Genetics and Evolution Flashcards
Independent Assortment
these genes separate and recombine independently of one another, with every combo of alleles having the same likelihood of occurring
division of genes during meiosis is random and therefore no 2 gametes will have same combo of genetic info, all combos have equal chance
Law of Segregation
genes separate into distinct alleles during gamete formation
Monohybrid and dihybrid
purpose is to isolate and study traits
monohybrid: P generation is selected based on one particular trait, one parent has dominant trait and other has recessive
dihybrid: P generation is selected for 2 traits that differ bw parents
Pedigree Analysis
diagram of familial genetic history and traces inherited traits from one generation to next
circles-females
squares-males
homozygous dominant- filled in
heterozygous dominant- partially filled in
Linkage
genes close together on chromosome are more likely to be inherited together
not found close- not inherited together
Sex-Linked Inheritance
traits that differ bw males and females
located on sex chromosome
genes on Y chromosomes only expressed in males
Y chr is smaller and has fewer genes
X chromosome larger and found in males and females
- -males have one allele for every X gene so this is the trait that will be expressed regardless if dominant or recessive
- -females have 2 X chromosomes so the dominant allele will express itself for X linked traits
Multiple alleles, codominance, and incomplete dominance
- -many genes have multiple alleles
- -multiple alleles means higher genetic diversity, more complex rules of dominance, and more combos of phenotypes
- codominance: appearance of 2 dominant alleles, both dominant genes are expressed
- incomplete dominance: one allele is not completely dominant over the other
Polygenic inheritance, epistasis, and pleiotropy
polygenic: traits determined by multiple genes, observed in continuous variation
epistasis: one gene suppresses the expressed phenotype of another gene
- -these are not alleles for the same trait
- -phenotype expressed by one gene dependent on modifier gene that masks the trait
pleiotropy: one gene can have multiple effects, one gene influences many traits
Organelle Inheritance
within mitochondria or chloroplasts
passed from parent to offspring
primary type of organelle inheritance from extranuclear organelles is called uniparental inheritance bc comes from mother
- most common in eukaryotic animals that undergo sexual reproduction
- -most important is mitochondrial inheritance
- —-major energy producers
- —-genetic material within this replicates independently of the material within the nucleus
- —at fertilization the egg provides a copy of the mothers mitochondrial DNA and this is passed on to offspring
Changes in Chr #
euploidy: equal # of chromosomes that is exact multiple of the haploid number
monoploid: half the normal number of chromosomes
- -monoploid in adult state
- -plants and fungi, insects
- -sterile non reproducing
polyploid: more than 2 pairs of chromosomes
- -flowering plants: exist and reproduce at increasingly higher ploidy levels
- -humans with this, rare and lethal
nondisjunction: results in chromosome abnormalities, which is the failure of one or more chromosomes to fully separate
monosomy: nondisjunction results in loss of single chromosome
trisomy: chromosome is added
Turner syndrome: monosomy that does not result in death or miscarriage, when females are missing X chromosome
Down syndrome: excess genetic material on chromosome 21
Changes in Chr Sruct
deletion: section of chromosome is lost during cell division
duplication: sections are duplicated, occurs when homologous chromosomes exchange unequal amounts of info during recombination or DNA is copied onto incorrect strand (Huntington’s)
translocation: nonhomologous chromosomes exchange info within a cell, normal set of traits but can be infertile
inversion: section of chromosome breaks off, becomes inverted, and reattaches to same chromosome
- -not usually genetic abnormalities unless accompanied with duplication or deletion
Common Genetic Disorders
cystic fibrosis- autosomal recessive, deletion of protein producing material on CFTR gene
–inherited by having 2 parents as carriers of mutated gene
huntingtons: degenerative disease, breaks down nerve cells in brain, presents later in life
- -duplication of genetic material causing large amts of huntingtons protein
- -autosomal dominant
- -parents have 50% chance of passing it on
sickle cell anemia: autosomal recessive
- -beta globin substituted
- -red blood cells sickle shape
- -cells break easily, low blood counts as result
muscular dystrophy: degeneration of skeletal muscle tissue
- -mutation in gene that prevents proper production of dystrophin–builds and repairs muscle
- -gene defect on X chromosome therefore X linked recessive
PKU: gene defect leads to increased phenylalanine levels which is amino acid in proteins
- -autosomal recessive
- -mutation in PAH gene which prevents amino acid from breaking down
Tay-Sachs: degenerative nerve disease, destroys brain and spinal cord cells
- -autosomal recessive
- -mutation in HEXA gene which makes enzymes that break down and remove toxins
Albinism: lacks proper amt of melanin
- -autosomal recessive
- -others passed thru X chromosome
- -mutation in TYR gene
Polydactyly: extra fingers or toes
- -mutation in GL13 gene
- -autosomal recessive or dominant
Hemophilia: X linked recessive, primarily in males
–linked to deleted or defected gene that produces blood clotting protein
Red green color blindness: X linked, mutation in genes that produce proteins in the retina to detect certain colors
Mutation
- -can have no effect or be harmful
- -some can cause variation in traits
–DNA mutations in gametes are passed on
genetic variation is more complex in eukaryotes that undergo sexual reproduction
–asexually reproducing organisms make offspring by replicating exact copies of DNA from one parent, this limits genetic variation
Crossing Over
also called recombination
happens during meiosis
source of genetic variation among eukaryotes
is during prophase 1
Genetic Exchange
bacteria and archaebacteria (protozoa and algae) exchange genetic info by the 3 methods below:
- -which creates variation
- -these below allow them to make new DNA sequences
transduction: host bacterium is infected by a bacterial virus or phage, that absorbs genetic info from the host to its own genetic code
transformation: bacterium takes up DNA from a source oustide the cell, this exogenous DNA is absorbed thru the membrane, must be in a state of competence for this (sufficiently permeable to receive info)
conjugation: genetic exchange in bacteria that requires cell to cell contact
- -plasmids are exchanged over a connection bw 2 diff bacteria
- -plasmids are small extrachromosal DNA from within bacteria
- –these plasmids replciate independently from the DNA in a chromosome
- –conjugation begins when bacterium produces sex pilus
- -portion of DNA is transferred thru pilus
- -the genetic info transferred can recombine with the genetic info within that new cell (host)
Sexual Reproduction
division of genes during meiosis happens randomly and independently of gene division in other gametes
therefore no 2 gametes will contain the exact same combo of genetic info and all combos of genetic info have an equal chance of occurring
Distrib and Mvmnt of Alleles w/in Pop
genetic drift: changes to allele distribution within pop
- -variation in gene frequency, accounts for random nature in which traits are passed on
- -affects small pop
- -exposed to natural disaster or disease
nonrandom mating: probability of 2 members of a pop. will mate is not equal to others in pop.
sexual selection (form of nonrandom mating): choose mates based on advantageous characteristics
