mapping and se linkage jan 29 chloe

"Describe the process of recombination in Drosophila."

"In Drosophila, only females undergo recombination, which involves the exchange of genetic material between homologous chromosomes during meiosis."

"Explain the significance of recombination frequency."

"Recombination frequency is the percentage of recombinant offspring resulting from a genetic cross, indicating the distance between specific loci on chromosomes."

"Define crossover frequency."

"Crossover frequency refers to how often crossing over occurs between chromosomes during meiosis."

"How are centimorgans related to genetic mapping?"

"Centimorgans are units of distance on chromosomes used in genetic mapping, representing the recombination frequency between loci."

"What is the relationship between crossing-over and map distance?"

"The relationship indicates that greater distances between genes on a chromosome typically result in higher recombination frequencies."

"Do recombination frequencies always add up perfectly?"

"No, while recombination frequencies will recover the correct gene order, the distances may not always add up perfectly."

"Explain the concept of three-point mapping in genetics."

"Three-point mapping involves analyzing the inheritance of three linked genes to determine their order and the distances between them."

"What does a double crossover indicate in genetic mapping?"

"A double crossover indicates that two separate crossover events have occurred, which can affect the frequency of recombinant offspring."

"Describe the classes of progeny in a testcross involving linked genes."

"Classes 1 and 2 show no evidence of recombination, while Classes 3-8 show evidence of recombination, with Classes 7 and 8 having the lowest frequency due to double crossovers."

"Who was Calvin Bridges and what was his contribution to genetics?"

"Calvin Bridges was a student of Thomas Hunt Morgan who contributed to genetics by naming the unit of distance on chromosomes 'centimorgans'."

"What are the dominant and recessive traits in the wild type and mutant classes described?"

"In the wild type, dominant traits are yellow color (p), elongated shape (r), and dry juiciness (j). In the mutant, recessive traits are purple color (p), round shape (r), and juicy juiciness (j)."

"Describe the two possible arrangements of three alleles in genetics."

"The two arrangements are called cis (coupling), where all three mutant alleles are on one chromosome and all three wild type alleles are on the other, and trans (repulsion), where one chromosome has one mutant allele and two wild type alleles, while the other has one wild type allele and two mutant alleles."

"Explain the significance of the homozygous parent in gamete production."

"A homozygous parent can only produce one type of gamete, which is crucial for understanding inheritance patterns in genetic crosses."

"How does the configuration of alleles affect progeny in a testcross?"

"If both parents are in the cis configuration, the progeny will exhibit specific phenotypes resulting from double crossing over, such as yellow, elongated, juicy or purple, round, dry."

"Define the term 'centimorgan' in genetics."

"A centimorgan (cM) is a unit of measure for genetic linkage, representing a 1% chance of recombination occurring between two loci on a chromosome."

"Explain the relationship between frequency of recombination and distance between loci."

"The frequency of recombination is directly related to the distance between loci on a chromosome; a higher frequency of recombination indicates a greater distance."

"What is the expected outcome when genes are farther apart on a chromosome?"

"When genes are farther apart, there is an increased probability of undetected crossovers, which can complicate genetic mapping."

"Describe the role of chromosome maps in genetics."

"Chromosome maps show the linear arrangement of loci on a chromosome, helping to visualize the genetic structure and relationships between genes."

"How is the genetic map distance calculated using recombination data?"

"The genetic map distance is calculated by adding the number of recombinant offspring and double crossovers, then dividing by the total number of offspring to determine the percentage of recombinants."

"Explain the concept of multiple crossovers in relation to genetic mapping."

"Multiple crossovers can interfere with the standard method of calculating genetic distance, particularly when loci are more than 7 centimorgans apart."

"What are the implications of using recombinant phenotypes for chromosome mapping?"

"Using recombinant phenotypes allows researchers to estimate the distance between genes on a chromosome, which is essential for constructing accurate genetic maps."

"Describe the concept of interference in genetics."

"Interference refers to the inhibition of further crossover events in one region of a chromosome due to another crossover event nearby, which reduces the expected number of multiple crossovers."

"Explain the relationship between crossing over in different regions of a chromosome."

"Crossing over in one region can affect the probability of crossing over in another region, leading to a calculated probability of double crossing over."

"Define the coefficient of coincidence (Coc) in genetics."

"The coefficient of coincidence (Coc) is calculated as the observed number of double crossovers divided by the expected number of double crossovers."

"How is interference calculated using the coefficient of coincidence?"

"Interference is calculated as 1 minus the coefficient of coincidence (I = 1 - Coc). If interference equals 1, no double crossovers occur; if it equals 0, all expected crossovers took place."

"Differentiate between positive and negative interference."

"Positive interference occurs when fewer double-crossover events than expected happen, resulting in a positive interference value. Negative interference occurs when more double-crossover events than expected happen, resulting in a negative interference value."

