Exam 2 Flashcards
Mendel’s First Law
Law of Segregation, every organism receives one allele from each parent for a total of 2
cells involved in reproduction have only one copy
diploid
cell with 2 alleles for each gene
haploid
cell with 1 allele for each gene
ploidy
number of alleles per gene
homozygous
both alleles for a gene are the same
heterozygous
two alleles for a gene are different from each other
dominant
allele that always expresses itself when present
recessive
allele that must be homozygous to show up in phenotype
null allele
one that does not function or show up
What two things are needed for sex?
Meiosis and Fertilization
What goes at the top of columns and in front of rows in Punnett squares?
Haploid genotypes derived from parents in meiosis
How do you determine the number of haploid products from a genotype?
2^(number of heterozygous genes)
Mendel’s 2nd Law
Independent Assortment: character inheritance is independent of other characteristics (unless in linked genes)
Linked genes
genes on the same chromosome
Incomplete dominance
when a heterozygous genotype does not fully express the dominant allele, 3 phenotypes instead of 2, partial expression of dominant gene
Codominance
Alleles are equally dominant, heterozygotes show both phenotypes
common with enzyme inheritance, blood types
epistasis
One phenotype controlled by two or more genes
pleiotropy
one gene controlling multiple phenotypes
Phenotypically plastic
environment affects gene functionality
What is the basis of evolutionary change?
Genetic variation generated during sexual reproduction
Secondary variation
variation from meiosis and fertilization
Where do all allelic variants come from?
mutation
What is evolution the product of?
Genetic variation and the environment
Meiosis
Process of nuclear division resulting in genetically variable haploid cells
Does meiosis always produce egg and sperm?
No, in plants produces egg and spore
Chromosome
Single, double-stranded molecule of DNA
46 in humans, bacteria have one circular chromosome
Genes
discrete regions of DNA that code for usable info
Many genes along one chromosome
Homologous chromosomes
chromosomes with same genes but different alleles
What holds DNA copies together?
Kinetochore protein complex at the centromere
Chromatid
condensed DNA molecule
Karyotype
displays the number and types of chromosomes in an organism
Autosomes
chromosomes that do NOT determine an individual’s sex, those are sex chromosomes
Four characteristics of meiosis
Double division process
change in chromosome number (diploid to haploid)
produces four genetically variable products (daughter cells)
produces egg, sperm, spores
Order of meiosis processes
IPMAT
interphase
DNA synthesis and chromosome replication
prophase 1
nuclear envelope breaks down
spindles begin to form
synapis occurs to form tetrads
crossing over occurs and chiasma form
metaphase 1
chromosomes line up randomly along equator
spindles attach to kinetochore
final DNA synthesis at centromeres
What forms between homologous chromosomes during cross over?
synaptonemal complex
anaphase 1
tetrads are split into individual homologues and transported to poles
telophase 1
chromosomes uncoil and reform chromatin
nuclear envelope reforms
sometimes is circumvented, heads straight to prophase 2
forms 2 haploid cells but chromosomes are still doubled
meiosis 2
essentially a mitotic division, separates sister chromatids
creates 4 haploid cells
Where does the variation occur in meiosis?
Independent Assortment and Crossing Over
crossing over
exchange of genetic material along length of chromosome
chiasmata
crossover events
Ultimate source of genetic variation
mutation
Other sources of genetic variation?
Independent assortment
crossing over
(mate choice)
amplexis
frogs holding onto each other
Differences between asexual and sexual reproduction
Asexual: genetically identical offspring, high in number, cheap and fast, mitotic cell division
Sexual: genetically variable offspring, low in number, slow and expensive, meiosis and fertilization, parental investment
Are all bees the same genetically?
No, males are haploids because they are unfertilized
Macroevolution
evolutionary changes that produce new species and groups, concerns diversity over long time periods
Microevolution
changes in a species’ gene pool (allele frequency) between generations
What did Darwin base his evolution ideas on?
Beak size
Founder effect
when a new population is started by a few individuals that do not represent the full gene pool of the larger source population
can begin from one pregnant female or one seed
CaM
Calcium modulating protein that causes finches’ beaks to grow long beaks
BMP4
Bone modulating protein that causes finches’ beaks to grow thick and squat
empirical thought
relies on observational data to form an idea or hypothesis rather than “common sense”
John Ray
basic classification that species do not interbreed
Carolus Linnaeus
Swedish naturalist that began systematic classification and the fixity of species
George Buffon
proposed that organisms change over time but hid it within 44 volumes
Lamarck
inheritance of acquired characteristics
Erasmus Darwin
early advocate of evolutionary change
Jean Baptiste Lamarck
published theory of evolution based on fossil observations
What is the difference between evolution and natural selection?
Natural selection acts on individuals
Evolution acts on populations
Why was the Origin of Species controversial?
It challenged old worldviews put down by people like Plato and Aristotle
What fossils does Ohio have?
Ordovician
Radiometric dating
most common method for determining the absolute ages of fossils
evaluates levels of radioactive isotopes in fossils or their rocks based on their decline after death
What does modern synthesis emphasize?
Populations are the units of evolution
Natural selection is the mechanism of evolution
gradualism
gradualism
many small changes over time add up to a large change
gene pool
all the genes in all loci in a population at a time
fixed gene
occurs when all organisms in a population are homozygous for a gene
Hardy-Weinberg Theorem
frequency of alleles and genotypes in a population will remain constant over generations unless acted on by agents other than Mendelian segregation and recombination of alleles
Five conditions for HWT
Large population size to minimize genetic drift No migration, to stop gene flow No net mutations Random mating No natural selection
Gene flow
transfer of alleles due to movement of individuals into or out of population
polymorphism
the presence of two or more traits for a characteristic in a population
polymorphic gene
a gene that has two or more alleles, each allele has a frequency of at least 1%
monomorphic
gene that only has one allele, or one allele has a frequency over 99%
Single Nucleotide Polymorphisms (SNPs)
smallest type of genetic change in a gene
CTA:GAT:ACC
CTA:GAG:ACC
T to G is a mutation (SNP)
genetic drift
when changes to genotype frequency from one generation to another occur because of chance errors caused by population size
4 Factors that alter allele frequencies in a population
genetic drift
natural selection
gene flow
mutation
Descent with modification
new species arise after many small modifications, new features are altered versions of ancestral features
homology
similarities in characteristics from common ancestry
species
best estimate of relatedness within organisms that can interbreed and produce viable offpspring
