Chapter 13 Flashcards
heredity
the transmission of traits from one generation to the next
genetics
the scientific study of heredity and hereditary variation
gametes
reproductive cells that are the vehicles to transmit genes from one generation to the next
asexual reproduction
single individual is sole parent and passes copies of all its genes to its offspring without the fusion of gametes, offspring are clones of mom/dad
o Ex: single-celled eukaryotic organisms
clone
a group of genetically identical individuals
sexual reproduction
2 parents give rise to offspring with unique combinations of genes inherited from both parents
life cycle
stages from conception to production of own offspring
homologous chromosomes/homologs
when two chromosomes of a pair have the same length
diploid cell
any cell with 2 chromosome sets
o Has 2n number of chromosomes
haploid cell
cells in which gametes contain a single set of chromosomes
o Has n number of chromosomes, n=23
fertilization
the union of gametes resulting from fusion of haploid sperm and egg
meiosis
reduces number of sets of chromosomes from 2 to 1 in gametes
alternation of generations
o includes diploid and haploid stages that are multicellular
o Exhibited by plant cells and certain types of algae
o Sporophyte
sporophyte (alternation of generations)
multicellular diploid stage in which sporophyte generation produces gametophyte as offspring and gametophyte generation produces the next sporophyte generation
• Meiosis here produces haploid cells called spores
Gametophyte (sporophytes)
multicellular haploid stage
sister chromatids
2 copies of one chromosome
o Make up one duplicated chromosome
Prophase I
o Centrosome moves
o Spindle is formed
o Nuclear envelope breaks down
o Chrom. condense
o Each chromosome pairs with its homolog
o Crossing over occurs
• Crossing over: when DNA molecules of non-sister chromatids are broken and rejoined
o Each homologous pair has a chiasmata where crossovers occurred
o Microtubules from one pole will attach to two kinetochores, one at the centromere of each homolog
o Homologous pairs then move toward metaphase plate
Metaphase I
o Pair of homologous chromosomes are at metaphase plate
o Both chromatids of one homolog are attached to kinetochore microtubules from one pole. Those of the other homolog are attached to microtubules from the opposite pole
Anaphase I
o Breakdown of proteins that are responsible for sister chromatid cohesion allow homologs to separate
o Homologs move toward opposite poles, guided by spindle apparatus
o Sister chromatid cohesion continues at centromere, causing chromatids to move as a unit toward the same pole
Telophase I and Cytokinesis
o When telophase I begins, each half of cell has complete haploid set of duplicated chromosomes
o Each chromosome is composed of 2 sister chromatids
o One or both chromatids include regions of nonsister chromatid DNA
o Cytokinesis occurs along with telophase I, forming two haploid daughter cells
o Cleavage furrow forms
o Chromosomes decondense and nuclear envelopes form
Prophase II
o Spindle apparatus forms
o Chromosomes still consist of 2 chromatids at the centromere
o Chromosomes move toward metaphase II plate
Metaphase II
o Chromosomes are positioned at metaphase plate
o Two sister chromatids of each chromosome are not genetically identical
o Kinetichores of sister chromatids attach to microtubules extending from opposite poles
Anaphase II
o Breakdown of proteins holding sister chromatids together at centromere allows chromatids to separate
o Chromatids move toward opposite poles as individual chromosomes
Telophase II and Cytokinesis
o Nuclei form
o Chromosomes begin decondensing
o Meiosis of 1 parent cell has produced four daughter cells each with haploid set of chromosomes
o Four daughter cells are genetically distinct from each other and parent cell
