Biology 105, Module 3, Topics 1, 2, & 3 Combined:
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What is the basic knowledge of what happens during Metaphase in MITOSIS?
The chromosomes line up in the middle of the cell or at the metaphase plate.
What is the basic knowledge of what happens during Anaphase in MITOSIS?
The sister chromatids are pulled apart towards opposite poles/ sides of the cell.
How many pairs/ types (haploid) of chromosomes do humans have?
Humans have 23 types of chromosomes. (haploid).
How many total (diploid) chromosomes do humans have?
Humans have a total of 46 chromosomes. (diploid).
What is the definition of haploid?
The number of types of chromosomes in a cell.
What is the definition of a diploid?
The number of total chromosomes in a cell.
What are two examples of haploid cells?
Two examples of haploid cells are a sperm and an egg.
What is the basic knowledge of what happens during interphase in MITOSIS?
During interphase copies of chromosomes are made to make the whole diploid chromosomes.
What is DNA called before going through replication and after?
Before replication DNA is called a chromosome, and after replication DNA is called a chromatid.
What are the two types of reproduction for organisms?
Asexual reproduction an sexual reproduction.
What is asexual reproduction?
Asexual reproduction requires only one organism, and produces genetically identical offspring unless a mutation occurs.
What is sexual reproduction?
Sexual reproduction requires two opposite sex organisms, and produces an offspring of a variation. The variation that occurs is crucial to the survival and reproduction of this offspring, because it helps with adaptation to the environment.
What is the only source of genetic variation for asexual organisms, and how does this affect them?
The only source for genetic variation among asexual organisms is mutation, due to this asexual organisms have a harder/ longer time adapting to their environment.
Where do the two copies of chromosomes come from in a diploid cell?
One chromosome comes from mom (female) and one comes from dad (male).
What happens to each chromosome before mitosis?
Each chromosome is copies before mitosis.
How many chromosomes does sperm and egg have?
A sperm has 23 chromosomes, and an egg has 23 chromosomes.
What happens when egg and sperm fertilize?
When egg and sperm fertilize each of their 23 chromosomes combine which is why the resulting zygote has 46 total chromosomes.
Due to the zygote having 46 chromosomes, their has to be some process after mitosis that goes back to the haploid (23 chromosome type cell). What would this process be called?
This process would be called Meiosis.
What is meiosis?
Meiosis is the process that produces haploid cells from diploid cells.
How many types of diploid cells do we have in our body, and what do each of these cells do?
We have two types of diploid cells in our body, Somatic cells and Germ cells. Somatic cells are “regular diploid cells” that go through the process of mitosis to produce diploid cells. Germ cells are “specialized diploid cells” that go through meiosis to produce haploid cells.
What is gametogenesis?
Gametogenesis is the production of haploid cells called gametes by the process of meiosis.
What is a male gamete and what is a female gamete?
A male gamete is a sperm, and a female gamete is an egg.
How is a diploid zygote produced?
A diploid zygote is produced when a haploid sperm fertilizes a haploid egg. These 23 chromosomes are the same type for each so they pair up in the diploid zygote as 23 pairs and 46 total chromosomes.
How many sets of division is required during meiosis?
During meiosis 2 sets of division are required, Meiosis I and Meiosis II.
What happens in Meiosis I that differs a little from Meiosis II during synapsis?
During synapsis in meiosis I homologous pairs of chromosomes are separated, but in meiosis II sister chromatids are separated and become daughter chromosomes.
What occurs during prophase I of Meiosis? (answer color coded to help easily identify the multiple parts of prophase I).
The homologous chromosomes are tightly paired in “synapsis”. first figure. Then segments of chromosomes are exchanged and cross over each other and are attached at the “chiasmata”. second figure. Finally 4 sister chromatids are visible which is called “tetrads”. However, notice that when the chromosomes are crossed over they are “recombinant” and when they have not crossed over they are “non-recombinant” which produces unique genetic material. figure 3.
What occurs during Metaphase I of Meiosis?
During Metaphase I chromosomes go through independent assortment after being copied from each parent to make a diploid cell. Independent assortment essentially means that there is no specified order for the chromosomes to line up therefore resulting in unique genetics.
What occurs during Anaphase I of Meiosis?
During Anaphase I chromosomes separate. Because chromosomes are still attached to their centromeres they are not sister chromatids like in Mitosis Anaphase. The chromosomes first line up at the metaphase plate, then they are pulled to opposite sides/ poles of the cell. Each new cell has one copy of each type of chromosome so it is a haploid cell.
What is the difference between Mitosis and Meiosis I? NEED TO KNOW THESE
In the first stage in mitosis chromosomes are copied, but in meiosis they are copied AND crossed over each other. In the second stage chromosomes are arranged differently in mitosis and meiosis. In the third stage in mitosis chromatids are separated but in meiosis chromosomes are separated. At the end of mitosis you have diploid cells BUT at the end of meiosis I you have haploid cells.
