meiosis
Zygote
a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum. (fertilized egg)
Tetrad
a pair of homologous chromosomes, each with two sister chromatids
What are diploid cells?
Cells that have two sets of chromosomes. Human body cells are diploid. (2n)
What may occur at the same time as telophase 2
Cytokinesis
meiosis 2 must take place because each of our new
DNA
How many replicated chromosomes does the cell contain during prophase?
4
how many chromosomes are in mitosis daughter cells?
4
how many cells are made in meiosis?
4 cells
at the end of Meiosis 2 you have made _____ ____ gametes
4 haploid
in telophase 2, __ ___ daughter cells are being formed. they are called ___
4 haploid, gametes
How many pieces of chromatin do humans have?
46
how many chromosomes are in a typical somatic cell?
46
recombinant chromosomes
A chromosome created when crossing over combines the DNA from two parents into a single chromosome.
What event must take place during interphase before a cell proceeds to division?
DNA replication
Gamete
A sex cell; a haploid egg or sperm. The union of two gametes of opposite sex (fertilization) produces a zygote.
Nondisjunction
An accident of meiosis or mitosis in which a pair of homologous chromosomes or a pair of sister chromatids fail to separate at anaphase.
the homologous chromosomes spilit up and move toward the opposite ends of the cell during ___
Anaphase 1
in what stage do the sister chromatids split up?
Anaphase 2
____ are made during meiosis. example of _____ are ____ and ____
Gametes, sperm, egg
DNA has ______ that determines traits of an organism
Genes
What are haploid cells?
Haploid cells have only one half of chromosome. Gametes are haploid. (n)
During anaphase 1, which structures separated,?
Homologous chromosomes separated
What would the ploidy of the zygote be if egg and sperm were produced by mitosis rather than meiosis? How would this affect the ploidy of each successive generation?
If the egg an sperm produced by mitosis, each would be diploid, so the zygote would be tetraploid (four sets of chromosomes) if this tetraploid organism produced tetraploid egg and sperm, the next generation would be octoploid (eight sets of chromosomes) and this doubling would continue with each generation
Meiosis
In a sexually reproducing organism, the division of a single diploid nucleus into four haploid daughter nuclei. Meiosis and cytokinesis produce haploid gametes from diploid cells in the reproductive organs of the parents.
What phrase is used to describe the chromatids after crossing over takes place and the homologous chromosomes separate?
Recombinant chromatids
___ is when DNA copies itself and it occurs during ___
Replication, interphase
What is the name given to the cells produced at the end of meiosis 1 in females?
Secondary oocyte
What two structures make up a single replicated chromosome?
Sister Chromatid
At the end of meiosis 2 in males, what cells are produced?
Spermatids
what stage of meiosis 1 are the cells haploid?
Telophase 1
Once the chromosomes have formed a pair, what are they called?
Tetrads
At the end of meiosis 2 are four daughter cells. Are they haploid or diploid?
The cells are still haploid. they each contain one chromosome (sister chromatid) from each homologous pair. Each chromosome contains a complete set of genes.
When the chromosomes come together as homologous pairs the arms of the sister chromatids may cross over, what are the crossover points called and describe what happens to the chromatids during crossover
The crossover points are Chiasma The section of the homologous pair switch places on the chromatids
Write a statement to explain the origin of the chromosomes found in the zygote. Include the term homologous pair.
The homologous paris of chromosomes found in the zygote have come from each parent. 1/2 of each pair is maternal and the other half is paternal.
chiasma
The microscopically visible site where crossing over has occurred between chromatids of homologous chromosomes during prophase I of meiosis.
What describes the relationship between the cells at the end of Telophase 1 and the original cell?
The new cells have 2 copies of half of the genetic information in the original cell.
How to describe the relationship between the cells at the end of meiosis 2 and the original cell?
The new cells have one copy of half of the genetic information in the original cell
Copare the recombinant chromatids with the original pair. a) are the genes on a recombinant chromatid the same as the original chromatid? b) are the alleles on a recombinant chromatid the same as the original chromatids?
a) yes each chromosome is in the homologous pair contains the same genes in the same place on the chromosome, so a switch between chromosomes would not affect the genes present b)no, the chromosomes in the homologous pair can have different alleles for each gene, so a switch in a portion of the chromosome would affect the information in that chromatid
different forms of genes are
alleles
somatic cells
any cell of a living organism other than the reproductive cells (sperm, egg).
When does interphase occur?
before meiosis
How are dominant alleles represented?
capital letters
during metaphase 1 the tetrads line up in the ___ of the cell
center
during prophase 1 the chromosomes ___ and become ____
condense, visible
Diploid
containing two complete sets of chromosomes, one from each parent.
