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