Unit 7: Nucleic Acids Flashcards

Question

role of hydrogen bonding and complementary base pairing in transcription

Answer 1

sense strand: contains the genetic information to be copied antisense strand: the strand used as a template for transcription complementary base pairing rules means that the RNA produced is an exact copy of the gene hydrogen bonds can only form between complementary bases, ensuring that correct sequence of bases is maintained

Answer 2

stable when strands are together, preventing changes in bases when strands are temporarily separated, mutations can occur

Answer 3

gene expression: protein production using the sequence of bases in a gene only the genes that need to be expressed will be transcribed

Answer 4

mRNA goes from DNA to polypeptide in the cytoplasm on a ribosome

Answer 5

codon: groups of 3 bases on the mRNA there is a start codon and a stop codon on each strand of mRNA tRNA - transfer RNA (transfers amino acids to ribosomes) - has an anticodon and a specific amino acid - anticodon that is complimentary to a specific mRNA codon bottom, smaller subunit binds to the mRNA large subunit binds to tRNA and also is a catalytic site to create peptide bonds see D1.2.6 for structure

Answer 6

1. mRNA attaches to ribosome 2. tRNA with anticodon complementary to the start codon attaches 3. the ribosome slides to the next codon and the next tRNA attaches 4. amino acids from tRNA are joined together (peptide bonds) 5. continues until a stop codon is reached 6. disassembly (small subunit of ribosome will detach, mRNA detach, polypeptide chain will detach)

Answer 7

codon = 3 bases anti codon = complimentary to codon, also 3 bases

Answer 8

code is read in triplets, allowing for 64 combos of the four bases 1. the code is universal. the same codons make the same amino acids in all organisms and viruses (GOOD) 2. degenerate: different codons can code for the same amino acid (GOOD)

Answer 9

1. A site (right side of large subunit of ribosome): initial binding site for tRNA, peptide bond is formed between the amino acid on the tRNA and the polypeptide chain 2. P site (middle of large subunit of ribosome): "empty" TRNA moves here as the ribosome slides down mRNA and the peptide chain is passed to the next tRNA that has entered A site 3. E site (left of large subunit of ribosome): exit site this occurs repeatedly, leading to the elongation of the polypeptide chain

Answer 10

mutation = change to the base sequence of a gene base substitution: change to one base in a gene - might change the amino acid - might change the overall protein structure

Answer 11

both in a 5' to 3' direction transcription = new RNA nucleotides can only be added to 3' end translation = ribosome moves down the mRNA starting from its 5' end and towards the 3' end

Answer 12

promoter = section of DNA that serves as a binding sit for RNA polymerase or other proteins that control transcription transcription factors = molecules that regulate gene expression by promoting/inhibiting transcription

Answer 13

both nucleotide sequences important for gene expression promoters on DNA, start codons on RNA promoters for transcription, start codons for translation

Answer 14

base sequences that do not code for polypeptides, so are not genes i.e. - base sequences that produce tRNA or rRNA - promoters - structural DNA at the end of chromosomes (telomeres) - introns (edited out after transcription

Answer 15

modification occurs in nucleus (hence only eukaryotes, prokaryotes have no true nucleus) allows for many diff versions of a protein to be made using 1 gene by eliminating different sections of the mRNA, can make different versions of the mRNA which will be translated into different amino acid sequences, even though they were all transcribed from the same gene production of mature mRNA 1. introns are removed and exons are spliced together (because the mRNA has to EXIT the nucleus, but only the EXons can) 2. addition of a 5' cap on the 5' carbon side, and a poly-A tail on the 3' end (a very long stream of nucleotides that all have adenine as their nitrogenous base)

Answer 16

removing diff introns to produce diff versions of protein from a single gene

Answer 17

1. tRNA activation tRNA activating enzyme: an enzyme attaches the correct amino acid to the tRNA --> aka aminoacyl-tRNA synthetase diff enzymes for each tRNA and amino acid (requires ATP) tRNA has 5' and 3' end, amino acid will attach to 3' end using the enzyme + ATP 2. tRNA carrying methionine attaches to the small subunit of the ribosome 3. small subunit slides down mRNA (5' to 3') until the tRNA anticodon binds with the complementary start codon on mRNA. 4. large subunit binds with the small subunit with the tRNA in the p site https://www.youtube.com/watch?v=qIwrhUrvX-k

Answer 18

polypeptides become proteins when they are modified into their functional shapes - removal of methionine or whole sections - modification of R groups on some amino acids - folding into tertiary structures - combining with other polypeptides (quarternary structure) - adding non-polypeptide components pre-proinsulin to insulin (110 amino acids) - rough ER removes 24 amino acids (proinsulin) - proinsulin is folded into tertiary structure using disulfide bonds - some amino acids are removed from the middle, leaving 2 linked chains - mature insulin has 2 chains help togheter by disulfide bridges, with a total of 51 amino acids

Answer 19

proteasome = enzyme complex that breaks down proteins into short polypeptides, which can be broken down into amino acids later on

Answer 20

needed for growth, repair and reproduction new cells come from existing cells --> continuity of life

