Chpt 14 chromosomal Basis Of Inheritance Flashcards
- Which scientist’s work was rediscovered shortly before the chromosome theory of inheritance gained widespread acceptance?* (a) Gregor Mendel* (b) Thomas Hunt Morgan* (c) Calvin Bridges * (d) Theodore Boveri *
*Answer:** (a)Explanation: The source mentions that shortly after Mendel’s work was rediscovered it became widely assumed that genes were located on chromosomes.
- What innovation in the 1880s enabled scientists to identify and track chromosome movement during cell division (a) Genetic sequencing(b) Electrophoresis(c) Microscopy and staining techniques (d) PCR
*Answer:** (c)Explanation: The source explicitly states that advancements in microscopy and staining techniques in the 1880s facilitated the identification and tracking of chromosomes.
- The chromosome theory of inheritance explains how the transmission of chromosomes accounts for: *(a) Protein synthesis(b) Mendelian patterns of inheritance (c) DNA replication (d) Enzyme function
Answer: (b)Explanation: The source states that the chromosome theory of inheritance describes how chromosome transmission explains Mendelian inheritance patterns.
- Which pair of scientists independently proposed the chromosome theory of inheritance in 1902-1903? (a) Watson and Crick (b) Mendel and Darwin(c) Boveri and Sutton (d) Morgan and Bridges
Answer: (c)Explanation: The source names Theodore Boveri and Walter Sutton as the scientists who independently proposed the theory.
- During meiosis each homologue segregates into?(a) The parent cell (b) One of the two daughter nuclei (c) The cytoplasm (d) The cell membrane
Answer: (b)Explanation: The source indicates that homologues segregate into one of the two daughter nuclei during meiosis.
- Which type of chromosomes segregate independently during gamete formation? (a) Homologous chromosomes (b) Non-homologous chromosomes(c) Sister chromatids (d) Sex chromosome
*Answer:** (a)Explanation: The source specifies that homologous chromosomes segregate independently during gamete formation.
- Mendel’s law of independent assortment can be explained by the behavior of:(a) Homologous chromosomes(b) Non-homologous chromosomes (c) Sister chromatids(d) Sex chromosomes*
Answer:** (b)*Explanation:** The source explains that the independent assortment of non-homologous chromosomes during meiosis explains Mendel’s law.
- The first conclusive evidence that genes are parts of chromosomes came from studies of: (a) Autosomal genes(b) Sex chromosomes (c) Mitochondrial DNA (d) Ribosomal RNA
Answer:** (b)Explanation:** The source highlights that the study of sex chromosome transmission provided the first definitive proof of genes residing on chromosomes.
- In some insect species the unpaired chromosome in males is called the: (a) Y chromosome(b) X chromosome (c) Autosome (d) Homologue
Answer:** (a)Explanation:** The source refers to the unpaired chromosome in males of some insect species as the y chromosome.
- What is the chromosome denoted as that pairs with the X chromosome in some species? (a) X chromosome(b) Z chromosome(c) Y chromosome (d) W chromosome
Answer: (c)*Explanation:** The source identifies the chromosome that pairs with the X chromosome as the Y chromosome.
- In the XX-XY sex determination system the female is the: * (a) Heterogametic sex (b) Homogametic sex (c) Sterile sex(d) Dominant sex
Answer:** (b)Explanation:** The source describes the female as the homogametic sex because they produce only one type of gamete (X-bearing).
- In the XX-XY system the male is the(a) Homogametic sex(b) Heterogametic sex(c) Recessive sex(d) Sterile sex
Answer:** (b)Explanation:** The source labels the male as the heterogametic sex due to their production of two types of gametes (X-bearing and Y-bearing).
- What is the expected sex ratio at fertilization in the XX-XY system with random gamete union?(a) 2:1(b) 1:2(c) 1:1(d) 3:1
Answer:** (c)Explanation:** The text indicates a 1:1 sex ratio due to equal numbers of X- and Y-bearing sperm.
