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Bio101 End
Meiosis and Inheritance (genes)
| Term | Definition |
|---|---|
| Meiosis | Specialized version of the cell cycle, ultimately generates haploid rather than diploid daughter cells No m phase, two meiotic stages |
| Embryo | Early development stage in multicellular organism After fertilization until major body parts begin forming Fertilization -> 8th week of pregnancy Phase involves rapid c division & differentiation as the organism develops Contained w/in seeds in plants |
| Meiosis I | Diploid (2N) cell initiating Separation of homologous chromosomes Generates two daughter cells that are each 1N, but chromosomes are still duplicated (contain sister chromatids) |
| Meiosis II | Separation of sister chromatids (more similar to mitosis) Each cell that completes meiosis II generates two daughter cells that are 1N, with unduplicated chromosomes End product yields 4 haploid cells |
| Crossing over | Happens during prophase I Here, homologs exchange DNA Genetic recombination, generating new & unique chromosomes |
| Somatic cells | Make up most of our cells (skin, muscle, bone) Diploid Contain 46 chromosomes (2x23) |
| Zygote | Egg and sperm fuse with one another during fertilization to create a _ Which will develop into a mature offspring Egg and sperm responsible for providing half the genetic content Diploid cell |
| Gametes | Cell that aren't diploid, they are haploid Egg and sperm cells 23 chromosomes total |
| Sexual reproduction | Gamete cells are produced specifically for How most cells reproduce Two parents contribute to half of the offsprings genetic content, producing an offspring that is not identical to either parent |
| Asexual reproduction | Single parent cell creates two identical offspring to itself |
| Prophase I | chromosomes condense & homologous chromosomes pair up, nuclear envelope disintegrates, spindle forms & microtubules attach to chromosomes via kinetochores – each chromosome in a homologous pair becomes attached to a diff spindle pole Crossing over |
| Metaphase I | Spindle lines up the homologous pairs of chromosomes along the metaphase plate – within each homologous pair, the two chromosomes are attached to opposite poles |
| Anaphase I | Spindle pulls homologs apart from one another, resulting in each spindle pole being attached to one complete set of chromosomes (although recall that each chromosome in that set contains two sister chromatids) |
| Telophase I and cytokinesis I | New nuclear envelopes form around the newly separated chromosome sets, and cytokinesis creates two new cells – each of which contains one set of chromosomes (each with 2 sister chromatids) |
| Independent assortment | During meiosis I, homologs are randomly assorted into new cells; resulting in a mixture of blue and red chromosomes in gametes So random assortment of chromosomes remixes genetic content during each generation, maintaining variation within population |
| Genetic diversity | Happens more in sexual reproduction than asexual -DNA from 2 parents -Independent assortment -Crossing over |
| Sexual reproduction | One sperm fertilizes one egg to produce a diploid |
| Oocytes | undergo meiosis to produce haploid eggs in the ovaries |
| Spermatocytes | undergo meiosis to produce haploid sperm in the testes |
| Gonads (testes and ovaries) | Where meiosis occurs |
| Euchromatin | Chromatin is loosely organized, some DNA is exposed, chromatin is "decondensed" Telophase -> to prophase (where it starts to condense again) Decondensed all of interphase |
| Heterochromatin | Chromatin tightly packed together |
| Replication origin | Site where DNA strands are separated Typically has more A and T's because the double h-bond between them is easier to break the the 3 hbonds b/w C and G's |
| Helicase | Untwisting and separating double stranded DNA |
| Single stranded binding proteins | bind to exposed single stranded DNA to prevent strands from repairing |
| Topoisomerase | Stabilizing DNA on either side of DNA, preventing strand & tighter twisting |
| Replication forks | Where DNA is still double stranded |
| DNA polymerase | Enzyme responsible for building new DNA strands Elongates one nucleotide at a time Can only add to 3' end of preexisting chain (going toward 3' end) Cannot start new chain |
| Primase | build short RNA primers at replication origins |
| RNA primers | act as a crucial "ignition switch" for DNA polymerase, allowing it to initiate the synthesis of a new DNA strand |
| Lagging strand | RNA primers prod close to center of replication origin, can't grow in direction of replication forks bc of 5' end Forms Okazaki fragments which are joined by DNA ligase |
| Leading strand | synthesized continuously in the 5' to 3' direction toward the replication fork, requiring only one primer |
| Okazaki fragments | Discontinuous pieces of new DNA on lagging strand, joined by DNA ligase |
| DNA ligase | Joins together Okazaki fragments on the lagging strand, with no breaks Fuses disconnected DNA pieces w/ no breaks |
| DNA polymerase I | Removes RNA primers and replaces them with DNA |
| DNA polymers | Adds nucleotides, can't start new strand, and only adds from 3' end Proofreads as it goes, and can fix mismatches as it goes |
| Mechanisms (besides DNA polymerase) to fix mismatches | DNA repaire enzymes Mismatch repair Nucleases |
| Nucleases | Removes mismatch & surrounding bases, and add correct nucleotides DNA ligase connect correct sequences by nuclease to original strand |
| Mutagens | Environmental factors that can change DNA; can be passed to daughter cell if not corrected Ex. UV light ,Radiation, Carcinogens, and Reactive oxygen species |
| UV | Forms thymine dimers (in as sequence where two thymines are next to each other, they bond together) Nucleotide excision repair |
| Nucleotide excision repair | fundamental DNA repair mechanism that removes and replaces bulky DNA damage, such as that caused by UV radiation or environmental mutagens Repairs pathways that don't work (that thymine dimers can cause) |
| Point mutation | Single mutated nucleotide, can disrupt protein function and lead to disease |