What is the difference between pro metaphase in meiosis I and meiosis II?
In pro metaphase I chromosomes are connected by the chiasmata and microtubules attach to fused kinetochores, but in pro metaphase II chromatids are connected by the centromere and microtubules attach to individual kinetochores.
What is the difference between anaphase in meiosis I and meiosis II?
In anaphase I whole chromosomes are pulled apart and sister chromatids remain attached at the centromere, but in anaphase II chromatids are pulled apart and chromatids do not remain attached at the centromere.
What is the Chromosome Number Abnormality of Nondisjunction?
Usually chromosomes separate in meiosis I and chromatids separate in meiosis II, but when these do NOT separate they can cause an extra chromosome or one less chromosome to occur in a gamete. This is called Nondisjunction.
What is Trisomy 21?
Trisomy 21 is the extraneous (extra) gain of a chromosome in humans. The gain of an extra chromosome 21 is what causes Down syndrome in humans. Using karyotypes we can identify nondisjunction.
What is a karyotype?
Karyotype is the pairing of chromosomes based on length.
What are the four types of chromosome structural abnormalities besides nondisjunction?
The four types are duplication, deletion, inversion, and translocation.
What is critical to producing correct proteins in a cell?
The order of DNA is critical to producing correct proteins in a cell.
What can alter the order of DNA?
A structural change to a chromosome can alter the order of DNA.
What is the chromosomal abnormality of duplication?
A chromosome segment is repeated in the same chromosme.
What is the chromosomal abnormality of deletion?
A part of the chromosome is essentially “lost”.
What is the chromosomal abnormality of inversion?
The original segment of chromosomes is basically inverted or written backwards.
What is the chromosomal abnormality of translocation?
A segment of one chromosome is basically swapped with a segment of another chromosome.
Asexual Reproduction
produces offspring that are genetically identical
to the parent because the offspring are all clones of the original parent. involves only one organism.
Advantages of Asexual Reproduction
a single individual can reproduce offspring
large numbers of offspring can be produced quickly
in a stable environment asexual reproduction is effective b/cus all the offspring will be adapted to that particular environment
Sexual Reproduction
is the combination of reproductive cells from two
individuals to form genetically unique offspring. involves a male and a female.
Advantages of Sexual Reproduction
increases genetic diversity in the population
in an unstable environment species that produce asexually may be at a disadvantage b/cus all of the offspring are genetically identical and may not adapt well to changing conditions
What determines if an individual will be successful in a certain environment? (give an example).
The genes of an individual determines if they will be successful in a particular environment (think about oak trees that persist on Grand Isle).
Why does genetic diversity matter?
A more genetically diverse population is likely to persist in a changing environment than a less genetically diverse population.
What is fission, asexual reproduction?
Instances in which an organism appears to split itself into two parts.
What is budding, asexual reproduction?
Results from the outgrowth of a part of the body leading to a separation of the “bud” from the original organism and the formation of two individuals, one smaller than the other.
What is fragmentation, asexual reproduction?
Breaking of an individual into parts followed by regeneration.
What is parthenogenesis, asexual reproduction?
An egg develops into an individual without being fertilized. The resulting offspring can be either haploid or diploid, depending on the process in the species.
Sex Determination
the mechanism that that determines which sex
an individual develops into (can vary; X and Y chromosomes for humans).
Disadvantage of Sexual Reproduction
only “half” of the population (females) can produce offspring, so fewer offspring will be produced in comparison to asexual reproduction.
Hermaphroditism (give examples)
occurs in animals in which one individual has both female and male reproductive systems at the same time. (Invertebrates such as earthworms, slugs, tapeworms, and snails are often hermaphroditic.)
Hermaphroditism/Self Fertilization
may self fertilize. but typically will mate with other species, fertilizing each other and both producing offspring. self fertilization is more common in animals that have limited mobility like barnacles and clams. most species have mechanisms to prevent self fertilization due to extreme forms of inbreeding that produce unfit offspring.
What chromosomes do female humans have?
XX (chromosome 23)
What chromosomes do male humans have?
XY (chromosome 23)
What does the presence of a Y chromosome result in, in humans?
results in the development of male characteristics
What does the absence of a Y chromosome result in, in humans?
results in female characteristics
How does bird sex determination differ from humans?
(ZZ) results in a male and (ZW) results in a female.
⮚ Notice that this system is the opposite of the mammalian system because in birds the female is the sex with the different sex chromosomes.
What is sex determination based on the environment/temperature?
Sex determination in alligators and sea turtles is dependent on the temperature during the middle third of egg development.
Sex Change Later in Life (give examples)
Individuals of some species change their sex during their lives, switching from one to the other.
⮚ Protogyny: female first then male
⮚ Protandry: male first then female
• Example: Oysters are born male and produce sperm, but become female and release eggs when they get large.
