BIO 1050 EXAM 3 PRACTICE QUESTIONS AND CORRECT ANSWERS
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Course
BIO 1050
Institution
BIO 1050
What are the two types of cell division in eukaryotes? mitosis and meiosis
What types of cells does meiosis create? sperm and eggs
What happens if there are errors during meiosis? nondisjunctions (ie. disorders like Down Syndrome)
Describe meiosis. The process that produces haploid gametes in di...
BIO 1050 EXAM 3 PRACTICE
QUESTIONS AND CORRECT ANSWERS
What are the two types of cell division in eukaryotes? ✅mitosis and meiosis
What types of cells does meiosis create? ✅sperm and eggs
What happens if there are errors during meiosis? ✅nondisjunctions (ie. disorders like
Down Syndrome)
Describe meiosis. ✅The process that produces haploid gametes in diploid organisms
How many cell divisions occur during meiosis and how many cells are produced? ✅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? ✅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? ✅a fertilized egg (diploid)
Describe the life cycle of a human. ✅Meiosis --> Fertilization --> Mitosis
What are the male sex chromosomes? ✅XY
What are the female sex chromosomes? ✅XX
Explain why fathers determine the sex of their offspring, instead of mothers. ✅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? ✅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? ✅random fertilization and crossing over
, random fertilization ✅source of genetic variation caused by the unlimited number of
possible sperm & egg combinations (64 trillion genetically different options)
What is crossing over? ✅exchange of genetic material between homologous
chromosomes (each individual chromosome becomes a mix of info from mom and dad)
Why is crossing over important? ✅-creates gene combinations different from those
carried by the parents' chromosomes
-main reason offspring of sexual reproduction are genetically unique
What is a nondisjunction? ✅-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?
✅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? ✅BOTH
What happens to a human embryo born with an abnormal # of autosomes?
✅Generally catastrophic and results in miscarriage or survival with a syndrome
What is a syndrome? ✅A characteristic set of symptoms that different people have to
varying extents
Down syndrome ✅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? ✅Incidence of down syndrome increases with age of mother, especially
after 35 (increases from less than 0.05% to greater than 1%)
Explain what we know about why the likelihood of Down syndrome increases with the
mother's age. ✅Likely has to do with the "pause" in egg's process in meiosis-- longer
lag time means higher chance of errors
Do offspring with abnormal numbers of sex chromosomes usually survive? ✅Yes, but
every cell has different combo of sex chromosomes.
Can cause Turner syndrome (just X, no Y), Klinefelter syndrome (XXY), XYY Male, XXX
Female
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