AP Biology Exam Review 2003-2004 Heredity and Evolution – 25%

Heredity and Evolution 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)

Eukaryotic DNA 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

DNA  RNA A  U T  A C  G G  C

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)

Bacterial replication

Using recombinant bacteria

Transduction

Plasmid biotechnology

Recombinant DNA Restriction enzymes cut host DNA and “gene of interest” Sticky ends complementary (match), enabling recombination

Genomic library 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 vector Transduction: using virus as a means to transport eukaryotic gene into bacteria