The phenotype is the description of the trait. For example: brown eyes, blonde hair, curly hair, etc… The genotype is the genetic code that determines an organism’s trait.
What is the sex chromosome for male and female? How can you tell them apart?
The male sex chromosome is a Y. A male has an XY genotype, the X from his mother and the Y from his father. The female sex chromosome is X. A female has an XX genotype, meaning she receives an X chromosome from both her father and mother.
What does fertilization accomplish?
Fertilization is significant because it adds a second haploid of chromosomes to the cell, in doing so it produces a complete genetic set for the fertilized cell. Fertilization also provides another means of variation in genetic make-up so that there is a little of both mother and father cell in the fertilized cell.
In addition to this, fertilization also causes the cell to grow into an organism by providing what is needed in order for it to become such. We all know the principle of fertilization of an egg with a sperm. This fertilization causes a baby to develop.
How is it that a sexually reproducing individual or organism can look similar to its parents, but not exactly alike?
There are a massive number of genetic combinations from which an organism can develop. During meiosis, there are 8,388,608 different genetic combinations of the material and fraternal genes. This leaves an awfully big gene pool from which to grab genes. The end result is that the organism inherits dominant traits that may look exactly like their parents, or that may only resemble them. For example, they may get their father’s brown eyes but their mother’s curly hair. As such, the new individual or organism only resembles their parents instead of looking exactly like them.
Can traits skip a generation?
Yes. There are traits that skip generations. While things like hair and eye color aren’t commonly noticed, they can skip a generation. What are very noticeable in science are genetic diseases that skip a generation and affect the next generation. These are called Autosomal Recessive Disorder.
An individual, deformed by accident, can have children who have no such deformities. Why?
The key words to look at here are “by accident.” In an accident you are not damaging the DNA. Despite the fact that the body now has a deformity, the DNA does not. Thus, the passed on DNA is normal and will not cause a deformity in the organism.
How does the probability of an outcome differ from the actuality of an outcome?
Probability is the number of possible outcomes. In terms of genetics, probability is the number of possible genetic combinations. For example, an offspring of the genetic combination Gg has the probability of four different genetic outcomes [GG, Gg (from mother), Gg (from father), gg].
Actuality deals with what will actually happen, a fact. In terms of genetics, this means the actual genetic combination that will take place. In the aforementioned situation, we cannot tell actuality until the new cell is produced. However, if we were to see mother cell AA combine with father cell aa, then we can tell that the daughter cell is Aa. This is the reality. It is a fact. We can predict it and tell what will happen. With probability, we can only predict the possibilities of what might happen.
Why is meiosis in cells necessary? What does it do?
Meiosis is important because it is the process of dividing haploid cells into gametes or sex cells that allow us to reproduce. Without meiosis, we wouldn’t have the sex cells necessary to sexually reproduce. The process of meiosis also divides the chromosomes into the gametes so that only one set is present as opposed to the two sets of chromosomes that are present in all other cells of the body. This allows the created cell to obtain a full copy of chromosomes from both parents without a gene overload that would cause mutations in the cell and thus mutations in the new organisms development.
Why is it that the term reduction division is sometimes used to describe the meiosis?
The term reduction division can be used to describe meiosis because the process of meiosis is reducing the number of chromosomes in a cell to half its typical number. The number of chromosomes in a gamete cell, those produced by meiosis is 23 and is represented by “N.” All other cells in the body have 46 chromosomes as are represented by “2N” meaning there are two sets of chromosomes in the cell.
Here are some chromosome counts on various animals:
Ferrets have 40 chromosomes.
Chinchillas have 64 chromosomes.
Cats have 38 chromosomes.
Dogs have 78 chromosomes.
Rabbits have 44 chromosomes.
Goldfish have 94 chromosomes.
It’s also interesting to note that chimpanzees have 48 chromosomes. A close number to our (human) 46 chromosomes.
Why is cross over necessary? When does it occur in meiosis?
Crossing over occurs during prophase 1 and takes almost the entire duration of prophase 1 to complete. The function of cross over to create new combinations in genes so as not to have any identical genes enter into the new gamete cell.
How are daughter cells different from their parent cell?
The daughter cells that result from meiosis have a different genetic make-up than that of their parent cell. They have a different allele combination from their parent cell due to the crossing over, independent assortment, and segregation sections of meiosis.
There are three combinations that create genetic variation in cells undergoing meiosis. What are they?
The three mechanisms leading to gene variation are:
Crossing over: Crossing over occurs when two chromosomes exchange a portion of their DNA. These chromosomes are paired up during prophase 1 of meiosis, and the exchange occurs at the end of prophase 1 and contribute to gene variation or new combinations in genes.
Independent assortment: During independent assortment, the chromosomes for the new gamete are chosen at random from both the material and paternal chromosomes. This allows for a great deal of variation in gene combinations.
Segregation: The segregation phase involves separating the homologous chromosomes (similar chromosomes) from one another. Once the homologous chromosomes are separate they are segregated into one of the two diploid cells.