L8 genot and phenot: patts of inher

Question 1

LO2: disting btw gene and allele.

Answer 1

-hum 25000 genes. each indiv 2 copies each gene, 1 mat 1 pat. each indiv 2 alleles of a gene. but many alleles of gene in pop.

Question 2

LO3: desc diff patts inher and eg’s.

Answer 2

-homoz=2 alleles of gene same.
heteroz= 2 alleles diff.
hemizyg= only one allele on X chrom, males only. males hemiz for ev gene on X.
-domin= domin allele of heteroz determs phenot.
- recess= non domin allele of heteroz.
gene A. alleles A1 and 2. genot A1A2. phenot?

Question 3

LO4: pedig LO’s

• draw fam pedig acc to convent from fam hx.
• interp pedig- relate info to desc fam.
• use genet data pedig to calc probab of inher and recomb freq.

Answer 3

• autos recess- heteroz unaff. eq male and fem. 2 heteroz 25% chance aff offsp. 2 homoz aff offsp only. eg CF. come from nowhere on pedig. skip gens. both parents of aff are heteroz carriers.
• autos domin- heteroz aff. eq male and fem. assume dis heteroz! ev aff indiv 50% chance aff offsp. eg huntingtons. ev aff indiv has at least 1 aff par. no skip gens.
• x linked recess- hemiz males and homox fems aff. more comm in male as fem can be heteroz unaff. heteroz fem carr 50% chance aff sons. aff male cant give to son. eg haemophilia A. if son aff then mum carr. ev aff fem has carr mum and aff dad. daught of aff male heterox, at least carrier.
• x linked domin-
• Y linked only aff males, rare, father to son.

Question 4

other patts

Answer 4

-co domin- both alleles contrib to phenot. eg hum ABO. isoglutamin gene codes gp’s on RBC surf. Ia, Ib, Io. A and B domin over O. A and B codomin.
-complementation- eg albinism inher in recess manner. if 1 gene inv then offsp of 2 aff=albino BUT offsp unaff. 2 genes inv- A1 and A2. 2x2 alleles A1, a1, A2, a2. dad phenot eg a1a1A2A2. mum A1A1a2a2. genots- a1A2 and A1a2. offsp genot A1a1A2a2 normal phenot. 1 aff gene in both pars but 1 complem other so offsp norm. more than 1 gene can be inv in phenot eg enz casc.
-linkage and recomb- genes on same chrom are linked. diff chrom not. linked genes NOT show indep assort in meiosis- alleles carried togeth. linked genes co segreg.
but CO and recomb can= 2 linked alleles sep. frew of recomb tells how close loci are. high freq=far apart.
unlinked ratio 1:1:1:1 offsp genot due to indep assort.
linke dtrav togeth= 2 genot. only get other 2 if CO bt the 2 loci, not 1:1:1:1 as dep how often CO occs. far apart behave as unlinked.

Question 5

LO1: expl how env facs infl genot and phenot.

disting clearly btw genot and phenot.

Answer 5

-genot- rfadiation, mutagens.
-phenot- chems aff cell growth, diet, lifestyle.
dis range from compl genet to env cause.
genetics- inher. var- mut, meiosis indep assort and CO. indep assort= 2^23 possib gametes bef CO!