Mitosis/Meiosis
S Phase of cell cycle
"synthesis" phase double (replicate) DNA
If a sperm of this type fertilized an egg of this type, and both the sperm and egg contributed all of their chromosomes to a zygote, how many chromosomes would the resulting zygote have?
184
during meiosis there are __ cell division
2
if a human egg receives two copies of a chromosome, and this egg is fertilized by a normal sperm, how many copies of this chromosome would there be in the resulting zygote
21
each human cell has __ pairs of homologous chromosomes
23
obliviously, if they body used mitosis to make sperm and eggs, the resultant zygote would have too many chromosomes to produce a normal baby. To produce a normal zygote , how many chromosomes should a sperm and egg have?
23
tetrad
4 chromosomes 2 pairs of sister chromatids
In humans, how many chromosomes should a zygote have, so the baby's body cells will have a normal set of chromsomes
46 chromosomes 23 pairs of homologous chromosome
remember that a typical cell in your body has 46 chromosomes (23 pairs of homologous chromosomes) suppose that human sperm and eggs were produced by mitosis. How many chromosomes would each sperm or egg have?
92
what phases of the cell cycle does interphase include
G1 Phase S Phase G2 Phase
prophase 1
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cell function
a cell cannot function properly when there are too many copies of some proteins due to an extra copy of one of the chromosomes. When the cells in an embryo do not function properly, the embryo develops abnormalities.
karyotype
a photograph or a magnified view of the chromosomes from a human cell, with pairs of homologous chromosomes arranged next to each other and numbered.
gene
a segment of the DNA molecule that gives the instructions for making a protein. For example, one gene gives the instructions for making a protein enzyme which helps to make the pigment melanin, a molecule that contributes to our skin and hair color
what cells in our body are diploid
all the rest practically
checkpoints in the cell cycle
along the cell cycle, there are checkpoints to check if the cell is growing correctly, replicating DNA correctly, and doing everything it's supposed to do correctly before it divides
next, the two sister chromatids of each chromosome are separated. After they separate, each chromatid is an independent chromosome. what is this phase of mitosis called?
anaphase
what process of meiosis results in an extra copy of chromosomes
anaphase, because non disjunction occurs, and sister chromatids do not separate, making 2 chromatids go to one side, and one having none. When the gamete with 2 chromatids combines with another w/ one, you would have 3 chromatids.
gametes
are haploid- they have half as many chromosomes as a normal cell
how does a child have different genetic make up than either parent
arrangement of different alleles different zygote development meiosis creates haploid cells
chromosome combinations
as a result of the different ways that the 23 pairs of homologous chomosomes can line up during Meiosis I, more than 8 million different combinations of chromosomes could be found in the different eggs or sperm produced by one person. If each different type of egg from one mother could be fertilized by each different type of sperm from one father, they could produce zygotes with approximately 70 trillion combinations of chromosomes!
down syndrome
babies born with an extra copy of chromosome 21 in each cell. Down syndrome is the result, with multiple abnormalities, including mental retardation, a broad flat face, a big tongue, short height, and often heart defects.
growth hormones in cancer cells
cancer cells have the ability to secrete their own growth hormone- blood vessels divert over to the cancer cells and supply them with nutrients, giving them supplies to keep growing out of control, and keeps nutrients from healthy cells
anaphase (mitosis)
centromeres connecting sister chromatids break down sister chromatids are pulled apart
DNA is wound tightly into compact chromosomes (each with two sister _____). These compact chromosomes are easier to move than the long thin chromosomes in a cell which is not undergoing cell division. Spindle fibers which will move the chromosomes begin to form
chromatids
spindle fibers putt the sister _____ apart to form separate chromosomes which are moved toward opposite ends of the cell
chromatids
cell in interphase:
chromatin has a nucleus: a lot of DNA (chromatin form)
why is it important that chromatin condense into chromosomes before dividing?
