Cell Division Flashcards
What do multicellular organisms use cell division for?
- Growth and development
- Heal wounds
- Replacing dying cells and maintaining healthy tissues
What do single cell organisms use cell division for?
to reproduce
How do cells arise?
through the division of preexisting cells
What are the two types of cell division?
- Meiosis leads to production of gametes
- Mitosis leads to production of somatic cells
What are both types of cell division usually accompanied by?
cytokinesis; in which the cytoplasm of the cell divides into daughter cells
Describe prokaryotic genomes
typically, circular and contained within the cytoplasm. They are small, containing a few thousand to several million base pairs. Prokaryotes genes are often arranged in operons, clusters of genes involved in related functions
What do prokaryotic genomes consist of?
the genome consists of one double-stranded, circular DNA molecule. (resides in the nucleoid)
What are additional smaller loops of DNA that may be present?
Plasmids;
- not necessary for normal growth but may have important info.
- exchange of plasmids with other cells allows gene transfer in prokaryotes.
How do prokaryotes reproduce?
Binary fission
Describe the process of binary fission
- the genomic DNA is replicated and divided, along with the cytoplasmic contents, resulting in two genetically identical daughter cells.
- the bacterial chromosome, consisting of a single circular DNA molecule, is attached to the plasma membrane, and replication occurs bidirectionally from the origin of replication. As the cell elongates, the chromosomes move towards opposite ends.
- a septum is formed gradually extending towards the center of the cell. Once the new cell walls are in place, the daughter cells separate.
Describe eukaryotic genomes?
typically, linear and contained within the nucleus. They are much larger in size, containing billions of base pairs. Eukaryotic genomes are organized into multiple chromosomes, that are composed of DNA wrapped around proteins called histones
How are eukaryotic genes organized?
typically organized into discrete units, which are separated by non-coding regions
What do eukaryotic genomes contain?
- contain genes (coding regions) providing instructions for protein synthesis - Exons
also - contain non-coding regions, that does not make any protein - Introns
What are chromosomes?
are structures that contain the genetic information of an organism. In prokaryotes, the entire genome is contained within a single chromosome, in eukaryotes, the genome is divided into multiple chromosomes
What are genes?
specific segments of DNA that code for functional RNA or proteins. Genes are the basic units of heredity that determine the traits and characteristics of an organism
Where are genes located?
located on chromosomes, which are physically transmitted from parent to offspring
What do diploid organisms have?
- two copies of each chromosome
- one chromosome from each parent (homologous chromosomes) is passed to offspring
What do eukaryotic genomes undergo?
chromatin remodeling, where DNA is tightly packaged around histone proteins to form a condensed structure
What is heterochromatin?
more condensed, silenced genes (methylated), stains darker (satellite sequences, centromeres, telomeres)
What is euchromatin?
less condensed, gene expressing, stains lighter
What are telomeres?
ends of chromosomes, repetitive DNA, protective
What are centromeres?
middle of chromosomes, essential to cell division, satellite DNA
Describe the p and q arm lengths in chromosomes
- p arm is short arm
- q arm is long arm
Describe DNA compaction
- To fit in the nucleus, DNA undergoes compaction into compact chromosomes during certain stages of the cell cycle.
- The first level of compaction involves DNA wrapping around histone proteins to form nucleosomes, creating a bead-like structure called chromatin.
- The second level of compaction occurs as nucleosomes and linker DNA are coiled into a 30-nm chromatin fiber, shortening the chromosome about 50 times.
(DNA in a human cell nucleus, if laid out end to end, would measure approximately two meters, but its diameter is only 2 nm)
After replication, what do chromosomes consist of?
two sister chromatids linked together, bound by cohesion proteins, with a highly condensed region called the centromere
How does the eukaryotic genome relate to DNA?
- The eukaryotic genome is the complete set of DNAS found in the nucleus. It is organized into linear chromosomes.
- DNA is condensed and packaged using nucleosomes, which consist of DNA wrapped around histone proteins.
- This chromatin structure protects DNA, facilitates compaction, and regulates gene expression.
Describe nucleosomes in DNA
- Nucleosomes are connected by linker DNA, forming higher-order structures, ultimately leading to chromosome formation during cell division.
- Nucleosome organization allows for efficient storage, transmission, and regulation of genetic information in eukaryotic cells.
How many DNA molecules are in each species?
- DNA molecules (chromosomes) in the cell nucleus varies among species.
- Within a species, chromosome number is consistent but may vary with developmental stage or specific cell type.
What are homologous chromosomes?
-two chromosomes, one inherited from each parent, that carry the same genes at the same loci but may have different alleles
- Alternative versions of the same gene are known as alleles
What are non-homologous chromosomes?
not part of a homologous pair, do not contain the same genes in the same locations as each other
What are sister chromatids?
identical copies of a chromosome that are produced during DNA replication
What are non-sister chromatids?
chromatids from different chromosomes
What type of organisms are humans?
Diploid
How do male and female human chromosomes differ?
Males have 22 pairs and females have 23 pairs
Describe diploid organism
Diploid organisms have two copies of every chromosome
What type of chromosomes are X and Y?
heterologous pairs
What is the cell cycle?
- Ordered sequence of stages
- Preparatory & division phases
- One cell transforms into two identical cells
