ECU BIO 1050 EXAM 3 QUESTIONS
AND ANSWERS
What are the two types of cell division in eukaryotes? - Correct Answers -mitosis and
meiosis
What types of cells does meiosis create? - Correct Answers -sperm and eggs
What happens if there are errors during meiosis? - Correct Answers -nondisjunctions
(ie. disorders like Down Syndrome)
Describe meiosis. - Correct Answers -The process that produces haploid gametes in
diploid organisms
How many cell divisions occur during meiosis and how many cells are produced? -
Correct Answers -2 cell divisions
Meiosis 1- homologous pairs separate
Meiosis 2- sister chromatids separate, resulting in 4 haploid cells, each containing a
copy of each chromosome instead of a homologous pair
What is a life cycle? - Correct Answers -Diploid organisms undergo meiosis to create
haploid gametes
Sperm fertilizes an egg to create a zygote which undergoes mitosis to grow
What is a zygote? - Correct Answers -a fertilized egg (diploid)
Describe the life cycle of a human. - Correct Answers -Meiosis --> Fertilization -->
Mitosis
What are the male sex chromosomes? - Correct Answers -XY
What are the female sex chromosomes? - Correct Answers -XX
Explain why fathers determine the sex of their offspring, instead of mothers. - Correct
Answers -Women have 2 X chromosomes, so an X is always present in every egg (half
of eggs get a copy of one X, the other half get the other X) whereas men have each
(half of sperm get X, half get Y). The type of sperm that reaches the egg determines the
sex.
, Do all animals have the same system of sex determination as humans? - Correct
Answers -No. In birds, mom determines sex in a way similar to human dads. In insects,
males are haploid and females are diploid. In turtles, sex determined by temperature at
which eggs are incubated.
What are 2 reasons why offspring from sexual reproduction are genetically different
from their parents & each other? - Correct Answers -random fertilization and crossing
over
random fertilization - Correct Answers -source of genetic variation caused by the
unlimited number of possible sperm & egg combinations (64 trillion genetically different
options)
What is crossing over? - Correct Answers -exchange of genetic material between
homologous chromosomes (each individual chromosome becomes a mix of info from
mom and dad)
Why is crossing over important? - Correct Answers --creates gene combinations
different from those carried by the parents' chromosomes
-main reason offspring of sexual reproduction are genetically unique
What is a nondisjunction? - Correct Answers --members of a chromosome pair fail to
separate in meiosis
-causes abnormal chromosome numbers
-we don't know what causes them
What happens if a sperm fertilizes an egg with an abnormal chromosome number? -
Correct Answers -Every cell resulting from this initial error (including the zygote) will
also have the wrong chromosome number
Can nondisjunctions lead to abnormal chromosome numbers in autosomes, sex
chromosomes, or both? - Correct Answers -BOTH
What happens to a human embryo born with an abnormal # of autosomes? - Correct
Answers -Generally catastrophic and results in miscarriage or survival with a syndrome
What is a syndrome? - Correct Answers -A characteristic set of symptoms that different
people have to varying extents
Down syndrome - Correct Answers -have an extra copy of chromosome 21 (also called
trisomy 21)
How does the age of the mother influence the likelihood of a baby having Down
syndrome? - Correct Answers -Incidence of down syndrome increases with age of
mother, especially after 35 (increases from less than 0.05% to greater than 1%)
AND ANSWERS
What are the two types of cell division in eukaryotes? - Correct Answers -mitosis and
meiosis
What types of cells does meiosis create? - Correct Answers -sperm and eggs
What happens if there are errors during meiosis? - Correct Answers -nondisjunctions
(ie. disorders like Down Syndrome)
Describe meiosis. - Correct Answers -The process that produces haploid gametes in
diploid organisms
How many cell divisions occur during meiosis and how many cells are produced? -
Correct Answers -2 cell divisions
Meiosis 1- homologous pairs separate
Meiosis 2- sister chromatids separate, resulting in 4 haploid cells, each containing a
copy of each chromosome instead of a homologous pair
What is a life cycle? - Correct Answers -Diploid organisms undergo meiosis to create
haploid gametes
Sperm fertilizes an egg to create a zygote which undergoes mitosis to grow
What is a zygote? - Correct Answers -a fertilized egg (diploid)
Describe the life cycle of a human. - Correct Answers -Meiosis --> Fertilization -->
Mitosis
What are the male sex chromosomes? - Correct Answers -XY
What are the female sex chromosomes? - Correct Answers -XX
Explain why fathers determine the sex of their offspring, instead of mothers. - Correct
Answers -Women have 2 X chromosomes, so an X is always present in every egg (half
of eggs get a copy of one X, the other half get the other X) whereas men have each
(half of sperm get X, half get Y). The type of sperm that reaches the egg determines the
sex.
, Do all animals have the same system of sex determination as humans? - Correct
Answers -No. In birds, mom determines sex in a way similar to human dads. In insects,
males are haploid and females are diploid. In turtles, sex determined by temperature at
which eggs are incubated.
What are 2 reasons why offspring from sexual reproduction are genetically different
from their parents & each other? - Correct Answers -random fertilization and crossing
over
random fertilization - Correct Answers -source of genetic variation caused by the
unlimited number of possible sperm & egg combinations (64 trillion genetically different
options)
What is crossing over? - Correct Answers -exchange of genetic material between
homologous chromosomes (each individual chromosome becomes a mix of info from
mom and dad)
Why is crossing over important? - Correct Answers --creates gene combinations
different from those carried by the parents' chromosomes
-main reason offspring of sexual reproduction are genetically unique
What is a nondisjunction? - Correct Answers --members of a chromosome pair fail to
separate in meiosis
-causes abnormal chromosome numbers
-we don't know what causes them
What happens if a sperm fertilizes an egg with an abnormal chromosome number? -
Correct Answers -Every cell resulting from this initial error (including the zygote) will
also have the wrong chromosome number
Can nondisjunctions lead to abnormal chromosome numbers in autosomes, sex
chromosomes, or both? - Correct Answers -BOTH
What happens to a human embryo born with an abnormal # of autosomes? - Correct
Answers -Generally catastrophic and results in miscarriage or survival with a syndrome
What is a syndrome? - Correct Answers -A characteristic set of symptoms that different
people have to varying extents
Down syndrome - Correct Answers -have an extra copy of chromosome 21 (also called
trisomy 21)
How does the age of the mother influence the likelihood of a baby having Down
syndrome? - Correct Answers -Incidence of down syndrome increases with age of
mother, especially after 35 (increases from less than 0.05% to greater than 1%)
