Chapter 3.2 Gametogenesis Flashcards
Gametogenesis is necessary for what phase of development
Reproductive phase
Hereditary information is carried on
Chromosomes
Human somatic cells contain how many pairs of chromosomes
23 pairs of chromosomes, 22 pairs of autosomes and one pair of sex chromosomes for a total of 46 chromosomes
Autosomes contain
Genetic information for most human characteristics, such as eye color, hair color, height, and skin pigmentation
A pair of similar autosomes are called
Homologous chromosomes
The pair of sex chromosomes primarily determines
Whether an individual is female (she will have two X chromosomes) or male (he will have one X chromosome and one Y chromosome)
If a cell contains 23 pairs of chromosomes it is said to be
Diploid
Sex cells are
Haploid because they contain 23 chromosomes only and not 23 pairs of chromosomes
The process of gametogenesis begins with cell division, called
Meiosis
The sex cells produced in the female are
Secondary oocytes
The sex cells produced in the male are
Sperm
A type of sex cell division that starts off with a diploid parent cell and produces haploid daughter cells
Meiosis
Mitosis produces
Two daughter cells that are genetically identical to the parent cell
Meiosis produces
4 daughter cells that are genetically different from the parent cell
Produces daughter cells that are diploid
Mitosis
Produces daughter cells that are haploid
Meiosis
Crossing over does NOT occur in
Mitosis
In meiosis a process called crossing over occurs, whereby
Genetic material is exchanged between homologous chromosomes. Crossing over helps shuffle the genetic deck of cards. It is a means of combining different genes from both parents on one of the homologous chromosomes
Meiosis begins with a
Diploid parent cell located in the gonad (testes or ovary)
The parent cell that is responsible for the production of gametes contains
23 pairs of chromosomes
For an organism to produce its own sex cells, the parent cell must divide by the process of
Meiosis
Prior to meiosis is a cell phase known as
Interphases
During interphase the DNA in each chromosome is
Replicated in the parent cell, resulting in identical or replicated chromosomes
Replicated chromosomes are double stranded chromosomes, composed of two identical structures called
Sister chromatids
Each sister chromatid in a double stranded chromosome contains an
Identical copy of DNA
The sister chromatids are attached at a specialized region termed
Centromere
A double stranded chromosome resembles a written letter X and is composed of
Two identical sister chromatids
A homologous pair of chromosomes is composed of a maternal chromosome and a
Paternal chromosome of the same number
After interphase there are how many pairs of double stranded chromosomes
23
Once the DNA is replicated in interphase, the phases of what begin
Meiosis
Homologous, double stranded chromosomes in the parent cell form
Pairs
The process by which homologous chromosomes pair up is called
Synapsis
The actual pair of homologous chromosomes is called
Tetrad
When does crossing over occur?
As the maternal and paternal chromosomes come close together
When the crossing over occurs what happens
The homologous chromosomes exchange genetic material
A tiny portion of the genetic material in a sister chromatid of a maternal chromosome is exchanged with the
Same portion of genetic material transferred in a sister chromatid of a paternal chromosome
The shuffling of the genetic material ensures
Continued genetic diversity in new organisms
The homologous pairs of double-stranded chromosomes line up above and below the equator of the cell, forming a double line of chromosomes. This alignment of paired, double-stranded chromosomes is random with respect of whether the original maternal or paternal chromosome of a pair is on one side of the equator or the other.
First meiotic metaphase (Metaphase I)
Pairs of homologous chromosomes separate and are pulled to the opposite ends of a cell. The pairs of chromosomes are no longer together, because the members of each pair are being pulled to opposite ends of a cell. However, each chromosome is still double-stranded
First Meiotic Anaphase (Anaphase I)
The chromosomes arrive at opposite ends of the cell, and a nuclear membrane re-forms around the chromosomes at each end of the cell. Then cleavage furrow forms in the cell, and the cell cytoplasm divides (cytokinesis) to produce two new cells. Each daughter cell contains 23 chromosomes only, but each of these chromosomes is double stranded, meaning it is composed of two sister chromatids. These two cells must undergo further cell division so that the new cells will be composed of single-stranded chromosomes only.
First meiotic telophase (telophase I) and cytokinesis
A single-stranded chromosome contains how many chromatids?
One
In each of the two new cells, the nuclear membrane breaks down, and the chromosomes collect together. However, crossing over does not occur in this phase because homologous chromosomes separated in anaphase I.
