16 terms

Biology: 1C

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Define Gamete
Gametes are haploid cells formed through meiosis, a type of cell division where haploid gamete cells are formed from diploid cells. They are sex cells where the male gametes are sperm and female gametes are eggs. They unite during fertilization to form a zygote, a diploid cell that contains two sets of chromosomes.
Define Fertilization
Fertilization is when male and female gametes fuse. During fertilization, the two haploid gametes become one diploid cell or zygote.
Define Haploid
Haploid cells have 1 set of chromosomes, 23 homologous chromosome pairs in humans. These cells are produced through meiosis where a diploid cell divides twice to produce 4 new daughter cells that are considered haploid. The most common type of haploid cells are gametes and sex cells.
Define Diploid
Diploid cells have 2 sets of homologous chromosomes, a total of 46 chromosomes. One set of chromosomes comes from each parent. Diploid cells are formed through mitosis. After 2 identical daughter cells are formed, both the parent and daughter cells are diploid.
Sexual Reproduction Advantages and Disadvantages
Advantages:
- Better adaptation to environment which makes it able to produce more offspring.
- Genetic diversity

Disadvantages:
- Takes more time
Asexual Reproduction Advantages and Disadvantages
Advantages:
- Best for single-celled organisms
- High chance of survival when reproducing quickly which makes it more likely to survive other organisms in environments that are stable and suit their characteristics

Disadvantages:
Lack of genetic diversity which makes it harder for cells to adapt to new environments
Mitosis vs. Meiosis
Mitosis:
1. Forms daughter cells.
2. Asexual
3. 2 diploid cells are formed that are identical to each other and the parent cell.
4. 23 chromosomes

Meiosis:
1. Sex cells - female egg or male sperm.
2. Sexual
3. 4 haploid cells are formed that are all different from the parent cell and eachother.
4. 46 chromosomes - 2 sets of homologous chromosomes.
Number of Chromosomes in a Typical Human Body Cell
23 paired chromosmes for a total of 46 chromosomes
Number of Chromosomes in Sex Cells
23 unpaired chromosomes for a total of 23 chromosomes
Process of Mitosis
The purpose of mitosis is to create two identical diploid cells from the parent cell. In mitosis, there is one round of cell division that occurs during cytokinesis.
Process of Meiosis
The purpose of meiosis is to create 4 gametes/sex cells that are haploid from a diploid parent cell. In meiosis, there are two rounds of cell division, one after Meiosis I and another after Meiosis II. During Prophase I of Meiosis I, each replicated chromosome pairs with its corresponding homologous chromosome which is called a tetrad. These tetrads than crossover where the cross sections of chromatids are exchanged which produces a new combination of alleles in the cell. Than in metaphase I, paired homologous chromosomes line up across the center of the cell.
Name the three ways eukaryote cells have genetic variation
crossing over, random/independent assortment, and random fertilization
Genetic variation eukaryotic offspring: Crossing over
When homologous chromosomes (one from dad and one from mom) wrap around each other and cross over during Meiosis I. Since the cross sections of the chromatids that contain alleles are exchanged, crossing over shares some genes from dad to mom and vice-versa.
Genetic variation eukaryotic offspring: Random/ independent assortment
Random assortment determines what happens to the offspring we have, and it is due to the random path tetrads take at the metaphase plate. It is a flip of the coin or 50% chance that a particular daughter cell of meiosis I gets the maternal chromosome and 50% chance that it receives the paternal chromosome.
Genetic variation eukaryotic offspring: Random fertilization
The odds that one egg meets with one sperm. Since any sperm cell can fuse with any egg, the odds that two fuse is extremely slim.
What is one mechanism that increases genetic variation in prokaryotic populations?
Transformation is one way that a prokaryotic cell can increase its genetic variation. When a prokaryote bacteria picks up the DNA that is still intact from a dead bacteria cell. If the DNA of the dead bacteria cell is still intact, a prokaryote cell can take in its DNA and make use of it. Prokaryotic organisms need to use methods other than solely reproduction to increase genetic variation to diversify its populations.