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sex and reproduction 2 Flashcards

1
Q

what do sex hormones affect

A

growth, development, reproductive cycles and sexual behaviour

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2
Q

what are the sources of sex hormones

A

gonads and the adrenal glands

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3
Q

what are the 3 types of steroid hormone secreted by the gonads

A

androgens, oestrogen and progesterone

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4
Q

what is the most important oestrogen in the female reproductive system

A

oestradiol

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5
Q

what is progesterone involved in

A

preparation and maintenance of tissues of the uterus required for the support and growth of an embryo

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6
Q

what is synthesis of gonadal hormones usually controlled by

A

two gonadotropins from the anterior pituitary - FSH and LH

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7
Q

what is gonadotropin secretion controlled by

A

secretion of GnRH from the hypothalamus

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8
Q

what is AMH

A

it is released from the testes along with testosterone and promotes the degeneration of female ducts

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9
Q

what is the bipotential gonad

A

it either forms testes or ovaries - it is the structure present in the embryo before sexual development occurs

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10
Q

what is DES

A

synthetic oestrogen prescribed to women at risk of pregnancy complications
it can alter the reproductive system of the fetus and is now recognised as an endocrine disrupter (a foreign molecule that interrupts the normal function of a hormone pathway)

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11
Q

what happens in asexual reproduction of aspen trees

A

all trees in a groove have developed from the roots of one founder tree - the grove is a somatic clone

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12
Q

what describes the sexual rituals of lizard mating even though parthenogenesis is occurring

A

pseudo mating

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13
Q

how doo bananas breed

A

asexually - they are all clones of the buds forming from the main plant - similar to aspen trees

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14
Q

what is fertilization

A

the fusion of gametes to form a zygote

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15
Q

what would happen if polyspermy were too occur

A

the entry of multiple sperm cells into the egg nuclei - the resulting abnormal number of chromosomes would be lethal to the embryo

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16
Q

what is an acrosomal reaction

A

the discharge of hydrolytic enzymes from the acrosome, a vesicle at the tip of the sperm, when the sperm approaches or contacts an egg

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17
Q

what is an acrosome

A

a vesicle at the tip of a sperm that contains hydrolytic enzymes and other proteins that help the sperm reach the egg

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18
Q

what do the hydrolytic enzymes of the acrosome of a sperm do during the acrosomal reaction

A

they partially digest the jelly coat of the egg enabling a sperm structure called the acrosomal process to form elongate and penetrate the coat

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19
Q

what do the protein molecules on the tip of the acrosomal process do

A

they bind to specific receptor proteins in the egg plasma membrane

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20
Q

what happens after the sperm has bound to the receptor proteins on the egg in the acrosomal reaction

A

the sperm nucleus enters the egg cytoplasm as ion channels open in the eggs plasma membrane.
sodium ions diffuse into the egg causing depolarization which acts as a fast block to polyspermy

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21
Q

how is the slow block to polyspermy established

A
  • once the sperm binds to the egg, vesicles called cortical granules fuse with the egg plasma membrane
  • the contents of the cortical granules are released into the space between the egg plasma membrane and the surrounding vitelline layer
  • enzymes and other granule contents then trigger a cortical reaction which lifts the vitelline layer away from the egg and hardens the layer to protect the fertilization envelope that has just been formed
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22
Q

what are the steps in the acrosomal reaction and the cortical reaction

A
  1. contact - the sperm contacts the eggs jelly coat
  2. acrosomal reaction - hydrolytic enzymes are released from the acrosome making a hole in the jelly coat. the acrosomal process protrudes from the sperm head, penetrates the jelly coat and binds to receptors in the egg plasma membrane
  3. contact and fusion of sperm and egg membranes - fusion triggers depolarization of the membrane which acts as a fast block to polyspermy
  4. cortical reaction - cortical granules fuse with the plasma membrane. the secreted contents clip off sperm binding receptors and cause the fertilization envelope to form. this acts as a slow block to polyspermy
  5. entry of the sperm nucleus
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23
Q

what does formation of the fertilization envelope require

A

high concentrations of calcium ions in the egg

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24
Q

what signal transduction pathway is activated when the sperm binds to the egg

A
  • a signal transduction pathway that triggers the release of calcium ions into the cytosol from the ER
  • the resulting increase in calcium ion concentration causes the cortical granules to fuse with the plasma membrane
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25
Q

fertilization initiates and speeds up the metabolic reactions that bring about the onset of ………………

