Exam 1: Week 4 and 5 Flashcards
sex defined by evolutionary biology
By sex in eukaryotes, we understand a more of less regular alternation of meiosis and syngamy
- traits and activities of bodies, such as the number of sexes and the differences between them, emerge as consequence of cellular processes
eukaryotes
(good nuts) organism whose cells have membrane bound nucleus
meiosis
a special type of cell division of germ cells in sexually reproducing organisms that produce the gametes, sperm or egg cells
- for the production of gamete cells which fuse in syngamy eventually ⇒ go from diploid to haploid
syngamy
the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or offspring
everyday language sex definition
something to do with bodies, categories of individuals, and certain activities and feelings
- The physical and behavioral characteristics that make males and females different from each other
- Either of two groups into which many living things are divided according to their roles in reproduction and which consist of males or females
- activity
mitosis
the division of somatic cells in eukaryotes => Greek for mitos = thread
- Each chromosome copies itself
- The microtubules pull threads apart and line up homologous pairs of chromosomes ⇒ homo in latin means same and logous in greek means origin
- Duplicated chromosomes are pulled apart so each daughter chromosome ends up with one copy of every chromosome present in the mother cell
T/F mitosis is asexual reproduction
True
diploid
two copies of every chromosome
haploid
one copy of every chromosome
crossing over
homologous chromosomes will swap sections of DNA
- Gametes are not identical to any chromosomes because they mix and match
- Nucleus divides into 2 daughter cells and these divide again which result in 4 daughter cells which are haploid (23 chromosomes only)
who was the first to publish crossing over in 1916?
Thomas hunt morgan
what happens to alleles for sexually vs asexually reproduction?
- in asexual reproduction you won’t get new combinations of alleles
- sexually reproducing creates 10 (for ex) different possible phenotypes that arise from the combination of 2 alleles
mullers ratchet
in asexual organisms, there is a ratcheting effect where evolutionary change only goes in one direction (downhill) ⇒ with every cell division there is a possibility for deleterious mutations which can exterminate the population
- If you are diploid, when you get two deleterious mutations then your lineage ends
- Problem for asexual reproducing species because they cannot recover from the mutations
how does sexual reproduction combat mullets ratchet?
because there is mixing of alleles they can prevent elimination because only some of the offspring will die ⇒ others will persist and keep reproducing
how do bacterium overcome mullets ratchet?
Some can engage in sex but not sexual reproduction and exchange genetic information
- They also have such a sheer number of offspring that doubles every hour or so then as long as the reproduction rate is faster than the mutation rate most of the daughter cells won’t have deleterious mutations ⇒ this is where benefits come in
Arguments for RQH (4)
- parasites have shorter generation time than their hosts
- Parasites evolve faster
- To keep even with parasites, hosts have sex
- Quick way to get genetic diversity
what is the arms race?
organisms are engaged in a race for reproduction and they are racing against other in the same species but also others that seek to exploit them (predators, parasites)
why is it that parasites reproduce faster?
they are small which means they can evolve faster
- live on or inside the prey and eats a little bit at a time
who came up with red queen hypothesis?
Hamilton
how does sex benefit individual genes?
sex increases the chance of each gene being on the winning team ⇒ selfish gene hypothesis
- In order to win the race genes must cooperate with one another
- If you can switch “teams” then eventually you can win ⇒ why genes recombine
explanations for evolution of sexual reproduction (3)
- Repairing DNA
- Eliminating bad mutations
- Increasing genetic diversity
Repairing DNA hypothesis
fixing errors during recombination that have occurred
Eliminating bad mutations hypothesis
escaping muller’s ratchet which helps populations evolve
increasing genetic diversity hypothesis
tracking variable environments ⇒ increases the rate at which populations can evolve and allowing organisms to keep up with parasites (arms race)
what are limitations of explanations for sexual reproduction? (3)
- Why is sexual reproduction limited to eukaryotes?
- Why are there generally just two sexes?
