AP BIO Unit 5 Review
DESCRIBE the process of meiosis 1 and EXPLAIN its importance.
- Meiosis 1 is initiated after the parental chromosomes have replicated 2 identical sister chromosomes which are separated into a pair of homologous chromosomes. -During Meiosis 1, once each homologous chromosome finds its pair (1 from dad, 1 from mom), it will then be segregated equally into 2 daughters cells.
Describe the process of Crossing over and its importance.
- Occurs between prophase 1 and metaphase 1 and is the process where 2 homologous non-sister chromatids pair up with each other and exchange different segments of genetic material to form 2 recombinant chromosome sister chromatids (of which then are passed on to a different daughter sex cell). - Crossing over is essential for normal segregation, and also accounts for genetic variation, which increases the likelihood that daughter cells contain different genetic material.
Identify the location where meiosis takes place and explain the importance of meiosis.
- Only occurs in the male testis and the female ovaries ( reproductive cells). - Produce the gametes (egg and sperm) so fertilization can occur and combine genetic material ( correct # of chromosomes) from 2 unrelated individuals.
Identify the type of cells that are produced as a result of meiosis.
- Produce sex cells (gametes). - A type of cell division that reduces the # of chromosomes in the parent cell by 1/2 and produces 4 gamete cells, the process results in four daughter cells that are haploid (contain 1/2 the # of chromosomes of the diploid parent cell).
Identify the number of chromosomes that would be in the cells after meiosis if the original number of chromosomes was 20.
-10, since Meiosis is a type of cell division which produces gametes, of which these gametes are haploid cell because they have half of the # of chromosomes as the parent cell.
Describe events that are similar to mitosis and meiosis.
-Both involve duplication of a cell's DNA content (Produce new cells). -Similar basic steps (PMAT). -Start with a single parent cell.
meiosis generates genetic diversity.
-Meiosis generates genetic variation in offspring because the process randomly shuffles genes across chromosomes and then randomly separates half of those chromosomes into each gamete. The 2 gametes then randomly fuse to form a new organism.
Explain how meiosis results in the transmission of chromosomes from one generation to the next.
-Meiosis is a process that ensures the formation of haploid gamete cells in sexually reproducing diploid organisms. -Meiosis results in daughter cells with half the number of chromosomes of the parent cell
Identify the differences between mitosis and meiosis.
-Mitosis involves the division of body cells (identical division), in which the division of a cell occurs once in mitosis, 2 daughter cells are produced after mitosis and cytoplasmic. - Meiosis involves the division of sex cells, in which the division of the cell occurs twice, and 4 daughter cells are produced with half the genetic material as the parent.
DESCRIBE the process of meiosis 2 and EXPLAIN its importance.
-Similar processes as meiosis 1, the only difference is that the sister chromatids are already crossed with each other and that the end results are 4 haploid cells, of which each has a unique combination of chromosomes. - The goal is to make daughter cells with exactly half as many chromosomes as the starting cell. ( From diploid cells to haploid cells).
Describe independent assortment (random assortment of alleles) and Explain how it contributes to genetic variation.
-The Principle of Independent Assortment describes how different genes independently separate from one another when reproductive cells develop. - During meiosis, the pairs of homologous chromosomes are divided in half to form haploid cells, and this separation, or assortment, of homologous chromosomes, is random.
Explain why interphase is needed before meiosis 1 but not before meiosis 2.
-The interphase before meiosis 1 is to ensure a cell is ready to divide (checks all of its systems). -There is no further need for replication or growth since meiosis's goal is to produce a haploid gamete.
In a cross between a white-eyed female fruit fly and a red-eyed male, DETERMINE the percent of the female offspring will have white eyes? (White-eyes are X-linked, recessive).
