Chapter 8: Inheritance, Genes, and Chromosomes Flashcards
Blending Inheritance
gametes contained “hereditary derminants (genessss)” that blended
think inks of different colors
short and tall = medium
smooth seed and wrinkled seed = intdeterminate
this would create the loss of parental characteristics
not real anymore
Particulate inheritance
when gametes fuse, each determinant was distinct and remained intact
wrinkled seeds and smooth seeds would have offspring with determinants for both
character
an observable physical feature
ex. seed shape
trait
a particular form of a character
ex. spherical or wrinkled seeds
true-breeding
when crossed wrinkled with another wrinkled, all wrinkled
homozygous
How did Mendel perform his experiments?
Step One: cut the stamen off one parental flower (why you may ask? so it can’t self-fertilize)
step two: fertilize it with pollen from another flower with contrasting chracters
step three: plant the seeds from this pairing and watch them grow (write down traits and how many)
optional step 4: The F1 plants (in step three) self-pollinate and see what happens
Parental generation P
the truebreeding plants that mendel used in his experiment
First filial generation F1
the first offspring generation in Mendel’s experiments
Second Filial Generation F2
the second offspring generation in Mendel’s experiments
hybrid
the offspring of crosses between organisms differing in one or more characters
monohybrid
Mendel’s F1 generation
the offspring between parental varieties with contrasting traits for a single character
smooth v. wrinkled
Dominant
the trait that “overpowers”
Recessive
the trait that will only be expressed if the gene for the dominant trait is not present
allele
different forms of a gene for particular characters
smooth seed allele vs wrinkled seed allele
Homozygous
two alleles that are the same
ex. two alleles for wrinkled seeds
Heterozygous
two alleles that are different
ex. one allele for wrinkled seedfs, another for smooth
Phenotype
the physical appearance of an organism
Genotype
genetic constitution of an organism
Law of Segregation
Mendel
when any individual produces gametes, the two copies of a gene separate, so that each gamete receives only one copy
Punnett square
with the blocks
grid
male gametes on top, female on the side
How is the recessive gene suppressed?
it can become mutated so it doesn’t get transcribed and translated or encode a nonfunctinoal protein
Test cross
used to determine whether or not someone showing a dominant trait is homozygous
this is done by crossing them with an individual who is homozygous recessive for the trait (which isn’t hard to identify becuase if they display the recessive phenotype then they are homozygous recessive)
Dihybrid cross
cross between indiciduals that are identical double heterozygotes
ex. two heterozygous smooth and yellow plants
9: 3:3:1 ratio
Law of Independent Assortment
Mendel
alleles of different genes assort independently of one another during gamete formation
Basic conventions of probability
certain= probability of one
impossible= probability of 0
everything else in between
Pedigrees
family trees that show the occurence of inherited phenotypes in several generations of related individuals
What are the key things to look for in a dominant pedigree?
every person with the abnormal phenotype has an affected parent either all (homozygous parent) or half (heterozygous parent) or the children in an affected family are affected
What are the key things to look for in a recessive pedigree?
Affected people often have two unaffected parents
about one fourth of children of unaffected parents in affected families are affected
Mutations
rare, stable, and inherited changes in the genetic material
True or false: an allele can mutate to become a different allele
true
What affects the prevalence of a new allele?
the fitness of the individuals carrying it
wild type
THE ALLELE THAT IS PRESENT in most of the individuals in nature
Mutant alleles
the not wild type
Polymorphic
a gene with a wild type allele that is present less than 90% of the time
Incomplete dominance
alleles are not dominant or recessive to one another
heterozygotes have intermediate phenotypes
red and white makes pink
Codominance
two alleles of a gene both produce phenotype when present in a heterozygote
ex. AB blood type
Epistasis
the phenotypic expression of one gene is affected by another
ex. labsssss (such cuties)
Ee or EE other gene is good to go
ee, other alleles turned off
Hybrid vigor (heterosis)
Darwin- corn offspring produced by different genetic barieties are tall
Shull- they are also heavier
Quantitative traits
traits conferred by multiple genes
must be measured, not assesed qualitatively
True or false: most complex phenotypes are determined by multiple genes
true
True or false: the phenotype of an indivdual results from its genotype alone
falsee
genotype and environment interact to create phenotype
Penetrance
the proportion of individuals in a group with a given genotype that actually show the expected phenotype
helps describe the eggects of genes and enviro on phenotype
ex. not everyone with the mutant BRCA1 develops breast cancer–> incompletely penetrant mutation
Expressivity
degree to which a genotype is expressed in an individual
ex. one person with BRCA1 may have breast and ovarian cancer, another just breast cancer, so it has variable expressivity
locus
a particular site on a chromosome where a particular sequence of DNA (gene) resides
`Thomas Hunt Morgan
gene linkage
Columbia University
Fruit fly experiments
Morgan Experiments with fruit flies
he did a test cross with two known genes B and Vg for wing shape and body color
expected 1:1:1:1 of different phenotypes
often the two traits were inherited together
loci linked on same chromosome
crossing over makes the coupled inheritance not absolute
recombination frequency
the number of recombinant progeny divided by the total number of progeny
greater for loci that are father apart on a chromosome, which means they
genetic linkage
association between genes on a chromosome so that they do not exhibit random assortment and only rarely recombine
the closer they are, the lower the frequency of recombination
autosomes
regular chromsomes (these pairs are similar in size to one another)
sex chromsomes
determine the sex of an individual
What are two differences between x and y chromsomes?
size
more genes are present on the x than the y
hemizygous
a gene that is present as a single copy in a diploid organism
sex-linked inheritance
inheritance of a gene that is carried on a sex chromosome
patterns of sex0linked recessive phenotypes
appears a lot more in males than females (men only need one copy)
men can only pass mutation to daughters (sons get the y chromosome)
daughters with one x linked mutation are heterozygous carriers
mutant phenotypes can skip a generation if it passes from father to daughter to son
Heterozygous carriers
phenotypically wild type, but can pass on mutant allele to children
True or false: the only organelle with genetic material in the cell is the nucleus
false
mitochondria and plastids
True or false: the inheritance of organelle genes differs from that of nuclear genes
true
mitochondria and plastids only inherited from mother (sperm only bring nucleus to fuse, no organelles)
Cytoplasmic inheritance
the inheritance of organelles and genes
come from maternal cytoplasm
True or false: prokaryotes can transfer genes from one to the other
truee
Bacterial conjugation
happens via physical contact initiated by the sex pilus
material then passes through a conjugation tube (JUST ONE WAY FROM DONOR TO RECIPIENT)
once inside, it can recombine
donor DNA can line up beside homolgous genes and cross over
genes from donor can be integrated and change the recipients genetics
only about hald of transfered genes become integrated, the integrated ones are passed on
sex pilus
extends from the donor prokaryotic cell to the recepient prokaryotic cell, initiating contact and gene transfer
Plasmids
smaller, circular DNA in bacteria
have a few dozen genes tops
generally these genes are for:
unusual metabolic abilities (like breaking down hydrocarbons)
antibiotic resistance (plasmids with these are R factors and are really dangerous)
True or false: plasmids transfer genes between bacteria
true
they can move between cells during conjugation
don’t need to recombine with main chromsome because they copy separately
