MODULE 2 Flashcards
What is the biological process that explains Mendelian laws?
a) Mitosis b) Meiosisc) Binary fissiond) DNA replication
b) Meiosis
What occurs during prophase I of meiosis?
a) Homologous chromosomes separateb) Crossing over between homologous chromosomesc) Sister chromatids separated) DNA replication
b
What structure facilitates synapsis in prophase I of meiosis?
a) Centromereb) Synaptonemal complexc) Spindle fibersd) Kinetochore
b
What did Morgan’s white-eyed Drosophila experiments demonstrate?
a) Gene linkage to the sex chromosomesb) Law of independent assortmentc) Cytoplasmic inheritanced) Polygenic inheritance
a
What was the significance of reciprocal crosses in Morgan’s experiments?
a) They confirmed sex-linked inheritanceb) They disproved the law of segregationc) They showed genes assort independentlyd) They demonstrated that traits blend
a
What determines sex in humans?
a) Number of autosomes b) Presence of the SRY gene on the Y chromosome c) X chromosome inactivation d) Ratio of X to autosomes
b
In Drosophila, how is sex determined?
a) Presence of the Y chromosomeb) Ratio of X chromosomes to autosomesc) Hormonal regulationd) Mitochondrial DNA
b
What is non-disjunction?
a) Failure of homologous chromosomes or sister chromatids to separate properlyb) Random assortment of chromosomesc) Mutations occurring in a single gened) Crossing over between homologous chromosomes
a
Which of the following is a viable monosomy in humans?
a) Trisomy 21b) Turner Syndrome (45, X0)c) Klinefelter Syndrome (47, XXY)d) Trisomy 13
b
Why does maternal age increase the risk of aneuploidy?
a) Eggs accumulate DNA mutations over timeb) Oocytes remain arrested in meiosis I for decades, increasing non-disjunction riskc) Sperm contribute more genetic errors in older malesd) Mitochondrial defects cause chromosomal errors
b
Synaptonemal Complex
Protein structure that forms between homologous chromosomes, facilitating crossing over.
What is Swyer Syndrome?
XY individuals develop as female due to deletion of the SRY gene.
X:A Ratio for Female Drosophila?
1.0
X:A Ratio for Male Drosophila?
0.5
What is X-Inactivation?
Process in females where one X chromosome is silenced to balance gene dosage.
Which of the following is NOT a key event of meiosis?
(a) Crossing over
(b) Synapsis
(c) DNA replication
(d) Homolog separation
(d) Homolog separation (While homologs do separate in meiosis I, it’s not the defining event. Meiosis II involves sister chromatid separation).
Meiosis I is primarily responsible for which aspect of Mendelian inheritance?
(a) The randomness observed in Mendelian ratios
(b) Sister chromatid separation
(c) DNA replication
(d) Formation of the synaptonemal complex
a
The discovery of which phenotype in Drosophila provided key insights into sex-linked inheritance?
(a) Red-eyed flies
(b) White-eyed flies
(c) Wingless flies
(d) Curly-winged flies
b
The inheritance pattern of white eye color in Drosophila seemed to contradict which Mendelian law?
(a) First Law (segregation)
(b) Second Law (independent assortment)
(c) Both First and Second Laws
(d) Neither First nor Second Law
b
What is the primary determinant of sex in Drosophila?
(a) Presence of the Y chromosome
(b) X:A ratio
(c) Number of X chromosomes
(d) Presence of the SRY gene
b
n mammals, what is the default developmental pathway in the absence of the SRY gene?
(a) Male
(b) intersex
(c) female
(d) Metafemale
c
What type of molecule does the SRY gene encode?
(a) A hormone
(b) A receptor
(c) A transcription factor
(d) An enzyme
c
Non-disjunction refers to the failure of which process during cell division?
(a) Chromosome replication
(b) Chromosome separation
(c) Chromosome condensation
(d) Chromosome synapsis
b
Non-disjunction of the X chromosome in Drosophila can result in which of the following?
(a) White-eyed females
(b) Red-eyed males lacking a Y chromosome
(c) Both (a) and (b)
(d) Neither (a) nor (b)
c