chromatin could tangle when separated into two groups
the two copies of each DNA molecule are attached to each other. Why can't you see the two copies of each DNA molecule at this point
chromatin is non-condensed, making it hard to see
prophase (mitosis)
chromosomes condense centrioles move to opposite sides of the nucleus and the spindle forms nuclear envelope (membrane) breaks down
metaphase (mitosis)
chromosomes line up across the center of the cell each centromere is connected to a spindle fiber
telophase/cytokinesis (mitosis)
chromosomes lose distinct shape nuclear envelope is reformed END OF MITOSIS Mitosis followed by cytokinesis (division of cytoplasm)
chromosome
contains a long molecule of DNA. This molecule of DNA contains many genes
in a process called _____, the cell begins to pinch in half, with one set of chromosomes in each half
cytokenesis
two _____ cells are formed. Each ____ cell has received a complete set of chromosomes. Each chromosome unwinds into a long thin thread so that genes can become active and give the instructions for making proteins
daughter; haploid
alleles
different versions of the same gene. Different alleles give the instructions for making different versions of the protein, and different versions of the protein can result in different characteristics
normal cells are _____
diploid; they have a full set of chromosomes. for humans, normal cells have 46 chromosomes (2n=46)
meiosis definition
division of cells to produce gametes (reproductive cells)
cytokinesis
division of cytoplasm
homologous chromosomes
each cell in your body has two copies of each chromosome, these are those two copies. The DNA in both homologous chromosomes contains the same genes at the same locations in the chromosome. However the two homologous chromosomes may have different versions of a gene
beginning of mitosis
each copy of the DNA is wound tightly into a compact chromosome, and the two chromatids in each chromosome are attached to each other at the centromere. The two chromatids are called sister chromatids because they are identical
embryo
eventually becomes a baby
nondisjunction
genetic problem in process of meiosis
what needs to happen before cells are ready for mitosis
go through interphase: grow and replicate DNA
cell division is needed for ___
growth
G1 Phase of the Cell Cycle
growth phase prepares for DNA replication
G2 phase of cell cycle
growth phase that prepares for division
frequency of mitosis depends on the kind of cell
hair cells divide frequently, while brain cells/neurons don't perform mitosis
gametes in humans
have 23 chromosomes (n=23)
meiosis 1 contains what kind of chromosomes
homologous
pair of similar chromosomes
homologous
daughter cells
identical
apoptosis
if a cell fails its checkpoint, the cell does apoptosis, where the cell destroys itself, it self destrcuts
If cells are always doing mitosis, they're always dividing
if this is the case, they can't carry out their natural function
histone proteins
in the first step of DNA compaction, DNA is wrapped around histone proteins
cells in your body are either in ____ or _____
interphase; mitosis
Meiosis II
is like mitosis, since the sister chromatids of each chromosome are seperated. As a result, each daughter cell gets one copy of a chromosome from the pair of homologous chromosomes that was in the original cell
what happens to the DNA after the DNA wraps around proteins?
it starts to coil and then turns into chromatin fiber, and eventually eventually becomes apart of chromosomes
Almost all the cells in your body were produced by mitosis. The only exception is sperm or eggs which are produced by a different type of cell division called ________
meiosis
meiosis 1
meiosis 1 is different from mitosis because homologous chromosomes line up next to each other and then the two homologous chromosomes separate. This produces daughter cells with half as many chromosomes as the parent cell, i.e. haploid cells. Notice that each daughter cell has a different chromosome from the homologous pair of chromosomes
why can brothers and sisters have different characteristics
meiosis and fertilization result in a different combination of alleles in each child
At the beginning of mitosis, each chromosome consists of a pair of chromatids, and the chromosomes are lined up in the center of the cell. What is this phase of mitosis called?
metaphase
during which phase of meiosis do tetrads line up at the equator
metaphase 1
is cancer contagious?
no, anyone can develop it
M phase of cell cycle
nuclear division
cell division
one cell divides to form two new cells, then each of these cells divides resulting in a total of four cells, etc.
