AP Biology Exam Review2003-2004
Heredity and Evolution – 25%
Heredity and Evolution Heredity – 8% Molecular Genetics – 9% Evolutionary Biology – 8%
Heredity Meiosis and gametogenesis Eukaryotic chromosomes Inheritance patterns
Asexual vs. Sexual Reproduction Asexual reproduction: binary fission,
regeneration, vegetative propagation, budding
Sexual reproduction: result of gametic fusion, gametes formed from meiosis, promotes genetic recombination (variety)
Meiosis: process of gametic nuclear transfer
Sexual life cycles Remember:
Asexual life cycles do not require the fusion (fertilization) of sperm and egg.
Meiosis overview Each “normal” 2N
(diploid) cell has 2 sets of chromosomes, one from each gamete.
Gametogenesis: specialized cells (spermatocyte, oocyte) undergoing meiosis to produce gametes with some combination of the 2 chromosome sets
Important vocabulary Homologous chromosomes: pair of
like chromosomes, having similar length, centromere position, gene loci
Linkage group: genes that are linked on the same chromosome (linked loci)
Locus (pl. loci): site on chromosome where gene is located on the chromosome
Meiosis
Meiosis
Crossing over Genetic variation in
meiosis result of crossing over when chromosomes aligned in tetrad formation
Breaks linkage groups (genes found on the same chromosome)
Oogenesis
Spermatogenesis
Pine life cycle
Eukaryotic chromosome
Allele: alternative form of the same genes
Chromosome: condensed double helix (DNA)
EukaryoticDNA packing
Nucleosomes: “beads on a string” (beads = histones)
Chromatin: condensed nucleosomes
Looped chromatin on protein scaffolding
Chromosomes
Mendel’s work Law of independent assortment Law of segregation
Dominant vs. recessive phenotype Used peas because of fast
generations, easily recognizable characteristics, two alleles
Inheritance patterns Mendelian inheritance: AA & Aa
= dominant phenotype; aa = recessive phenotype
Codominance: Aa = shows both A and a equally
Incomplete dominance Intermediate
inheritance AA = dominant Aa = half way
between AA and aa
aa = recessive phenotype
Inheritance patterns Hybrid: mixed genes between two
species
Pleiotropy: ability of one gene to affect many different genes
Epistasis Expression
of one gene determines the expression of another gene
Polygenic inheritance Many genes
affecting a phenotype
Leading to many possible phenotypes of a trait
Multiple alleles
Test cross If Mendelian
inheritance, AA and Aa genotypes are indistinguishable.
Crossing dominant phenotype with aa. 100% dominant = PP; 1:1 = Pp
Sex-linked Sex-linked: gene loci
on sex chromosome (X or Y)Ex: hemophilia, color blindness
First discovered in 1910 by Thomas Hunt Morgan
Autosomal: gene loci on non-sex chromosome
Sex linkage
Look for inheritance patterns that deviate from 3:1 or 1:1.
Also look for disorders affecting mostly males.
Recombination frequencies
X-inactivation & Barr bodies
Nondisjunction
Nondisjunction disorders
Human pedigrees Square = male Circle = female Colored in = affected
Molecular Genetics – 9% RNA and DNA structure and
function Gene regulation Mutation Viral structure and replication Nucleic acid technology and
application
DNA structure Nucleotide: nitrogen
base, deoxyribose sugar, phosphate group
Nitrogen bases: adenine, thymine, cytosine, guanine
Joined 5’ – 3’ (phosphodiester bonds)
Sugar-phosphate backbone
RNA structure Nucleotide: nitrogen base, ribose,
phosphate group Nitrogen bases: uracil, adenine,
guanine, cytosine Single stranded Joined 5’-3’ In eukaryotes: RNA produced in
nucleolus of nucleus. tRNA, rRNA, mRNA
Griffith experiment
Avery did a follow-up experiment and coined “transformation.”
Phage
Hershey and Chase
DNA replication models
Meselson and Stahl
Origin of replication
DNA elongation
DNA synthesis Leading
strand: made continuously
Lagging strand: Okazaki fragments
DNA priming Necessary for
starting DNA synthesis
Okazaki fragments
Telomeres Necessary to
preserve DNA through successive rounds of DNA replication
Controlling gene expression Gene expression = transcription
RNA transcript is translated into amino acid polymer.
Operons are examples of prokaryotic gene expression control.
Methylation is an example of eukaryotic gene expression control.
One enzyme, one protein (controlling gene expression) Beadle and Tatum
Overview Transcription: DNA
RNA
Translation: RNA amino acid polymer (peptide)
Transcription Initiation Elongation Termination
A U T A C G G C
DNA RNA
RNA processing Removing
introns that interrupt the express-able code (exons)
Also adding poly-A tail and 5’-CAP
tRNA tRNA
“charged” with amino acid
“assists” ribosomes with protein synthesis
Translation - initiation
Translation - elongation
Translation - termination
Point mutation Codon can be
mutate due to substitution.
Insertion& deletion Frameshift
mutation
Mutation: spontaneously occurs; basis of variation in populations
Viral reproduction Lytic vs. lysogenic life
cycle Viruses are not cells. Viruses are particles of
nucleic material and protein that requires host cells for reproduction.
Bacteriophage: viruses that infect bacteria
Lytic life cycle
Lysogenic life cycle
HIV Retrovirus RNA
nucleic acid Requires
reverse transcriptase enzyme (RNA DNA)
Bacterialreplication
Using recombinant bacteria
Transduction
Plasmid biotechnology
RecombinantDNA Restriction
enzymes cut host DNA and “gene of interest”
Sticky ends complementary (match), enabling recombination
Genomiclibrary
Having multiple copies of DNA or phage
PCR Polymerase
chain reaction: heat, cool, add primer
Forms cDNA (clonal DNA) library
Gel electrophoresis
RFLP: cut sites in junk DNA Restriction fragment length
polymorphism
Southern blotting
Sanger Method to
deduce the DNA sequence that is unknown
Gene therapy
Phage as a vectorTransduction: using virus as a means to transport eukaryotic gene into bacteria