Genetics & Evolution Flashcards
genetics
study of how traits are inherited from one generation to the next
genes
composed of DNA and are located on chromosomes
Mendel’s First Law (law of segregation)
- genes exist in alternative forms, a gene controls a specific trait
- organism has 2 alleles for each trait
- the 2 alleles segregate during meiosis, resulting in gametes that carry 1 allele
- if 2 alleles are different, 1 will be dominant, and the other will be recessive
Mendel’s Law of Dominance
dominant allele is expressed in the phenotype
Mendel’s Second Law (law of independent assortment)
- inheritance of one trait is completely independent of any other
- modern genetics: genes on the same chromosome will not follow this rule and will stay together unless crossing over occurs
incomplete dominance
- progeny phenotypes are blends of parental phenotypes
- heterozygote is an intermediate of the phenotypes of the homozygotes
codominance
- multiple alleles exist for a given gene and more than one of them is dominant
- ex: ABO blood groups, Ia and Ib are codominant and produce IaIb blood type
sex determination
- women have XX, men have XY
- gender of a zygote is determined by the contribution of the male gamete (if sperm carries and X or a Y)
- sex-linked: genes located on the X or Y chromosomes
sex linkage
- recessive genes carried on the X chromosome will produce the recessive phenotypes when they occur in men, ex: hemophilia and color blindness
- sex linked recessives generally affect only men, can be passed from grandfather to grandson via a daughter who is a carrier
nondisjunction
-failure of homologous chromosomes to separate properly during meiosis I or failure of sister chromatids to separate properly during meiosis II
trisomy
3 copies of a chromosome, ex: Down syndrome
monosomy
1 copy of a chromosome
chromosomal breakage
may occur spontaneously or by environmental factors such as mutagenic agents and X-rays
mutagenic agents
- induce mutations
- cosmic rays, X-rays, UV rays, and radioactivity, colchicine, or mustard gas
- sometimes also carcinogenic (cancer-causing)
point mutation
nucleic acid is replaced by another nuclei acid, affects between 1-3 nucleotides
silent mutation
the new codon codes for the same AA and no change is seen
missense mutation
new codon codes for a new AA, may or may not lead to problems in the resulting protein
nonsense mutation
new codon is a stop codon, lethal or severely inhibit the function
frameshift mutation
nucleic acids are deleted or inserted, often lethal bc it throw off entire sequence
examples of genetic disorders
- phenylketonuria (PKU): inability to produce the enzyme for the metabolism of phenylalanine
- sickle cell anemia: RBCs become crescent shaped, substitution of valine for glutamic acid
bacterial genome
- consists of a singular circular chromosome located in the nucleic region of the cell
- also contain smaller rings of DNA called plasmids
episomes
plasmids that are capable of integration into the bacterial genome
replication of bacterial chromosomes
- begins at a unique origin of replication and proceeds in both directions
- DNA is synthesized in the 5’-3’ direction
binary fission
- process by which bacterial cells reproduce
- asexual process
transformation
-a foreign chromosome fragment (plasmid) is incorporated into the bacterial chromosome via recombination, creating new inheritable genetic combinations
conjugation
- transfer of genetic material b/w 2 bacteria (that have a sex factor) that are temporarily joined
- genetic material is transferred from the donor male (+) to the recipient female (-)
F factor
- best studied sex factor
- F+ contain this plasmid, F- does not
- F+ replicates its F factor and donates the copy to F-
antibody resistance
genes that code for other characteristics may be found on the plasmids