Studied by 23 people
What are 5 reasons a cell reproduces?
Reproduction, growth, development, replacement, and repair
Things copied during cell reproduction include…
DNA
organelles
cell membrane
lots of other molecules
A dividing cell…
duplicates its DNA.
The DNA starts as _________ in the nucleus.
chromatin
Why does chromatin become chromosomes for cell division?
If you tried to divide it like that, it could tangle & break.
Chromosomes are found in cells that…
are ready to divide.
DNA in chromatin form must be ______ __ into chromosomes before division
coiled up
Chromosomes
rod-shaped structure of DNA molecules, wrapped around proteins called histones
What is the purpose of histones in chromosomes?
To maintain shape
Chromatid
Each half of a duplicated chromosome.
Chromatids form as…
DNA making a copy of itself.
When the cell divides, each of the new cells will receive ___ _________ from each chromosome
one chromatid
What is the waist of chromatids?
Centromere
Sex chromosomes
responsible for development of reproductive organs and characteristics of an organism
Autosomes
all other chromosomes, besides the sex chromosomes
The pair of autosomes together are called…
homologous chromosomes
Diploid cells…
have a full set of chromosomes, containing both chromosomes for each homologous pair.
Haploid cells…
have half the number of chromosomes that are present in diploid cells.
Mitosis
division of the nucleus in somatic (body) cells
Mitosis results in…
new cells with genetic material identical to the original cell.
Cytokinesis
division of the cytoplasm
Meiosis
division reducing the chromosome number in half to form gametes
Cell Cycle
Repeating events that make up the life of a cell
Interphase
Time between divisions.
What are the three phases of interphase?
G1, S, G2
In G1…
cells grow to full size.
In S…
DNA is copied.
In G2…
cell gets ready for cell division.
G0 phase
Cells do not copy their DNA and do not prepare for cell division
What is an example of cells that enter the G0 phase?
Nerve Cells
When do cells enter G0 phase?
After they finish mitosis.
Chromatin
DNA wrapped around proteins (mess). How DNA is found most of the time.
Sister Chromatid
½ of a replicated chromosome.
Centromere
Protein disc that helps with division
What are the four phases of mitosis?
Prophase, Metaphase, Anaphase, Telophase
During prophase…
the nucleus disappears
chromatin becomes chromosomes
spindle fibers form
During metaphase…
chromosomes line up in the middle
spindle fibers attach to centromere
During anaphase…
spindle fibers shorten, pulling away chromosomes
During telophase…
nucleus reforms
chromosomes become chromatin
spindle fibers disappear
During cytokinesis…
either a cleavage furrow or cell plate is formed
ends with 2 daughter cells
Prophase
Prepare
Metaphase
Middle
Anaphase
Apart
Telophase
Two nuclei
Does the cell cycle occur in prokaryotes or eukaryotes?
Eukaryotes
What process NEVER occurs in interphase?
Cell Division
Cells obtain ________ and duplicate or copy their __________ or genetic material during interphase.
nutrients, chromatids
Telomere
A region of repetitive DNA sequences at the end of a chromosome that maintains chromosomal stability and prevents chromosomal degradation
Centromere vs Centrioles
Centrioles are paired barrel-shaped organelles located in the cytoplasm of animal cells near the nuclear envelope. The centromere is the central region of the chromosome which consists of highly constricted DNA.
Since proteins and _______ are being made during g1, there is a great amount of ______ _________ occuring.
enzymes, protein synthesis
What are body cells called?
Somatic Cells
What are reproductive cells known as?
Germ Cells
Centriole
A barrel-shaped organelle which lives normally within the centrosome
Cell growth can be turned on and off within the cell by proteins called _______.
cyclins
Cancer
A disorder in which cells lose the ability to control their growth and division.
Malignant
invasive, cancerous cells; spreading the message of rapid growth to other cells
Metastasis
spreading of malignant cells
Carcinoma
External or internal body coverings.
Sarcoma
Tissues that support the body.
Leukemia and lymphoma
Blood-forming tissues.
What is the difference between cell division in an animal cell and cell division in a plant cell?
In animals, cytokinesis takes place through the formation of a furrow in the plasma membrane whereas, in the case of plants, cytokinesis takes place through the formation of a cell wall.
Diploid
Containing two complete sets of chromosomes, one from each parent
Haploid
A cell that contains a single set of chromosomes
What is crossing over?
the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring
When does crossing over occur?
Prophase I
What is the purpose of meiosis?
To produce gametes.
Fertilization
A process in sexual reproduction that involves the union of male (sperm) and female (ovum) gametes (each with a single, haploid set of chromosomes) to produce a diploid zygote.
Asexual Reproduction
The formation of offspring from one parent
Sexual Reproduction
Formation of offspring from two parents
Zygote
A diploid cell resulting from the fusion of two haploid gametes
WHat would happen if we made gametes through mitosis?
We would have 92 chromosomes and die.
Are gametes haploid or diploid?
Haploid
True or False: haploid n + haploid n = diploid 2n
True
Meiosis
Process of nuclear division that cuts the chromosome number in half.
How many rounds of cell division are there in meiosis?
Two
How many rounds of cell division are in mitosis?
One
How many haploid gametes are formed after mitosis?
Four
True or False: Meiosis is described as “reduction duplication.”
False
How many polar bodies are formed when a female sex cell goes through meiosis?
Three
Polar Body
A nonfunctional cell formed at the same time as an egg cell.
Homologous chromosomes
A pair of chromosomes holding information controlling the same inherited characteristics
What happens in prophase I in meiosis??
Nucleus and nucleolus break down.
The chromatin condenses into chromosomes.
spindle fibers appear
Homologous chromosomes containing the two chromatids come together to form tetrads, joining at their centromeres.
“crossing over” occurs, which creates genetic variation.
What happens in metaphase I?
Tetrads line up in the middle of the cell along the metaphase plate
Spindle fibers attach each homologous chromosome.
What happens in anaphase I?
Tetrads are separated by spindle fibers, sending the homologous chromosomes to opposite ends of the cell
Independent Assortment: genetic material is pulled apart at random
What happens during telophase I?
Nuclei are separated
Nuclear membranes form again
New cells are haploid, containing half the amount of DNA
One of each homologous pair
Telophase I is followed by Cytokinesis I, when cytoplasm is separated.
What happens during prophase II?
Same as prophase in mitosis.
What happens during metaphase II?
Same as metaphase in mitosis.
What happens during anaphase II?
Same as anaphase in mitosis.
What happens during telophase II?
Same as telophase in mitosis?
How many chromosomes are there in a cell before meiosis?
46
How many chromosomes are there in a cell after the first phase of meiosis?
23
How many chromosomes are there in a cell after the second phase of meiosis?
23 chromosomes
How many chromatids are there in a cell before meiosis?
92
How many chromatids are there in a cell after the first phase of meiosis?
46
How many chromatids are there in a cell after the second phase of meiosis?
23 chromatids
Meiosis allows for ___________ over time.
consistency
Spermatogenesis
Original cell produces four haploid, unique sperm cells by meiosis
Oogenesis
Original cell produces one egg cell and three polar bodies by meiosis
Egg cell receives most of the original cell’s cytoplasm
