Chapter 14: Gentetics Flashcards
Gregor Mendel
Founder of modern genetics, as a monk documented inheritance in peas
– used experimental method
– used quantitative analysis
– excellent example of scientific method
Self-Pollination
Pollen from the anther is transferred to the stigma of the same plant
Cross-Pollination
when pollen from a plant is transferred to the stigma of another plant
What exactly was Mendel’s process with observing the pea plants?
P=parental
f=Filal Generation
1st: Cross-Pollinate true breeding parents pea plants (Plants that are not heterozygous)
2nd: Raise seeds & then observe traits (F1)
3rd: Allowed offspring to self-pollinate & observed next generation (F2)
What did Mendel discover?
He leaned that after breeding two pure pea plants that the dominant trait will only appear in the F1. However, If the F1 cross or self-pollinate the recessive trait will show up again about 25% of the time.
Alleles
Traits come in alternative versions.
different alleles vary in sequence of nucleotides at the specific locus of a gene.
Ex: Purple-flower allele & white-flower allele are two DNA variations at the flower color locus.
For each characteristic, an organisms inherit….
2 alleles , 1 from each parent
diploid organism
- inherits 2 sets of chromosomes, 1 from each parent
-homologous chromosomes
What did Mendel’s findings of the purple and white flower traits of the pea plants mean?
some traits masks others
Dominant allele
functional protein
masks other alleles
a.k.a: wild type
Recessive allele
allele makes a malfunctioning protein.
- mutant
Phenotype
description of an organism’s trait
the “physical”
Genotype
description of an organism’s genetic makeup
What are the proportion of genotypes?
1:2:1
Wat are the proportions of phenotype?
3:1
Homozygous
same alleles
Ex: PP, pp
Heterozygous
different alleles Pp
Is it possible for 2 organisms can have same phenotype but have different genotypes?
Yes
Test Cross
breed the dominant phenotype– the unknown genotype– w/ a homozygous recessive(pp) to determine the identity of the unknown allele.
What is Mendel’s 1st law of hereditary?
Law of Segregation
- during meiosis, alleles segregate
- homologous chromosomes separate
- each allele for a trait is packaged into a separate gamete
monohybrid cross
- single trait
Which stage of meiosis creates the law of segregation?
Metaphase 1
Monohybrid Cross
Following the inheritance of single characters
Ex: flower color, seed color
Dihybrid Cross
Following the inheritance of 2 different characters
Ex: seed color & seed shape
Mendel’s 2nd Law of Heredity
Law of independent assortment
- different loci (genes) separate into gametes independently
- non-homologous chromosomes algin independently
- classes of gametes produced in equal amounts
- YR= Yr=yR=yr
- only true for genes on separate chromosomes or on same chromosome but so far apart that crossing over happens frequently
dihybrid (or more) crosses
Which stage of meiosis creates the law of independent assortment?
Metaphase 1
