ch. 7 Flashcards
what is genetics
the science that describes the inheritance of traits from one generation to another
what is the chromosome theory of inheritance
genes are located on chromosomes
dipoid organisms have
2 copies of the genome in each cell
haploid organisms have
1 copy of the genome
gene
a length of coding of dna for a particular gene product, it is the fundamental unit of inheritance
two non identical chromosomes are
homologous chromosomes
different versions of a gene is called
an allele
genotype
dna sequence of the alleles a person carriers
heterozygous vs homozygous
hetero: a person carrying 2 different alleles homo: a person carrying 2 of the same alleles
phenotype
the physical expression of a genotype
what is a dominant trait
a trait that will always be expressed in phenotype regardless of genotype
what is a recessive trait
an allele not expressed in the heterozygous state
meiosis is
a method of cell division that produces haploid cells (gametes) from a diploid cell that ends up reducing the number of copies of each chromosome to one
meiosis occurs where in males? females? what are each special cells name?
males: testes and spermatogonia females: ovaries and oogenia
what do mitosis and meiosis have in common
they both go through one round of replication of the genome (s phase) leaving a diploid cell with four copies of the genome
mitosis gives rise to what while meiosis give rise to
mitosis: two diploid cells meiosis: 4 haploid cells
when does recombination occur
it occurs when homologous chromosomes exchange genetic material with each other during prophase 1
what occurs in prophase 1? what is similar/different compared to mitosis?
like mitosis, the chromosomes condense and envelope breaks down. unlike mitosis, homologous chromosomes pair with each other and this is called crossing over/recombination
a paired homologous chromosome is called
a tetrad or bivalent
the formation of the tetrad is regulated by the
synaptonemal complex
what occurs in metaphase 1? what is similar/different compared to mitosis?
like mitosis: alignment along the metaphase plate occurs but unlike mitosis: the tetrads are getting in line not sister chromatids
what occurs in anaphase 1?
homologous chromosomes separate and sister chromatids stay together
what occurs in telophase 1?
the cell divides into two cells that are diploid
what occurs in meiosis part 2?
the same thing occurs but it separates the sister chromatids so each cell has a single set of Unreplicated chromosomes (SAME AS MITOSIS)
what is nondisjunction? example?
failure of chromosomes to separate correctly during meiosis where a cell has 2 copies instead of one or no copies of a given chromosome. ex. trisomy down syndrome
what is mendels first law
law of segregation: 2 alleles of a person are separated and passed onto the next generation
when does the law of segregation occur?
Anaphase 1 & 2
what is mendels second law
the law of independent assortment: the alleles of one gene will separate into gametes independent of alleles for another gene
what is a pure breeding strain
any strain that consistently yields progeny with the same characteristics if bred within the same strain
what is a test cross? what do you call the progeny of a test cross?
a test cross is when one organism is crossed with another that has homozygous (or pure breeding) recessive genotype. the offspring is called f1 generation
what is the rule of multiplication
the probability of 2 independent events happening can be found by multiplying the odds of either event alone
what is the rule of addition
the chance of either A or B happening is equal to the probability of A added to the probability of B minus the probability of AB occurring together
what is incomplete dominance
phenotype is a blended mix of both alleles like red and white make pink baby
what is codominance
when 2 alleles are both expressed but not blended
pleiotropism
if a genes expression alters many different seemingly unrelated aspects of a persons total phenotype (ex. Sickle cell anemia as it affects eyes, heart, and liver)
polygenism
complex traits that are influenced by many genes
penetrance
the likelihood that a person with a given phenotype will express that expected phenotype
epistasis
expression of alleles for one gene is dependent on a different gene
recessive lethal alleles
mutant alleles that can cause death when present homozygously
women have what sex chromosomes? men? the absence of a – will cause what
women: xx man: xy, the lack of a y will cause female development
sex linked traits
traits that are determined by x or y chromosomes
linkage
failure of independent assortment because a gene is too close to another gene that it causes it to assort together
the frequency of recombination
the # of recombinant phenotypes resulting from a cross divided by total # of offspring
autosomal traits
traits caused by genetic variation on the autosomes
autosomal dominant
where a single copy will cause the trait automatically
autosomal recessive
where 2 copies of the alleles must be present to cause trait
can autosomal dominant skip generations? autosome recessive?
autosomal recessive can skip generations while dominant cannot
mitochondrial traits can cause what
hemizygosity where you can have only one copy in diploid organism because only one genome exists from mitochondrial genome
x linked traits can be what? why?
dominant or recessive because women have two x’s
what is important to note about x linked traits in men
they will alway show because men only have one x
x linked dominance will cause what three things?