Answer 21

division of the cytoplasm of a cell to form 2 daughter cells animal 1. cleavage furrow (bit in between the 2 daughter cells) 2. contractile rings made of actin and myosin 3. then pinch apart plant 1. vesicles form in the center to create new membranes 2. microtubule scaffold 3. each new cell builds a cell wall

Answer 22

equal = parent cell equally divides into 2 daughter cells unequal = can be possible, as long as the new cell has a nucleus, at least 1 mitochondrion, and any other organelle that cannot be synthesised by the cell example = budding in yeast oogenesis: meiosis has 2 cell divisions, produces one viable oocyte and 3 polar bodies

Answer 23

cells MUST replicate nucleus before division to prevent the formation of anucleate cells --> cannot synthesise proteins, limited lifespan (i.e. red blood cells) Mitosis = diploid, produces 2 genetically identical daughter cells (asexual repro) --> maintains chromosome number and genome of cells Meiosis = haploid (sexual repro) halves the chromosome number and generates genetic diversity

Answer 24

before cell division, DNA is elongated, replicated and condensed into chromosomes before replication, 1 chromatid After replication, each chromosome consists of 2 sister chromatids held together using cohesin loops until anaphase after anaphase, 2 chromatids pulled apart

Answer 25

condensation of chromosomes helps move DNA safely and efficiently supercoiling: DNA wraps around histones (always is to form nucleosome) but then the histones link together again and again until they form the chromosome cytoskeleton microtubules are disassembled to form the spindle (used to move chromosomes during mitosis) the spindle microtubules link with a structure called the kinetochore on the centromere (the middle of the chromatid). this acts like a microtubule motor (think chores, kineto = movement), remove microtubules to shorten the spindle, which pulls the chromatids apart

Answer 26

prophase, metaphase, anaphase and telophase

Answer 27

DNA is in the form of chromatin (not yet chromosomes) growth, normal cell function, DNA replication

Answer 28

chromatids condense to chromosomes spindle microtubules are starting to assemble nuclear membrane breaks down

Answer 29

microtubules attach to the centromeres chromosomes align on the equator

Answer 30

cohesin loops are cut tension from the spindle pulls sister chromatids apart chromosomes are moving towards the poles

Answer 31

new nuclear membranes form chromosomes decondense back into chromatin happen simulaneously with cytokinesis

Answer 32

a reduction division --> creates genetically different haploid cells (usually gametes) ensures zygote has 46 chromosomes DNA is replicated once, but there are 2 cell divisions

Answer 33

anaphase 1 separation of chromoSOME pairs anaphase 2 separation of chromaTID pairs

Answer 34

failure of the chromosomes to separate results in gametes with too many or too few chromosomes, usually resulting in cell death if 21st chromosome experiences nondisjunction, then Down syndrome (trisomy 21) --> highly correlated with maternal age

Answer 35

in prophase 1: bivalent is the structure (pair of homologous chromosomes), synapsis is the formation of a bivalent chiasma is the point of crossing over CROSSING OVER = exchange of alleles on non sister chromatids of homologous chromosomes number of chiasma and amount of genetic exchange seems to be random RANDOM ORIENTATION alignment of chromosomes is random = therefore there will be 2^n combos of alleles when chromosomes/chromatids are separated phases: 1. DNA replication 2. Meiosis I 3. Cytokinesis 4. Meiosis II 5. Cytokinesis under meiosis I, you have the same steps as mitosis Prophase I - crossing over metaphase I - homologous pairs align on the equator anaphase I - separation of homologous pairs telophase I - ends w/ 2 haploid cells under meiosis II: metaphase II - chromosomes align in center anaphase II - sister chromatids separate telophase II - ends w/ 4 haploid cells

Answer 36

cell proliferation = rapid increase in the number of cells for growth (apical meristems), repair (wound healing) and cell replacement (skin cells)

Answer 37

1. interphase: G1 (growth), S (synthesising DNA), G2 phase (prep for mitosis) 2. mitosis: prophase, metaphase, anaphase, telophase 3. cytokinesis

Answer 38

chromatin is relaxed, making it possible for it to be transcribed and translated. the membrane will increase in size, more organelles, high level of metabolism

Answer 39

cyclin = protein that controls cell cycle cell must produce enough of each cyclin to progress to the next stage

Answer 40

cells have genes that ensure mitosis only happens when new cells are needed -> proto-oncogenes (good) -----> genes that control the cell cycle -----> if mutate --- oncogenes (BAD) -> tumour-suppressor genes -----> correct errors due to DNA damage -----> most of these tumours are benign (harmless) tumour = uncontrolled cell division due to the mutation in division-controlling genes random mutation heritable mutation mutagens (chemical/radiation)

Answer 41

primary tumour = tumour cells that stick together secondary tumour = tumour cells migrate and/or invade neighbouring tissue metastasis = spreading of tumour cells to different parts of the body malignant tumours = capable of metastasising (cancer) --> more common in areas with more cell mutation mitotic index = (number of cells in mitosis)/total number of cells higher mitotic index = more aggro