A

embryonic development

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26
Q

what causes egg activation

A

the rise in calcium ion concentration

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27
Q

artificial fertilization is possible even if the nucleus has been removed from the egg - what does this suggest

A

the proteins and mRNAs required for activation are already present in the cytoplasm of an unfertilised egg

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28
Q

what marks the end of the fertilization stage

A

it is complete once the egg and sperm nuclei have fused and the first cell division has taken place

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29
Q

what is a key difference between sea urchin and human fertilization

A

sea urchins eggs have already completed meiosis once they are released from the female whereas human eggs are arrested at metaphase II until a sperm binds

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30
Q

terrestrial animals fertilise their eggs internally/externally

A

internally

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31
Q

in mammals what surrounds the egg before and after ovulation

A

a layer of follicle cells - support cells

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32
Q

in mammals what is the zona pellucida

A

the extracellular matrix of the egg

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33
Q

where on the egg does the binding of sperm result in initiation of the acrosomal reaction

A

the sperm receptor

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34
Q

what does sperm binding to the egg trigger

A

the cortical reaction

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35
Q

In mammals what happens in the cortical reaction

A
  • sperm binding triggers the release of enzymes from the cortical granules to the outside of the cell
  • the enzymes catalyse changes in the zona pellucida which acts as the slow block to polyspermy
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36
Q

do mammals have a fast block to polyspermy like sea urchins

A

no - they only have the slow block that results from the cortical reactions

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37
Q

what is the next stage of development after fertilization

A

cleavage

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38
Q

the nucleus in a newly fertilised egg has too little DNA to synthesis enough …………… to meets the cells need for new proteins

A

mRNA

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39
Q

initial development is carried out by proteins and mRNA deposited in the egg during which process

A

oogenesis

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40
Q

what is cleavage

A

a series or rapid cells divisions during early development

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41
Q

during cleavage the cell cycle consists mainly of which 2 steps

A

M (mitosis) and S (DNA synthesis)

the G1 and G2 phases are skipped and little or no protein synthesis occurs

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42
Q

what is the result of little or no protein synthesis occurring in cleavage

A

the cell doesn’t increase in mass

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43
Q

what is the result of cleavage

A

it partitions the cytoplasm of the large fertilised egg into many smaller blastomeres

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44
Q

what is the need for blastomeres

A

because they are smaller the DNA is able to produce enough RNA to make the proteins the cell requires for programming further development

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45
Q

what do the first 5-7 cleavage divisions produce

A

hollow balls of cells (blastula) surrounding a fluid filled cavity called the blastocoel

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46
Q

what are the 4 steps of cleavage in sea urchins

A
  1. fertilized egg - zygote surrounded by the fertilization envelope
  2. four cell stage - cells have completed the second cleavage division
  3. early blastula - after further cleavage divisions the embryo is a multicellular ball that is still surrounded by the fertilisation envelope. the blastocoel has begun to form in the centre of the cells
  4. later blastula - a single layer of cells surround a large blastocoel and the fertilisation envelope is still present
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47
Q

in the eggs of frogs and many other animals, stored nutrients called ………….. are concentrated to one pole called the ……….. pole and away from the ………. pole

A

yolk
vegetal pole
animal pole

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48
Q

what results from the asymmetrical distribution of yolk in the eggs of frogs

A

it give the animal and vegetal hemispheres different colours and influences the pattern of cleavage divisions

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49
Q

when an animal cell divides an indentation called a …….…….……………. forms in the cell surface as cytokinesis divides the cell in half

A

cleavage furrow - forms a small groove in line with the old metaphase plate and on the cytoplasmic side contains a contractile ring of actin and myosin that interact to pinch the cell in 2

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50
Q

in the frog embryo where do the fist cleavage furrows form

A

parallel to the line connecting the 2 poles

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51
Q

what happens as a result of the yolk having slow cytokinesis

A

the fist cleavage furrow is still dividing the yolky cytoplasm in the vegetal hemisphere when the second cell division begins

