Genetics Quiz 2 Flashcards
An organism’s DNA, with its genes, is organized into
Chromosomes
Mitosis
Leads to production of two cells, each with the same number of chromosomes as parent cell (2n)
Meiosis
Reduces genetic content and leads to production of sex gametes, which contains half the number of chromosomes (n)
Chromatin
Uncoiled chromosomes form a diffuse network within the nucleus
Prokaryotic
non nucleated, bacteria and archaea
Eukaryotic
Nucleated, protists, plants, fungi, and animals
Transmission electron microscopy
Allowed scientists to see the cell in its highly varied and organized structure
Plasma membrane
-defines cell boundary
-delimits cell from its external environment
- controls movement of material in and out of cell
Plant cells are composed of
Polysaccharide (cellulose)
Animal cells are surrounded by cell coat
Glycocalyz
Nucleolus
-Location where rRNA is synthesized and initially assembled
-NOR (nucleolus organizer region)- portions of DNA that encode rRNA
Prokaryotic organisms
-Lack nuclear envelope
-long, circular DNA molecule compacted into nuclei area
-does not undergo extensive coiling like eukaryotic cells
-Prokaryotic cells lack distinct nucleolus but do contain genes for rRNA synthesis
Cytosol
Colloidal material which surrounds cellular organelles
Cytoskeleton
Made of microtubules and microfilaments, and provides lattice of support for structures within cell
Microtubules
Made of protein tubulin
Microfilaments
Derived from protein actin
Contents of Eukaryotic Cells
Endoplasmic reticulum
Ribosomes
Mitochondria
Chloroplast
Chloroplast (plant, algae, and protozoa)
Centrioles
Centrosome
Smooth ER
Site of lipid(fatty acid) synthesis
Rough ER
Studded with ribosomes: site of protein synthesis
Ribosomes
Site where genetic information in mRNA is translated to protein
Mitochondria
-Site of ATP synthesis
-Site of oxidative phases of cell respiration
Chloroplasts
-Found in plants, algae, and some protozoans
-Site of photosynthesis
Centrioles
-Cytoplasmic bodies located in centrosome
-Centrioles organize spindle fibers that function in meiosis and mitosis
Spindle fibers
-Composed of microtubules consisting of polymers of protein tubulin
-Play important role in movement of chromosomes as they separate during cell division
Centromere
-Constricted region on chromosomes
-Location of centromere dictates appearance of chromosomes
Metacentric
Centromere location in the middle
Submetacentric
Centromere location between middle and end
Acrocentric
Centromere location close to end
Telocentric
Centromere location at end
Homologous chromosomes
Pairs of chromosomes
Karyotype
number of chromosomes
Locus
Specific gene site along lengths of homologous chromosomes
Biparental inheritance
Diploid organisms
-inheritance form two parents (ovum and sperm)
-each pair of loci derived from each parent
Allele
Alternative forms of the same gene
Mitosis
-Single-celled fungi, protozoa, and algae-mitosis serves as a basis for asexual reproduction
-Multicellular organisms- responsible for wound healing, cell replacement, and growth
Zygote
Single-celled fertilized egg
Karyokinesis
Genetic material even dived into two daughter cells during nuclear division (2 nuclei)
Cytokinesis
After karyokinesis
- Cytoplasmic division
-Partitions cellular volume into two parts and encloses each cell with a plasma membrane
Cell cycle
-Continuous alternation between division and non division of cells
-Composed of interphase (G1, S, G2) and Mitosis
Interphase
-Initial stage of cell cucle
-Interval between divisions
-Replication of DNA of each chromosome
-Two phases of interphase are G1(gap 1) and G2(gap 2)
G1 and G2 occur in
Cytoplasm
- No DNA synthesis occurs
-Phase of metabolic activity and cell growth differentiation
- by end of G2, cell has doubled in size (DNA replicated and mitosis initiated)
- now mitosis is initiated
G0
Point in G1 phase where cells withdraw from cell cycle and enter nondividing but metabolically active state
Mitosis stages
-prophase
-prometaphase
metaphase
-anaphase
-telophase
Prophase(mitosis)
-Chromosomes condese
-Centrioles (in animal cells only) divide and move to opposite end of cell
-Nuclear envelope
-Nucleolus disintegrates
-Chromatin fibers condense and become visible chromosomes
Sister chromatids
Two parts of each chromosome
-genetically identical–visibly connected at centromere
Cohesin
-Protein complex that hold sister chromatids together
-Complex formed during S phase
Prometaphase
Period of chromosome movement
Metaphase
Chromosome configuration following migration
