TedTest

From the Ted Talk by Aaron Reedy: Sex determination More complicated than you thought

Unscramble the Blue Letters

My wife is pregnant right now with our first child, and when people see her with her big baby bump, the first question people ask, almost without fail, is, "Is it a boy or is it a girl?" Now, there are some aonpumsstis behind that question that we take for granted because of our ftaialimiry with our own human biology. For human babies, we take it for gratend that there's a 50/50 chance of either awesnr, boy or girl. But why is it that way? Well, the answer depends on the sex determination system that has evolved for our species. You see, for most mammals, the sex of a baby is determined genetically with the XY commsoorhe system. mmaalms have a pair of sex chromosomes, one passed down from mom, and one from dad. A pair of X's gives us a girl, and an X and a Y together gives us a boy. Since females only have X's to pass on in their egg cells, and males can give either an X or a Y in their serpm cells, the sex is determined by the father and the chance of producing a male or a female is 50/50. This system has worked well for mammals, but throughout the tree of life, we can see other systems that have worked just as well for other animals. There are other groups of animals that also have genetic sex determination, but their smyetss can be pretty different from ours. Birds and some rtepiels have their sex genetically dereeitnmd, but instead of the sex being determined by dad, their sex is determined by mom. In those groups, a pair of Z sex chromosomes produces a male, so these males only have Z's to give. However, in these animals, one Z and one W chromosome together, as a pair, pudceros a female. In this system, the chance of a male or a female is still 50/50, it just deepdns on whether mom puts a Z or a W into her egg. Certain groups have taken genetic sex determination in completely other directions. Ants, for example, have one of the most interesting systems for denmnriteig sex, and because of it, if you are a male ant, you do not have a father. In an ant colony, there are dramatic divisions of labor. There are soldiers that defend the cnoloy, there are workers that collect food, clean the nest and care for the young, and there's a queen and a small group of male rtuirovceepds. Now, the queen will mate and then sorte sperm from the males. And this is where the system gets really interesting. If the qeuen uses the stored sperm to fertilize an egg, then that egg will grow up to become female. However, if she lays an egg without fertilizing it, then that egg will still grow up to be an ant, but it will always be a male. So you see, it's impossible for male ants to have fathers. And male ants live their life like this, with only one copy of every gene, much like a walking sex cell. This system is called a haplodiploid ssytem, and we see it not only in ants, but also in other highly social insects like bees and wasps. Since our own sex is determined by genes, and we do know of these other amialns that have their sex determined by geens, it's easy to assume that for all animals the sex of their babies still must be determined by genetics. However, for some animals, the question of whether it will be a boy or a girl has nothing to do with genes at all, and it can depend on something like the weather. These are animals like alligators and most turtles. In these animals, the sex of an embryo in a depoeilnvg egg is determined by the temperature. In these species, the sex of the baby is not yet determined when the egg is laid, and it remains undetermined until sometime in the mdlide of the overall dveenleopmt period, when a critical time is reached. And during this time, the sex is completely determined by ttreaupmere in the nest. In pintaed turtles, for example, warm turmpeareets above the ciitrcal temperature will produce females within the eggs, and cool temperatures will produce a male. I'm not sure who came up with this mmonniec, but you can remember that when it comes to painted turtles, they are all hot chicks and cool dudes. For some tropical fish, the question of will it be a boy or will it be a girl isn't settled until even later in life. You see, clownfish all start out their lives as males, However, as they mature, they become female. They also spend their lives in slmal gruops with a strict dominance haerirhcy where only the most dominant male and felmae rcrpdeoue. And alnmgaizy, if the dianmont female in the group dies, the legsrat and most dominant male will then quickly become female and take her place, and all of the other melas will move up one rank in the hierarchy. In another very different ocaen animal, the geren spoonworm, the sex of the babies is determined by a completely different aspect of the environment. For this species, it is smlipy a matter of where a larva happens to randomly fall on the sea floor. If a larva lnads on the open sea floor, then it will become a female. But if it lands on top of a female, then it will become a male. So for some species, the question of boy or girl is asrnweed by genetics. For others, it's answered by the environment. And for others still, they don't even bother with the qosietun at all. Take whiptail lizards, for example. For those desert lizards, the answer is easy. It's a girl. It's always a girl. They are a nearly all-female species, and although they still lay eggs, these eggs hatch out female clones of themselves. So will it be a girl or will it be a boy? Throughout the etnire animal kingdom, it does really all deepnd on the system of sex determination. For haunms, that system is a gneetic XY system. And for me and my wife, we found out it's going to be a baby boy. (Kiss)