- they dont skip generations
- affected fathers will have affected daughters
- affected mothers can have both affected or not affected kids
population genetics
the inheritance of traits in populations over time
population is
a group of species that can reproduce with each other
gene pool
sum of genetic info in population
hardy-weinburg law
the frequency of alleles in the gene pool of a population will not change overtime
what conditions are needed for HW law
- no mutations, 2. no migration 3. no natural selection, 4. random mating 5. population big enough to stop random drift
what is HW equation? what does it mean?
p+q=1 where p^2+2pq+q^2=1. p is dom q is res and pq is hetero
what will happen after one generation in a population in Hardy-W
it will reach HW equilibrium where allele frequencies will not change
why cant HW law actually occur
we will always have natural selection, cannot control migration, mutations are inevitable etc
evolution is? natural selection?
evolution is the changes in life. natural selection is an interaction between organisms and their environment that causes differential reproduction of diff. phenotypes and alters gene pool
when does evolution occur
when natural selection acts on genetic variation to drive changes in genetic composition of a population
natural selection is based on what? define it
fitness: how successful it is to pass its genes (its survived long enough to reproduce)
does natural selection create new alleles
no it does not, it only affects the frequency of existing alleles
what can cause genetic diversity
new alleles from mutation and new combinations from independent assortment, recombination, and segregation
what is directional selection
polygenic traits follow a bell curve, those at ONE end die while the middle and other end survive. ex. giraffe gets taller as short giraffes die
what is divergent selection
the middle or average of the bell curve die ex. big deer fight small deer hide while middle deer die
what is stabilizing selection
those at the ends at BOTH extremes will die while middle survive,
what is artificial selection
humans interfering with mating like dog breeding
sexual selection
animals dont randomly mate, they have evolved to create rituals or bright displays to attract partners
kin selection
animals that live socially often share alleles with other individuals and will sacrifice to save them for the sake of the shared allele
species
a group of organisms that can reproduce sexually and make kids
prezygotic
barriers of hybridization that prevent development of offspring.
example of prezygotic: hybrid inviability
offspring doesnt develop normally
example of prezygotic:: hydrid sterility
offspring develops well but cant mate
example of prezygotic: hybrid breakdown
offspring can make but F2 cannot
what creation is a new species is called
speciation
cladogenesis
one branch of species branches to make 2 or more species
anagenesis
when one animal chnages so much that it couldn’t mate with past animals, SPECIATION WITHOUT SPLITING
homologous structure
physical features shared by 2 diff. species because they have same common ancestor
analogous structure
physical features have the same function but not because of common ancestors
convergent evolution
2 diff species come to posses many analogous structure because of similar pressures
divergent evolution
when a subgroup of a species evolves traits different from its ancestors.
parallel evolution
where 2 species go through similar evolutionary changes due to selective pressures, ex. animals in ice age survived cold temps
taxonomy and what kind of classification? what are the two names
biological classification through binomial classification with genus and species
what are the 8 principal taxonomic categoriees
domain, kingdom, phylum, class, order, family, genus, and species
what are the two axes
dorsal ventral and anterior posterior
anterior is ? posterior?
anterior: front posterior: back
dorsal? ventral?
dorsal: on top ventral: on bottom
superior? inferior?
superior : toward head inferior: toward feet
earth’s early days had water, co2, co, no2 meaning it was a
reducing environment where e- donors were prevalent
with o2 coming in the picture it became a what? and caused what
it was an e- acceptor and caused spontaneous monomers to form
abiotic synthesis and what were the products of them
metal ions on rock surfaces are thought to have acted as catalysis and its products were proteinoids
proteinoids in water would spontaneously make ? when we added lipids, it became ?
proteinoids would like microspheres and with lipids, liposomes
more complex particles were called
coacervate
microsomes, liposomes, polysaccharides are all called
protobionts
When does the law of independent assortment occur in meiosis?
Metaphase 1
Two heterozygous parents with independent assortment will give what genotype to their kids? In ratio and percentage format.
Ratio: 9:3:3:1 and 25% homo recessive 25% homo dominant and 50% heterozygous
