chapter 5

Question 1

Thomas Hunt Morgan’s work on Drosophila (fruit flies) established what?

Answer 1

the chromosome theory of inheritance, genetic linkage, and recombination.

Question 2

What are synthetic genes?

Answer 2

Genes located on the same chromosome

Question 3

What are linked genes?

Answer 3

Syntenic genes that are close enough to each other that their alleles do not independently assort.

Question 4

When does recombination occur during meiosis?

Answer 4

when crossing over reshuffles alleles between homologous chromosomes

Question 5

If crossing over does not occur between linked genes, the genes are said to exhibit what?

Answer 5

complete gene linkage

Question 6

What is Incomplete genetic linkage?

Answer 6

When there is a mix of parental and recombinant gametes, with recombination frequencies varying depending on the distance between genes on the chromosome

Question 7

Do linked genes assort independently?

Answer 7

No, meaning there will be a higher frequency of parental allele combinations compared to nonparental combinations

Question 8

What is recombination frequency?

Answer 8

The frequency at which recombination occurs between genes; this frequency is used to estimate the distance between genes on a chromosome

Question 9

What did Bateson and Punnett discover?

Answer 9

They discovered evidence of genetic linkage in their sweet pea experiments, and Morgan’s work with Drosophila provided further evidence.

Question 10

What was the cytological evidence?

Answer 10

Work by Creighton and McClintock (in corn) and Curt Stern (in fruit flies) showed that genetic recombination corresponds to physical exchange between chromosomes, providing direct evidence of the crossover process

Question 11

What are recombinant chromosomes?

Answer 11

Alleles of syntenic genes can be reshuffled when crossing over occurs between homologs

Question 12

What are nonrecombinant chromosomes?

Answer 12

Homologs that do not reshuffle alleles under study

Question 13

What is genetic linkage mapping?

Answer 13

plots the positions of genes on
chromosomes

Question 14

What did Morgan study?

Answer 14

the white (eye color) and miniature (wing
size) genes

Question 15

What is a two-point test cross?

Answer 15

Morgan realized that linkage of autosomal genes in Drosophila could be interpreted

Question 16

What is genetic linkage?

Answer 16

When genes are located close to each other on the same chromosome, they tend to be inherited together

Question 17

The closer genes are together the _______ recombination frequency

Answer 17

lower

Question 18

Who created the first genetic linkage map?

Answer 18

Alfred Sturtevant, working with Thomas Morgan by analyzing recombination frequencies in Drosophila

Question 19

What are map units?

Answer 19

Recombination frequencies are used to calculate genetic distances, measured in map unit. 1% = 1 cM (centiMorgan)

Question 20

What factors influence hot spots?

Answer 20

species, age, sex, and environmental factors

Question 21

What is the chi-squared analysis?

Answer 21

Statistical methods like chi-square tests are used to confirm whether the observed genetic linkage is significantly different from independent assortment.

Question 22

What are hotspots?

Answer 22

They influence the apparent distance between genes in genetic maps.

Question 23

What are challenges with gene mapping?

Answer 23

Human genes are more challenging to map due to limitations in controlled mating and sample size

Question 24

What are Genome-Wide Association Studies (GWAS)?

Answer 24

They use SNPs to locate genes associated with traits and diseases across the genome. they are then plotted using manhattan plots

Question 25

What is linkage disequilibrium?

Answer 25

When alleles of genes are inherited together more often than expected by chance

Question 26

What are genetic markers?

Answer 26

Different variants of DNA sequence constitute the genetic markers used to study locations of genes

Question 27

What are the genetic markers?

Answer 27

variable number tandem repeats (VNTRs), single nucleotide polymorphisms (SNPs), and restriction fragment length polymorphisms (RFLPs)

Question 28

What are restriction fragments?

Answer 28

Pieces of DNA resulting from restriction enzyme cutting

Question 29

What are restriction enzymes?

Answer 29

RFLPs are changes in DNA sequence that are detected using DNA-cutting enzymes

Question 30

What is a haplotype?

Answer 30

The specific array of SNPs in a small region on a single chromosome

Question 31

What is the allelic phase?

Answer 31

The arrangement of alleles of linked genes on parental chromosomes

Question 32

The logarithm of the odds ratio gives what?

Answer 32

The lod score

Question 33

What is the theta value?

Answer 33

Lod score determines the likelihood of linkage for many recombinant frequencies

Question 34

The highest lod score value is what?

Answer 34

Zmax

Question 35

A theta value of 0 means what?

Answer 35

complete linkage

Question 36

A theta value of 0.5 means what?

Answer 36

independent assortment

Question 36

GWAs look for what?

Answer 36

Associations between traits and groups of alleles in populations

Question 37

A lod score of 3.0 or higher is...

Answer 37

considered significant evidence in favor of linkage at the theta value

Question 38

Lod scores of less than −2.0...

Answer 38

represent significant evidence against genetic linkage

Question 39

Lod scores between these two values are...

Answer 39

inconclusive regarding linkage

Question 40

What is linkage equilibrium?

Answer 40

The genotype for a chromosome at one gene is expected to be independent of its genotypes for other genes

Question 41

The CARD15 gene was suggested to be associated with what disease?

Answer 41

Crohn’s Disease (C D) based on GWAS results

Question 42

What are Mendelian Conditions?

Answer 42

Caused by a single gene mutation, following inheritance patterns like autosomal dominant, autosomal recessive, and X-linked

Question 43

What are chromosomal conditions?

Answer 43

Result from changes in chromosome number or structure, such as trisomy 21 (Down syndrome)

Question 44

What are Multifactorial Conditions?

Answer 44

Involve both genetic factors and environmental influences (e.g., diabetes).

Question 45

What are the types of genetic testing?

Answer 45

molecular analysis, biochemical analysis, and chromosome analysis. They help diagnose genetic conditions, detect carriers, and assess the risk for future offspring.

Question 46

What do carrier testing and presymptomatic testing allow?

Answer 46

allow individuals to understand their genetic risks and make informed decisions, especially for diseases like Huntington's.

Question 47

What are consultands?

Answer 47

Individuals working with genetic counselors

Question 48

What is the Bayesian analysis?

Answer 48

determines the probability of a certain genotype occurring in a certain family member

Question 49

What is presymptomatic testing?

Answer 49

used for genetic conditions that have a late age of onset

Question 50

What is newborn testing?

Answer 50

set of mandated genetic tests that together require only a few drops of blood

Question 51

What is prenatal testing?

Answer 51

testing performed during pregnancy for the purpose of determining whether a fetus has a particular condition or disorder.

Question 52

know the indicators and goals for genetic counseling

Answer 52

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