exam 2 Flashcards
stem cells
- self renewal (divide/renew for a long time)
- differentiation (unspecialized, can give rise to specialized cells)
- found in embryos and some places in adults (long bones)
other dividing cells
liver cells will only divide into more liver cells
permanently differentiated cell
some cells normally do not divide (dormant)
ex. brain and cardiac muscle
binary fission (prokaryotic cell replication)
- chromosome attached to cell membrane
- DNA in single, circular chromosome replicates
- two chromosomes separate and move apart
- new membrane added
- cleavage in between
- two new daughter cells
differences between eukaryotic and prokaryotic chromosomes
- bound in membraned nucleus
- linear instead of circular
- contain much more proteins and different proteins
- contain far more DNA
structure of eukaryotic chromosome
- DNA is would up tightly around histone proteins
- other proteins coil up DNA/histone beads like a slinky
- coils are attached in loops to protein scaffolding to complete chromosome packaging
telomere
protective caps at each end of chromosome, keeps them located in replication
centromere
holds two daughter DNA double helices together after replication and attaches to spindle during cell division
growth factors
molecules that bind to receptors on target cells to enhance their rate of cell division/differentiation
check points in cell replication
- g1 to s: is the cell’s DNA intanct and suitable for replication?
- g2 to mitosis: has the DNA been completely and accurately replicated?
- metaphase to anaphase: are all the chromosomes attached to the spindle and aligned properly at the equator of the cell?
chromosome replication
- single chromosome
- duplicated chromosome (made of two sister chromatids, identical replicated DNA, attached at centromere)
- independent chromosomes (sister chromatids are separated, independent daughter chromosomes)
homologues
- chromosome pairs, contain the same genes (not necessarily the same DNA/alleles)
- one from each parent
- humans have 23 homologues (46 chromosomes total)
diploid vs. haploid
- somatic cells that have pairs of homologous chromosomes (2n)
- gametes have 1 chromosome in each homologous pair (1n)
mitosis interphase
acquires nutrients, grows and differentiates, prepares for division
- G1: growth and differentiation
- S: DNA synthesis
- G2: growth and division prep
mitosis prophase
chromosomes condense, spindle forms, nucleolus disappears; nuclear membrane dissolves, kinetochore holds chromosomes to spindle
mitosis metaphase
kinetochores attached to centromeres line up on equator
mitosis anaphase
sister chromatids separate and move to poles
mitosis telophase
chromosomes decondense, nuclear envelope reforms around 2 new nuclei, spindle disappears
cytokinesis
the rest of the cell separates, 2 identical daughter cells are formed
chromosome replication before meiosis
each homologue is replicated (one homologous pair: 2 duplicated chromosomes –> 4n)
meiosis prophase I
duplicated chromosomes condense, homologues pair up and cross over (DIVERSITY!!!), nuclear envelope disappears, spindle forms
meiosis metaphase I
paired homologues line up on equator, kinetochores attach to spindle
meiosis anaphase I
homologue pairs separate, move to opposite poles, one duplicated chromosome (2 sister chromatids + centromere) to each side
meiosis telophase I
spindle disappears, cytokinesis follows, two 2n cells are formed
meiosis prophase II
chromosomes recondense, nuclear envelope disappears (if it re-formed), spindle reforms and attaches to sister chromatids
meiosis metaphase II
chromosomes line up on equator, attached to spindle by kinetochore
meiosis anaphase II
duplicated sister chromatids separate, move to opposite poles
meiosis telophase II
nuclear envelope reforms, chromosomes decondense, microfilaments contract, spindle dissolves, cytokinesis.
