Chapter 8: Mitosis and Meiosis Flashcards
Why do cells reproduce? What purpose does cell division serve?
Replaces damaged or lost cells.
Permits Growth
Allows for Reproduction
Prokaryotes reproduce by…?
Binary Fission. (dividing in half)
It is considered asexual reproduction.
Chromatin
A mixture of DNA and proteins that form the chromosomes (unorganized)
Chromosomes
Bundles of DNA molecules and proteins but organized.
When do chromosomes become visible?
when the process of cell division begins, specifically in prophase.
What is the centromere?
The centromere is the narrowed waist in the sister chromatids.
*Rememember that the number of chromosomes is determined by the number of centromeres
The cells cycle consists of two distinct phases.
Interphase and Mitotic Phase.
How much time is spent in interphase? what occurs during interphase?
90% of the time.
The cell performs its normal functions, doubles everything in its cytoplasm (chromosomes), and grows in size.
Mitosis
The division somatic cells.
Meiosis
The division of a single diploid cell into four haploid daughter cells.
Meiosis and cytokinesis produce haploid gametes from diploid cells in the reproductive organs of parents.
What are the four main phases of mitosis?
Prophase
Metaphase
Anaphase
Telophase
PMAT
What begins during telophase?
cytokinesis
Mitotic Spindle
a football-shaped structure of microtubules guides the separation of two sets of daughter chromosomes.
Centrosomes
Spindle microtubules grow from structures
Asexual reproduction
Produces offspring that are identical to the original cell or organism. Involves the inheritance of all genes from one parent. MITOSIS
Sexual Reproduction
Produces offspring that are similar to the parents but show variations in traits. Involved inheritance of unique sets of genes from two parents.
MEIOSIS
Mitosis
What occurs during prophase?
***CHROMATIDS CONDENSE SO THEY ARE VISIBLE.
NUCLEAR MEMBRANE DISSEMBLES AND NUCLEI DISAPPEAR.
MITOTIC SPINDLES FORM FROM CENTROSOMES.
CENTRIOLES WILL HELP MOVE SISTER CHROMATIDS.
Mitosis
What occurs during metaphase?
Sister chromatids are organized into a single row END TO END.
METAPHASE PLATE.
Mitosis
What occurs during anaphase?
Sister chromatids are being seperated by spindles.
Mitosis
What occurs during telophase?
Chromosomes decondense.
The nuclear membrane and nuclei now reform.
Mitotic spindles disappear.
Cytokinesis begins.
Cytokinesis in animal cells.
Begins with the appearance of a cleavage furrow and indentation at the equator of the cell known as cleavage.
Cytoplasm is divided
Cytokinesis in plants
Begins when vesicles containing cell wall material collect in the middle of the cell and then fuse, forming a membranous disk called the cell plate.
The cell plate grows outward to reach the edges dividing into two cells.
THE CELL PLATE WILL EVENTUALLY TURN INTO CELL WALL!
Autosomes
non-sex chromosomes
there are 22 pairs of autosomes
Which chromosomes determines the sex of the child?
23rd chromosome
How many chromosome does a somatic cell have?
46 chromosomes.
Homologous Chromosomes
They are matching pairs of chromosomes.
Homologous Pairs of Chromosomes
Pairs of chromosomes are similar in shape, size, appearance, and types of genes; one from the mother and one from the father.
How are mitosis and meiosis connected?
MEIOSIS FOR REPRODUCTION
MITOSIS FOR GROWTH AND MAINTENANCE.
In the ovaries and testes meiosis occurs, producing haploid gametes (eggs and sperm)
When fertilization occurs the sperm and egg unite to form a diploid zygote.
Then mitosis will occur to produce a diploid multicellular organism.
Karyotype
An image that reveals an orderly arrangement of chromosomes.
How many sets of chromosomes do body cells have?
2 sets. (2n)
Zygote
fertilized egg
Fertilization
Haploid sperm fuses with a haploid egg
Diploid cells
These cells have two complete sets of chromosomes.
Haploid Cells
These cells contain a single set of chromosomes
How many divisions does meiosis have?
2
Meiosis
Prophase I
Chromosomes condense so they are visible.
The nuclear membrane dissembles and disappears.
The nucleus is no longer visible.
Synapsis occurs (pairing of two homologous chromosomes prepares for crossing over)
CROSSING OVER occurs for genetic mixing of two NON-SISTER chromosomes.
Meiosis
Metaphase I
HOMOLOGOUS chromosomes will align into a single row SIDE BY SIDE.
Meiosis
Anaphase I
HOMOLOGOUS chromosomes are separated.
From diploid to haploid (REDUCTION)
Meiosis
Telophase I
Chromosomes decondense
Nuclear membrane and nucleus reform.
Meiotic spindles disappear and cytokinesis begins.
Meiosis
Prophase II
Chromosomes condense so they are visible.
The nuclear membrane dissembles and disappears, and the nucleus is no longer visible.
Spindles form.
Meiosis
Metaphase II
SISTER chromatids are organized into a single row END TO END.
Meiosis
Anaphase II
SISTER chromatids separate
Meiosis
Telophase II
Chromosomes decondense
The nuclear membrane and nucleus reappear.
Spindles disappear
Cytokinesis begins.
Nondisjunction in meiosis
The members of the chromosome pair to fail to separate at anaphase. Produces gamete with the incorrect number of chromosomes.
Can occur during meiosis I or II
Trisomy 21 (Down Syndrome)
an extra copy of chromosome 21.
Chronic Myelogenous Leukemia (CLM)
results from part of chromosome 22 switching places with a small fragment from a tip of chromosome 9.
During crossing over non-sister chromatids…
of homologous chromosomes exchange corresponding segments.
Genetic recombination
the production of gene combinations different from those carried by parental chromosomes
Chiasma
location of crossing over
Tertrad
consist of four chromatids (pair of chromosomes)
Mitosis uses one cell division and produces…?
2 diploid cells.
Meiosis uses two divisions and produces…?
4 haploid cells
Spermatogenesis
Creates 4 haploid cells. (sperm cells)
Oogenesis
one egg is produced
SECONDARY OOCYTE IS RELEASED BUT CREATES 3 POLAR BODIES.
Sexual reproduction may convey an evolutionary advantage by…
Speeding adaptation to a changing environment
It allows a population to rid itself of harmful genes more easily.
