Lecture 9 Flashcards
What are 2 things that make up the sexual life cycles of cells?
- Meiosis
- Fertilization
What are diploid cells?
Somatic cells (nonreproductive) that have 2 sets of chromosomes (2 sets of 23 chromosomes)
What are haploid cells?
Gametes (egg and sperm) that have only 1 set of chromosomes (23 chromosomes).
Which is the dominant state of reproduction in animal cells?
The diploid state.
What makes up meiosis?
Meiosis I and Meiosis II.
What makes up Meiosis I & II?
Prophase I, Metaphase I, Anaphase I, Telophase I, & Prophase II, Metaphase II, Anaphase II, Telophase II.
What is the reduction division?
The first meiotic division that results in daughter cells that contain one homologue from each chromosome pair.
Is there DNA replication in meiotic division?
no.
In Meiosis what happens after Interphase?
The germ-line cells enter meiosis I.
What is synapsis?
The pairing of homologous chromosomes.
Wheb does synapsis occur?
During prophase I.
When does crossing over occur?
During Prophase I.
What is the site of crossing over called?
Chiasmata.
What is crossing over?
Genetic recombination between non-sister chromatids.
What is the purpose of crossing over?
To mix up genes.
Which phase of meiosis is the same as mitosis?
Meiosis I.
What happens during prophase I?
The chromosomes coiled tighter, chromosomes form x’s, and synapsis occurs.
What happens during Metaphase I?
Homologous chromosomes lock together after crossing over, microtubules attach, and they align in a double line.
How are chromosomes align during Metaphase I?
Randomly.
What happens during anaphase I?
Chiasmata break and the homologous chromosomes separate.
What happens during Telophase 1?
Nuclear envelope reforms.
What happens during Prophase II?
Same as Mitosis Prophase and Prophase I.
What happens during Metaphase II?
The chromosomes align in a single line and microtubules attach to sister chromatids.
What happens in Anaphase II?
Sister chromatids are separated
What happens during Telophase II?
Nuclear membrane reforms and after cytokinesis occurs, resulting in 4 haploid cells.
What are 4 features of meiosis that is different from mitosis?
- Homologous pairing and crossing over
- Homologous chromosome line up as a double line in metaphase I
- Sister chromatids remain joined at their centromeres and segregating together during anaphase I
- DNA replication is suppressed between meiosis I and Meiosis II. (4 haploid cells instead of 2 diploid cells)
Before the 20th century what were the 2 ideas about heredity?
- Heredity occurs within species
- Traits are transmitted directly from parent to offspring
Who discovered many of the things we know about genes?
Gregor Mendel.
Why did Gregor Menel use a pea plant for his experiments?
- Research showed that pea hybrids could be produced
- Many pea varieties were available
- Pea plants are small
- They can self-fertilize or cross fertilize
What was Mendel’s experimental method?
- Produce true-breeding strains for each trait he was studying
- Cross-fertilize true-breeding strains having alternate forms of a trait
- Allow the hybrid offspring to self-fertilize for several generations and count the number of offspring showing each form of trait.
What is a dominant trait?
The trait that if it is present will be shown.
What is a recessive trait?
The trait that will only be shown if no dominant traits are present.
What is F1 generation?
Offspring produced by crossing 2 true-breeding strains.
What is F2 generation?
Offspring resulting from the self-fertilization of F1 plants.
What is the ratio of organisms with dominant traits to organisms with recessive traits?
3:1 (dominant to recessive).
What is the 3:1 ratio actually?
1 true breeding dominant plant, 2 non-true-breeding dominant plants, 1 true-breeding- recessive plant.
What is Mendel’s 5 element model?
- Parents transmit discrete factors (genes)
- Each individual receives one copy of a gene from each parent
- Not all copies of a gene are identical
- Alleles remain discreate (no blending)
- Presence of allele does not guarantee expression
What is an allele?
An alternative form of a gene.
What is a homozygous?
2 of the same allele.
What is heterozygous?
Different alleles.
What is a genotype?
A total set of alleles an individual contains.
What is a phenotype?
Physical appearance.