Open Cloze

My wife is pregnant right now with our first child, and when people see her with her big baby bump, the first question people ask, almost without fail, is, "Is it a boy or is it a girl?" Now, there are some ___________ behind that question that we take for granted because of our ___________ with our own human biology. For human babies, we take it for _______ that there's a 50/50 chance of either ______, boy or girl. But why is it that way? Well, the answer depends on the sex determination system that has evolved for our species. You see, for most mammals, the sex of a baby is determined genetically with the XY __________ system. _______ have a pair of sex chromosomes, one passed down from mom, and one from dad. A pair of X's gives us a girl, and an X and a Y together gives us a boy. Since females only have X's to pass on in their egg cells, and males can give either an X or a Y in their _____ cells, the sex is determined by the father and the chance of producing a male or a female is 50/50. This system has worked well for mammals, but throughout the tree of life, we can see other systems that have worked just as well for other animals. There are other groups of animals that also have genetic sex determination, but their _______ can be pretty different from ours. Birds and some ________ have their sex genetically __________, but instead of the sex being determined by dad, their sex is determined by mom. In those groups, a pair of Z sex chromosomes produces a male, so these males only have Z's to give. However, in these animals, one Z and one W chromosome together, as a pair, ________ a female. In this system, the chance of a male or a female is still 50/50, it just _______ on whether mom puts a Z or a W into her egg. Certain groups have taken genetic sex determination in completely other directions. Ants, for example, have one of the most interesting systems for ___________ sex, and because of it, if you are a male ant, you do not have a father. In an ant colony, there are dramatic divisions of labor. There are soldiers that defend the ______, there are workers that collect food, clean the nest and care for the young, and there's a queen and a small group of male _____________. Now, the queen will mate and then _____ sperm from the males. And this is where the system gets really interesting. If the _____ uses the stored sperm to fertilize an egg, then that egg will grow up to become female. However, if she lays an egg without fertilizing it, then that egg will still grow up to be an ant, but it will always be a male. So you see, it's impossible for male ants to have fathers. And male ants live their life like this, with only one copy of every gene, much like a walking sex cell. This system is called a haplodiploid ______, and we see it not only in ants, but also in other highly social insects like bees and wasps. Since our own sex is determined by genes, and we do know of these other _______ that have their sex determined by _____, it's easy to assume that for all animals the sex of their babies still must be determined by genetics. However, for some animals, the question of whether it will be a boy or a girl has nothing to do with genes at all, and it can depend on something like the weather. These are animals like alligators and most turtles. In these animals, the sex of an embryo in a __________ egg is determined by the temperature. In these species, the sex of the baby is not yet determined when the egg is laid, and it remains undetermined until sometime in the ______ of the overall ___________ period, when a critical time is reached. And during this time, the sex is completely determined by ___________ in the nest. In _______ turtles, for example, warm ____________ above the ________ temperature will produce females within the eggs, and cool temperatures will produce a male. I'm not sure who came up with this ________, but you can remember that when it comes to painted turtles, they are all hot chicks and cool dudes. For some tropical fish, the question of will it be a boy or will it be a girl isn't settled until even later in life. You see, clownfish all start out their lives as males, However, as they mature, they become female. They also spend their lives in _____ ______ with a strict dominance _________ where only the most dominant male and ______ _________. And _________, if the ________ female in the group dies, the _______ and most dominant male will then quickly become female and take her place, and all of the other _____ will move up one rank in the hierarchy. In another very different _____ animal, the _____ spoonworm, the sex of the babies is determined by a completely different aspect of the environment. For this species, it is ______ a matter of where a larva happens to randomly fall on the sea floor. If a larva _____ on the open sea floor, then it will become a female. But if it lands on top of a female, then it will become a male. So for some species, the question of boy or girl is ________ by genetics. For others, it's answered by the environment. And for others still, they don't even bother with the ________ at all. Take whiptail lizards, for example. For those desert lizards, the answer is easy. It's a girl. It's always a girl. They are a nearly all-female species, and although they still lay eggs, these eggs hatch out female clones of themselves. So will it be a girl or will it be a boy? Throughout the ______ animal kingdom, it does really all ______ on the system of sex determination. For ______, that system is a _______ XY system. And for me and my wife, we found out it's going to be a baby boy. (Kiss)

Solution

painted
colony
systems
store
critical
genes
determined
reptiles
answered
answer
produces
humans
developing
genetic
middle
familiarity
simply
lands
entire
queen
depends
sperm
assumptions
temperature
largest
ocean
dominant
temperatures
animals
chromosome
granted
development
groups
males
reproductives
green
amazingly
system
mnemonic
hierarchy
question
mammals
depend
female
determining
small
reproduce