- Chromosomes other than sex chromosomes are called:(a) Allosomes(b) Heterosomes (c) Autosomes(d) Homosomes
Answer:** (c)Explanation:** The source uses the term “autosomes” to refer to chromosomes other than sex chromosomes.
- Which chromosome carries few genes other than those related to male determination?(a) X chromosome(b) Y chromosome(c) Autosomes (d) All of the above
nswer:** (b)*Explanation:** The source mentions that the Y chromosome primarily contains genes related to male determination.
- The wildtype eye color in *Drosophila (a) White(b) Red(c) Brown(d) Yellow
Answer:** (b)Explanation:** The passage states that the wildtype eye color is a combination of red and brown pigments
- The white-eye mutation in Drosophila results in: (a) Increased pigment production(b) A metabolic block affecting pigment production(c) Enhanced eye development(d) No change in eye color
Answer:** (b)Explanation:** The source describes the white-eye mutation as a metabolic block knocking out both red and brown pigments.
- In Morgan’s initial cross what was the phenotype of the F1 generation? (a) All white eye$(b) All red eye (c) Half red eyes half white eye(d) Mostly white eyes
Answer:** (b)Explanation:** The text indicates that all F1 progeny from the initial cross (red-eyed female x white-eyed male) had red eyes.
- What was unusual about the white-eyed phenotype in Morgan’s F2 generation?(a) It was only observed in females(b) It was only observed in males(c) It was equally distributed between males and females (d) It was not observed at all
Answer:Explanation: The source highlights that all the white-eyed flies in the F2 generation were male.
- When Morgan crossed white-eyed females with wildtype males what were the phenotypes of the offspring?(a) All wildtype females and white-eyed males(b) All white-eyed females and wildtype males(c) All offspring had red eyes (d) All offspring had white eyes
Answer:** (a)Explanation: The passage notes that this reciprocal cross resulted in all female offspring having wildtype eyes and all males having white eyes.
- Where is the allele for white eyes in Drosophila located? (a) Y chromosome (b) X chromosome (c) Autosome (d) Mitochondria
Answer: (b) Explanation: The source explains that the different results in reciprocal crosses led Morgan to realize that the allele for white eyes resided on the X chromosome.
- What term describes a gene located on the X chromosome? (a) Y-linked (b) Autosomal (c) X-linked (d) Mitochondrial
Answer: (c) Explanation: The term “X-linked” specifically refers to genes present on the X chromosome as stated in the source.
- Which phenomenon did Calvin Bridges propose to explain exceptional offspring in Morgan’s crosses? (a) Crossing over (b) Independent assortment (c) Nondisjunction (d) Segregation
Answer: (c) Explanation: The text explains that Bridges attributed the exceptional offspring (white-eyed females and red-eyed males) to nondisjunction of the X chromosomes during meiosis.
- What is nondisjunction? (a) The normal separation of chromosomes during meiosis. (b) The failure of chromosomes to separate properly during meiosis (c) The exchange of genetic material between homologous chromosomes. (d) The independent assortment of chromosomes.
Answer: (b) Explanation: The source defines nondisjunction as the failure of two X chromosomes to separate during meiosis in the mother.
- What were the sex chromosome compositions of the exceptional offspring in Bridges’ experiments? (a) White-eyed females: XXY; Red-eyed males: XO (b) White-eyed females: XO; Red-eyed males: XXY (c) White-eyed females: XXX; Red-eyed males: XY (d) White-eyed females: XX; Red-eyed males: YY
Answer: (a) Explanation: The source details that exceptional white-eyed females had an XXY composition while exceptional red-eyed males were XO.
- What was the significance of Bridges’ experiments? (a) They disproved the chromosome theory of inheritance. (b) They provided definitive proof of the chromosome theory of inheritance (c) They showed that genes are not located on chromosomes. (d) They demonstrated that Mendel’s laws were incorrect.
Answer: (b) Explanation: According to the text these experiments offered conclusive evidence supporting the chromosome theory of inheritance.
- Mendel’s law of segregation can be explained by: (a) The independent assortment of chromosomes during meiosis (b) The homologous pairing and segregation of chromosomes during meiosis (c) The replication of chromosomes during interphase (d) The behavior of non-homologous chromosomes during meiosis
Answer: (b) Explanation: The provided text states that Mendel’s law of segregation can be explained by homologous chromosome pairing and separation in meiosis.