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52
Q

what is the result of the first two cleavage divisions

A

four blastomeres of equal size extend from the animal pole to the vegetal pole

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53
Q

what happens during the third cleavage division in frog embryos

A
  • the yolk begins to affect the relative size of the cells produced in the 2 hemispheres
  • as each of the 4 blastomeres begin the division, yolk near the vegetal pole displaces the mitotic apparatus and the cleavage furrow from the egg equator towards the animal pole
  • the result of this is smaller blastomeres in the animal hemisphere than the vegetal hemisphere
  • the division is equatorial - perp. to the line connecting the poles - and produces an 8 cell embryo
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54
Q

what causes the blastocoel to form entirely in the animal hemisphere

A

the displacing effect of the egg yolk on the mitotic apparatus and the cleavage furrow persists in subsequent divisions after the third division of cleavage

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55
Q

cleavage in amphibian development is said to be holoblastic, what does this mean

A

complete - the cleavage furrow still passes right through the egg even though the yolk affects where it divides it

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56
Q

describe the cleavage in animals whose eggs contain little yolk e.g. humans

A

it is holoblastic
the blastocoel forms centrally
the blastomeres are generally of similar size

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57
Q

give examples of animals whose volume of yolk is so large that the cleavage furrow cannot pass through it

A

birds, reptiles, many fish and insects

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58
Q

what happens if the volume of yolk is so great that the cleavage furrow cannot pass through it

A

only the region of the egg lacking yolk undergoes cleavage - this is called meroblastic cleavage

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59
Q

for chickens the part of the egg that we call the yolk is not actually the yolk, what is it

A

the entire egg cell

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60
Q

in early development of drosophila, multiple rounds of replication occur without cytokinesis - what does this account for

A

no cell membranes form around the early nuclei
the nuclei spread throughout the yolk and later migrate to the outer edge of the embryo
after further mitosis the plasma membrane forms around each nucleus
the embryo is now the equivalent of a blastula

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61
Q

what occurs over the last 2 stages of embryonic development

A

morphogenesis

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62
Q

what are the last 2 stages of embryonic development

A

gastrulation and organogenesis

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63
Q

what are the stages of embryonic development in order

A

fertilization
cleavage
gastrulation
organogenesis

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64
Q

give an overview of gastrulation

A

sets of cells at or near the surface of the blastula move to an interior location, cell layers are established and a primitive digestive tube is formed

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65
Q

give an overview of organogenesis

A

the formation of organs

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66
Q

gastrulation id the dynamic reorganisation of the hollow blastula into a 2 or 3 layered embryo called a …….…..

A

gastrula

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67
Q

only the embryos of animals ……………

A

gastrulate

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68
Q

what are the cell layer produced in gastrulation called collectively

A

germ layers

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69
Q

in the gastrula, …………….. forms the outer layer and …….…….…. forms the lining of the digestive tract

A

ectoderm - outer

endoderm - inner

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70
Q

what are diploblasts

A

animals that only form ectoderm and endoderm layers in gastrulation - occurs in radially symmetric animals

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71
Q

what are tripoblasts

A

a third germ layer is formed between the ectoderm and endoderm in gastrulation - occurs in bilaterally symmetric animals

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72
Q

what does gastrulation typically begin with

A

invagination

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73
Q

what is invagination

A

the infolding of a sheet of cells

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74
Q

describe invagination

A
  1. at the end of cleavage single cells cover the surface of the blastula
  2. a group of cell buckle into the blastocoel forming a shallow depression
  3. continued invagination forms a blind ended tube, the archenteron
  4. the open end of the archenteron is called the blastopore
  5. the tip of the archenteron reaches the embryo surface completing formation of the primitive gut of the embryo, now a gastrula
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75
Q

at the end of embryogenesis each germ layer gives rise to what

A

specific tissues and organs

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76
Q

what are the major derivatives of the ectoderm (outer layer)

A
  • epidermis of the skin and its derivatives
  • nervous and secretory systems
  • pituitary gland and adrenal medulla
  • jaws and teeth
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77
Q

what are the major derivatives of the mesoderm (middle layer)

A
  • skeletal and muscular systems
  • circulatory and lymphatic systems
  • excretory and reproductive systems (except germ cells)
  • dermis of the skin
  • adrenal cortex
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78
Q

what are the major derivatives of the endoderm (inner layer)

A
  • epithelial lining of the digestive tract and associated organs
  • epithelial lining of the respiratory, excretory and reproductive tracts and ducts
  • thymus, thyroid and parathyroid glands
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79
Q

when does embryo development begin in humans

A

when the embryo makes its way down the oviduct to the uterus

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80
Q

what are the 4 steps of embryonic development gastrulation in humans (detailed)