____ is the division of the cytoplasm to make 2 new cells
cytokinesis
At the start of Meiosis 1 you had 1 _____ cell
diploid
What is the ploidy of the zygote produced by fertilization - haploid or diploid?
diploid
if gametes are produced by a female they are called
eggs or ova
Karyotype of down syndrome
extra chromosome 21
what is it called when sperm and an aegg join
fertilized egg
What are the 2 alleles for fur color in Snurfles and which letters represent those alleles?
g= green fur. G= yellow fur
what are the meiosis cell that undergoes cell division
gametes
What is a genotype?
genetic makeup of an organism
The nucleus _____ during Prophase II.
goes away
the 2 new cells that are formed from meiosis 1 are ___ because they contain half of the chromosomes of the original cell that started meiosis
haploid
Haploid
having a single set of unpaired chromosomes
chromosomes that are the same size and have the same genes are called
homologous chromosomes
sister chromatids of a chromosome are what
identical
what type of organs are the cells that enter meiosis 1 found
sex organs (ovaries and testes)
Each half of a replicated chromosome is called
sister chromatid
In meiosis 2, during anaphase 2, which structures separated?
sister chromatid
what are the mitosis cell that undergoes cell division
somotic
If the gametes are produced by a male, they are called _____.
sperm
homologous chromosomes pair up during prophase 1 to form a ___
tetrad
How many rounds of cell division occur in meiosis?
two
how many cells are made in mitosis?
two
homologous chromosomes
two chromosomes- one inherited from the mother, one from the father- that have the same length and general appearance
What does heterozygous mean?
two different alleles (Gg)
What does homozygous mean?
two of the same alleles (GG, gg)
The chromosomes _____ to form _____.
uncoil, chromatin
what i a fertilized egg called
zygote
how many chromosomes are in meiosis daughter cells?
2
_____ independent cells begin to form during _____.
2, telophase 1
At which stage in Meiosis 1 do the pairs of homologous chromosomes come together?
Late prophase 1
locus
Location of a gene on a chromosome
Where did each of the cells come from that started meiosis 2?
Meiosis 1
the main differences between Mitosis and Meiosis
Mitosis occurs in Somatic cells ONLY. These somatic cells are diploid in number, and mitosis DOES NOT change that. The parent cell is diploid and the new daughter cells are diploid. Meiosis produces gametes ONLY. The reproductive cell that undergoes meiosis is diploid and then the new daughter cells are haploid.
During meiosis 2 the secondary oocyte divides unevenly, with one cell (the ovum) receiving half of the chromosomes and nearly all the cytoplasm and organelles, while the other cell, the polar body, is much smaller and eventually degenerates. Write an explanation to explain why the secondary oocyte divides in this way.
The ovum will recieve more organelles, such as mitochondria for making energy, which will provide the zygote with all of its cytoplasm and organelles (note that the sperm contains only scant cytoplasm. A dew mitochondria and haploid chromosomes.) but nuclear division is necessary to produce the correct number of chromosomes in the oocyte.
Meiosis and sexual reproduction each lead to variation in the genetic make-up of every person. Explain how meiotic events, as well as the random fertilization of eggs and sperm, together lead to this genetic variation.
independent assortment leads to multiple different maternal and paternal gene combinations being produced in the cells at the end of meiosis 1. chiasma formation between homologous pairs of chromosomes leads to blocks of genes being swapped between non sister chromatids during separation at anaphase 1. this leads to allele combinations on the chromosomes being shuffled, and farther varies the chromosomes that end up in egg and sperm after meiosis 2. random fertilization of eggs and sperm means that when zygotes are formed, the gene combination will be different each time, even if they come from the same two parents.
what it means when the karyotype has the word trisomy
its adding a chromosome
what it means when the karyotype has the word mono
its taking away a chromosome
crossing over
its when shuffled genes make an important contribution to the genetic variability that results from sexual reproduction. during prophase 1, 4 sets of chromatids are aligned and physically touching each other, and in this configuration nonsister chromatids may trade segments.
How are recessive alleles represented?
lowercase letters
What do these cells (referring to question above) eventually become?
mature sperm
During fertilization which two cells come together?
mature sperm and secondary oocyte
in a picture how can you tell if the nondisjunction occurred in meiosis 1 or 2?
meiosis 2 has one n+1 and one n-1 and has a pattern of n+1, n-1, n, n. meanwhile meiosis 1 has n+1, n+1, n-1, n-1
in Metaphase 2 the chromosomes line up single file down the ___ of the cell
middle
Considering the genetic makeup of the homologous pairs, will the cells at the end of telophase I be genetically identical to each other?
no, they will not be genetically identical to each other because the homologous pairs separated and the alleles on each homologous pair are not necessarily identical.
Autosomes
non-sex chromosomes
What occurs during interphase?
normal cell activities like making proteins
Each newly formed cell will form a _____ around the chromosomes.
nucleus
How many rounds of cell division occur in mitosis?
one
What is a phenotype?
physical characteristics of an organism
Before fertilization, what happens to the secondary oocyte?
proceeds to meiosis 2
The nucleus disintegrates during...
prophase 1
What stages of meiosis 1 are the cells diploid?
prophase, metaphase, and anaphase
wht phase is used to describe chromatids after crossing over takes place and homologous chromosomes separate
recombinant chromatids
What is the name given to the cells produced at the end of meiosis 1 in males?
secondary spermatocyte.