Original Text

My wife is pregnant right now with our first child, and when people see her with her big baby bump, the first question people ask, almost without fail, is, "Is it a boy or is it a girl?" Now, there are some assumptions behind that question that we take for granted because of our familiarity with our own human biology. For human babies, we take it for granted that there's a 50/50 chance of either answer, boy or girl. But why is it that way? Well, the answer depends on the sex determination system that has evolved for our species. You see, for most mammals, the sex of a baby is determined genetically with the XY chromosome system. Mammals have a pair of sex chromosomes, one passed down from mom, and one from dad. A pair of X's gives us a girl, and an X and a Y together gives us a boy. Since females only have X's to pass on in their egg cells, and males can give either an X or a Y in their sperm cells, the sex is determined by the father and the chance of producing a male or a female is 50/50. This system has worked well for mammals, but throughout the tree of life, we can see other systems that have worked just as well for other animals. There are other groups of animals that also have genetic sex determination, but their systems can be pretty different from ours. Birds and some reptiles have their sex genetically determined, but instead of the sex being determined by dad, their sex is determined by mom. In those groups, a pair of Z sex chromosomes produces a male, so these males only have Z's to give. However, in these animals, one Z and one W chromosome together, as a pair, produces a female. In this system, the chance of a male or a female is still 50/50, it just depends on whether mom puts a Z or a W into her egg. Certain groups have taken genetic sex determination in completely other directions. Ants, for example, have one of the most interesting systems for determining sex, and because of it, if you are a male ant, you do not have a father. In an ant colony, there are dramatic divisions of labor. There are soldiers that defend the colony, there are workers that collect food, clean the nest and care for the young, and there's a queen and a small group of male reproductives. Now, the queen will mate and then store sperm from the males. And this is where the system gets really interesting. If the queen uses the stored sperm to fertilize an egg, then that egg will grow up to become female. However, if she lays an egg without fertilizing it, then that egg will still grow up to be an ant, but it will always be a male. So you see, it's impossible for male ants to have fathers. And male ants live their life like this, with only one copy of every gene, much like a walking sex cell. This system is called a haplodiploid system, and we see it not only in ants, but also in other highly social insects like bees and wasps. Since our own sex is determined by genes, and we do know of these other animals that have their sex determined by genes, it's easy to assume that for all animals the sex of their babies still must be determined by genetics. However, for some animals, the question of whether it will be a boy or a girl has nothing to do with genes at all, and it can depend on something like the weather. These are animals like alligators and most turtles. In these animals, the sex of an embryo in a developing egg is determined by the temperature. In these species, the sex of the baby is not yet determined when the egg is laid, and it remains undetermined until sometime in the middle of the overall development period, when a critical time is reached. And during this time, the sex is completely determined by temperature in the nest. In painted turtles, for example, warm temperatures above the critical temperature will produce females within the eggs, and cool temperatures will produce a male. I'm not sure who came up with this mnemonic, but you can remember that when it comes to painted turtles, they are all hot chicks and cool dudes. For some tropical fish, the question of will it be a boy or will it be a girl isn't settled until even later in life. You see, clownfish all start out their lives as males, However, as they mature, they become female. They also spend their lives in small groups with a strict dominance hierarchy where only the most dominant male and female reproduce. And amazingly, if the dominant female in the group dies, the largest and most dominant male will then quickly become female and take her place, and all of the other males will move up one rank in the hierarchy. In another very different ocean animal, the green spoonworm, the sex of the babies is determined by a completely different aspect of the environment. For this species, it is simply a matter of where a larva happens to randomly fall on the sea floor. If a larva lands on the open sea floor, then it will become a female. But if it lands on top of a female, then it will become a male. So for some species, the question of boy or girl is answered by genetics. For others, it's answered by the environment. And for others still, they don't even bother with the question at all. Take whiptail lizards, for example. For those desert lizards, the answer is easy. It's a girl. It's always a girl. They are a nearly all-female species, and although they still lay eggs, these eggs hatch out female clones of themselves. So will it be a girl or will it be a boy? Throughout the entire animal kingdom, it does really all depend on the system of sex determination. For humans, that system is a genetic XY system. And for me and my wife, we found out it's going to be a baby boy. (Kiss)

Frequently Occurring Word Combinations

ngrams of length 2

collocation	frequency
sex determination	3
genetic sex	2
male ants	2
dominant male	2

Important Words

alligators
amazingly
animal
animals
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answered
ant
ants
aspect
assume
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baby
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birds
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genetically
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kiss
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sea
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systems
temperature
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