zygote
produces through fertilization; contains chromosomes from both the sperm and egg, and undergoes mitosis to begin the development of the embryo which eventually becomes a baby
meiosis overview
production of haploid gametes (n) from diploid (2n)
when does crossing over occur
prophase 1
meiosis
reduces the number of chromosomes by half, and produces four haploid daughter cells Ex. in humans, each sperm and egg produced by meiosis has only 23 chromosomes , including one chromosome from each pair of homologous chromosomes
In preparation for mitosis, DNA is copied; this is called DNA ____
replication
goal of meiosis 1
separate homologous chromosomes
goal of meiosis 2
seperate sister chromatids
identical chromosomes
sister chromatids
meiosis 2 contains what kind of chromosomes
sister chromatids
mistake in meiosis
sometimes meiosis doesn't happen perfectly, so the chromosomes are not divided completely equally between the daughter cells produced by meiosis. For example, an egg or a sperm may receive two copies of the same chromosome
what cells in our body are haploid
sperm and egg
fertilization
sperm and egg unite to form a single cell called the zygote which contains chromosomes from the sperm and egg. The zygote undergoes mitosis to begin the development of the embryo which eventually becomes a baby
_______ attach to the chromosomes and line the chromosomes up in the middle of the cell
spindle fibers
nucleosome
structure that consists of DNA wrapped around proteins
chemotherapy
targets cells that go through the cell cycle quickly (why someone would lose their hair)
anaphase 1
tetrad is pulled apart
cytokinesis..
the cell begins to pinch together in the middle. Cytokinesis proceeds to produce two separate daughter cells
what happens when a cell has three copies of a chromosome?
the extra copies of the genes on this chromosome result in abnormal cell function and abnormal embryonic development. To understand how an extra copy of one chromosome could result in abnormalities, remember that each chromosome has genes with the instructions to make specific types of proteins, so the extra chromosome could result in too many copies of these specific proteins.
mitosis
the type of cell division that produces almost all the cells in our bodies. In mitosis, one cell divides to produce to identical daughter cells. Each of the daughter cells needs to have a complete set of chromosomes containing an exact copy of all the DNA in the original cell
purpose of apoptosis
to ensure that you don't have messed up cells continue on and divide, because they might not do what they're supposed to-they might start to grow out of control and not be regulated correctly
preparation for mitosis
to get ready for mitosis, the cell makes a copy of the long strand of DNA in each chromosome (DNA replication). This occurs during the S phase of the cell cycle (interphase)
mitosis completed
two new daughter cells have been formed. Each daughter cell has received one copy of each chromosome, so each daughter cell has a complete copy of all the DNA in the original cell
major cause of cancer
uncontrolled cell growth (some cancers have genetic links, making someone more likely to develop it
Each of these pairs of homologous chromosomes has its own ___ set of genes
unique
fertilization overview
when an egg and sperm are untied during fertilization, the resulting zygote has 23 pairs of homologous chromosomes, one in each pair from the egg and one from the sperm. Thus the zygote has 46 chromosomes, and when the zygote undergoes mitosis to begin to form an embryo , each cell will have the normal number of 46 chromosomes
crossing over
when gametes from one chromatid swap places w/ genes from another chromatid benefit: it increases genetic variation
crossing over
when the chromosomes between a mother and father cell cross over and the mom chromosome has some of the dad chromosome, and the dad chromosome has some of the moms
female chromosome
xx
human male chromosomes
xy
at the end of meiosis
you start with one diploid cell and you end up with 4 haploid cells (different versions of chromosome 1 and 2)
cancer cells
your body's own cells that are growing out of control. Not following the rules of the checkpoints, going through the cell cycle, frequently doing mitosis, dividing very often. By doing that, they grow into tumors, which are masses of cancer cells
you can see why no two people are genetically alike, except for identical twins who both develop from the same ____
zygote