0% Percent. - The reason was that if you do a punt square (dominate~# , recessive ~ *) the female is X*X* since the white eyes are a recessive trait, and the male would be X#Y since, he has red eyes which is a dominate trait. Once you do the punt square, you will see that you got X#X*, X#X*, X*Y, X*y, which were only trying to find the percentage of female offspring and we know that only males have Y alleles, so we can cross out the ones with Y. Now we have to boxes left, the X#X*, and X#X*, and we know that have red-eyes is a dominate trait (#), so, therefore, in theory, there would be no female white-eyed offspring since the dominate trait (red-eyed) takes over the recessive trait (white-eyed).
monohybrid cross
A genetic mix between 2 individuals who have homozygous genotypes, or genotypes that have completely dominate or completely recessive alleles.
Homozygous
An organism that has two identical alleles for a trait (aa).
Heterozygous
An organism with one dominant and one recessive allele (Aa).
Phenotype
An organism's physical appearance, or visible traits.
For sex-linked traits, Explain why females can be carriers to a trait but males cannot be carriers.
Because females have 2 copies of the X chromosome while males have only one X and one Y chromosome (males either have it or don't). IMAGE EX: The female carries the disease, but doesn't have since the non-carrier allele is dominant (H) and the disease is a recessive allele (h).
Explain how segregation during meiosis leads to variation.
During sexual reproduction, meiosis generates genetic variation in offspring because the process randomly shuffles genes across chromosomes and then randomly separates half of those chromosomes into each gamete. The two gametes then randomly fuse to form a new organism.
Explain how fertilization results in genetic variation.
In sexual reproduction male and female gametes come together. Gametes are formed as a result of meiosis. When fertilization occurs there is shuffling of genes. This shuffling of genes causes genetic variation.
Describe how the resulting daughter cells at the end of meiosis compare to the original cell.
Meiosis gives rise to four unique daughter cells, each of which has half the number of chromosomes as the parent, which resulting from meiosis are haploid and genetically distinct.
Segregation
Separation of 2 alleles, which there is a 50% chance that you're going to get either of these genes (Ex: Heads and Tails).
Explain how an independent assortment of chromosomes leads to genetic variation.
The Law of Independent Assortment states that separate genes for separate traits are passed independently of one another from parents to offspring The idea that the way one pair of homologous chromosomes separates into gametes does not affect the way another pair separates, it makes it so that each gamete could get many different combinations of chromosomes.
phenotypic plasticity
The ability of an organism to change its phenotype (Appearance trait) in response to changes in the environment.
6 genetically identical hydrangea plants were planted locations around the house. 3 were placed in the back yard and 3 in the front yard. The plants that were placed in the front yard grew blue flowers while the plants placed in the backyard grew pink flowers. The pH of the soil was 5.6 in the front yard, while the soil in the back had a pH of 8.6. EXPLAIN the difference in flower color even though they were genetically identical
The color difference relates to how much pH the plants had received since, through phenotypic plasticity, the plant changed color responding to the conditions in its environment.
In cats, one of several genes that control fur color is found on the X chromosome. Some cats have calico color which is patches of black and orange fur. In order to have this color combination, the car has to be heterozygous containing one black gene and one orange gene. EXPLAIN why males will almost never have the calico color (having both orange and black fur).
The reason is because males only have one X chromosome, and to have this color combination of black and orange, the cat has to have 2 of the same alleles (heterozygous) on the X chromosome while the male-only has 1. VISIBLE REPRESENTATION: Dominate (#) Recessive (*). Orange and black patches: X#X#, non-Orange and black patches: X#X*. Males chromosomes: X#Y or X*Y, which to be orange and black has to have 2 of the same alleles on the X chromosomes.
independednt assortment
Traits that don't affect each other (Ex: A couple where one parent has freckles and the other has curly hair can have a child with curly hair and freckles; those traits come separately).
Sex-linked.
a gene located on the X or Y (sex)chromosomes. *Still follow the rules of dominant and recessive.
In peas, round seed (R) is dominant to the wrinkled seed (r) and Yellow seeds (E) are dominant to green (e). Two parents were crossed that were heterozygous for both traits producing 2346 offsprings in the F1 generation. Determine the number of offspring that should express both R and E.
need help
Genotype
refers to the genetic makeup of a specific set of genes.
