Chapter 4: Nucleic Acids and Cell Cycle Flashcards
What is DNA?
- A single nucleotide is made of one sugar (deoxyribose), one phospjate group, and one nitrgenous base
- The nitrogenous bases in DNA are purines (double ring) and pyrimidines (single ring)
- Purines: Adenine, Guanine
- Pyrimidines: Cytosine, Thymine (RNA has Uracil instead)
- Base patterns are: A and T, C and G
What is the structure of DNA?
- double helix (resembles spiral staircase)
- nitrogenous bases are united by hydrogen bonds
- law of complementary base pairing (purine with pyrimidine–A and T, C and G)
- the outside lines contain alternating sugar and phosphate groups
Define the following: chromatin, gene, genome
- chromatin: fine filamentous DNA material complexed with proteins
- gene: an information containing segment of DNA that codes for the production of RNA that plays a role in synthesizing one or more proteins
- genome: all the genes of one person (about 20,000)
What is the structure of a chromosome?
- formed when cell is preparing to divide
- two parallel filaments of identical DNA come together: sister chromatids (joined by centromere)
- these are now visible with a light microscope
What is the function and 3 types of RNA?
- RNA interprets the genetic code in DNA to synthesize proteins (functions mainly in the cytoplasm)
- Messenger RNA (mRNA)-gets code from DNA take info to the ribosome
- Ribosomal RNA (rRNA)-ribosome
- Transfer RNA (tRNA)-bring in amino acids
How do DNA and RNA differ?
- ribose replaces deoxyribose as the sugar
- Uracil replaces Thymine as nitrogenous base
- Single stranded (one nucleotide chain, not a helix)
- RNA functions mainly in the cytoplasm
What is a base triplet and its counterparts in RNA?
- Base triplet: a sequence of 3 DNA nucleotides that stands for one amino acid
- Codon: 3 base sequence in mRNA
- Anticodon: 3 base sequence in tRNA
How many codons are possibly and which ones are start and stop?
64 possible codons
- 61 for amino acids
- 3 stop codons (UAG, UGA, and UAA)
- 1 start codon (AUG)
What is transcription in protein synthesis?
Transcription is when messenger RNA is made from a DNA strand.
- mRNA is made to match DNA strand
What is translation in protein synthesis?
Translation is when a protein is made from an mRNA strand at a ribosome.
- tRNA molecules bring the correct amino acid by matching their anticodons to mRNA’s codons
- mRNA learns to speak the language of amino acids
- combining the amindo acids creates peptide bonds, which creates protein
What are the 4 steps of DNA Replication?
- DNA unwinds from histones
- DNA helicase unzips a segment of the double helix
- makes a new bracket with each (outside layer)
- DNA polymerase builds new DNA strands
- new nucleotides join on inside with dehydration synthesis and and enzyme
- Newly made DNA wraps around the histones to make new nucleosome
What are the phases and subphases of the Cell Cycle?
Interphase
- Gap 1 (G1)
- Synthesis (S)
- Gap 2 (G2)
Mitotic Phase
- Prophase
- Metaphase
- Anaphase
- Telophase
Cytokinesis
What occurs during each subphase of the Interphase of Cell Cycle?
Gap 1 (G1)
- normal tasks
- accumulates material for next phase
- between cell birth and DNA replication
Synthesis
- cell replicates all nuclear DNA and duplicates centrioles
Gap 2 (G 2)
- interval between DNA replication and cell division
- cell repairs DNA replication errors
- Grows enzymes to help with cell division
What is the definition and function of mitosis?
- Mitosis is cell division resulting in two genetically identical daughter cells
- Functions:
- Develops from one fertilized egg into 50 trillion cells (individual)
- growth of all tissues and organs
- replacement of dead cells
- repair of damaged tissues
What is the order and function of prophase?
- 1st mitotic phase
- genetic material condenses into compact chromosomes
- nuclear envelope disintegrates
- centrioles (replicated) move to opposite pols and sprout spindle fibers
- spindle fibers attach to chromosomes
What are the orders and functions of metaphase and anaphase?
- Metaphase is second
- chromatids align on the cell equator (spindle lines them up)
- anaphase is third
- enzymes cleave the two sister chromatids apart at the centromere
- single strand daughter chromosomes go to each pole of the cell
- cytokinesis starts here–cleavage furrow is formed
What is the order and function of telophase?
- telophase is the 4th and final phase
- chromosomes cluster on each side of the cell
- Rough ER makes a new nuclear envelope around each cluster
- chromosomes uncoil to chromatin
- each nucleous forms nucleoli
- spindle disappears
- 2 daughter cells are formed
What is the definition and function of cytokinesis?
- division of the cytoplasm into two cells
- overlaps with anaphase and telophase
- creates cleavage furrow around cell equator
- cell pinches in two and creates two daughter cells
When do cells start/stop dividing?
Start
- they have enough cytoplasm and/or nutrient supply for two daughter cells
- they are stimulated by growth factors (chemical signals)
- neighboring cells die so space is open
Stop
- snugly contact neighboring cells, contact inhibition
- nutrients or growth factors are withdrawn
What cells might be amitotic and why?
- after a certain age, neurons, heart muscle, and skeletal muscle no longer grow
Deoxyribonucleic acid [DNA]
A long, threadlike molecule with uniform diameter, but varied light