A
  1. at the end of cleavage the embryo is called a blastocyst (mammalian name for blastula). at one end of the blastocyst is the inner cells mass which will develop into the embryo proper
  2. implantation of the embryo is initiated by the trophoblast (the outer epithelium of the blastocyst). enzymes secreted by the trophoblast breakdown the endometrium allowing invasion by the blastocyst. the trophoblast also extends finger like projections that cause capillaries in the endometrium to spill out blood so it can be captured by the trophoblast tissues. during implantation the inner cells mass forms a flat disc with an inner layer of cells (epiblast) and an outer layer (hypoblast)
  3. as implantation is completed, gastrulation begins. some epiblast cells remain as ectoderm on the surface while others move inwards through a primitive streak and form the mesoderm and endoderm. after implantation, the trophoblast continues to expand into the endometrium and 4 new membranes appear (extraembryonic membranes). the membranes arise from the embryo but they enclose structures located outside the embryo
  4. by the end of gastrulation the embryonic germ layers have formed. extraembryonic mesoderm and extraembryonic membranes now surround the embryo. cells of the trophoblast, epiblast and endometrial tissue all contribute to the formation of the placenta
81
Q

what part of the blastocyst is the source for the embryonic cell lines

A

the inner cell mass

82
Q

the human embryo develops almost entirely from epiblast/hypoblast cells

A

epiblast

83
Q

what are the four stages of embryonic development and gastrulation in humans (short)

A
  1. blastocyst reaches uterus
  2. blastocyst implants
  3. extraembryonic membranes start to form and gastrulation begins
  4. gastrulation has produced a 3 layered embryo with 4 extraembryonic membranes: amnion, chorion, yolk sac, allantois
84
Q

what is the basic process of organogenesis

A

regions of the 3 embryonic germ layers develop into the rudiments of organs

85
Q

what is neurulation

A

the early steps in the formation of the brain and spinal chord in vertebrates

86
Q

what does cell migration in embryonic development involve

A

the cytoskeleton and the extracellular matrix

87
Q

what can happen in metamorphosis from larval to adult form

A

programmed cell death (apoptosis) of structures no longer required

88
Q

what defines a cells development fate

A

where it resides, how it appears and what it does

89
Q

what is meant by determination

A

the process by which a cell or group of cells becomes committed to a particular fate

90
Q

what is meant by differentiation

A

the specialization in structure and function

91
Q

every diploid cell formed during development has the same genome except from which cells

A

mature immune cells

92
Q

how do cells have different fates if they all have the same genome

A

they undergo gene expression so that only the genes required for their specialised functions are expressed

93
Q

what are fate maps

A

diagrams showing structures arising from each region of an embryo

94
Q

describe bilateral symmetry

A

body plan exhibits symmetry along the dorsal-ventral and anterior-posterior axes

95
Q

in the frog when is the position of the anterior-posterior axes determined

A

during oogenesis

96
Q

why is asymmetry apparent in the frog egg

A

because it forms 2 distinct hemispheres: dark melanin granules are embedded in the cortex of the animal pole, whereas the yolk fills the vegetal hemisphere

97
Q

the animal-vegetal asymmetry dictates where …………………. axis forms in the embryo

A

anterior-posterior

98
Q

how is the dorsal-ventral axes of the frog embryo determined

A

at random - wherever the sperm enters in the animal hemisphere determines where the dorsal-ventral axis forms

99
Q

what is a cortex

A

the outer layer

100
Q

what are the steps in axis establishment in an amphibian

A
  1. the polarity of the egg determines the anterior-posterior axis before fertilization (animal-vegetal poles)
  2. after fertilization, the pigmented cortex slides over the underlying cytoplasm towards the point of sperm nucleus entry. this rotation exposes a region of lighter-coloured cytoplasm, the gray crescent which is a marker of the future dorsal side
  3. the first cleavage division bisects the gray crescent. once anterior-posterior and dorsal-ventral axes are defined so is the left-right axis
101
Q

once the 16 cell stage is reached, mammalian cells are determined to form the ………….or the inner cell mass

A

trophoblast

102
Q

how do twins result

A

when cells or groups of cells from a single embryo become separated

103
Q

in general the tissue specific fates of cells are fixed in the late ……………

A

gastrula

104
Q

as embryonic development continues cells influence each others fate by …………….