| Mutations | Can have severe negative consequences if it causes a change in protein coding information |
| NF1 Gene (tumor suppressor) | Mutation in this gene can cause neurofibromatosis, abnormal growth throughout nervous system and lead to predisposed cancer |
| Xeroderma pigmentosum | rare, inherited condition causing extreme sensitivity to ultraviolet (UV) light due to a defect in DNA repair mechanisms |
| DNA polymerase | as it elongates the new strand of DNA, it can pause if it recognizes a mismatch between the nucleotide it just added and the nucleotide on the template strand Removes error and replaces it with correct nucleotide before moving on |
| Central Dogma | DNA replication: DNA is used as a template to replicate itself DNA stores genetic information too that information flows from DNA to RNA to protein |
| Gene expression | Process of transcription (DNA to make RNA) and translation (RNA to make protein) |
| Gene | Which parts of a chromosome contain DNA sequences that are used as templates to make RNA |
| Transcription | In nucleus Genes in DNA used as templates to make RNA |
| RNA | Can be built on template strand of DNA following the same rules of base pairing |
| Initiation step in transcription | Transcription factors bind to the promoter first, and help RNA polymerase bind to the promoter region (TATA box in euk) RNA polymerase then separates strands of DNA and begin to build a new strand of RNA using one of the DNA strands as a template |
| RNA polymerase | Enzyme that reads sequence of template and uses it to build an RNA |
| Synthesis of RNA by RNA Polymerase | can unwind the DNA to expose single strands Initiate a new strand of RNA and elongate the strand by adding new nucleotides to the 3’ end Grows in 5' to 3' direction of NEW Strand |
| Elongation step in transcription | RNA polymerase must use the 3-> 5 strand of DNA as the template strand, so the RNA is elongating in 5 -> 3 direction |
| Coding strand | 5 -> 3 strand of DNA that matches the new sequence of RNA since both are complementary to template strand (but with differences of Us and Ts) |
| Termination step in transcription | Region at end of gene called terminator, signaling to stop transcription Include "polyadenylation signal" with sequence AAUAAA |
| Polyadenylation signal | Signals to stop transcription Sequence AAUAAA |
| Synthesis of mRNA | Initially immature and required additional processing before it can be used to make a protein Add cap, poly A tail, and splicing |
| Modification to mature mRNA | Addition of cap on the 5’ end & poly-A tail on the 3’ end Cap is a modified version of guanine, while the poly-A tail consists of 50-250 adenines Modifications help the mRNA exit the nucleus, increase stability, and help interact with the ribosome |
| Splicing | euk mRNA, intron region cut out of the mRNA + removed Exons stay behind & are pasted back together to form the final sequence of the mRNA Introns aren't present in the mRNA that gets translated, therefore don't contribute to sequence of final protein |
| Transcription and RNA processing | Gene transcribed by the RNA polymerase in nucleus to produce an pre-mRNA While still in the nucleus, the pre-mRNA undergoes cap, tail, and splicing Mature mRNA can then leaves nucleus, enter the cytoplasm, and participate in translation |
| Translation | Unique nucleotide sequence of the mRNA is used to create a unique sequence of amino acids in a polypeptide chain |
| Genetic Code | How cells convert nucleotide seq to AA seq mRNAs are "read” as a series of codons–nucleotide triplets Each codon specifies an AA, some AA have multiple codons This translation key – matching a given codon to the amino acid it specifies |
| mRNA | read from 5' to 3' to interpret codons Start with a "start codon", like Met, and end with a "stop codon" Reading frame is a way of diving a DNA or RNA sequence into a set of consecutive, non-overlapping triplets called codons |
| Translation | occurs in cytoplasm on ribosomes Ribosomes are small non-membrane bound structures comprised of both proteins and small RNAs called ribosomal RNAs (rRNAs) Ribosomes bind to mRNAs and serve as a platform on which the mRNA is used to build a protein |
| Ribosomes | small non-membrane bound structures comprised of both proteins and small RNAs called ribosomal RNAs (rRNAs) Bind to mRNAs and serve as a platform on which the mRNA is used to build a protein Where translation occurs |
| Transfer RNA | has a unique “anticodon” sequence and a unique amino acid Binds to AA + mRNA codons anticode binds to complementary mRNA codon and delivers AA to ribosome Responsible for “reading” the codon and matching the codon with its specified amino acid |
| Initiation of translation | Small ribosomal subunit binds to an mRNA (mRNA 5’ cap assists with this) An initiator tRNA, bound to methionine, recognizes the start codon in the mRNA The large ribosomal subunit is recruited and translation can begin |
| Elongation of the new polypeptide (translation) | While initiator tRNA is in the center of ribosome (P site), tRNA for 2nd codon is recruited into A site of ribosome Two AA joined by peptide bond Initiator tRNA shifts to E site of ribosome, so it can exit 2nd tRNA shifts to P site awaiting 3rd tRNA |
| Termination of Translation | RNA stop codon recruits a release factor rather than a tRNA Release factor binding prompts the disassembly of the ribosome, releasing the now complete polypeptide/protein |
| SIlent mutation | Does not affect protein structure Change in a nucleotide but not changing the AA it codes for |
| Missense mutaiton | Mutation results in a change in the AA seq of a protein In some cases this isn't a problem (like if one polar AA is replaced with another polar AA) In others, it can significantly affect protein structure and function; polar AA replaced w/ nonpolar AA |
| Nonsense | Mutations create premature stop codons in the mRNA The resulting protein is truncated/shortened, and may be missing important functional regions |
| Sickle-cell anemia | caused by a missense mutation in the hemoglobin gene Sickle-shaped red blood cells can’t travel through capillaries – they get stuck, failing to deliver oxygen, causing pain and fatigue |
Created by:
phillipchristopherr