BSC 114 Chapter Notes - Chapter 14-18: Adenine, Intron, Euchromatin
10 Jan 2017
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Biology Review Test #3
Chapter 14: Mendel and the Gene Idea
Mendel breeded garden peas in the abbey garden to study inheritance
Character: heritable feature that varies among individuals (ex. Flower color)
Trait: each variant for a character
True-breeding: over many generations, same variety as the parent plant
Hybridization: mating (or crossing) of two true bleeding varieties
P generation(parental): true bleeding parents
F1 generation (first filial): hybrid of offspring
F2 generation (second filial): second filial generation
Medel’s Model
1. Alternative versions of genes account for variations in inherited characters
Alleles: alternative versions of genes
2. For each character, an organism inherits two copies (two alleles) of a gene, one from
each parent
3. If the 2 alleles at a locus differ, then one, the dominant allele, determines the
ogais’s appeaae, the othe, the eessie allele has o otieale effet o the
ogais’s appeaae
4. The Law of Segregation: 2 alleles for a heritable character segregate (separate from
each other) during gamete formation and end up in different gametes
Punnett Square: a handy diagramatic device for predicting the allele composition of offspring
from a cross between individuals of known genetic make up
Homozygous: organism that has a pair of identical alleles for a character (PP) (pp)
Heterozygous: organism that has two different alleles (Pp)
Pheotype: ogais’s appeaae o oseale taits
Genotype: genetic make up
Testcross: breeding an organism of unknown genotype with a recessive homozygote, this
reveals the genotype of that organism
Monohybrids: heterozygous for the one particular character being followed in the cross (Yy)
Dihybrid: individuals heterozygous for the two characters bring followed in the cross (YyRr)
The Law of Independent Assortment: two or more genes assort independently, that is, each
pair of alleles segregate independently of each other pair of alleles-during gamete formation
Like two separate coin tosses, the alleles of one gene segregate into gametes independently of
aothe gee’s alleles
Codominance: two alleles each affect the phenotype in separate, distinguishable ways
Tay-Sachs disease: inherited disorder, child suffers seizures, blindness, and degeneration of
oto ad etal pefoae eause of uial ezye does’t ok popely
Polydactyly: extra finger or toe
Blood Types: A, B AB, O
Pleiotropy: have multiple phenotypic effects (ex. Cystic fibrosis, sickle-cell)
Epistasis: the phenotypic expression of a gene at one locus alters that of a gene at a second
locus (ex. Chocolate/yellow labs)
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Polygenic inheritance: (normally quantitative) where multiple genes independently affect a
single trait (ex. Height, skin pigmentation)
Multifactorial: both genetic and environmental collectively influence phenotype
A ogais’s pheotype eflets its oeall geotype ad uiue eioetal histoy
Achondroplasia: form of dwarfism- dominant allele
Chapter 15: The Chromosomal Basis of Inheritance
Genes: segments of DNA located along chromosomes
Chromosome theory of inheritance: Mendelian genes have specific loci (positions) along
chromosomes, and it is the chromosome that undergo segregation and independent
assortment
Wild type: phenotype for a character most commonly observed in natural population
Mutant phenotypes: traits that are alternative to the wild type
Specific genes are carried on a specific chromosome
Sex linked gene: gene located on either sex chromosome
Duchenne Muscular Dystrophy and Hemophilia are X-linked disorders
Barr Body: inactive X in each cell of a female condenses into a compact body, lies along inside of
nuclear envelope
Linked genes: tend to be inherited together because they are located near each other on the
same chromosome
Genetic recombination: the production of offspring with combinations of traits that differ from
those found in either P generation parent
Parental types: matching offspring
Recombinant types: offspring have new combinations
Frequency greater than 50% indicates that the genes are linked
Genetic map: ordered list of the genetic loci along a particular chromosome
Linkage map: genetic map based on recombination frequencies
Map units: 1% recombinant frequency
The farther apart two genes are, the higher the probability that a crossover will occur between
them and therefore the higher the recombination frequencies
Nondisjunction: where members of a pair of homologous chromosomes do not move apart
properly during meiosis I or sister chromatids fail to separate during meiosis II
Aneuploidy: zygote has an abnormal # of a particular chromosome
Down syndrome: result of trisomy in humans
Polyploidy: entire extra set of chromosomes
Breakage of a Chromosome
1. Deletion
2. Duplication
3. Inversion
4. Translocation
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Genome imprinting: some variation in phenotype depending on whether an allele is inherited
from the male or female parent
Some genes are located in organelles in the cytoplasm (extra nuclear genes or cytoplasmic
genes)
Chapter 16: Molecular Basis
the two chemical components of chromosomes are DNA and protein
transformation: change in genotype and phenotype due to the assimilation of external DNA by
a cell
DNA is a polymer of nucleotides-nitrogenous base, pentose sugar called deoxyribose, and a
phosphate group
Chagaff’s Rules
1. The base composition of DNA varies between species
2. For each species, the percentages of A and T and G and C are roughly equal
James Watson and Francis Crick discovered the shape of DNA
Double helix, sugar-phosphate akoe, itogeous ases i the iside, ios ae held
together by hydrogen bonds
Purine and pyrimidine (Pure as Gold)
A&T G&C
Semiconservative model: when a double helix replicates, each of the two daughter molecules
will have one strand (from the parental molecule and one newly made strand)
origins of replication: replication of a chromosome begins at particular sites
replication bubble then replication fork- a Y shaped region where the parental strands of DNA
are unwound
Helicases: enzymes that untwist the double helix at the replication fork (zipper)
Two parental strands are separated, single strand binding proteins bind to the unpaired DNA
strands
Topoisomerase: relieves the strain by breaking, swiveling, and rejoining DNA strands
Primer: RNA chain that is produced during DNA synthesis, synthesized by the enzyme-primase
DNA polymerase: catalyze the synthesis of new DNA by adding nucleotides to a preexisting
chain
DNA is antiparallel like lanes on a divided highway
Oly add uleotides to the fee 3’ ed
5’ to 3’ dietio is elogated
segments of lagging strand: Okazaki fragments
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