"Explain how the distance between genes affects interference and mapping accuracy."

"As the distance between genes increases, interference decreases, leading to a decrease in the accuracy of genetic mapping."

"What does a recombination frequency greater than 50% indicate about gene loci?"

"A recombination frequency greater than 50% indicates that the loci are either on different chromosomes or very far apart on the same chromosome."

"Describe the significance of Drosophila in genetic mapping."

"Drosophila has a large number of mutants, allowing for extensive chromosome mapping and the study of gene linkage."

"What is X-linkage in genetics?"

"X-linkage describes genes that are located on the X chromosome, which can affect inheritance patterns based on the sex of the individual."

"Summarize Mendel's first law of segregation."

"Mendel's first law states that each allele segregates independently when gametes are formed, and organisms inherit two alleles for each character, one from each parent."

"What is Mendel's second law of independent assortment?"

"Mendel's second law states that alleles for different traits segregate independently during gamete formation."

"Identify what Mendel did not know about genes and chromosomes."

"Mendel did not know that genes (alleles) are located on chromosomes, that chromosomes independently assort during meiosis, or that recombination can occur during meiosis, adding to phenotypic variation."

"Explain how sex determination works in Drosophila and humans."

"In Drosophila and humans, sex is determined by unlike chromosomes: males have XY chromosomes and females have XX chromosomes. Males are hemizygous (XY) while females are homozygous (XX)."

"Describe the contribution of Nettie Maria Stevens to genetics."

"Nettie Maria Stevens discovered sex chromosomes in 1905."

"Explain the significance of Mendel's work by 1910."

"By 1910, Mendel's work had been rediscovered, and subsequent experiments verified his results, leading to the acceptance of the laws of Segregation and Independent Assortment."

"Define the role of chromosomes in heredity as proposed by Sutton and Bovieri."

"Walter Sutton and Theodor Bovieri independently proposed that chromosomes are the actual physical source of Mendel’s hereditary factors, supported by evidence from meiosis and abnormal development in organisms missing chromosomes."

"How did Thomas Hunt Morgan contribute to the field of genetics?"

"Thomas Hunt Morgan, who lived from 1866 to 1945, won the Nobel Prize in 1933 for his work in genetics."

"Explain the concept of hemizygosity in males."

"Males are hemizygous because they have one X and one Y chromosome, making them the heterogametic sex capable of producing two different kinds of gametes."

"Describe the genetic nomenclature for alleles on different chromosomes."

"Alleles located on different chromosomes are separated by a slash, for example, w+/w+ indicates a wild type homozygote."

"How does the presence of the white-eyed allele in fruit flies demonstrate sex-linked inheritance?"

"In the F2 generation, white-eyed flies only appeared in males, indicating that the white-eyed allele is recessive and located on the X chromosome."

"Explain the significance of reciprocal crosses in genetics."

"Reciprocal crosses show different ratios in progeny of different sexes, indicating that genes must be located on chromosomes."

"Define sex-linked recessive traits and their appearance in males."

"Sex-linked recessive traits appear in all males where the allele is present, due to their hemizygous condition."

"How do the genotypes of male and female fruit flies differ in terms of eye color inheritance?"

"Males have one X chromosome with the allele for eye color, while females have two X chromosomes, which can be homozygous or heterozygous for the eye color alleles."

"Explain the concept of homogametic sex in females."

"Females are the homogametic sex because they have two X chromosomes and can only produce one kind of gamete."

"Describe the inheritance pattern observed in the F1 generation of fruit flies."

"In the F1 generation, all flies had red eyes, indicating that the allele for red eyes is dominant over the allele for white eyes."

"What does the notation w+ signify in genetic nomenclature?"

"The notation w+ indicates the wild type (normal) allele for eye color in fruit flies."

"How does the F1 x F1 cross produce the F2 generation in fruit flies?"

"The F1 x F1 cross produces the F2 generation, where the offspring exhibit a 1:2:1 ratio of genotypes, including both red-eyed and white-eyed flies."

"Explain the concept of genetic ratios in progeny of different sexes."

"Genetic ratios differ in progeny of different sexes due to the presence of sex-linked traits, which are inherited differently in males and females."

"Describe the implications of the findings from Morgan's experiments on sex-linked inheritance."

"Morgan's experiments demonstrated that sex-linked traits could be traced through generations, revealing the distinct inheritance patterns based on the sex of the offspring."

"Describe the appearance of sex-linked recessive traits in females."

"Sex-linked recessive traits appear in homozygous females but do not appear in heterozygous females, who are carriers."

"Explain the significance of Calvin Bridges' discovery in genetics."

"Calvin Bridges discovered that a cross between a white-eyed female and a red-eyed male could produce flies with unexpected phenotypes, indicating exceptions to typical inheritance patterns."

"Define aneuploidy in the context of genetics."

