Mod 5 Flashcards
Define diploid cell.
A diploid cell has two complete sets of chromosomes, with one chromosome inherited from each parent (e.g., human cells have 23 pairs of chromosomes).
Define somatic cell.
A somatic cell is any cell of a living organism other than the reproductive cells, having 46 chromosomes (23 pairs) and is diploid.
What is mitosis?
Mitosis is a type of cell division that somatic cells undergo, resulting in daughter cells that are genetically identical to the original cell.
What is the role of mitosis?
The role of mitosis includes growth of multicellular organisms, maintenance and repair, asexual reproduction, and genetic stability.
What is the cell cycle?
The cell cycle is a series of events that take place in a cell as it grows and divides, spending most of its time in interphase.
Define interphase.
Interphase is the preparation phase before a cell divides, subdivided into G1, S, and G2 stages.
What happens during G1 phase?
In the G1 phase, cellular contents excluding the chromosomes are duplicated, and cells increase in size.
What happens during S phase?
In the S phase, each of the 46 chromosomes is duplicated, resulting in 92 chromatids, as DNA replicates and becomes double-stranded.
Define chromatid.
A chromatid is one of the two identical halves of a chromosome that has been replicated in preparation for cell division.
What is the function of the centromere?
The centromere is a constricted region of a chromosome that connects sister chromatids.
What occurs during G2 phase?
During the G2 phase, the cell checks the duplicated chromosomes for errors and makes any needed repairs.
What is G0 phase?
The G0 phase is a resting phase where the cell is neither dividing nor preparing to divide, performing maintenance and other functions.
Describe prophase in mitosis.
In prophase, chromosomes condense and become visible as two identical strands, the nuclear membrane breaks down, and centrioles move to opposite ends, forming spindle fibers.
What happens in metaphase?
In metaphase, chromosomes line up in a single file at the center of the cell, and spindle fibers attach to their centromeres.
What occurs during anaphase?
In anaphase, spindle fibers shorten and pull apart the sister chromatids towards opposite poles, causing the cell to elongate.
Describe telophase in mitosis.
In telophase, spindle fibers dissolve, new nuclear membranes regenerate around daughter chromosomes, and a furrow forms, pinching the cell into two.
Define cytokinesis.
Cytokinesis is the physical process of cell division that divides the cytoplasm of the parental cell into two daughter cells.
How does cytokinesis differ in plant and animal cells?
In plant cells, cytokinesis is centrifugal, starting at the center, while in animal cells, it is centripetal, starting at the edges.
What is meiosis?
Meiosis is a type of cell division that produces gametes with a haploid number of chromosomes, resulting in four daughter cells that are not identical to parent cells.
Define haploid.
Haploid refers to the presence of a single set of chromosomes in an organism’s cells.
What are homologous chromosomes?
Homologous chromosomes are pairs of chromosomes of the same length and centromere position, one inherited from the mother and one from the father.
What is crossing over?
Crossing over occurs during the formation of tetrads when homologous chromosomes align, exchanging genetic information, leading to genetic variation.
What happens during prophase I of meiosis?
In prophase I, chromosomes condense, the nuclear membrane disappears, and homologous chromosomes undergo synapsis and crossing over.
Describe metaphase I in meiosis.
In metaphase I, pairs of homologous chromosomes line up at the equator in tetrads, with one chromatid facing each pole.
What occurs during anaphase I?
In anaphase I, chromosomes move towards either pole, with sister chromatids remaining attached at the centromere, resulting in independent assortment.
Describe telophase I and cytokinesis in meiosis.
Each half of the cell has a haploid set with two sister chromatids, the spindle disappears, and cytokinesis occurs, forming two haploid cells.
What happens during prophase II?
In prophase II, the nuclear membrane disintegrates again, and a spindle apparatus forms at right angles to the previous spindle.
What occurs during metaphase II?
In metaphase II, sister chromatids line up at the equator, attaching to spindle fibers in a single file.
Describe anaphase II.
In anaphase II, centromeres separate, and sister chromatids are pulled apart to opposite poles, each now considered an individual daughter chromosome.
What happens during telophase II and cytokinesis?
In telophase II, chromosomes reach poles, the spindle disappears, nuclei regenerate, and cytokinesis produces four daughter cells, each with half the number of chromosomes.
Define linked genes.
Linked genes are genes located close together on the same chromosome, usually inherited together.
What are chromosomes?
Chromosomes are thread-like structures found in the nucleus, carrying genetic information in the form of genes, made of 40% DNA and 60% protein.
What are genes?
Genes are small lengths of DNA that encode for specific traits that can be passed from parent to offspring.
Define locus.
A locus is the position of a gene on a chromosome.
What are peptides
Peptides are short chains of amino acids linked by peptide bonds.
What is a polypeptide?
A polypeptide is a longer, continuous, unbranched peptide chain, and one or more folded polypeptides form a protein.
What is the structure of DNA?
DNA is a double helix made of two strands held together by weak hydrogen bonds, consisting of nucleotides made up of a phosphate group, a sugar group, and nitrogenous bases.
What are the differences between DNA and RNA?
RNA exists as single strands, has ribose sugar instead of deoxyribose, and contains uracil instead of thymine. It has three forms: mRNA, rRNA, and tRNA.
What is DNA replication?
DNA replication is the production of two identical double-stranded molecules of DNA from one original double helix, occurring during interphase.
What is the role of helicase in DNA replication?
Helicase unwinds the DNA helix, breaking weak hydrogen bonds and exposing nucleotide bases, forming the replication fork.
What are RNA primers?
RNA primers are made by primase and act as markers for where DNA polymerase begins synthesis on the existing DNA template.
What does DNA Polymerase III do?
DNA Polymerase III adds nucleotides to the growing DNA chain, synthesizing the new strand in the 5’ to 3’ direction.
What is the difference between the leading and lagging strands?
The leading strand is synthesized continuously towards the replication fork, while the lagging strand grows away from the fork in segments called Okazaki fragments.
What is the function of DNA Polymerase I?
DNA Polymerase I proofreads and edits newly synthesized DNA, correcting errors by cutting out incorrect bases and inserting the correct ones.
What is the end result of DNA replication?
The end result is two identical double-stranded DNA molecules, each containing one original and one newly synthesized strand, making the process semi-conservative.
Why is DNA replication important?
DNA replication is crucial for heredity, gene expression, and maintaining continuity of a species through genetic stability and variation.
What is the location of prokaryotic DNA?
Cytoplasm (chromosomal DNA located in nucleoid region)
What is the location of eukaryotic DNA?
Nucleus
What is the chromosomal structure of prokaryotes?
One circular loop (small plasmid is separate)
What is the chromosomal structure of eukaryotes?
Multiple linear chromosomes
How is prokaryotic DNA packaged?
Not associated with histones. Supercoiled around dense proteins
How is eukaryotic DNA packaged?
Associated with histones (supercoiled)
Do prokaryotes have introns?
No, prokaryotes do not have introns
Do eukaryotes have introns?
Yes, eukaryotes have introns that can be spliced out
What is the size of prokaryotic genomes?
Small genome, not complex
What is the size of eukaryotic genomes?
Larger genome, complex
What is the process of polypeptide synthesis?
DNA → (transcription) → mRNA → (translation) → polypeptide
Define gene expression.
When a cell is actively using a certain gene to make polypeptides
What is a polypeptide?
A series of amino acids joined together to form a unit
How is a protein formed?
One or more polypeptides twisted together into a particular shape
What determines the configuration of a protein?
The sequence and arrangement of amino acids
What are the key components of polypeptide production?
DNA, mRNA, tRNA, ribosomes, enzymes