Chapter 13 Flashcards
Genetic Mapping, Inherited Disorders
Progeny that exhibit the same allele combinations as parents
Parental type
result from nonhomologous recombination in Meiosis
non-parental type
study of genomes
genomics
process by which homologous chromosomes undergo reciprocal physical exchanges at their arms, also crossing over
homologous recombination
finding the location of genes on each given chromosome
genomic mapping
failure of synapsed homologs to completely separate and migrate to separate poles during the meiosis’ first cell division
nondisjunction
an individual’s chromosome number and appearance; includes the size, banding patterns, and centromere position
karyotype
individual with the appropriate number of chromosomes for their species
euploid
individual with an error in chromosome number; includes chromosome segment deletions and duplications
aneuploid
otherwise diploid genotype in which one chromosome is missing
monosomy
otherwise diploid genotype in which one entire chromosome duplicates
trisomy
amount of gene products coded for
gene dose
individual with an incorrect number of chromosome sets
polyploid
condensing X chromosomes into Barr bodies during embryonic development in females to compensate for the double genetic dose
X inactivation
detachment, 180° rotation, and chromosome arm reinsertion
Inversion
segment of a chromosome dissociates and reattaches to a different chromosome
Translocation
inversion that involves the centromere
Pericentric
inversion that occurs outside the centromere
Paracentric
What were the two key experiments that led scientists to the Chromosomal Theory of Inheritance?
Theodor Boveri-embryonic development of sea urchins doesnt occur unless chromosomes are present
Walter Sutton-seperation of chromosomes in meiosis
What did the Chromosomal Theory of Inheritance say?
chromosomes are the genetic material responsible for mendelian inheritance
Who was the scientist who provided most of the scientific evidence in support of the theory? What species of animal did he work with?
Thomas Hunt Morgan, fruit fly
What was the significance for Morgan of finding two physical mutations that arose from genes on the same chromosome? What genetic questions did this allow him to study? How did Morgan test these questions? What did his experiment consist of? What did the results indicate?
he could study how genes moved with chromosomes and how genes moved in relation to other genes on the same chromosome; he demonstrated random segragation and genes on the same chromosome disrupted predicted frequency of traits; indicated linked genes
What are parental types? Under what circumstances would you expect to see them in the chromosomes of offspring?
offspring have same allele combinations as parents; linkage occured
What are non-parental types? Under what circumstances would you expect to see them in the chromosomes of offspring?
chromosomes with combinations of alleles not seen in the parent; this followed mendels laws
Who is Frans Janssen and what did he observe?
synapsis events and suggested that chromosomes may physically exchange segments in meiosis
Who is Alfred Sturtevant and what were his contributions to genetics?
undegrad in morgans lab, created first chromosome map
What two assumptions did Sturtevant make about genes?
genes are ordered serially on thread like chromosomes
the incidence of crossing over between two homologous chromosomes could occur with equal liklihood anywhere along the length of the chromosome
What where Sturtevant’s hypotheses?
the average number of crossovers between alleles correlated with their genetic distance from each other, relative to the locations of other genes on the chromosome
If a genetic cross tracking two traits produces parental types 90 times out of 100, what is the likelihood of homologous recombination?
10%
On a genetic map, how are the frequencies of homologous recombination related to the placement of genes on the map?
Close together has a lower recombination frequency and a lower chance the genes are swapped in crossing over
When the frequency of producing parental types approaches 0.5, it becomes less accurate in predicting linkage. Why is this?
.5 is the largest possible because more than that would be unclear if far apart or on other chromosome
What are the two broad ways that chromosomal abnormalities can happen?
- Abnormalities in chromosome number
- Chromosomal structural rearrangements
Why are chromosomal abnormalities usually of such high consequence?
Small segments of chromosomes can span many genes that would be altered
What is a karyotype?
Visualization of chromosomes in a cell where homologous pairs are in numerical order
What is the primary cause of all disorders in chromosome number?
Nondisjunction-chromosomes do not separate correctly
Name two examples of how nondisjunction could happen.
Misaligned or incomplete synapsis
Disfunction of the spindle apparatus
What are the results of non-disjunction if it occurs in meiosis I vs. meiosis II?
Meiosis I= 2 diploid gametes, 2 gametes with 0 chromosomes
Meiosis II=2 normal haploid gametes, 1 diploid gamete, one gamete with 0 chromosomes
What do we call an individual who has an error in chromosome number?
aneuploid
What is monosomy? What is trisomy?
Monosomy=loss of 1 chromosome (typically don’t develop)
Trisomy=gain of an extra chromosome
What is the most common type of trisomy? Why is it less lethal than trisomy involving other chromosomes?
Down Syndrom/Trisomy 21; 21 is the shortest autosomal chromosome
What is gene dose? How does it affect the outcome of chromosomal abnormalities?
Amount of configuration; extra does can lead to functional challenges for the organism
What do we call an organism with multiple sets of all their chromosomes?
polyploid
What types of organisms successfully utilize polyploid genomes?
Plants are the best but flatworms, fish, amphibians, lizards, and crustaceans can but will be sterile
Why is nondisjunction is sex chromosomes less lethal than in autosomes?
X-inactivation, one X chromosome will inactivate by tightly condensing into a Barr body
What is a Barr body and where does it come from?
Dormant, inactive X-chromosome that is tightly condensed
What happens if an individual inherits multiple X chromosomes?
One is inactivated and there are mild mental/physical side effects with sterility
What happens if an individual inherits no X chromosome?
Non-viable
What is Triple-X Syndrome? What are the physical traits?
3 X chromosome, physically female but developmentally delayed and reduced in fertility
What is Klinefelter Syndrome? What are the physical traits?
XXY, physically male with small testes, enlarged breasts, reduced body hair
What is Turner Syndrome? What are the physical traits?
X0, physically female with webbed skin in the neck, short stature, hearing deficits, cardiac problems, and sterility
What causes Cri-du-chat and what are the physical traits?
deletion of most of the small arm of chromosome 5, infants have a high pitched cry; nervous and cardiac abnormalities with identifiable physical features
How are abnormalities in structural arrangement different from other forms of chromosomal abnormalities?
Move genes and rearrange sections of the chromosome, typically more mild
How are inversions and deletions different? How are they similar?
inversions are flipped 180 with relatively more mild while deletion is to get rid of
What do the terms pericentric and paracentric refer to? Which scenario may result in a visible lengthening of one of the chromosome arms?
Pericentric include the centromere while Paracentris is outside the centromere. Pericentric tends to make longer an is easier to see in a karyotype
Which chromosomal abnormality has been associated with Schizophrenia?
translocations