- Other puzzling features of eukaryotes
prokaryote
refers to pre nuclear ⇒ DNA is a single circular loop and there can be more than one
- Karyote: nut
- DNA is not in a nucleus
Stromatolites
the biggest and most complex biological thing on the planet for a very long time ⇒ mats of accumulating bacteria
- most diversity today on the planet comes from prokaryotes
what is one of the major divisions in prokaryotes?
bacteria and archaea
archaea
group of microbes that are found only in extreme environments ⇒ boiling water, or frozen water, salty, acidic, etc.
what is interesting about eukaryotes and archaea?
They are microbes but occupy a different branch of the tree of life that we are on ⇒ we have similarities but also DNA that comes from bacteria
- bacteria DNA is most identified in our mitochondria
Endosymbiotic theory
circa 1.5 BYA there was a fusion between archaea and bacterial cells and archaea incorporated bacteria to live inside of them ⇒ mitochondria
- This process happened with plants as well when their ancestor incorporated a blue/green algae which evolved a process of making sugar from sunlight and water
- This is why plants have chloroplasts and can undergo photosynthesis
why did symbiosis help eukaryotes gain in size?
Allowed eukaryotic cells to grow bigger because mitochondria produce ATP ⇒ powerhouse of the cell as its currency for energy
- Mitochondria take input and turn it into ATP ⇒ thing the cell absorbs in its environment to things it can use ⇒ supports a larger genome
cambrian explosion
where we find in different fossil layers that evolution went from almost no detectable life (aside from microbes) to numerous amounts of living things (about 540 mya)
- we had an explosion of hard body parts including shells ⇒ life became diverse because there were things that preserved and fossilized well (eukaryotic evolution)
Intragenic region (intron)
region on a pre-mRNA that get spliced out
Expressed region (exon)
both in pre-mRNA and mRNA that get turned into proteins
metazoa
multicellular animals (us included)
- sex is ubiquitous, ancient, and inherent attribute of eukaryotic life
LECA-meca
the last eukaryotic ancestor where sex existed
- sex is always something eukaryotes do even though some can also reproduce asexually
mitochondria
organelle of cells in which biochemical process occur
- From greek mitos (thread) and khondrion (little granule)
- Khondros = granule, lump of salt
mitonuclear ecology theory
eukaryotes resulted from fusion of host cell and endosymbiont cells (mitochondria, chloroplasts)
- nucleus protects host DNA from endosymbiont DNA and oxidative stress
what happens when mitochondria die in the cell?
its DNA can then move about the cell and without a nucleus it will integrate into the nuclear genome ⇒ why there is a nucleus
- Oxidative stress is pollution that results from having the mitochondria create ATP
- Results in free radicals that integrate into the DNA and can cause mutations that are very harmful to the cell
free radicals
chemical products of energy production system that combine with other molecules and threaten DNA ⇒ problem for the cell
what are introns a result of?
from endosymbiont DNA contaminating host DNA
what does recombination do?
recombination repairs host DNA from contamination and mutations from oxidative stress
who proposed endosymbiotic theory?
Lynn Margulis and her husband
- proposed that organelles in eukaryotic cells originated as free living bacteria, swallowed up by larger cells
what supported endosymbiotic theory?
in 1980s when mitochondria and chloroplasts were found to have prokaryotic like DNA
proto-eukaryotes
the organisms that engulfed a bacterium and started to live in symbiosis with them
3 hypotheses for why sex would evolve
- Sex with recombination corrects corruption from mitochondrial genome
- Sex with recombination enhances compensatory coevolution (adjusts for changes to evolve together)
- Sex with recombination enhances natural selection against deleterious alleles
how does sex with recombination prevent mitochondrial corruption?
The segments of mitochondrial DNA will incorporate into the nucleus so the solution is to have sex with recombination
how does recombination enhance coevolution?
