L7 inher of genes

Question 1

LO1: desc proc and role DNA replic.

Answer 1

-2 str sep= templs. catal by DNAP- can ext 3’, add complem base, P on new base joins OH on 3’ of primer str. PPi pryoP rel.
dNMP primer +dNTP substr forms dNMPn+1 + PPi.
DNA helicase seps str. stepw 5’ to 3’ chain growth. reac driven by PPi hydrol. semi cons.
-init- recog seq ori of replic. req recruit DNAP and other specif prots. reqs kick start by primase as DNAP can only ext 3’ end. primase makes few nt RNA first, DNAP elongs, get rid.
-elong- ext 3’. DNAP read templ 3’ to 5’= lead str synth contin. on other str DNAP binds at fork, replic ag direc of replic as strs open, discontin okazaki frags made on lagg str. DNA ligase joins. moving replic forks.
-termin- 2 forks come togeth. ligase. each old str has complem new.
-one chrom=1 dsDNA molec. one chrom also= 2DNA molecs-one replic chrom, so chrom numb const. sis chromatids ident. non sis on mat and pat homol pair non identic. metacentric, submetacentric, acrocentric, telocentric.

Question 2

LO2: desc proc and role of cell cyc. complex contr.

Answer 2

-somat cell diploid 2 chrom pairs. gamete hap 23 chroms.
INTERPHASE:
-G0 outs cyc, not div anymore eg nerve, can re-ent.
-gap 1 cell content replic.
cell cyc checkpt, can go to apop.
-S- DNA replic. synthesis. 8 hr.
-G2 doub check and rep, main DNA.
cell cyc checkpt.
DIVISION:
-M- cell div. x chrom as replic already. sis chromatids.

Question 3

LO3: desc proc and role mitosis and meiosis, comp and contrast.
MITOSIS

Answer 3

MITOSIS: 1 rnd replic, 1 div.
-cell div for somat cells. dip cell to 2 dip daught ident. mitot growth req some tiss eg epidermis, mucosae, BM, spermatogonia. growth/maint. not nerve cell.
PROPH- nuc mem disint. pair centrioles and spind fibs app, chrom condense.
PROMETAPH- centrioles to poles. spind fibs connec kinetochore prot complex which specif bound centromere. chroms cond.
METAPH- chroms line up metaph plate. rand ord incl homol pairs.
ANAPH- centrom div. chromatids split pulled tow opp poles by kinetoch fibs. =daught chrom.
TELOPH- nuc mem reform. chrom decond. spind disapp. cleavage furrow forms.

Question 4

MEIOSIS: dip cell 1 rnd replic, 2 div. one dip to 4 non ident hap daught.
spermatogen and oogen.

Answer 4

MI: homol chroms of each chrom pair div.
-PROPH I- nuc mem disint. homol pair up as have same seq.
gen of genet div- non sis chromatids slight diff seq. they CO and swap DNA str=mix pat and mat. many COs. critic for meiosis. forms chiasmata of non sis chromatids.
-METAPH I- line up in pairs but which side each copy on is rand=rand assort.
-ANAPH I- each replic chrom to either pole.
-TELOPH I- compl replic chrom to daught, each has one of each homol. has undergone CO.
M II: chromatids of each chrom div. CO still present.
-PROPH II-
-METAPH II- rand line up.
-ANAPH II- chromatids split= chroms.
-TELOPH II- cytokinesis=4 hap daught, 1 chromatid of each chrom.
meiosis maint const no chroms btw gens. gens genet div.
-spermatogen- spermatogonium 2n, to prim spermatoc 2n, to 4 hap spermatids, 4 hap mat sperm. 48 d.
-oogen- oogonium to prim oocyte, to 3 hap polar bods and 1 hap to become mat ovum. 12-50 yr. all prim oocytes in fem fetus. all ent MI bef birth. arrested in MI, ev period 1 oocyte through meiosis again up to metaph II, compl only at fert. old arrested LT.
-w/o CO= 2 copies chrom some cells, none others. meiosis misaggreg 30/100. faulty meiosis= 1/3 identif miscarr chrom abnorm. infert. ment retard.