A

induction

105
Q

inductive signals play a major role in …………………

A

pattern formation

106
Q

what is pattern formation

A

a process governing the arrangement of organs and tissues in their characteristic places in 3D space

107
Q

what are the molecular cues that control pattern formation called

A

positional information - these tell a cell where it is with respect to the body axes

108
Q

what do vertebrate limbs begin as

A

limb buds - bumps of mesodermal tissue covered by a layer of ectoderm

109
Q

how do non motile cilia function in development

A

they act as antenna on the cell surface receiving signals from proteins. the cilia are responsive to particular signals. when cilia are defective, signalling is disrupted

110
Q

how do axis formation and pattern formation differ

A

axis formation establishes the location and polarity of the 3 axes that provide the coordinates for development
pattern formation positions particular tissues and organs in 3D space defined by the coordinates from axis formation

111
Q

there is never more than one ………… in one genus

A

asexual species

112
Q

how can aspen reproduce

A

sexually and asexually
asexually - trees develop from the root system of a founder tree - slow mutation rate
sexual - variation produced

113
Q

how do dandelions reproduce

A

they are obligate asexual reproducers by apomixis

- diploid ovules become seeds and they are disseminated in the wind

114
Q

in parthenogenic lizards how are eggs produced

A

by mitosis

115
Q

what is the relative hormone concentrations of the lizard on top in pseudo sex

A

low level of oestradiol
high levels of progesterone
small ovary

116
Q

what is the relative hormone concentrations of the lizard on the bottom in pseudo sex

A

high oestradiol
low progesterone
increase in ovary size –> ovulation

117
Q

giving up sex is an evolutionary …………..

A

dead end

118
Q

explain how bananas being genetic clones was disadvantageous

A

when panama disease came about it was able to infect a banana host and so it was able to infect every gros michel banana because they are identical
a new strain evolved and was then able to exploit cavendish bananas too
if a virulent pathogen arises that can affect one host of a single genotype species then it can affect them all

119
Q

which race of the panama disease is cavendish resistant to

A

race 1

but is sensitive to race 4

120
Q

is different virulence of a pathogen in one species common

A

yes - but only if they reproduce sexually to introduce variation
with asexual reproduction the genotypes are the same without mutations so pathogens have similar virulence in each species

121
Q

what is the red queen hypothesis

A

when the evolution of the host drives the evolution of the pathogen - coevolution
continual evolution is required to maintain relative fitness compared to the other evolving system

122
Q

..……….. in host species reduces the likelihood of a pathogen wiping out an entire population

A

genetic diversity

123
Q

give examples of red queen arm races

A

predator/prey

host/pathogen

124
Q

explain how sexual selection can be an evolutionary arms race

A

sexual preference in one gender drives the physical or behavioural functions in the other gender
e.g. peacock tail - why they are always perfect

125
Q

is a male human heterogametic or homogametic

A

heterogametic - 2 sex chromosomes

126
Q

why in XXY does Y still promote maleness

A

because the Y chromosome has the SRY gene which is dominant

127
Q

how do XX males occur

A

if a region of Y translocates onto X

128
Q

how do XY females arise

A

by rare Y chromosome deletions

129
Q

which sex is the default sex

A

female

130
Q

what does SRY control

A

the mammalian switch that controls mammalian sex determination

131
Q

how does SRY work

A

it triggers a regulatory cascade of other genes and their encoded proteins

  • the SRY gene encodes a protein that is a transcription factor
  • transcription factors regulate gene expression by binding to specific DNA sequences adjacent to genes
132
Q

what is the indifferent gonad

A

the bipotent gonad
A gonad in an embryo that has not differentiated into a definitive testis or ovary. An indifferent gonad becomes a testis if the embryo has a Y chromosome, but if the embryo has no Y chromosome, the indifferent gonad becomes an ovary.

