come from
a few mitochondria from sperm, centrosome from sperm, rest from egg
Sperm fusion means the egg is now what
egg is activated
What does an activated egg mean
conception
What events occur to complete conception
release metaphase block, dumping of chromosomes, programming of sperm genes
initiation of mitosis
increase of synthetic activity needed for rapid cell division
blocks to polyspermy
How is programming of sperm genes occurring
sperm chromosomes released into the egg are unfolded. TFs and methylases in the egg’s cytoplasm switch on certain genes promoting development
What are the steps to initiate mitosis
replication of male and female chromosomes
sperm’s centriole constructs mitotic spindles
chromosomes line up and separate
cell divides
What increase of synthetic activity occurs
synthesis of extra PM synthesis of nucleotides DNA replication synthesis of histones to fold newly replicated DNA no time for transcription maternal ribosomes
What are the only things being replicated
chromosomes
what translates into proteins, histones, ect
mRNA stored by the egg
What is polyploidy
where there is an extra entire set of chromosomes
What animals are ok with polyploidy
fish, insects, heart and muscle cells
Why is blocking polyspermy
so you don’t get polyploid
What percentage of pregnancies are triploid
3%
What is digyny
two sets from egg
What is diandry
2 from sperm/ 1 from egg
In mitosis is extra chromosomes a problem
no
In meiosis is extra chromosomes a problem
yes
What percentage of polyploidy babies are born
0.1%
How is blocking polyspermy achieved
block and inactivate Juno receptors in PM
What occurs first to block Juno receptors
membrane depolarizes
How does membrane depolarizes
change in ion distribution
Is the membrane polarized or unpolarized
polarized
What is high ion concentration on outside
sodium
What is high concentration on inside
potassium
Does inside have greater negative or positive charge
negative
Upon membrane fusion between PM and sperm what occurs
membrane de-polarizes
How does the membrane depolarize
sodium channels open
What happens when sodium channels open
sodium flood inside
What follows sodium flooding in
potassium channels open
What happens when potassium channels open
potassium floods out
What happens to the charges
outside goes negative
What happens when the charge becomes negative
the juno egg surface proteins wilt
how long does this block last
1 minute
Is the block of depolarization fast or slow
fast
How fast is it
takes a second to start
What is the second mechanism to help block polyspermy
cortical reaction
what does cortical reaction include
cortical granules
What does the cortical granules contain
proteases
polysaccharides
peroxidase
When sperm binds to membrane initially, what happens
calcium influx
What does this calcium influx cause
granules are exocytosed releasing the 3 P enzymes
What does protease enzyme do
destroy Juno proteins permanently so no sperm can attach again
What does polysaccharides do
absorb water between PM and the zona pellucida
What does absorbing water do
causes the region to swell distancing the sperm from the egg PM
What is the function of the peroxidase enzymes
cross link the zona pellucida, cementing zona pellucida
What does cross linking the zona pellucida do
makes it harder for sperm to penetrate, no longer can be dissolved by acrosomal enzymes
After all the enzymes have taken effect what occurs to the chopped up Juno proteins
exocytosis
How long does it take for cortical block to initiate
1 minute to initiate but is permanent
What is parthenogenesis
development of unfertilized eggs
What does parthenogenesis mean
virgin origin
Is parthenogenesis normal
in other organisms, not humans
What other organisms use parthenogenesis
bees, ants, wasps,
What are rare organisms that use parthenogenesis
Komodo dragons, sharks, chickens, snakes, fish
Is parthenogenesis lethal
for the most part
In humans, what does parthenogenesis cause
dermoid cysts in the ovary
What is a dermoid cyst
egg still in ovary starts to develop
What is seen in a developing dermoid cyst
teeth, hair, glands
A dermoid cyst can also be referred to as a
teratoma
Why does parthenogenesis not explain the virgin birth of Jesus
Jesus was not female, all progeny would have to be female
What makes parthenogenesis rare
regaining a diploid state
How would a diploid state be retained
skipping second meiotic division fusion between two haploid daughter cells activate development similar to molar pregnancies egg undergoes mitosis not meiosis
What would happen if second meiotic division was skipped
identical pairs of chromosomes
What is negative part of having identical pairs of chromosomes
homozygous for all traits=recessive mutations are activated
What is the fusion between two haploid daughter cells
polar body fuses with the egg
What would happen if the fusion would occur chromosomaly
identical chromosomes
What occurs with activated development that could occur to cause parthenogenesis
activate mitosis but block cytokinesis
What is the occurrance of molar pregnancies
1:1000
What is a molar pregnancy
egg that has no chromosomes gets fertilized with sperm
How many copies of chromosomes would the molar pregnancy have
1C
Is the molar pregnancy a cyst or an actual pregnancy
pregnancy
After the 1C is released into empty egg, what happens
mitosis and division of cell into multiple cells
What is the result of division in the molar pregnancy
overproliferation of trophoblasts
What is the end result of molar pregnancy
10-15cm cluster of cysts that need removed
How are chromosomes seperated in meiosis
get seperated by homologs
How are chromosomes seperated in mitosis
get seperatied by identicals to create pairs of homologs
If a primary egg undergoes mitosis instead of meiosis what occurs
the baby is a clone to the mom
What is another rare way that could cause parthenogenesis to occur
activating egg development
What ways may activate egg development
squeezing egg too much that it opens calcium channels,
heat/ oxidizing agents activate protein kinases or unblock mRNAs that lead to TF activation
needle prick or nuclear transplantation
What does poking a hole in the egg cause it to activate
lets calcium in
