Chromosomal and Molecular Basis of Inheritance Online Quiz

DNA replication is semi-conservative. Each daughter cell receives one original strand and one newly synthesized strand. Since the thymine in the medium is radioactive, the new strands in both daughter cells will incorporate it, making both cells radioactive.

DNA polymerase cannot start a new strand from scratch; it requires a short segment of RNA, known as an RNA primer, to provide a free 3'-OH group to which it can add nucleotides.

The two strands of the DNA double helix are held together by hydrogen bonds between the complementary nitrogenous bases (A-T and G-C).

Because DNA polymerase can only synthesize in the 5' to 3' direction, the lagging strand must be synthesized in short, discontinuous segments called Okazaki fragments.

Repairing thymine dimers involves a multi-step process: excision enzymes (like uvrABC endonuclease) remove the damaged segment, DNA polymerase fills the gap, and DNA ligase seals the nick.

DNA polymerase adds nucleotides to the growing strand by forming phosphodiester bonds between the 3'-OH of the existing strand and the 5'-phosphate of the incoming nucleotide. It does not form the hydrogen bonds between base pairs; those form spontaneously based on complementarity.

The leading strand is synthesized continuously in the direction of the replication fork movement, while the lagging strand is synthesized discontinuously.

According to Chargaff's rules, A=T and G=C. If Thymine is 20%, then Adenine is also 20%. The remaining 60% must be split equally between Guanine and Cytosine, so Guanine is 30%.

Transformation is the process by which a bacterium takes up naked DNA from its environment and incorporates it into its own genome.

A Barr body is the inactive X chromosome in female somatic cells. Since women have two X chromosomes, one is inactivated in each cell. Men (XY) and gametes (sperm/ovum) do not have Barr bodies.

The SRY gene (Sex-determining Region Y) is located on the Y chromosome and acts as a master switch to trigger the development of testes in the embryo.

An inversion occurs when a segment of a chromosome is reversed. Because no genetic material is lost or gained, the genic balance remains the same, but the change in gene order can alter the phenotype due to position effects.

X inactivation, tortoise-shell coat patterns, and Barr bodies are all phenomena related to the dosage compensation mechanism in mammals. Fragile X syndrome is a genetic disorder caused by a mutation in the FMR1 gene, which is distinct from the regulatory mechanism of X inactivation.

Color blindness is an X-linked recessive trait. A son receives his only X chromosome from his mother, so if he is color-blind, he must have inherited the affected X chromosome from her.

In this analogy, a chromosome is a floor and a gene is a page. Aneuploidy refers to an abnormal number of chromosomes, which corresponds to having an incorrect number of floors in the building.

Linkage refers to genes being located close together on the same chromosome. In the analogy, if a chromosome is a CD and genes are songs, linkage is represented by the order or sequence in which those songs appear on the disc.

Linkage describes genes that are located near each other on the same chromosome and tend to be inherited together. Red hair and freckles are classic examples of traits that are genetically linked.

A man has one X chromosome and one Y chromosome. He passes his X chromosome to all of his daughters and his Y chromosome to all of his sons.

The frequency of recombination through crossing over is directly related to the physical distance between two genes on a chromosome. The further apart they are, the more likely a crossover event will occur between them.

A locus is the specific, fixed position on a chromosome where a particular gene or genetic marker is located.

A Barr body is the inactive X chromosome in a female somatic cell. Males do not have a Barr body because they only have one X chromosome.

Independent assortment occurs during meiosis I when homologous chromosome pairs align randomly at the metaphase plate, leading to the independent distribution of alleles into gametes.

A zygote with a YO genotype lacks an X chromosome entirely. Because the X chromosome contains essential genes for development, a YO embryo cannot survive.

Human males inherit their X chromosome from their mother. Additionally, mitochondrial DNA is inherited exclusively through the maternal line (the egg cytoplasm).

For a sex-linked recessive trait, males are more frequently affected than females because they only have one X chromosome. It is incorrect to say the trait would be more common in females.

Genomic imprinting is an epigenetic phenomenon where the expression of a gene depends on whether it was inherited from the mother or the father.