- 4 haploid (1n) gametes are formed
- 1 member of each pair of homologues, each is unique
true breeding
some trait that is inherited unchanged by all offspring of self-fertilization
law of segregation
pairs of alleles on homologous chromosomes separate during meiosis
law of independent assortment
genes (alleles) are inherited independently of each other
- UNLESS the genes are on the same chromosomes, they’re most likely inherited together (linked genes)
- cross over can unlink linked genes
dominant disorders
- heterozygotes have a minor form of the condition, carriers
- homozogotes have the condition in more severe form
recessive disorders
- heterozygotes are carriers but don’t show the condition
- homozygotes express the condition
sex-linked conditions
- gene is carried on the sex chromosomes, much more likely on the X than the Y
- not expressed by female unless it’s carried on BOTH of her X chromosomes (carrier)
- expressed by male because his Y doesn’t cover up the affected X chromosome
different strategies for meiosis
protists, algae, fungi: asexual
- fuse two 1n cells for meiosis, then stay at 1n
animals: sexual
- live as 2n, meiosis makes 1n gametes which fuse and become new 2n organism
plants: alternation of generations
- live as 1n spore, fuse to become 2n and grow until you make 1n spores again
structure of DNA
4 nucleotides each made of phosphate group, deoxyribose sugar, and nitrogen base (A, T, G, or C)
- rails of the ladder are phosphates and sugars (one end 5 prime and the other 3 prime)
- rungs are nitrogenous bases held together with hydrogen bonds (A = T, G = C)
genome
the complete set of genetic information in an organism (depends on the SEQUENCE of the nucleotides)
DNA helicase
breaks the H bonds holding nitrogen bases together, unzips the two strands of DNA
DNA polymerase
pair up the exposed bases with complimentary free nucleotides
DNA ligase
stitch okazaki fragments together from the lagging strand
leading strand
creates 5’ to 3’ strand on the parent strand being read from 3’ to 5’, replicated continuously toward the replication fork
lagging strand
creates 5’ to 3’ strand on the 3’ 5’ parent strand, working away from the replication fork, created in okazaki fragments (which are bound together by DNA ligase)
point mutation
single nucleotide base is incorrect or incorrectly changed
substitutions
repair enzymes replace with the wrong base
insertion
extra base(s) added to the strand
deletion
deletion base(s) incorrectly taken out of the strand
frame shift
when insertion or deletion mutations cause the codons (which are read in the 3s) to be read differently
inversion
piece(s) of DNA taken out, turned around, and re-inserted
translocation
whole globs of DNA are taken off one chromosome and attached to another
- common between 8/22, 8/11, and trisomy 21
beadle & tatum
“one gene, one enzyme”
- but not all proteins are enzymes
- actually: one gene one protein
transcription vs. translation
- DNA –> mRNA (same language) vs. mRNA –> tRNA –> amino acids (different langauge)
- occurs in the nucleus vs. the cytoplasm
types of RNA
- mRNA: code for amino acid sequence of protein, travels from nucleus to cytoplasm
- rRNA: makes up ribosomes
- tRNA: transfers amino acids to ribosome, anticodon to attach to mRNA on one end, amino acid on the other (attached to other amino acids using ATP)
stages of transcription
- initiation: RNA polymerase binds to beginning of gene (promotor), DNA unwinds
- elongation: polymerase moves down DNA template strand from 3’ to 5’ and builds complementary mRNA strand (5’ to 3’)
- termination: DNA end signal, mRNA is released, DNA rewinds
stages of translation
- initiation: start tRNA binds to start mRNA, large and small ribosomal subunits bind together
- elongation: each codon paired with anticodon, bond btwn amino and tRNA breaks, bonds btwn amino acids form
- termination: stop codon is reached, mRNA and chain released, ribosomal subunits separate
mRNA modification
- more RNA nucleotides form cap and tail (prevent degradation in cytoplasm)
- splicing: introns (non coding regions) are cut out
- exons (coding regions) are pasted together
why splice?
- many possible splicing arrangements = many possible proteins from a single gene
- introns can be the source of evolution of proteins
- exons will change places during splicing –> new proteins can be harmful, helpful, or neutral
direction of transcription
5’ to 3’ direction
