chapter thirteen/fourteen Flashcards
animal sexual life cycle
- only multicellular and zygote diploid
- only gametes haploid
plant/algae sexual life cycle
- alternation of generations
- zygotes diploid, gametes haploid - unicellular
- sporophyte diploid stage, multicellular
- gametophyte haploid stage, multicellular
sporophyte
- diploid stage, multicellular
- produces spores (haploid), divides mitotically, gametophyte
gametophyte
- haploid stage, multicellular
- gives rise to gametes by mitosis, develops next sporophyte generation through fertilization
fungi/protist sexual life cycle
- zygote only diploid, unicellular
- all multicellular = haploid (except some species)
ancient theories of inheritance
Homunculus, blending, deGraaf
Homunculus theory
a miniature human was already present in sperm that would increase in size
blending theory of inheritance
many generations would blend toward a uniform population of individuals
deGraaf theory of inheritance
egg of mom has mini human, sperm serves as activation
character
a hereditable feature
- ear shape, flower color
trait
a variant for a character
- attached ear lobes, purple flower
true (pure) breeding
will always produce identical offspring with regard to character under study
- homozygous for genes
self-pollinating
plant which produces pollen to fertilize its eggs
hybridization
crossing of 2 pure-breeding parents to form a hybrid (mixture)
3 generations of Mendel’s genetics
- P
- F1
- F2
P generation
parental generation, true bred
- hybridized them (purple x white)
F1 generation
first filial generation, hybrid offspring
- all purple
F2 generation
second filial generation, result from hybrids (self-pollinating for plants) of F1
- purple & white (3:1)
ex. of reciprocal cross
white male X purple female or purple male X white female
Law of Segregation
(Mendel’s 1st Law)
2 alleles of a gene separate during gamete formation
- only 1 allele per gamete
- occurs in meiosis I unless cross-over occurred, then can be meiosis II
phenotypic ratio of F2
3 purple : 1 white
genotypic ration of F2
1 PP : 2 Pp : 1 pp
what do alternative versions of genes account for
variations in inherited characters
allele
different versions of a character gene, each allele is a gene, produces a trait
where are alleles located
on homologous chromosomes
- one maternal in origin, one paternal
- same locus (location) on chromosome
gene
section of DNA that codes for an RNA molecule
- if an mRNA is made, gene codes for a protein
for each character, an organism inherits 2 alleles, one from each…
parent
dominant allele
- observable in organism’s appearance and heterozygous phenotype
recessive allele
- has no noticeable effect on organisms appearance unless completely recessive
when do 2 alleles for a hereditable character separate
gamete formation
- Law of Segregation, 1 allele/gene
homozygous
having 2 identical alleles for a gene
heterozygous
having 2 different alleles for a gene
phenotype
dominant or recessive - actual physical appearance due to gene expression
- 3 purple : 1 white
genotype
composition of genes (alleles) of given trait
- genetic makeup
- 1 PP : 2 Pp : 1 pp
what is used to work genetic crosses
Punnett square
test cross
cross dominant phenotype with unknown genotype (P-) with homozygous recessive (pp)
Law of Independent Assortment (Mendel’s 2nd Law)
each pair of alleles segregates independently of other pairs during gamete formation
monohybrids
heterozygous for 1 character (could be F1 generation above)
dihybrids
heterozygous for 2 characters
Mendel’s dihybrid cross ratio
self-crossing dihybrids (F1) to get an F2
- 9:3:3:1