Sex Changes in fish
Some fish species live in closely coordinated schools with a dominant male (protogyny) or a dominant female (protandry) and a large number of smaller individuals of the other sex (or
undifferentiated).
⮚ If the dominant dies, the next largest increases in size, changes
sex, and becomes the new dominant.
⮚ Sex changes as size increases
Fertilization
The fusion of a sperm and an egg, either internally (mammals) or externally (fish) the body of the female.
External Fertilization
Usually occurs in water
Sperm and Eggs are released into the environment
Requires coordination between females and male
Requires environmental cues: temperature, day length, tides, etc.
Internal Fertilization
Sperm is deposited inside of the female
Mostly terrestrial organisms but happens in aquatic systems too
Oviparity, internal fertilization
An internal egg is formed and then laid outside to
continue development until hatching (chickens, turtles). The yolk provides nutrients.
Ovoviparity, internal fertilization
An internal egg is formed, but development is
completed inside of the mother. The internal egg hatches and live birth is given (some sharks, lizards). The yolk provides nutrients.
Viviparity, internal fertilization
No egg is formed and the young are born alive.
Nutrients are provided directly by the mother (mammals and some sharks).
What ensures only one complete diploid set of chromosomes upon fertilization?
To ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg.
What is an acrosome?
At the tip of the head of a sperm cell is a structure like a lysosome called the acrosome, which contains enzymes.…
What starts the acrosomal reactions?
When a sperm binds to the zona pellucida, a series of events, called the acrosomal reactions, take place.
What happens as a result of the acrosomal reactions?
These reactions, involving enzymes from the acrosome, allow the sperm plasma membrane to fuse with the egg plasma membrane and permit the sperm nucleus to transfer into the ovum..
What happens when the first sperm enters the egg, to prevent more than one fertilization?
Once the first sperm enters the egg, the
Zona Pellucida forms a barrier to prevent all
other sperm from entering the egg.
What is Cleavage?
After fertilization, the zygote goes through multiple cell divisions.
What is Blastulation?
In mammals, the blastula forms the blastocyst in the next stage of development by having the cells arrange themselves in two layers: the inner cell mass, and an outer layer called the trophoblast.
What is the inner cell mass?
The inner cell mass (embryoblast) will form the embryo.
What is the outer layer?
The trophoblast secretes enzymes that allow implantation of the blastocyst. The trophoblast will contribute to the placenta and nourish the
embryo.
What happens after trophoblast continues to nourish the embryo?
The cells in the blastula then rearrange themselves spatially to form three layers of cells.
⮚ This process is called gastrulation.
What happens during gastrulation?
During gastrulation, the blastula folds in on itself and cells migrate to form three layers of cells (called germ layers) in a structure, the gastrula, with a hollow space that will become the digestive tract.
The opening is called the blastopore and will either form the mouth or the anus.
Three germ Layers: Ectoderm, Mesoderm, Endoderm
Development from Zygote to Gastrula
cleavage (cell division), blastulation (blastula forms), gastrula (germ layers form).
Organogenesis
Development to the different organs in the animal body from the germ layer.
Ectoderm (outside)
the nervous system and skin/epidermis
Mesoderm (middle)
muscle and connective tissue
Endoderm (inside)
digestive system and other internal organs
What are stem cells?
Cells that have not developed into a specific
type of cell
What is differentiation?
The process that develops Stem Cells into a
specific type of cell
Are cells differentiated or stem cells during cleavage?
During Cleavage, all cells are not differentiated and are considered Stem Cells.
What regulates the process of differentiation?
The process of differentiation is regulated by location-specific chemical signals from the cell’s embryonic environment that sets in play a cascade of events that regulates gene expression.
What happens to stem cells during differentiation?
During differentiation, the embryonic stem cells
express specific sets of genes that will determine their ultimate cell type.
⮚ For example, some cells in the ectoderm will express the genes specific to skin cells.
⮚ As a result, these cells will take on the shape and characteristics of epidermal cells.
Testis
the part of the reproductive system in men and people assigned male at birth (AMAB) that makes sperm and hormones. They're located outside your body.
Seminiferous Tubules
are highly coiled tubes, which are lined on the inside by. (i) male germ cells called spermatogonia that undergo meiotic division to form sperm cells.
Ovaries
small, oval-shaped glands located on either side of your uterus. They produce and store your eggs (also called ovum) and make hormones that control your menstrual cycle and pregnancy.
Fimbriae
are the finger-like projections located at the ends of the fallopian tubes, closest to the ovaries. activated by hormones to catch a released egg and move it down into the fallopian tube.
Very early in human development (gender)
no difference between male and female morphology.
7 weeks after fertilization (gender)
If small levels of testosterone is released then male sexual organs develop
If small levels of testosterone are NOT released, then female sexual
organs developThus the male and female anatomies arise from a divergence in the development of a common embryonic structures, and is
chemically regulated.
Spermatogenesis
the production of sperm
Note 
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