"Aneuploidy refers to the condition where one or more chromosomes of a normal set are missing or present in an unusual number."

"How does genotypic sex determination work in mammals?"

"In mammals, the presence of a Y chromosome determines male sex; if the Y chromosome is absent, the individual is female."

"Explain the role of the X:A ratio in determining sex in flies."

"In flies, the ratio of X chromosomes to autosomes determines sex; if the ratio is greater than or equal to 1, the fly is female, and if the ratio is 0.5, the fly is male."

"Describe the process and consequences of nondisjunction during meiosis."

"Nondisjunction occurs when chromatids fail to separate normally during Anaphase I or II of meiosis, leading to daughter cells with abnormal chromosome numbers."

"What are the results of nondisjunction in Anaphase I?"

"Nondisjunction in Anaphase I results in two daughter cells with n+1 chromosomes and two daughter cells with n-1 chromosomes."

"What are the results of nondisjunction in Anaphase II?"

"Nondisjunction in Anaphase II results in one daughter cell with n+1 chromosomes, one with n-1, and two with n chromosomes."

"Explain the genetic basis of Down's Syndrome."

"Down's Syndrome, also known as Trisomy 21, is caused by the presence of an extra copy of chromosome 21 due to nondisjunction."

"Describe the inheritance pattern of white-eyed and red-eyed flies in the context of sex-linked traits."

"A cross between white-eyed females (XwXw) and red-eyed males (Xw+Y) should typically produce white-eyed males and red-eyed females, but rare exceptions can occur."

"How do environmental factors influence sex determination?"

"Environmental factors can determine sex through a series of internal or external influences, differing from genotypic sex determination."

"What happens to white-eyed females when crossed with red-eyed males according to Bridges' findings?"

"Bridges found that white-eyed females crossed with red-eyed males could produce unexpected phenotypes, indicating genetic anomalies."

"Explain the concept of lethal alleles in the context of sex-linked traits."

"Lethal alleles can result in the death of individuals with certain genotypes, such as females with two copies of a recessive allele that may not survive."

"Describe the implications of the Y chromosome in sex determination across different species."

"While mammals use the Y chromosome method for sex determination, other species, like flies, use different mechanisms based on the ratio of X chromosomes to autosomes."

"Describe Turner Syndrome and its prevalence."

"Turner Syndrome, characterized by the absence of one X chromosome (XO), occurs in approximately 1 in 2000 to 2500 births."

"Explain Klinefelter syndrome and its diagnosis rate."

"Klinefelter syndrome, which involves an extra X chromosome (XXY), occurs in 1-2.5 in 1000 births, but only 25-50% of individuals are diagnosed in their lifetime."

"Define the role of Y chromosomes in sex determination."

"Y chromosomes determine maleness, but it is the type of gonads that ultimately determines secondary sexual characteristics."

"How does translocation occur in chromosomes?"

"Translocation occurs when a fragment of a chromosome breaks off and reattaches to a different chromosome."

"Explain the significance of the SRY gene."

"The SRY gene, expressed in the gonadal ridges of the embryo, is crucial for male sex determination; its insertion into XX mice can produce male phenotypes."

"What is dosage compensation in mammals?"

"Dosage compensation is the process by which the gene products from the X chromosome in females are downregulated to balance the expression with males, who have only one X chromosome."

"Describe Barr bodies and their significance in female somatic cells."

"Barr bodies are highly condensed, inactivated X chromosomes found in female somatic cells, representing one of the two X chromosomes being silenced."

"Outline the steps involved in X inactivation."

"X inactivation involves three steps: Step 1 - Count the number of X chromosomes; Step 2 - Select one X chromosome at random for inactivation; Step 3 - Inactivate the selected X chromosome."

"What is the XIC and its role in X inactivation?"

"The X inactivation center (XIC) is located on the X chromosome and is essential for inactivation, requiring two XICs for the process to occur."

"Explain the function of the X controlling element (XCE) in X inactivation."

"The X controlling element (XCE) within the XIC contains alleles that determine the probability of which X chromosome will be inactivated."

"What is the role of XIST in X inactivation?"

"X inactive specific transcript (XIST) is transcribed from the inactive X chromosome and produces RNA that coats the chromosome, rendering it inactive."

"Describe how mammalian females can be genetic mosaics."

"Mammalian females, such as calico cats, can be genetic mosaics due to X inactivation; different X chromosomes can carry different alleles, resulting in varied fur colors."

"Explain environmental sex determination in reptiles."

"In some reptiles, the temperature of the nest determines the sex of the offspring; higher temperatures may produce males, lower temperatures produce females, and intermediate temperatures yield a mix."

"What is the inheritance pattern of hemophilia as shown in Queen Victoria's pedigree?"

"Hemophilia follows an X-linked recessive inheritance pattern, as demonstrated in the pedigree of Queen Victoria and her descendants."