quiz 3 deck Flashcards
Explain why pedigrees are often used in the study of human genetics.
pedigrees are used to study human inheritance, humans are not a good model organism because controlled mating is not possible, long generation time, small family size
a pedigree is a pictorial representation of a family history; a family tree that oulines the inheritance of one or more characteristics
Draw a pedigree using standard symbols.
check good notes study set
Determine the most likely mode of inheritance of a trait based on characteristics observed in a pedigree, use practice
check notes and practice
Use concordance values of twins to assess the importance of genes and environment in the variation of human
traits
Concordant trait: the trait shared by both twins
COncodrance: the percentage of twin pairs that are concordant for a trait
higher concordance in monozygotic twins suggests genetic influence
however, higher concordanance in mono than dizyg does not mean environmental indicator not involved.
even in both means all enviorment
Explain how adoption studies are used to analyze genetic variation of human traits
Adoptive parents:
-adoptees share mo more genes than a random individual
- chare enviorment
-similarties in characteristics due to environment
Biological:
-adoptees share 50% of their genes with each of their biological parents
do not envioorments
similaries in characteristics can be attributed to genetic factors
List some common reasons for seeking genetic counseling
- a person knows of a genetic disease in the family
- a couple has given birth to a child with a genetic disease, birth defect, or chromosome abnormality
- an older woman becomes pregnant or wants to become pregnant
4 husband and wife are closely related - a pregnant woman is concerned about exposure to an environmental substance that causes birth defets
etc
List the different types of genetic tests, along with their uses and limitations.
ultrasound
amniocentesis : fetal sample can happen 15-18 weeks of being pregnant, invasive
Chorionic villus sampling: can happen before or after birth, mom or baby, 10-11 week fetus, save time, invasive
maternal blood: do this after quad screen testing, you are not looking at fetus, examining certain blood levels, can detect risk of some increased risks of genetic conditions, do not determine the presence of a genetic problem
Non invasive prenatal screening (NIPS)
-directly examines fetal DNA found in maternal blood
- can be performed as early as the 9th week of pregnancy, could reveal info about mothers genetic makeup or health
Newborn screening: test newborn directly
adults
- presympotomatic genetic testing, seeing for genes that might predispose them in the future
-Heterozygote screening: members of population are tested to identify hererosygous carriers of a recessive disease
-pharmacogenetic testing: drugs effectiveness or potential adverse reaction is influences by a patients genotype
Discuss some of the complications involved in interpreting the results of genetic tests
may cause people to freak out, not always 100%
Some genes caused by numerous mutations, genetic test screen for most common
incomplete penetrance and environmental factors
for many genetic traits no genetic test exists
fear results impact insurance or employability
Explain direct-to-consumer genetic testing and list concerns about its use
Tests may not include appropriate info to allow consumers to accurately interpret results -ancestry databases have been used by researchers in ways not anticipated by the participants
Explain how the inheritance of linked genes is different from the inheritance of genes that assort independently
he inheritance of linked genes is different from the inheritance of genes that assort independently due to their physical location on the same chromosome. Linked genes are located close together on the same chromosome and tend to be inherited together as a package, rather than independently. This is because during meiosis, the homologous chromosomes that carry the linked genes can only exchange genetic information at specific locations called crossover points, resulting in a recombination of the genetic material.
As a result, the frequency of recombinant gametes (gametes with new combinations of alleles) is lower for linked genes compared to genes that assort independently. Conversely, the frequency of parental gametes (gametes with the same combinations of alleles as the parents) is higher for linked genes.
This phenomenon of linked genes is explained by the principle of genetic linkage, which states that the closer two genes are on a chromosome, the more likely they are to be inherited together. Genetic linkage can be used to map the relative positions of genes on a chromosome and to identify genes associated with certain traits or diseases.
In contrast, genes that assort independently are located on different chromosomes or are far enough apart on the same chromosome that they are not physically linked. Therefore, they are inherited independently of each other and the frequency of recombinant gametes is higher compared to linked genes. This principle is known as the law of independent assortment, and it is one of the basic principles of Mendelian genetics.
Compare the outcomes of test crosses for genes that exhibit complete linkage, independent assortment, and
linkage with some crossing over. Calculate recombination frequency using the progeny of a cross
Use the recombination frequency to make predictions about the proportions of offspring in crosses involving
linkage.
Use a series of pairwise recombination frequencies to create a genetic map
Describe the methods used in physical gene mapping, including somatic cell hybridization, deletion mapping, and
fluorescence in situ hybridization (FISH)
Somatic cell hybridization: This method involves fusing two different types of cells, usually a human cell and a mouse cell, to create a hybrid cell. The hybrid cell contains chromosomes from both parent cells, and by analyzing the chromosomes of the hybrid cell, researchers can identify which human chromosome carries the gene of interest. This technique is especially useful for mapping human genes that are difficult to study directly.
-presence of extra chromosome in mouse genome used to assign human genes to specific chromosomes
Deletion mapping: This method involves the study of individuals with chromosomal deletions or duplications that result in specific genetic disorders. By analyzing the genotype and phenotype of individuals with these chromosomal abnormalities, researchers can identify the specific chromosomal region that contains the gene responsible for the disorder. This technique is particularly useful for identifying disease-causing genes.
-if gene of interest is in the deletion region, half of the progeny will display the mutant phenotype, if gene is NOT within the deletion region, all of the progeny will be wild type
Fluorescence in situ hybridization (FISH): This method involves the use of fluorescent probes that bind to specific DNA sequences on a chromosome. By using a microscope to visualize the fluorescent signals, researchers can identify the location of genes on the chromosome. FISH is a highly sensitive and accurate method of physical gene mapping, and it can be used to detect even small chromosomal abnormalities or gene rearrangements. FISH is widely used in cancer research to identify genetic mutations associated with specific types of tumors.
-creation of probe for a gene and probe is fluorescent so it can be visualized. the gene of interest has a SSDNA complement that bins to probe
Describe variation in recombination rates.
1% recombination rate equals one map unit
Recombination rates vary because levels of recombination fvary widely; among species, among chromosomes of a single species, between male and females
recombination hotspots: recombination is at least 10 times as high as the average elsewhere in the genome, tend to be found near, not within active genes
