Chapter 14 Flashcards
what is the “blending” hypothesis?
the idea that genetic material from the two parents blends together and can never go back to what it was before
what is the “particulate” hypothesis?
the idea that parents pass on discrete heritable unites (genes)
-explains reappearance of traits after several generations
what did mendel discover?
the basic principles of heredity by breeding garden peas in carefully planned experiments
characters
distinct heritable features (such as flower color)
traits
character variants (such as purple or white)
true breeding
an organism that always passes down certain phenotypic traits (i.e. physically expressed traits) to its offspring
hybridization
two contrasting, true breeding varieties
P generation
the true breeding parents
F1 generation
hybrid offspring of the P generation
F2 generation
when F1 individuals self pollinate or cross pollinate with other F1 hybrids
what is the law of segregation?
stating that during the production of gametes the two copies of each hereditary factor segregate so that offspring acquire one factor from each parent.
-happens during anaphase 1 of meiosis 1
what is the ratio that mendel came up with for the offspring of the f1 generation
3:1
alternative versions of genes account for ______ in inherited characters
variations
alleles
alternative versions of a gene
each gene resides at a specific ____ on a specific chromosome
locus
for each character, an organism inherits ___ alleles
two (one from each parent)
if the two alleles at a locus differ, then the _____ allele determines the organism’s appearance, and the ______ allele has no noticeable effect on appearance.
- dominant
- recessive
homozygous
An organism with two identical alleles for a character
heterozygous
An organism that has two different alleles for a gene
true or false: heterozygous is true breeding
false
phenotype
physical appearance
genotype
genetic makeup
testcross
breeding the mystery individual with a homozygous recessive individual
monohybrids
individuals that are heterozygous for one character
monohybrid cross
cross between monohybrids
dihybrids
heterozygous for two characters
dihybrid cross
a cross between two dihybrids….can determine whether 2 characters are transmitted to offspring as a package or independently
law of independent assortment
each pair of alleles segregates independently of each other pair of alleles during gamete formation
–Strictly speaking, this law applies only to genes on different, nonhomologous chromosomes or those far apart on the same chromosome
—Genes located near each other on the same chromosome tend to be inherited together
EXAMPLE:
Hh hH
J j or J j
Multiplication rule
the probability that two or more independent events will occur together is the product of their individual probabilities
Addition rule
states that the probability that any one of two or more exclusive events will occur is calculated by adding together their individual probabilities (uses words either/or)
complete dominance
occurs when phenotypes of the heterozygote and dominant homozygote are
identical….the dominant is the only one apparent in physical terms
incomplete dominance
the phenotype of F1 hybrids is somewhere between the phenotypes of
the two parental varieties….two dominant alleles are mixed together to create a certain phenotype such as straight and curly hair = wavy hair (something like this)
what is codominance
two dominant alleles affect the phenotype in separate distinguished ways….both dominant alleles show up such as when you have alleles for both straight and curly hair and they both show up on your hair, some strands straight and some curly (something like this)
remember !!!
A dominant allele does not subdue a recessive allele
Tay-Sachs disease
- what does it look like @ the organismal level
- biochemical level
- molecular level
organismal level: asymptomatic-shows no symptoms because normal allele is dominant so covers for tay sachs
biochem: normal allele makes correct protein (an enzyme) so accumulation does not occur in brain
molecular: one normal allele on one chromosome and one tay sach allele on the other…normal allele is dominant
what are the three alleles for blood types
A, B, and O
what does blood type A look like
a red blood cell that has a tag (a carbohydrate) that represents that it is A blood type
what does blood type B look like?
a red blood cell that has a tag (a carb) that represents that it is B blood type
what does AB blood type look like?
a red blood cell that has two tags, one that represents A and the other that represents B
what does the O blood type look like?
it has no tags…just the red blood cell
pleiotropy
multiple phenotypic effects… when one gene influences two or more seemingly unrelated phenotypic traits….. a mutation in a pleiotropic gene may have an effect on some or all traits simultaneously.
true or false: some traits may be determined by two or more genes
true
epistasis
what ratio does it have?
a gene at one locus alters the phenotypic expression of a gene at a second
locus
-example: the golden retrievers that should be black or brown but have a gene that prevents this
9:3:4
quantitative characters
characters that vary in the population along a continuum
polygenic inheritance
an additive effect of 2 or more genes on a single phenotype
-so two or more genes affect the phenotype of someone
norm of reaction
the phenotypic range of a genotype influenced by the environment
ex)hydrangea flowers of the same genotype range from blue-violet to pink depending on soil
multifactorial
when genetic and environmental factors collectively influence phenotype
pedigree
a family tree that describes the interrelationships of parents and children across generations
carriers
heterozygous individuals who carry the recessive allele but are phenotypically normal
albinism
a recessive condition characterized by a lack of pigmentation in skin and hair
consanguineous mating
-what is it and why is it bad
incest
-it is bad because it increases the change of mating between two carriers of the same bad and rare allele
cystic fibrosis
cystic fibrosis allele results in defective or absent chloride transport channels in plasma membranes leading to a buildup of chloride ions outside the cell
- -symptoms include mucus buildup in some internal organs and abnormal absorption of nutrients in the small intestine.
- —serious breathing problems
sickle cell disease
- caused by the substitution of ONE amino acid in the hemoglobin protein the the red blood cells
- -in homozygous individuals all hemoglobin is abnormal (sickle cell)
- —symptoms include physical weakness, pain, organ damage, bursting of cells
- people heterozygous for this are usually healthy but may have some symptoms
true or false: some human disorders are caused by dominant alleles
true
what is achondroplasia
a form of dwarfism caused by rare dominant allele….NEVER HOMOZYGOUS FOR DOMINANT ALLELE BECAUSE THAT IS LETHAL
Huntington’s disease
- a degenerative disease of the nervous system
- -no phenotypic effects until the individual is about 35 to 40 years of age
- irreversible and fatal
- don’t know until later in life which is why people pass on the allele for this disease, because they don’t know they have it until later on in life after having kids
amniocentesis
the liquid that bathes the fetus is removed and tested for any disease the fetus might have when born….look at the karyotype
chorionic villus sampling (CVS)
a sample of the placenta is removed and tested ….scrape DNA material from placenta (an organ you grow when pregnant)