133
Q

for the first 6 weeks of gestation in humans what is important to notice

A

sex development has not begun - at this point all embryos express the same genes

134
Q

what does the indifferent gonad develop from

A

the genital ridge

135
Q

which two types of cells do the gonads contain

A

germ cells and somatic cells

136
Q

where do the somatic cells develop

A

in the genital ridge

137
Q

where do the germ cells migrate from

A

they migrate from the hind gut to the genital ridge

138
Q

what do the indifferent gonads develop into

A

the testes or the ovaries

139
Q

in XX embryo what do the Mullerian ducts differentiate into

A

the oviduct

140
Q

in an XX female what happens to the Wolffian duct

A

it degenerates

141
Q

what happens to the Wolffian and Mullerian ducts in the XY embryo

A

each Wolffian duct differentiates to form and epididymis, vas deferens and seminal vesicle and the Mullerian ducts degenerate

142
Q

what are the structures found in the indifferent gonad

A
  • mesonephros - embryonic kidney (distinct from adult kidney) - contributes ducts to the males and female reproductive organs
  • metanephric - kidney - persists as an adult
  • ureter - persists in adults
    gonads
  • gonads
  • Wolffian duct
  • Mullerian ducts
143
Q

what happens to the cloaca in the indifferent gonad

A

it becomes 2 openings: urethral and anal

it later becomes 3 in females - vaginal

144
Q

how does the indifferent gonad develop into a penis

A

genital swellings fuse together - to form the penis

145
Q

how does the indifferent gonad develop into the female reproductive organs

A

the genital swellings stay separate forming the labia majus and the glans become the clitoris

146
Q

what are the 4 transcription factors central to mammalian sex determine

A

SF1 - expressed in somatic gonadal precursor genital ridge cells. it is required for proper gonad development in males and females
SRY - making the sex decision
SOX9 - needed in males for the full male phenotype
DMRT - needed in females for the full male phenotype

147
Q

describe the path of sex development form the indifferent gonad

A
  • SF1 expressed in the indifferent gonad
  • DMRT on NO SRY - pre-female
  • DMRT stays on
  • ovary and female
  • SF1 expressed in the indifferent gonad
  • DMRT on SRY on pre-male
  • DMRT off SOX9 on
  • male and teste

(DMRT is only transiently expressed and is turned off by the presence of SRY)
(SRY turns on SOX9)

148
Q

describe the path in the production of testosterone

A
  1. MALES: SRY expressed in somatic gonadal precursor cells of genital ridge, SOX9 activated & DMRT off, cells differentiate into Sertoli cells.
  2. Sertoli cells secrete Anti-Mullerian Hormone (AMH).
  3. AMH promotes Leydig cell differentiation in gonad.
  4. Leydig cells produce testosterone.
  5. Testosterone promotes the male phenotype
149
Q

why can men continue to produce sperm throughout their life

A

because the spermatogonium continually divides

150
Q

what are the basic steps in the ovarian cycle

A
  1. primary oocyte within follicle
  2. growing follicle
  3. mature follicle
  4. ruptured follicle
  5. ovulated secondary oocyte
  6. corpus luteum formation
  7. corpus luteum degenerates
151
Q

what is the oocyte surrounded by

A

follicle cells

152
Q

which hormone increases with follicle cell growth

A

oestradiol

153
Q

what happens in ovulation

A

the follicle ruptures and ovum released into the oviduct

154
Q

what does the corpus luteum develop from

A

the remnants of the follicle

155
Q

what does the corpus luteum release

A

progesterone and oestradiol

156
Q

where are corticosteroids made

A

adrenal glands on the top of the kidney

157
Q

where are sex steroids made

A

the gonads or the placenta -they are synthesised from cholesterol

158
Q

what are the roles of corticosteroids

A

• Regulate various aspects of homeostasis, blood pressure, water retention, salt balance, immune system & inflammation

159
Q

where are sertoli cells found

A

the seminiferous tubules

160
Q

where are the Leydig cells found

A

in between the seminiferous tubules

161
Q

a large follicle synthesises high levels of what

what does this stimulate

A

oestradiol - which in high levels stimulates the hypothalamus to produce GnRH which stimulates the anterior pituitary to produce FSH and LH

162
Q

what happens to the levels of progesterone and oestradiol when the corpus luteum degenerates

A

they decrease removing the inhibition on the hypothalamus

163
Q

what inhibits the anterior pituitary

A

low levels of oestradiol

164
Q

what are the 3 steps in the ovarian cycle

A
  1. follicular phase
  2. ovulation
  3. luteal phase
165
Q

what do progesterone and oestradiol promote

A

the thickening of the endometrium

166
Q

when are the oestradiol and progesterone levels low

A

early in the follicular phase and in the menstrual flow phase

167
Q

what happens in the menstrual flow phase

A

bleeding

168
Q

what happens in the proliferative phased

A

build-up of endometrium

169
Q

when are hormone levels high

A

in the secretory phase

need high levels of hormones for the uterus to be able to receive an embryo.