Second Meiotic Prophase (Prophase II)
Crossing over occurs in what prophase
Crossing over occurs in the first meiotic prophase only
The double-stranded chromosomes form a single line along the equator in the middle of the cell. Spindle fibers extend from the centrioles at the poles to the centromere of each double-stranded chromosome
Second meiotic metaphase (metaphase II)
The sister chromatids of each double-stranded chromosome are pulled apart at the centromere. Each chromatid, now called a single stranded chromosome, is pulled to the opposite pole of the cell
Second meiotic anaphase (anaphase II)
The single-stranded chromosomes arrive at opposite ends of the cell. Nuclear membranes re-form, a cleavage furrow forms, and the cytoplasm in both cells divides, producing a total of four daughter cells. These daughter cells are haploid, because they contain 23 chromosomes only (not 23 pairs). These daughter cells mature into sperm (in males) or secondary oocytes (in females)
Second Meiotic Telophase (Telophase II) and Cytokinesis
Meiosis I (the first meiotic division) separates maternal and paternal pairs of chromosomes, while meiosis II (the second meiotic division)
Separates the remaining double-stranded chromosomes into single-stranded chromosomes.
Secondary oocyte is
The sex cell produced in females
Oogenesis is
The process of oocyte development
The secondary oocyte cell will have how many autosomes and how many X chromosomes
22 autosomes and one X chromosome
Oogonia is
The parent cells, or stem cells, that produce oocytes, they reside in the ovaries
Diploid cells that undergo meiosis
Oogonia
In the female fetus, all the oogonia start the process of
Meiosis and form primary oocytes prior to birth
Primary oocytes are arrested in
Prophase I and remain this way until the female reaches puberty
Each month a number of primary oocytes begin to mature; usually only one becomes
A secondary oocyte
When the primary oocyte completes the first meiotic division (prophase I, metaphase I, anaphase I, and telophase I), what happens
Two cells are produced
Is the division of cytoplasm equal or unequal?
It is grossly unequal
The cell we call the secondary oocyte receives the bulk of the cytoplasm and is the cell that is arrested in
Metaphase II
The polar body is
The second cell, which receives only a tiny bit of the cytoplasm
What has the potential to be fertilized
Only the secondary oocyte
The secondary oocyte is ovulated along with
Two other components surrounding the oocyte-cuboidal cells that form the corona radiate and a thin ring of proteins and glycoproteins called the zona pellucida
Form protective layers around the secondary oocyte
The corona radiata and the zone pellucida
The further development of the secondary oocyte varies, depending on what
Depending upon whether or not it is fertilized by a sperm
If the secondary oocyte is not fertilized what happens?
It degenerates about 24 hours after ovulation, still arrested in metaphase II
If the secondary oocyte is fertilized it
First finishes the process of meiosis. Two new cells are produced and the division of cytoplasm is unequal.
The cell that receives very little cytoplasm becomes
Another polar body and eventually degenerates
The cell that receives the majority of the cytoplasm becomes
Ovum
It is the ovum nuclear that combines with the sperm nucleus to produce the
Diploid fertilized cell, or zygote
Typically how many secondary oocyte is expelled each month?
Only one secondary oocyte is expelled (ovulated)
The left and right ovaries
Take turns
In males their bodies produce and release how many gametes (sperm) throughout the entire month?
Millions
In males the sex cell produced is called
Sperm (spermatozoon)
Spermatogenesis is
The process of sperm development
The parent or stem cells that produce sperm are called
Spermatogonia
Spermatogonia are diploid cells that reside in the
Male gonads, the testes
Each spermatogonium first divides by
Mitosis to make an exact copy of itself, a new cell called primary spermatocyte
Primary spermatocytes undergo meiosis and produce haploid cells called
Spermatids
Although spermatids contain 23 chromosomes only, they still must undergo what
Further changes to form a sperm
The process where spermatids lose much of their cytoplasm and grow a long tail called a flagellum
Spermiogenesis
The newly formed sperm are haploid cells that exhibit what
A distinctive head, a mid piece, and a tail
What forms from a single spermatocyte
Four new sperm are formed
Of the four newly formed sperm from a single spermatocyte have how many autosomes and chromosomes are present?
Two of the sperm have 22 autosomes and one X chromosome and two have 22 autosomes and one Y chromosome
