22638264
Description
Flashcards by Evian Chai, updated more than 1 year ago
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Created by Evian Chai
about 4 years ago
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| Question | Answer |
| What is the difference between heterochromatin and euchromatin? | Hetero: Highly condensed, at periphery Eu: More open chromatin |
| What is the site of DNA coding for ribosomal RNA and the synthesis/assembly of ribosomal subunits? | Nucleolus |
| How many layers is the nuclear envelope? | Double nuclear membrane Outer layer continious with ER Inner nuclues membrane supported by nucleur lamins |
| What allows for communication across the nuclear membrane? | Nuclear pores |
| How do larger molecules (>9nm) enter the nucleus? | 1. Nuclear import receptors bind to Nucleur localisation sequences (basic AAs), delivering protein to pore complex 2. Receptor/protein disassociate once inside 3. Energy for this from GTP hydrolysis |
| What is the structure of a chromatin? | String of nucleosomes (200bp per interval) Can be open (beads on a string) or closed |
| What is the structure of a nucleosome? | DNA wrapped TWICE around 8 histone proteins |
| Highly condensed genes are ... Open genes are... | Silent Transcriptionally active |
| What do centromeres do? | They are special DNA sequences that hold chromatids together and enable formation of the Kinetochrome |
| What does the kinetochore do? | Binds chromatids to microtubules, then attaches them to mitotic spindle |
| What are telomeres? What are they for? What makes them? | Tandem repeats of short, G rich sequences at chromosome ends Prevent chromosome fusion/protect coding sequence Telomerase enzyme |
| What is the karyotype? | THe #, size, shape of chromosome, chracteristic of species |
| Humans have ... chromosomes made up of ... autosomal homologous pairs and ... pair of sex chromosomes | 46 22 1 |
| Most chromosomes are ..., sex gamates are ... | Diploid (46) Haploid (23) |
| What is polypoid? | More than diploid number of chromosomes eg. megakaryotes |
| What is aneuploid? | Abnormal # of chromosome (eg. extra chromosome 21 in Down's syndrome) |
| Interphase is made of: G1 S G2 What do they do? | G1: Replication of organelles+growth Regulation of cell cycle S: Duplication of chromosomes/DNA replication G2: Second gap phase |
| Mitosis and cytokinesis takes .... and is ... and ... dependant | 1 hr microtubule (mitosis) actin (cytokinesis) |
| What is the G0 phase? | Absence of growth factor in G1 leads to resting phase |
| What is the R point in the cell cycle? | Restriction point, after which cell enter complete cell cycle |
| Which phase? Nucleur envelope breaks down, chromosomes attach to spindle via kinetochromes | Prometaphase |
| Which phase? Kinectorchore microtubules shorten, sister chromatids seperate Cytokinesis begins as actin band contracts | Anaphase |
| Which phase? Chromosomes condense, nucleolus disappears, spindle begins to form (aided by centrosome) | Prophase |
| Which phase? Chromosomes line up along metaphase plate | Metaphase |
| Which phase? Spindle disappears Nucleus envelope reforms Chromosomes decondense | Telophase |
| How does the spindle form? | Centriole (9 triplet of microtubules) duplicates As mitosis begins, mother/daughter centriole seperates forming spindle between them |
| What initiates mitosis? | Mitosis promoting factor (cyclin dependant kinase with 2 subunits) CdK (catalytic), Cyclin B (regulatory) |
| What peaks during mitosis and must be degraded to exit it? | Cyclin B |
| What are the two subunits of S phase promoting factor? | 1. cDK 2 (catalytic) 2. Cyclin E/A (regulatory) |
| Homologous chromosomes are held together with? | Chiasmata at site of crossing over |
| What is the purpose of meiosis? | 1. Create genetic variety between maternal/paternal (2^23 combos) 2. Crossing over recombines genes WITHIN a chromosome (infinite combos) |
| Mitosis vs meiosis? | Mit: 1 division to produce 2 genetically identical diploid cells. homologous chromosomes act independantly Mei: 2 divisions to produce 4 genetically different haploid cells Homologous chromosomes pair |
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