Chapters11-16 Flashcards
Mitosis
Segregation and replication of the DNA in a Diploid cell.
A single nucleus gives rise to two nuclei that are geneticall identical to each other and to the parent nucleus. Accurate segregation of the eukaryotic cells multiple chromosomes into daughter nuclei.
Diploid Cell
diploid cell is a cell that contains two sets of chromosomes.
Chromatin
single strand of a chromosome, and it is the complex of DNA and proteins
Centromere
Is part of the chromosome that holds the two sister chromatids together.
Histones
Are proteins that are positively charged, and they help package the eukaryotic DNA. They are positively charged because of their high content of the basic amino acids lysine and arginine.
Nucleosomes
Is the basic unit of DNA packaging in Eukaryotes, consisting of a segment of DNA wound in sequence around four histone protein cores.
Centrosome
An organelle in the cytoplasm near the nucleus. It serves as the main microtubule organizing center. It usually consists of a pair of centrioles
Centrioles
A pair in each centrosome, Hollow tube formed by nine triplets of micotubules. The two tubes are right angles to each other.
How does the Centrosomes determine the plane of cell division?
During S phase the centrosome doubles to form a pair of centrosomes. G2 to M transition, two centrosomes separate from one another moving to opposite ends of the nuclear envelope. Positions of the centrosomes determine the plane at which the cell will divide.
What are microtubules and how are they formed?
Centrioles are surrounded by high concentrations of tubulin dimers these proteins then form the microtules that orchestrate chromosomal movement.
What happens in prophase in mitosis?
1) chromatin fibers become coiled into chromosomes with each chromosome having two chromatids that join at a centromere.
2) the mitotic spindle, composed of microtubules and proteins form in the cytoplasm (serves as a structure to which the chromosomes attach and act as a framework)
3) the two pair of centrioles move away from one another and it serves as a mitotic center(poles of the cell)
What is the Spindle?
Array of microtubules spreading out from both poles of a dividing cell during mitosis.
What are the two types of microtubules in the spindle?
Polar microtubules and kinetochore microtubules
What is a polar microtubule?
Acts as a frame work of the spindle, and runs from one pole to the other attaching to the centrosomes
What is a kinetochore microtubule?
Attach to the kinetochores on the chromosomes
What is a Kinetochore?
is the protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart
List the steps in Mitosis
Prophase, Prometaphase,Metaphase,Anaphase and telophase
What happens in Mitosis prometaphase?
The nuclear envelope breaks down and the compacted chromosomes attach to the kinetochore microtubules.
What happens in Mitosis Metaphase?
The microtubules pull the chromosomes to a equatorial position in the cell.
What happens in Anaphase in Mitosis?
The paired sister chromatids separate, and the new daughter chromosomes begin to move toward the poles. Separation occurs because on subunit of the cohesin protein holding the sister chromatids are hydrolyzed by an enzyme called protease but a specific variation of this enzyme called separase. After they separate the chromatids are called daughter chromosomes.
What happens in telophase in mitosis?
Occurs after the chromosomes have reached the poles, a nuclear envelope forms around each set of chromosomes, The chromatin decondenses.
What happens in Cytokinesis in a eukaryotic cell?
A single eukaryotic cell is divided to form two daughter cells. It begins with a pinch of the plasma membrane called a contractile ring. It is composed of microfilaments of actin and myosin, they pinch the cell in two.
Asexual reproduction.
Mitosis based, the offspring are clones, they are genetically identical to the parents.
Sexual reproduction
Consists of both mitosis and meiosis, the organism is not identical to its parents.
Haploid
It is a Gamete( is a cell that fuses with another cell during fertilization) which contains only a single set of chromosomes. N
Gamete
Mature sexual reproductive cell” the egg or the sperm.
Zygote
Two haploid gametes fuse to form a zygote in fertilization, Have two sets of chromosomes. Its chromosome number is 2n. This is basically a diploid cell.
Somatic cells
All cells of the body that are not specialized for reproduction.
Homologous pair
Two chromosomes bear corresponding, might not be identical genetic information.
Homologs
one pair of chromosomes having the same ove
What does meiosis do?
Nucleus divides twice, but DNA is replicated only once.
Reduce chromosome number from diploid to haploid
Ensure the haploid products have a complete set of chromosomes
Generate genetic diversity
What happens in Meiosis 1.
Homologus chromosomes come together to pair along their entire lengths.
The homologous chromosome pairs separate but the individual chromosomes, consisting of two sister chromatids remain intact.
What happens in Meiosis prophase 1:
The homologous chromosomes pair by adhearing along their lengths called synapsis. The chromosomes coil and compact, then these sister chromatids take on a X-shaped appearance called Chiasmata, This causes the chromatids to Crossover, which causes the transfer of genetic material. The final product is recominant chromatids.
What is Synapsis
Homologous chromosomes pair by adhearing along their lengths
Karyotype
Number shape and sizes of the chromosomes in a cell
Tetrad
When four chromatids of each pair of homologous chromosomes to form a tetrad
Chiasmata
Regions having attachments mediated by cohesins take on an X-shaped appearance
Crossing over
Chiasma reflects an exhange of genetic material between nonsister chromatids on homologous chromosomes
Recombinant
Crossing over results in recombinant, it increases genetic variation among the products of meiosis by reshuffling genetic information among the homolgous pairs.
What happens in Metaphase 1 in meiosis
Homologous pairs align at the equatorial plane
What happens in Anaphase 1 in meiosis
Centromers do not separate: sister chromatids remain together during anaphase, homologs separate.
Telophase 1
Two homologs are segregated from one another and the cell pinches in two.
Reciprocal crosses
Plants were crossed (mated with each other) in both directions like white flower with red.
Gregor Mendel who is he and what did he do?
An Austrian monk who worked on genetics of pea plants
Character
An observable physical feature, such as flower color
Trait
A particular form of a character, such as purple flowers or white flowers
Heritable trait
Is a trait that is passed from parent to offspring
True-breeding
Observed trait was the only form present for many generations, they have the same alleles
How did Mendel perform his crosses?
He removed anthers from the flowers so that it couldnt self pollinate. He then collected pollen from the other parental strain and placed it on the stigmas of flowers of the removed anthers. Plants providing and receiving the pollen were the Parental generation.
First filial generation
F1: seeds formed producing new plants this is the first generation
Second filial generation
F2: the second generation from self pollination
Hybrid
Offspring of crosses between organisms differing in one or more traits
Monohybrid cross
F1 seeds allowed to self-pollinate to produce the F2 generation
Particulate Theory
The units of inheritance retain their integrity in the presence of other units.
Haploid
Single set of heritable units
Diploid
Two copies of genes unit in an organism
Gene
A sequence of DNA that is transcribed into a functional RNA molecule.
Genome
Totality of all the genes of an organism
Alleles
Different forms of a gene Example (S and s)
Homozygous
They have two copies of the same allele (ss)(SS)
Homozygote
An individual that is homozygous for a character
Heterozygous
They have two different alleles of the gene
Phenotype
The physical appearance of an organism
Genotype
Genetic consitituion, S or s dominate or Ressesive. SS,Ss,ss
Law of Segregation
When any individual produces gametes, the two copies of a gene separate, so that each gamete receives only one copy.