Mutational changes can occur in mitochondria and the nuclear DNA needs to compensate for this
- The nuclear DNA and the mitochondrial DNA need to be a good match for one another as most of the ancient mitochondrial genes have integrated to the nucleus
- Mitochondria are important for the electron transport chain and the krebs cycle making ATP
- Some proteins in this chain are coded for in the nucleus
- Other proteins are in the mitochondrial DNA
T/F The nuclear gene products and mitochondrial gene products must match perfectly or mitochondrial metabolic disorders occur
True
anisogamy
the merging of two different gametes
- in some species (including all animals and maybe all plants but not fungi) we have two different kinds of gametes
- size, flagellum, etc.
game theory
approach to think about competition as a game where there are certain strategies that work better than others
- Evolutionary stable strategies allow organisms to “at least break even” ⇒ gamete production is like a game and producing just one kind of gamete is a strategy
who came up with game theory for anisogamy?
Parker et al.
what type of selection created gametes?
divergent selection
- If you are small you can make more and have a tail to move around but less resources
- If you are large you can contain many nutrients but you cannot make as many or move as far
what did Hill hypothesize about mating types?
result from need to ensure that only one parent transmits mitochondria to offspring
- If you are one gamete type then you can only fuse with another mating type
- the winning strategy is to have both offspring types as it helps create the most offspring
what does game theory not explain?
mating types => Why can’t big gametes fuse?
- hill argues that mating types result from need to ensure that only one parent transmits mitochondria to offspring
what does syngamy tell us about having both mitochondrial types from parents?
selfish gene theory tells us if we have syngamy where mitochondria from both parents to live in the same cell, there will be an advantage for mitochondria that are not identical
- the cell does not need two types of mitochondria competing against one another
mating types
refer to incompatibilities between otherwise phenotypically similar partners (isogamy)
sexes
implies some anisogamy (asymmetry) between the interacting gametes or partners
what is interesting about slime molds?
they have mating types, not sexes
- They spend most of their lives living as independent amoebas but periodically join together to form a blob which crawls around and produces fruiting structures
- Some of the cells in the blob sacrifice themselves to be stocks while others produce spores involved in sexual reproduction
what are main reproductive differences between prokaryotes and eukaryotes?
prokaryotes exchange genes freely and dont have clear species boundaries while eukaryotes mate preferentially with certain partners and have species with reproductive boundaries
- species boundaries emerge from need to identify mates with compatible nuclear and mitochondrial genes
asexuality
individuals clone themselves when reproducing
monoecious (plants)/hermaphroditic (animals)
individuals have both male and female reproductive organs
Dioecious (plants)/gonochoristic (animals)
individuals have either male or female reproductive organs
what is interesting about barnacles?
Darwin spent much of his adult life studying them ⇒ they are crustaceans so they start out like crab animals which settle down before mating
T/F it’s uncommon to see sexual dimorphism across species between the sexes
False => it is common
what did Aristotle think about sex determination?
sex of child depends on temperature of semen at time of copulation
- Hot: males
- Cold: females
- this is common in reptiles
human sex determination
sex determination starts with chromosomes
- Female = XX
- Male = XY => Males can contribute either an X or Y chromosome
fruit fly sex determination
females are XX and males are XY
- Same genetic pattern as us ⇒ this is not universal
honey bee sex determination
Queen is XX, worker is XX, and drones are X
- Drones are typically male and haploid, produced from unfertilized eggs
chickens sex determination
male is ZZ and female is ZW
- W is the sex determining chromosome where the female is heterozygous
platypus sex determination
Its a mammal that produces milk ⇒ what offspring survive on, they also lay eggs which hatch and then nurse, males have a venomous spur on their hind feet
- Male: XYXYXYXYXY
- Female: XXXXXXXXXX
temperature dependent sex determination (TSD)
warmer temperatures result in female offspring while cooler temperatures result in male offspring
- this is problematic with climate change
what are the sex determination systems are there in vertebrates? (5)
- XX/XY
- XX/XY many
- ZZ/ZW
- ZZ/ZW multiple
- TSD
what is special about clownfish?
when the female dies, one of the males will become female and change sex to become bigger/fertile
- when born they are hermaphrodites (social sex determinism)
why is the Y chromosome so small?