Chromosomes move to ____ of cell
metaphase plate
Spindle fibers bind to ____ and move chromosomes
Kinetochore (protein layers)
During Prometaphase/Metaphase
-Cohesin is degraded by enzyme separase
-Sister chromatid arms disjoin and except at centromere
-Enzy
me shugoshin prevents degradation of cohesion at centromere
Anaphase(mitosis)
Chromosome distribution during mitosis
-centromeres split and sister chromatids separate from each other(disjuction); they are no longer chromatid but daughter chromosomes
Complete disjunction occurs when:
-Shugoshin degrads
- Cohesin complex is cleaved y separase
-Sister chromatids are pulled toward opposite poles of cell
Telophase(mitosis)
Final stage of mitosis with two complete sets of chromosomes, one set at each pole
Cytokinesis (mitosis)
Divides cytoplams
-Chromosomes uncoil and become chromatin again
-Nuclear envelope reforms
-Spindle fibers disappear and nucleolus reforms
- Cell enters interphase
Kinases
Enzymes products of mutated genes
Cyclins
Proteins that bind with kinases - activating them at appropriate times during cell cycle
If checkpoints fail to recognize and stop errors, cell division proceeds and __ results
tumor
Meiosis
-produces gametes or spores
-only one haploid set of chromosomes
-reduces amount of genetic material by one-half
-fertilization restores diploid number
Crossing over
-Results in genetic exchange between members of homologous pairs of chromosomes
-created intact chromosomes-mosaics of maternal and paternal homologs
Meiosis 1
Reductional division
Meiosis 2
Equational division
Meiosis- Prophase 1
-First meiotic division
-Diploid cell duplicated its genetic material
-Homologous chromosomes pair up (synapsis)
-Nuclear envelope and nucleolus break down, and two centromeres of tetrad attach to spindle fibers
Bivalent
Each synapses pair of homologs
-Number of bivalents is equal to haploid number
Synapsis
each bivalent gives rise to a unit - tetrad(two pairs of sister chromatids)
Chiasma
-Region where chromatids are still intertwined
-Point where non sister chromatids have undergone genetic exchange through crossing over
Metaphase 1 (meiosis)
-Chromosomes are at maximum shortness and thickness
-Terminal chiasmata hold nonuser chromatids together
-Tetrads bind to spindle fibers and moves chromatids to metaphase plate
-Alignment of tetrodes is random
Anaphase 1 (meiosis)
-Homologous chromosomes separate
-At the end of anaphase 1, number of dyads equals haploid number present at poles
Disjunction
-Half of each tetrad (dyad) is randomly pulled to opposite poles
-Nondisjuction may occur– separation not achieved
Telophase 1 (meiosis)
-Reappearance of nuclear membrane around dyads
-Nucleus enters into short interphase period
-Chromosomes do not replicate, since they already consist of sister chromatids
Prophase 2 (meiosis)
Each dyad composed of one pair of sister chromatids attached by common centromere
Metaphase 2 (meiosis)
Centromeres are positioned at metaphase plate
Anaphase 2 (meiosis)
Centromeres divide; sister chromatids are pulled to opposite poles
Telophase 2 (meiosis)
One member of each homologs chromosomes (now called monads) is at each pole
Cytokinesis (Second Meiotic Division)
Results in four haploid gametes from a single mitotic event
Spermatogenesis
Begins with undifferentiated spermatogonium germ cell enlarges to become primary spermatocyte
Secondary spermatocytes
-undergoes meiosis II
-Produce two haploid spermatids
-Undergo developmental changes, spermiogensis
-Become motile spermatozoa or sperm
Oogenesis
Formation of ova in ovaries
Oogonium
Undifferentiated germ cell, enlarges to become primary oocyte
Cell with little cytoplasm forms __
First polar body
Secondary oocyte
-Receives bulk of cytoplasm
-Undergoes secondary division
-Divides unequally: produces two haploid cells, an ootid with bulk of cytoplasm and a second polar body
Crossing over
-Occurs during first meiotic prophase
-Further reshuffles alleles between homologs maternal and paternal chromosomes
-Chromosomes segregate and assort independently into gametes
-Results in great amount of genetic variability in gametes
Diploid organisms store __ in the form of homologous Paris of chromosomes
genetic information
Fungi
-Predominant stage of life cycle consists of haploid vegetative cells
-Arise through meiosis and proliferate through mitosis
Multicellular plants
-Life cycles alternate between diploid sporophytic stage and haploid(gametophyte stage)
Electron microscopy revealed
Dispersed chromatin fibers are present in nucleus during interphase
