Flashcards in Meiosis Deck (47):
What is being made in meiosis?
What are the two goals of meiosis?
Cut chromosomes in half (1N)
Why do we want to shuffle genes in meiosis?
To increase genetic variation for adaptation
What are homologous chromosomes?
Gene #1 from Mom, Gene #1 from Dad, same size and shape, they code for the same things but the traits might be different
What are alleles?
Versions of genes (blue, brown, green eyes)
What are autosomes?
every other chromosome besides sex chromosomes
What are sex chromosomes?
Last chromosome set in a karyotype, codes for whether the zygote will develop to be male or female
What is ploid?
Number of chromosomes
The only haploid cells we have are what?
In meiosis, one mother cell (2N) is converted into what?
4 daughter cells (1N)
How many total phases are in meiosis?
What is special about prophase I of meiosis?
tetrads form at synapsis
What is a tetrad?
When chromosomes come together (synapse) to form 4 legs (tetrads)
What is crossing over?
legs of non-sister chromatids cross over for genetic diversity
In metaphase I, what happens to the tetrads?
They line up at the equator
In anaphase I, what happens to the tetrads?
tetrads separate into dyads
What is a dyad?
One crossed over homologous chromosome
What are the 2 basic aspects of meiosis?
Maintains chromosome number
Fertilization does what two things after meiosis?
Re-establishes diploid status
Produces new genetic combinations
How many genetically different zygotes are there?
What happens during prophase I?
Crossing-over occurs (only here)
Nuclear envelope fragments
What happens during metaphase I?
Tetrads line up randomly at spindle equator
Spindle fibers attach to chromosomes or reach across equator
What happens during anaphase I?
Tetrads separate randomly
Homologous chromosomes separate and move to poles
What happens during telophase I?
2 daughter nuclei form
Haploid (2 sister chromatids from homologous pair)
What are the accomplishments of meiosis I?
genes shuffled through crossing over
haploid cells were generated
What happens during prophase II?
Spindle fibers form
Daughter cell nuclei disappear
What happens during metaphase II?
Chromosomes line up at spindle equator randomly
Spindle fibers either attach to chromosomes or reach across equator
What happens during anaphase II?
Sister chromatids separate randomly
Daughter chromosomes move to poles
What happens during telophase II?
4 daughter nuclei form
At the end of telophase, what is different about the daughter cells?
They are genetically different from each other and the parent cell
What are the accomplishments of meiosis II?
Chromosomes were randomly sorted into daughter cells
The occurrence of meiosis is dependent on what?
Species and gender
Explain why deer hunting season is in the fall.
The rut. Buck can sense doe pheromones, which are only released during meiosis, which occurrs randomly
Males form how many gametes from one mother cell?
Females form how many gametes from one mother cell?
What happens during a female's meiotic process?
The cells divide unequally, and the larger daughter cell proceeds to absorb the smaller polar bodies produced
When does a human male undergo meiosis?
It starts at puberty and never ends
When does a human female undergo meiosis?
It starts in utero by doing meiosis I, pauses until puberty, completes meiosis II once a month until menopause
Happy, healthy fertilization happens at the fallopian tubes
Takes 6 days to reach the uterus
Large egg cleaves to about 64 cells to survive the trip
What is nondisjunction?
Chromosomes fail to separate
Meiosis I- tetrads don't separate
Meiosis II- sister chromatids don't separate
What is trisomy?
Three instances of a particular chromosome, rather than just 2
What is monosomy?
Absence of one member of a pair of chromosomes
What is down syndrome?
What are some recognizable characteristics of down syndrome?
The chance of a woman having a Down syndrome child increases with what?
Age, starting at 40
What are the aspects of abnormal sex chromosome numbers?
too few or too many X or Y chromosomes
greater chance of survival (fewer genes, barr bodies)