Y doesn’t have a homologous chromosome to pair with during meiosis => Errors accumulate
- Leads to decay of sex chromosomes => evolving
fertilization
the chromosome from the sperm and egg unite to give a diploid set of chromosomes ⇒ females are born with all the eggs they will have in their lifetime
- after fertilization eggs migrate to uterus and implant into the uterine wall ⇒ every 28 days an egg matures in the female
ectopic pregnancy
when the fertilized egg fails to make it to the uterus and stays in the fallopian tubes ⇒ resulting in death of the mother unless medically altered
menopause
when the female stops menstruating at a certain age
- Running out of eggs, stop cycling, stop going through the process
- Dramatically reduced sex hormones ⇒ especially estrogen
T/F menopause is the norm for vertebrates
False only 5-6 species including humans, whales, and chimps
what body parts make up the undifferentiated stage of development? (4)
- Gonads
- Mesonephros
- Wolffian duct
- Mullerian duct
what body parts make up the male stage of development? (5)
- Seminal vesicle
- Vas deferens
- Prostate
- Epididymis
- testes
what body parts make up the female stage of development? (4)
- Fallopian tube
- Ovary
- uterus
- Vagina
what happens to certain tubes during male development?
Wolffian duct leads to vas deferens, seminal vesicle, prostate
- Mullerian duct degenerates
what happens to certain tubes during female development?
Mullerian duct leads to fallopian tubes
- Wolffian duct degenerates
what are the steroid hormones?
- Testosterone
- Androgens - Estradiol
- Estrogens
T/F Every human has both of the hormones but their levels differentiate
True
- simple changes can change one hormone to another ⇒ estradiol is made from testosterone
steroids
come from cholesterol ⇒ they are a closely related group of chemical messengers
- Mechanism through which behavior is expressed
what hormones do the gonads secrete (glands)?
- Testes make testosterone
- Ovaries make estrogens
what types of things preserve hormone levels?
anything with keratin preserves the signature of our hormone levels ⇒ blood, urine, feces are also ways
what things cause hormonal fluctuation?
- Puberty causes huge increases
- pregnancy or cycling
- menopause
- diurnal cycles daily
which structures are ovaries, labia, and clitorus homologous to?
the testes, scrotum, and penis
how are female vs male haploid cell productions different?
- females are born with lifetime supply of eggs (1-2 million and 1,000 los with each cycle) => only 400 ever mature
- for males, starting at puberty, testes produce 300 million sperm daily
what is the human karyotype like?
we have 23 pairs of chromosomes total but 22 are autosomal and the sex chromosomes can differ
X inactivation
in female mammals, one X chromosome is turned off (inactivated)
- This happens in early embryo formation, after a number of cell divisions have taken place
- Female mammals are a mosaic of different chromosomes => before the second X chromosome gets turned off some early cell activity comes from mother and father
mosaicism
female mammals are a mosaic of two different X chromosomes due to delayed inactivation of one sex chromosome
anhidrotic dysplasia
different pigments activated in different regions of the skin
turners syndrome
instead of two X chromosomes, either 1 entire chromosome or there is a problem with one of the X chromosomes
- Low hairline
- Shield shaped thorax
- Wide nipples
- Shortened metacarpal IV
- No menstruation
- Poor breast development
- Characteristic facial features
Klinefelter’s syndrome
XXY genotype resulting in a mix of male and female characteristics => the X extra chromosome dilutes the testosterone
- Poor beard growth
- Narrow shoulders
- Fewer chest hairs
- Wide hips
- Female type pubic hair
- Testes and penis but smaller
- Long arms and legs
- Less hair loss
Androgen insensitivity syndrome
karyotype of XY where testes produce androgens but receptors don’t respond
- Female external appearance, undescended testes
- Infertile as there is no uterus/ovaries
5-alpha reductase deficiency
karyotype of XY but deficient in enzyme that changes testosterone to dihydrotestosterone (DHT)
- Born with female genitalia
- Male genitalia and other traits emerge at puberty
- Scant beard growth
- No hairline recession
- No acne
- Prostate is small
which developmental disorder lead to the development of a drug that treats older men with prostate enlargement?
5-alpha reductase deficiency
end card
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