- Which sex in the XX-XY system produces only one type of gamete? (a) Male (b) Female
Answer: (b) Explanation: The female is referred to as the homogametic sex because they produce only X-bearing gametes.
- In which organisms is the XX-XY type of chromosomal sex determination found? (a) Mammals including humans (b) Birds (c) Reptiles (d) All of the above
Answer: (a) Explanation: The passage mentions mammals including humans among the organisms exhibiting the XX-XY system.
- The Y chromosome in most organisms primarily carries genes related to: (a) Female determination (b) Male determination (c) Eye color (d) Wing shape
Answer: (b) Explanation: The source states that the Y chromosome mainly contains genes related to male determination. Multiple Choice Questions (without options):
31 Fundamental Principles of the Chromosome Theory of Inheritance:
The chromosome theory of inheritance rests on these key principles• Genes are located on chromosomes This is the core principle Specific traits are determined by genes and these genes reside at specific locations loci on chromosomes.• Chromosomes are replicated and passed from parent to offspring During cell division meiosis and mitosis chromosomes are duplicated and accurately segregated into daughter cells ensuring that each offspring receives a complete set of chromosomes from each parent.• Homologous chromosomes segregate during meiosis Pairs of homologous chromosomes one from each parent separate during meiosis I leading to the segregation of alleles into different gametes This aligns with Mendel’s Law of Segregation.• Nonhomologous chromosomes assort independently Different chromosome pairs assort independently during meiosis I leading to a variety of combinations of parental chromosomes in gametes This corresponds to Mendel’s Law of Independent Assortment.
32 Criss-Cross Inheritance of the X Chromosome:
Criss-cross inheritance refers to the pattern where the X chromosome from a male parent is passed only to his female offspring daughters while the X chromosome from a female parent is passed to both male and female offspring.• Males receive their X chromosome from their mother Since males are XY their only X chromosome comes from their mother.• Females receive an X from each parent Females receive one X chromosome from their mother and one from their father.This pattern explains why X-linked recessive traits like hemophilia or red-green color blindness are more frequent in males Males only need one copy of the recessive allele on their single X chromosome to express the trait whereas females need two copies one on each X.
33 Role of Autosomes in Development:
Autosomes are all chromosomes except the sex chromosomes X and Y They carry the vast majority of an organism’s genes and play a crucial role in development by:• Determining most traits Autosomes carry genes that determine a wide array of characteristics including physical traits metabolic processes and susceptibility to diseases.• Controlling cell differentiation and growth Genes on autosomes regulate processes essential for proper cell differentiation and growth during embryonic development.• Influencing overall development Many complex developmental processes are controlled by the coordinated action of multiple genes located on various autosomes.
34 Morgan’s Reciprocal Crosses and the Challenge to Mendelian Patterns
:Morgan’s experiments with Drosophila fruit flies involving reciprocal crosses with X-linked traits challenged traditional Mendelian patterns In a typical Mendelian cross the phenotypes in the offspring are the same regardless of which parent carries the dominant or recessive allele reciprocal crosses give similar results However Morgan’s reciprocal crosses with eye color showed a different pattern:• A cross between a white-eyed male and a red-eyed female produced all red-eyed offspring in the F1 generation but the F2 generation showed a skewed ratio of phenotypes white-eyed males were significantly more frequent than white-eyed females.• The reciprocal cross red-eyed male x white-eyed female resulted in different phenotypic ratios in the offspring.This difference demonstrated that the eye color gene was located on the X chromosome deviating from the expected Mendelian pattern of equal inheritance regardless of parental sex.
35 Homogametic and Heterogametic Sex (XX-XY System):
In the XX-XY sex determination syst• Homogametic sex This sex produces gametes eggs or sperm that carry only one type of sex chromosome In this system females are homogametic XX producing gametes all carrying an X chromosome.• Heterogametic sex This sex produces gametes with two different tThere isn’t a single
