Chapter 15 Flashcards
chromosome theory of inheritance
- mendelian genes have specific loci (positions) on chromosomes
- chromosomes undergo segregation and independent assortment
who had the first solid evidence associating a specific gene with a specific chromosome
thomas hunt morgan
–experimented with fruit flies provided convincing evidence that chromosomes are the location of mendel’s heritable factors
morgan noted wild type which is really…
normal phenotypes that were common in the fly populations
traits alternative to the wild type/ normal phenotypes are called
mutant phenotypes
what did morgan’s experiment deal with and how did he figure out it had to do with chromosomes?
Correlating Behavior of a Gene’s Alleles
with Behavior of a Chromosome Pair
• In one experiment, Morgan mated male flies with white eyes (mutant) with female flies with red eyes (wild type)
– The F1 generation all had red eyes
– The F2 generation showed the 3:1 red:white eye ratio, but only males had white eyes
• Morgan determined that the white-eyed mutant allele must be located on the X chromosome
• Morgan’s finding supported the chromosome
theory of inheritance
—sex linked genes
are x and y chromosomes homologous?
technically yes but only the ends of y chromosome have regions that are homologous to regions of the x chromosome
true or false:
eggs can have either x or y and sperm can have either x or y
FALSE;
eggs are only x and sperm can be x or y
sex linked gene
a gene that is located on either sex chromosome
_ chromosome have genes for many characters unrelated to sex, whereas the _ chromosome mainly encodes genes related to sex determination
- x
- y
for a recessive x-linked trait to be expressed in a girl what has to happen?
-what about a boy?
- a girl needs two recessive x chromosomes
- a boy only needs one
True or false: x-linked recessive disorders are much more common in males than in females
true
what are some disorders caused by recessive alleles on the x chromosome in humans
- colorblindness
- duchenne muscular dystrophy
- hemophilia
what is the Barr body
when one of the x chromosome in mammalian females condenses and does not work anymore.
*
if a female is heterozygous for a particular gene located on the x chromosome she will be a _____ for that character
mosaic- a picture or pattern produced by arranging together small colored pieces of hard material, such as stone, tile, or glass.
linked genes
genes located on the same chromosome that tend to be inherited together
who crossed flies with different traits to see how linkage affects inheritance
thomas hunt morgan
wild type is recognized with….
wild type is normal
it is recognized with a plus +
what would be the ratio if genes are located on different chromosomes?
1:1:1:1
what would be the ratio if genes are linked
1:1:0:0
dihybrid cross would have what ratio?
9:3:3:1
genetic recombination
the production of offspring with combinations of traits differing from either parent
parental types
offspring with a phenotype matching one of the parental phenotypes
recombinant types or recombinants
offspring with nonparental phenotypes (new combinations of traits)
crossing over was discovered by who?
thomas hunt morgan
genetic map
an ordered list of the genetic loci along a particular chromosome
the farther apart two genes are, the _____ the probability that a crossover will occur
higher
linkage map
genetic map of chromosome based on recombination frequencies
map units
represents a 1% recombination frequency
-indicate relative distance and order, not precise locations
cytogenetic maps
indicate the positions of genes with respect to chromosomal features
nondisjunction
pairs of homologous chromosomes do not separate normally during meiosis
-as a result one gamete receives two of the same type of chromosome, and another recieves no copy
aneuploidy
results from the fertilization of gametes in which nondisjunction occured
-offspring with this condition have an abnormal number of a particular chromosome
monosomic
zygote has only one copy of a particular chromosome
trisomic
zygote has three copies of a particular chromosome
polyploidy
condition in which an organism has more than two complete sets of chromosomes
triploidy
three sets of chromosomes
tetraploidy
four sets of chromosomes
polyploidy is common in ___, not _____
plants, animals
deletion
removes a chromosomal segment and that removed segment usually goes into another DNA
duplication
repeats a segment within the DNA
inversion
reverses orientation of a segment within a chromosome
translocation
moves a segment from one chromosome to another
an aneuploid condition that results from three copies of chromosome 21
down syndrome
an extra chromosome in a male, producing XXY individuals
OR;
XYY (male but still fertile)
Klinefelter
produces X0 females who are sterile …only known monosomy
monosomy x called Turner Syndrome
results from a specific deletion in chromosome 5, a child born with this syndrome is mentally retarded and has a catlike cry, usually die early in life
Syndrome Cri du Chat
genomic imprinting
the silencing of certain genes that are “stamped” with an imprint during gamete production.
If the allele inherited from the father is imprinted, it is thereby silenced, and only the allele from the mother is expressed.
extranuclear genes
found in organelles in cytoplasm…Mitochondria, chloroplasts, and other plant plastids carry small circular DNA moleculess….extranuclear genes are inherited maternally because zygotes cytoplasm comes from the egg …mostly in plants
