Inheritance Flashcards
Fertilization
Fertilization = fusion of two haploid cells (sperm and egg) to create a new diploid cell (zygote) that will develop into a new individual
Pros of Sexual Reproduction
Introduces genetic variation more than random mutations alone
- Variation may be an advantage for an offspring due to the changing environment or new pathogens
Cons of Sexual Reproduction
Lots of energy spent :
- Finding & attracting mates
- Forming haploid cells
Less offspring is created compared to asexual reproducing species
Asexual: Budding
Occurs when a portion of the parent pinches off as an offspring
Asexual : Regeneration
Occurs when a new individual is produced from a portion of the old one
Example : A new sea star (a small portion of it ) regenerating from an old limb
Life Cycle Types in Protists
(H.D, D.D, AoG)
Haploid-dominant : the multicellular diploid stage is the most obvious life stage and there is no multicellular haploid stage
- Occurs with most animals including humans
Diploid-dominant : the multicellular haploid stage is the most obvious life stage and there is no multicellular diploid stage
- Occurs to all fungi and some algae
Alternation of generations : the two stages, haploid and diploid, are apparent to one degree or another depending on the group
- Occurs with plants and some algae
Alternate Hosts for Parasites
Parasites can use more than one host to complete their life cycles
- Example : mosquitos and how they cam transfer malaria from one person to another
How is the human-infested portion of the
Plasmodium life cycle different from the mosquito-infested portion?
- The infected mosquito carries the disease from one human to another while infected humans transmit the parasite to the mosquito
- In contrast to the human host, the mosquito does not suffer from the presence of the parasites.
Meiosis
Process where somatic diploid cell divides into gamete cells
- Gamete cells are a type of haploid with one set of chromosomes
Meiosis results in four unique daughter cells, each of which has half the number of chromosomes as the parent cell
Process consists of:
- One round of chromosome duplication
- Two rounds of nuclear division (Meiosis I & II)
Begins with interphase
- Also has G1, S & G2 phases like mitosis
Prophase I
- Membrane around nucleus breaks apart
- Centrosomes migrate to poles
- The mitotic spindle extends from
centrosomes - Crossing over occurs, which is an exchange of chromosome segments between non-sister homologous chromatids
- Chiasma is the site of crossover
- Crossing over results in a source of variation in resulting daughter cells
The end of prophase I is the creation of a tetrad, which is a set of 4 sister chromatids
Prometaphase I
- Centrosomes continue to migrate and the spindle continues to develop
- Also the tetrads attach to the forming spindle
- Tetrad = a set of 4 sister chromatids
Metaphase I
- Chrome align
- Indep a of tetrads
- Chromosomes align along the metaphase plate
- There is an independent assortment of tetrads
- This causes another source of
variation in daughter cells
- This causes another source of
Anaphase I
- Chrome pulled –> chiasmata
- SC stay together
- Chromosomes are pulled apart at chiasmata
- Sister chromatids stay together
Telophase I
- Chrome reach
- NM forms
- Chromatids reach the poles
- They may decondense
- The nuclear membrane forms around the chromosomes
Cytokinesis
Separation into two daughter cells occurs
- The separation takes places because of the cleavage furrow, which is the site along equator
that pulls inward and pinches together causing the separation
Meiosis II
- Prophase II : A new spindle forms around the chromosomes
- Metaphase II : Chromosomes line up at equator
- Anaphase II : Centromeres divide & chromatids move to the opposite poles of the cells
- Teleophase II & Cytokinesis : A nuclear envelope forms around each set of chromosomes & the cytoplasm divides