170
Q

what does low progesterone promote

A

the proliferative phase

171
Q

what happens in the follicular phase

A

the new follicle is developing

172
Q

what do the hydrolytic enzymes in the acrosome do

A

digest carbohydrate bonds
digest peptide bonds
sperm receptor for egg protein

173
Q

what is capacitation

A
  • occurs in female tract as sperm swims out of seminal fluid into female tract secretions
  • acrosome membrane fuses with sperm cell membrane which exposes sperm receptor for egg protein
  • sperm now ready to fuse with the egg
174
Q

what happens to the egg when a sperm penetrates it

A

Extracellular matrix is changed by enzymes so that it Is no longer permeable to sperm. All the sperm receptor proteins on the membrane are also destroyed. By this process it is ensured that triploids are not produced

175
Q

cells progressively lose …………… when they commit to specific cell fates

A

totipotency

176
Q

Terrestrial embryos have true embryonic tissue PLUS …………………….. that helps surround the embryo in a reservoir of fluid - the amnion or amniotic sac.

A

extraembryonic tissue

177
Q

does the trophoblast contribute to the embryo

A

no - only thee placenta

178
Q

what does the trophoblast secrete

A

human chorionic gonadotropin (hCG) (a hormone). Acts like LH – maintains the corpus luteum which continues to secrete oestradiol and progesterone. Maintains endometrium (no menstrual bleeding).

179
Q

what are the steps in gastrulation

A

hypoblast cells displaces by inward migrating epiblast cells - internal epiblast become endoderm, outer ectoderm
more epiblasts squeeze between ecto and endo and becomes the mesoderm

180
Q

The ……………….. genes specify regional identity to body segments and work by work by regulating the expression of other genes to control differentiation.

A

Homeotic - they contain HOX which encode transcription factors

181
Q

expression of …………. proteins is global positioning giving regional identity in animals

A

HOX - shorts for homeotic box containing genes

182
Q

what is an enucleated egg

A

an egg with its nucleus removed

183
Q

describe gurdons experiment

A
  • he used UV light to destroy the nucleus of tadpole egg cells
  • he transplanted either a cell from a tadpole embryo or an intestinal cell from a fully developed tadpole into an enucleated egg
  • the results showed that the embryo cell when transplanted into the egg was able to regenerate an entire organism whereas the intestinal cell test stopped developing before tadpole stage
184
Q

what do homeotic genes determine

A

the special arrangement of structures about the body axes

185
Q

the products of which class of homeotic genes provides positional information in an embryo

A

HOX genes - prompts cells to develop into structures appropriate for a particular location

186
Q

when expressed what does the ubx HOX gene suppress

A

leg formation

187
Q

what are three major parts of a fruit fly

A

head, thorax (midbody where wings and legs extend), abdomen

188
Q

what is the anterior-posterior axis of a fruit fly

A

head to tail

189
Q

what is the dorsal-ventral axis of a fruit fly

A

back to belly

190
Q

what does much of the genetic variation of humans seem to be in the from of

A

SNPs - single nucleotide polymorphisms - single base pair mutations

191
Q

what are CNVs

A

when people have more or lees than the standard 2 copies of a gene - copy number variants

192
Q

what is a homeobox

A

a 180 nucleotide sequence within homeotic genes that is widely conserved in animals

193
Q

do all homeobox containing genes act as homeotic genes

A

no - the ones that don’t act as homeotic genes do not directly control the identity of body parts

194
Q

what do homeobox encoded homeodomains do

A

they bind to DNA and function as a transcription factor regulating gene expression

195
Q

the luteal phase of the ovarian cycle is coordinated with what phase of the uterine cycle

A

secretory

196
Q

the follicular phase of the ovarian cycle is coordinated with what phase of the uterine cycle

A

proliferative phase

197
Q

what are the 2 key apoptosis genes in C. elegans

A

ced-3 and ced-4 - apoptosis occurs when their proteins are present in inactive forms - this results in ced-9 releasing the “brake” on apoptosis and the apoptotic pathway activates proteases and nucleases that cut up the proteins and DNA of the cell

198
Q

when cytochrome c is released from the mitochondria what does it act as

A

a cell death factor

B (19 decks)

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