Ch 14 Flashcards
explain how a mutation can be good, bad, or have no effect at all
beneficial-if it allows an organism to survive in a changing environment
bad-if it harms the organism or causes death
no effect-if a 2nd mutation can cancel out the first mutation
what is a mutation
changes in the genetic sequence
what is a point mutation
it results from a single substitution, deletion, or insertion
what effects does a substitution mutation have on the codons?
they usually only affect a single amino acid
what effect does a frame shift mutation have on the codons
(deletions & insertions) affect every amino acid past the point mutation
distinguish between the 4 different types of chromosomal mutations
deletion- a piece of chromosome is lost
duplication- results in copies of genes
insertion- piece of chromosome breaks off and reattaches backwards
translocation- piece of chromosome breaks off and attaches to ANOTHER chromosome
what is nondisjunction
occurs during meiosis when homologous chromosomes fail to separate
what is polyploidy
condition when organisms have extra sets of chromosomes
what type do organisms are often polyploidy
plants
how many alleles must be inherited in the case of a dominant gene or disorder
1 copy
list 3 dominant genetic disorders and describe each
achondroplasia- on C4 form of dwarfism affecting growth of long bones, most cases appear spontaneously
hunting tons disease- on C4 causes DNA, CAG repeat, to repeat more times, progressive loss of muscle control & brain. ( longer sequence earlier it appears)
hypercholesterolemia- cholesterol 19, alot of cholesterol and heart disease
how many alleles must be inherited in the case of a recessive gene or disorder?
2 copies
list 5 examples of recessive genetic disorders
phenylketonuria(PKU) Tay-sachs albinism galactosemia cystic fibrosis
describe what happens in someone who is PKU+ and what treatments are available
the enzyme can’t break down phenylalanine in milk. it accumulates in brain & can lead to mental retardation. they can have a special diet as infants, mothers must be on a special diet
describe what happens in someone with Tay-Sachs
they can’t produce hexosaminidase A to break down lipids(gangliosides). builds up & breaks down nervous system. blindness, deafness, and seizures, usually death occurs
what causes albinism
a mutation in a gene that provides instructions for making a protein in melanin
describe what happens in someone with galactosemia
the body is unable to use galactose. it can build up & damage liver, brain, kidneys, eyes
describe what happens in someone with cystic fibrosis
the protein that allows chloride ions to pass through membranes isn’t formed properly. too much mucus is produced which interferes w/ breathing and digestive processes of the pancreas
what mutation results in sickle cell anemia
a single point substitution which results in glutamic acid instead of valine for protein hemoglobin. hemoglobin sticks in long strands, RBC become sick shaped
what are the results of inheriting sickle cell anemia?
blood flow is blocked-severs pain, weakness, damages brain, heart, spleen. results in resistance to malaria
why has the gene for sickle cells not been removed from the gene pool
the cells destroy the parasite causing malaria in Africa
what is an example of a multiple allele trait
blood type
who discovered Sex chromosomes
thomas hunt Morgan
describe his experiment that led to the discovery of sex-linked traits
he bred fruit flies. he crossed red eyes f w/ white eyes m (P1). all F1 offspring had red eyes. he crossed m&f from F1. F2 gen F had red eyes, M had red or white. there were no white eyes f. gene for eye color is on X chromosome
describe 3 sex linked traits found on the X chromosome
color blindness- inability to distinguish certain colors
hemophilia- failure to produce protein required for normal blood clotting
duchenne muscular dystrophy- gene coding for muscle protein, progressive weakening of skeletal muscle
what is a pedigree
a chart that shows relationships in a family can be used to trace the inheritance of various traits
distinguish between trisomy and monosomy
trisomy results when individuals have an extra chromosome
monopsony results when individuals are missing a chromosome
describe Down’s syndrome
results from trisomy 21. 1 in 800 babies. mild to severe mental retardation, increases frequency if birth defects, higher susceptibility of many diseases
describe 2 sex chromosome disorders
turners syndrome- XO, monosomic, females don’t mature sexually and are often times sterile
klinefelters syndrome-XXY, males often sterile, abnormal body proportions
what is a karyotype
microphotograph of the chromosomes during cell division, homologous pairs arranged from largest to smallest
describe morgans experiment that led to the discovery of linkage groups
flies w/ gray bodies had long wings, black bodies had short wings. he crossed P1 & got gray long wings. Two F1 produced F2, short black and gray long. some “weirdoes” w/ both characteristics. 2 genes next to each other on chromosome, but to make “weirdo” the genes were swapped in crossing over
explain how X chromosome inactivation leads to calico female cats
cats have an orange fur gene and black fur gene on chromosomes. the random silencing of on X in each cell generates the pattern of their coats
